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Subject: "Alarmingly low oil pressure at idle" Archived thread - Read only
 
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Jeff McNealadmin
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Oct-18-03, 03:16 PM (PST)
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"Alarmingly low oil pressure at idle"
 
I finally got around to connecting my oil pressure gauge late yesterday afternoon and was monitoring my pressure on the long drive to Riverside and Triumphest 2003 early this morning. At startup, I was seeing 70lb, which is what I was expecting, but as the engine fully reached it's warm operating temperature, I was seeing about 45-50lb at 3000 RPM, which is smack in the center of the gauge. That bothered me a little bit, because with a freshly rebuilt engine with new bearings like I have, I was expecting to see at least 60 or even 70lb at that engine speed.

The shocker came on my way home when I pulled off the freeway and to a stop, and the gauge dropped to read less than 10lbs of pressure at 1000 RPM!!! As I started driving, it went back up to about 40-50lb, but during stops it would fall back to below 10!! The oil light never came on, even though I have it connected.

At the show, I bumped into Joe Curry and he said I could increase the pressure by installing shims in the oil relief valve. Is that what I need to do? I don't mind seeing 20-30 lbs of pressure at idle, but 7 or 8 positively gave me the willies!!

What do the experts advise?

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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  Subject     Author     Message Date     ID  
  RE: Alarmingly low oil pressure at idle 76 Oct-18-03 1
  RE: Alarmingly low oil pressure at idle Lance Oct-18-03 2
     RE: Alarmingly low oil pressure at idle Lance Oct-18-03 3
         RE: Alarmingly low oil pressure at idle Jeff McNealadmin Oct-18-03 5
     RE: Alarmingly low oil pressure at idle Jeff McNealadmin Oct-18-03 4
         RE: Alarmingly low oil pressure at idle Lance Oct-18-03 6
             RE: Alarmingly low oil pressure at idle Bill A Oct-19-03 7
                 RE: Alarmingly low oil pressure at idle Lance Oct-19-03 8
                 RE: Alarmingly low oil pressure at idle Jeff McNealadmin Oct-19-03 9
                     RE: Alarmingly low oil pressure at idle Lance Oct-19-03 10
                         RE: Cautiously optimistic resolution Jeff McNealadmin Oct-19-03 11
                             RE: Cautiously optimistic resolution clshoreteam Oct-19-03 12
                                 RE: Cautiously optimistic resolution Jeff McNealadmin Oct-19-03 13
                                     RE: Cautiously optimistic resolution clshoreteam Oct-19-03 14
                                         RE: Cautiously optimistic resolution Jeff McNealadmin Oct-19-03 15
                                             RE: Cautiously optimistic resolution psliceteam Oct-20-03 16
                                             RE: Cautiously optimistic resolution Jeff McNealadmin Oct-20-03 18
                                             RE: Cautiously optimistic resolution John R Daviesmoderator Oct-20-03 17
                                             RE: Cautiously optimistic resolution tonymrfixitteam Oct-20-03 19
                                             RE: Cautiously optimistic resolution vagt6 Oct-20-03 21
                                             RE: Cautiously optimistic resolution Jeff McNealadmin Oct-20-03 22
                                             RE: Cautiously optimistic resolution foxtrapper Oct-21-03 25
                                             RE: Cautiously optimistic resolution Voda2000 Oct-21-03 26
                                             RE: Cautiously optimistic resolution 76 Oct-21-03 27
                                             RE: Cautiously optimistic resolution Voda2000 Oct-21-03 28
                                             RE: Cautiously optimistic resolution Lance Oct-21-03 29
                                             RE: Cautiously optimistic resolution foxtrapper Oct-22-03 31
  RE: Alarmingly low oil pressure at idle 76 Oct-20-03 20
     RE: Alarmingly low oil pressure at idle Bill A Oct-20-03 23
         RE: Alarmingly low oil pressure at idle Jeff McNealadmin Oct-20-03 24
             RE: Alarmingly low oil pressure at idle Bill A Oct-21-03 30
                 RE: Alarmingly low oil pressure at idle clshoreteam Oct-25-03 32
                     RE: Alarmingly low oil pressure at idle Jeff McNealadmin Oct-25-03 33
                         RE: Alarmingly low oil pressure at idle rowsinski Oct-26-03 34
                     RE: Alarmingly low oil pressure at idle foxtrapper Oct-26-03 35
                         RE: Alarmingly low oil pressure at idle vagt6 Oct-27-03 36
                             RE: Alarmingly low oil pressure at idle Richard & Daffy Oct-27-03 37
                             RE: Alarmingly low oil pressure at idle Jeff McNealadmin Oct-27-03 38
                                 RE: Alarmingly low oil pressure at idle tonymrfixitteam Oct-27-03 39

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76
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Oct-18-03, 03:40 PM (PST)
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1. "RE: Alarmingly low oil pressure at idle"
In response to message #0
 
LAST EDITED ON Oct-18-03 AT 03:45 PM (PDT)
 
Hey Jeff - I read somewhere that 12psi at idle on a well worn engine was no cause for concern. Certainly something that low on a newly rebuilt one is. On my rebuilt (5000mi) 1500 on the hottest days after a freeway buzz run I'll idle at 20psi, at 3000rpm its about 55psi. 20/50 Castrol.

I was thinking an oil cooler might help as my pressure is only that low when things get really hot. I'd be interested in the shimming the relief spring too.

Anyone have a comment on either of these two issues?

By the way Jeff, back east here it's barely cracking 55 degrees mid-day so this is really not going to be an issue for me until next June. Must be nice to have temperate weather all year. 100 deg. may seem real hot to you but us eastern Spits will kill for 60 in another couple of months.

Brian B. Ready
76 Spit (aka Little Blue)
94 Stratocaster (aka #2)
http://www.angelfire.com/blues2/spitfire/


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Lance
Member since Jul-17-03
138 posts (Dedicated enthusiast)
Oct-18-03, 08:33 PM (PST)
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2. "RE: Alarmingly low oil pressure at idle"
In response to message #0
 
   What weight of oil are you running? I am thinking that you oil might be too light. If you are running 5-30, try switching up to 10-30 or 10-40.


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Lance
Member since Jul-17-03
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Oct-18-03, 10:37 PM (PST)
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3. "RE: Alarmingly low oil pressure at idle"
In response to message #2
 
   I could not edit. In addition to my above post, shimming the relief valve increases the maximum oil pressure. Since you are no where near max pressure at idle, it would not help. I could be wrong here, if so, someone please enlighten me.


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Jeff McNealadmin
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Oct-18-03, 10:46 PM (PST)
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5. "RE: Alarmingly low oil pressure at idle"
In response to message #3
 
If shimming increases max pressure, wouldn't that mean it would increase the idle pressure as well? Wouldn't shimming increase the pressure across the board?

I suppose there's always a chance that I've got a kink in the nylon pressure line or the gauge has a fault of some sort. I certainly hope so! I've been in low pressure situations before where the bearings chatter and so forth, but I hear none of that. I wonder what else could be causing this?

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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Jeff McNealadmin
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Oct-18-03, 10:42 PM (PST)
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4. "RE: Alarmingly low oil pressure at idle"
In response to message #2
 
I'm running 20w50. And it's time for an oil change. But still...

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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Lance
Member since Jul-17-03
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Oct-18-03, 11:16 PM (PST)
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6. "RE: Alarmingly low oil pressure at idle"
In response to message #4
 
   Regarding the shimming, the valve does not open until there is a predetermined amount of pressure pushing against it. If it is not near that pressure, the valve will not bypass the oil back into the pan. You could shim it to see what happens. I would check the accuracy of the gauge before doing anything else.


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Bill A
Member since Dec-8-01
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Oct-19-03, 08:09 AM (PST)
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7. "RE: Alarmingly low oil pressure at idle"
In response to message #6
 
   LAST EDITED ON Oct-19-03 AT 08:10 AM (PDT)
 
Jeff,

I'm with Lance on this. Smith gauges weren't always that great when new, who knows how accurate they will be after 30 odd years. I'd go to the parts store and spend $20.00 on a new gauge to check it against your Smith gauge first. Cheap insurance. Your engine is too new and you're using a good weight oil so I'm inclined to think that the problem is not in the engine.


Bill Allison
74 Spitfire
69 GT6
65 Jag XKE
70 VW Karmann Ghia


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Lance
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Oct-19-03, 08:22 AM (PST)
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8. "RE: Alarmingly low oil pressure at idle"
In response to message #7
 
   Jeff, another thing. Do you have the external rocker shaft oil feed? I do not personal experience with these, but I remember reading somewhere that they can drop the oil pressure. I guess there is less restriction for the oil then going the traditional way or something. IF anyone here has one , could you shed some light on this?


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Jeff McNealadmin
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Oct-19-03, 09:48 AM (PST)
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9. "RE: Alarmingly low oil pressure at idle"
In response to message #7
 
Thanks for the replies gents. I do not have an external rocker oil feed. I think I would be more inclined to invest that money towards a set of roller rockers and an oil cooler.

The gauge in question is a vintage Jaeger (which I was very happy to find since it's a perfect match with the rest of my Jaeger gauges). I used it on my last car and it gave good readings so I really hadn't considered it as suspect for potential problems, but during installation, I did manage to kink the nylon feed line and while I thought I successfully un-kinked it, there's always the chance that there is some partial restriction going on. I also used teflon tape to seal the threads and there might also be a (remote) chance that some pipe dope got into the line, causing possible partial blockage, which would certainly result in the lower readings.

But then again, I seem to be registering exactly what I would expect when the engine is cold at idle (70lbs).

I think I'll go with the advice to invest in a $20 gauge and see what my readings look like with it. I also have an old metal capillary tube that I could try... But I felt like the nylon version would be less prone to rupture.

The only other thing I did differently this time was to mount the T so that the pressure switch fit on the end of it and the gauge capillary fit on the side, which was the reverse of how I had it mounted on my last car.

Old way:

New way:


The new configuration made more sense to me since it put less of a bend in the capillary line, but maybe there was a reason for having it configured the old way that I've forgotten about. I shouldn't think it would make any difference.

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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Lance
Member since Jul-17-03
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Oct-19-03, 12:12 PM (PST)
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10. "RE: Alarmingly low oil pressure at idle"
In response to message #9
 
   No, it wont make a difference. I hate to be the bad guy, but having good pressure when its cold and losing it when its hot sounds like some excessive clearence to me. As the oil heats up & thins out, it will follow the path of least resistance. Start with the gauge, but I personally would not bet money on it. Did you rebuild the engine yourself or have it done? I assume your engine has cam bearings, were they replaced? Everyone checks the crank & rod bearings. I had a friend who built a small block chev, had the same problem, and it ended up he never had mic'd the cam & bearings and had a loose one. Another thing to check before tearing into the engine is the oil temp. MAybe it is getting too hot. Sorry I am hitting three different angles here, just trying to offer as many ideas as possible.


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Jeff McNealadmin
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Oct-19-03, 01:31 PM (PST)
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11. "RE: Cautiously optimistic resolution"
In response to message #10
 
Upon checking the capillary feed to the gauge this morning, I made a few observations. Notably, there was still a minor kink where I had straightened out the last one, but perhaps more significantly, I noted that the capillary was having to make a pretty sharp bend where it feeds into the gauge itself due to my placement. I swapped the gauge position with another one in the same bank, so the oil feed is more or less straight into the gauge. I think there might have been some slight pinching to the tube the way I originally installed it.

I started the engine, let it warm up for 10 minutes and while it was still relatively cool, increased the RPM to 2500 and noted 80 lbs of pressure. I let the car go back to idle, then blocked off the radiator in the front with a couple of sheets of paper until the temp was in the upper range of normal. At 800 RPM, I saw 20 lbs of pressure, at 1100 RPM, it increased to 30 lbs and at 2500 RPM it was running at 70 lbs, which all strikes me as being exactly where it should be, and what I was expecting to see in the first place.

My best guess is that the capillary was pinched just enough to restrict the full flow of oil to the gauge, resulting in artificially low numbers. Now granted, this was sitting in my garage and only running the engine for a total of about 20 minutes in about 90 degree ambient air temperature. But yes, I feel cautiously optimistic that the engine itself is just fine. I'll see how it looks with more driving later this afternoon or early evening.

Thanks to all for your thoughtful advice. As always, I greaty appreciate it!

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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clshoreteam
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Oct-19-03, 01:59 PM (PST)
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12. "RE: Cautiously optimistic resolution"
In response to message #11
 
   Jeff,
FWIW, I think there's nothing wrong with your guage, or your nylon tube (since there's no oil flow in the tube, a kink would not affect the steady state reading). Shimming the oil pressure relief valve won't help at idle. And your rod and main bearings are also most likely OK.

The culprit is almost certainly the cam bearing clearance. I believe that there have been several TTN threads on the subject. It's a design issue common to many motors.

Good news: At low RPM in a Spitfire motor, the bearing loads are minimal, so lower pressure is not a big issue. To be safe, I would not lug the motor at lower RPM and WOT, but I suspect that you don't drive that way often.

If you run cam bearings, they can be replaced. If not, they can be fitted. You could run straight 50W (70W is available), or add a couple of cans of STP, or fit a mondo oil cooler, or a bigger sump, but what's the point? As long as oil pressure is OK at higher RPM, you ought to be fine.

Carter



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Jeff McNealadmin
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Oct-19-03, 02:10 PM (PST)
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13. "RE: Cautiously optimistic resolution"
In response to message #12
 
LAST EDITED ON Oct-19-03 AT 02:21 PM (PDT)
 
Hey Carter,

Thanks for the info. I do NOT have cam bearings fitted as they were omitted on the large journal 1300s. But what do you mean that "no oil flows through the tube". I'm a little confused by that remark, since the flow of oil is what drives the mechanical gauge. Not only that, but I can see the oil in the line as I start the motor (it drains back into the block when the engine is turned off).

I'm not sure why the readings would appear normal now, versus what I was getting yesterday if tube restriction has nothing to do with what I was seeing, but in general, I'd have no objection to fitting a cooler or running straight 50w to improve things, if need be. But for now -- pending further testing, neither may be necessary anyway. Especially after what you had to say in the "good news" paragraph.

I think I'm beginning to understand why Triumph never fitted oil pressure gauges to these cars to begin with (aside from simply being too cheap to bother adding another gauge). I get the strangest sense of deja vu with that last sentence. I think I've written it before!

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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clshoreteam
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Oct-19-03, 05:40 PM (PST)
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14. "RE: Cautiously optimistic resolution"
In response to message #13
 
   Consider, if there was constant oil flow, where would it go?
The guage measures pressure. Typically there is a curved piece of brass (like 3/4 of a donut) that, when pressurized, distorts as it tries to straighten out. The movement causes the deflection of the needle on the face. Thus, a tiny amount of oil does flow initially, and when the pressure changes, plus if air is trapped inside, there will be enough flow to compress the air. Once compressed, no substantial flow takes place. A kink, or blockage, unless it completely blocks the passage, only slows down the time needed for enough oil to flow, from say, 1/10 second, to a couple of seconds. The final pressure reading will still be the same at equilibrium.

But I digress.

The good news is that your readings are better; absolute accuracy is not the strong suite of these guages anyway, probably no better than 5-10%.

But you're OK, it's just seems like normal wear. Some folks put restrictors in the oil passages that feed cam bearings at rebuild time. The hazard is not just the lower oil pressure, it's that loose cam bearings divert oil flow away from the main and conrod bearings. The oil pump is constant volume, 1/2 rev for each engine rev, so the total oil flow is fixed at any given RPM.

I *would* ask you to consider changing the way your oil pressure sensor is mounted. The heavy oil pressure switch at the end will cause flexure bending in the long fitting from engine vibrations, and brass does not stand up well to such stresses.

If that brass fitting snaps at speed (a common failure), you will lose all the oil in about 10 seconds, followed by your main and conrod bearings and the crank journals 1/2 second later.

A better way is to mount a fitting solidly, either to the block, or chassis, and run tubing from the motor's pressure port over to the fitting. You could uses brake line tubing, but the same Nylon tubing that the guauge uses works well for this.

Not saying it will fail tomorrow, or even next week, just that it's something that you should add it to the list of must-do's.

Carter


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Jeff McNealadmin
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Oct-19-03, 07:49 PM (PST)
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15. "RE: Cautiously optimistic resolution"
In response to message #14
 
Well, I take back everything I said about the improved pressure. 20 minutes of different engine speeds sitting in the garage versus a real drive out on the highway for the same amount of time yields very different results.

I went out on the freeway this evening and as I tooled up I-15 doing 3500 RPM with the temp reading dead center, I watched as the pressure went from about 70lbs to about 55 lb, the longer I drove.

When I turned around and came back, once I coasted to the stopsign on the offramp I saw the pressure drop way down to the first hash mark again, or around 10 lbs, at 850 RPM. It bounced back up as I picked up the revolutions and went through the gears.

Really, really interesting. It seems that I'm losing significant viscosity when the oil is fully warmed up. I suppose this is a normal occurance.

I've just hit 1,000 miles on the engine now, and the oil needs changing anyway. I've been using Castrol 20w50, but I think I may give a different brand a try and see if it makes any difference at all. I'm still giving serious thought to adding an oil cooler. I don't see any downside in doing that, other than the expense and labor of installation.

Thanks for your recommendation on relocating the brass T fitting. I had no idea they were prone to breakage like that. VERY scary. From your description, there would be no way to assess the problem and react before the engine seized up. Seems that stainless or even mild steel would be a better material for the fitting, I take it?

While this will definitely go on my "must do" list, your caution leads me to another reminder... If I EVER see the oil light come on while driving at speed, I will IMMEDIATELY throw my left foot into the clutch and turn the ignition off as quickly as I can get my hand to the key. At least then, the engine would have a chance...

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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psliceteam
Member since Jul-30-03
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Oct-20-03, 04:19 AM (PST)
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16. "RE: Cautiously optimistic resolution"
In response to message #15
 
Hey Jeff,
My 80 Spit and 78 MGB both have rebuilt engines, I did the B and have the receits for the Spit. I have installed aftermarket mechinical oil pressure gauges on both cars. Both of the engines have between 600 and 1000 miles on each since the rebuild and are using Castoroil 20w50 in each. The oil pressure in each is in the same range as yours and both drop to 10 to 15 lbs when completely warmed up at around 900 RPM. This weekend my brother drove his 72 TR6 from Tennessee to my house,and guess what his pressure when hot was in the 10 lbs range also. This makes me think that this is the normal pressure variation for our engines, as the motors do not make any non-normal noises at this seamingly low pressure. It kind of makes you want to change the idle speed to 1500 RPMs. (LOL)
Paul Slice
South Carolina
80 Spitfire
78 MGB
66 Mustang
89 CRX-Si
85 MR2
95 Accord


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Jeff McNealadmin
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Oct-20-03, 08:15 AM (PST)
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18. "RE: Cautiously optimistic resolution"
In response to message #16
 
Hi Paul,

If you're tryint to make me feel better, it's working!

Thanks for the info.

I guess the reason I sort of panicked in the first place is because my last Mk3 never fell below about 20lb at idle.

It was a small journal high comp Mk3 engine (that also had cam bearings), and maybe the variation is to be expected, then...

In addition to having a better understanding why Triumph didn't fit pressure gauges, I'm beginning to feel a bit like Chicken Little, too.

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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John R Daviesmoderator
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Oct-20-03, 05:43 AM (PST)
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17. "RE: Cautiously optimistic resolution"
In response to message #15
 
Jeff,
Following your last remark, and previous on the lowest pressure registered, I think your oil pressure switch is the standard low pressure one, that triggers at about 2psi. Suggest you follow racing practice and fit one that triggers at a higher pressure, so giving you a little more time to take protective action. Off the top, I think they are available at 15 and 25psi. Racers also fit a LARGE lamp such as an indicator unit to replace the tiny original, to make sure they see it!
John


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tonymrfixitteam
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Oct-20-03, 08:19 AM (PST)
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19. "RE: Cautiously optimistic resolution"
In response to message #17
 
I think if I were to do that I would soon end up with stomach ulcers from sitting at traffic lights on a hot day with the oil pressure warning light blazeing at me, In the hand book it says 'the light should extinguished as the engine speed increases' to me, this implies that the warning light 'might' be lit at idol speed. seems likely, as I once had a 1300 that, on a hot day, in heavey traffic, at idol, the warning light would glow if I lifted the clutch and let the revs drop. I can see a racer wanting to know PDQ if there OP drops to below 15 or 25psi if they are at 5500 rpm, but I don't think I need to see that light flashing at me as I drive around town. Use a good quality, full bodied oil, Castrol is good, I don't think it is the 'Best' and don't worry.

Tony M
74 Spitfire 1500
84 Toyota Pickup
03 VW Golf


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vagt6
Member since Oct-7-03
447 posts (Triumphant in just about everything)
Oct-20-03, 01:01 PM (PST)
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21. "RE: Cautiously optimistic resolution"
In response to message #19
 
Jeff, for whatever it's worth, my '70 GT6+ exhibits the same thing -- very low indicated oil press. at idle when fully warmed up. I drove to the DC MG Brit car show yesterday, about 130 mi. each way. I have a Smith's oil pressure gauge that was added to my left vent by the PO. Oil pressure at 3000 rpm highway speeds, fully warm, is about 55 psi. However, at idle it is about 10 lbs, maybe less. If I increase idle to about 900rpm, it goes up to about 25.

This drives me nuts and I've been driving it like this for about 1,000 miles. Just before this 260 mile-plus trip, I changed to Mobil 1 synthetic (0w40: "European car formula) with no appreciable change to the oil press. By the way, my car seems to run great all the way up to 5,000 rpm. I don't rev it past there, ever.

So, I'm where you are with your Spit. Should we not fix what ain't broke? Please let us know if you find anything significant.

Thanks!

Mark K. Brown, Charlottesville


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Jeff McNealadmin
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22. "RE: Cautiously optimistic resolution"
In response to message #21
 
Okay, I'm beginning to calm down and relax a little again. It looks like I'm in good company, at least.

Fellow member Dave Kloehn, who I had the priviledge of parking next to at Triumphest the other day, tells me that the mercury actually hit 102 in Riverside on Saturday. No wonder I was so blasted hot!!

So long as there are no dangers involved, I think that during my next oil change I might try substituting one quart of 20w50 for straight 50w, though if others keep showing up in this thread exhibiting similar readings, I may not even bother...

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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foxtrapper
Member since Feb-27-02
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Oct-21-03, 03:39 AM (PST)
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25. "RE: Cautiously optimistic resolution"
In response to message #15
 
   I cannot remember, is this a freshly rebuilt engine? If so, things seem a bit sloppy on clearance. Not the end of the world, but not "fresh and tight" either.

I've seen a number of blown Spitfire engines in recent years, albet all 1500. None of them ever had camshaft damage or wear, all had blown out bottom end bearings, especially #2 and #3. A number of these engines had been rebuilt and promptly blew. Many had the caps loosen, several had wrong bearings, others had clearly poor quality (QH) bearings.

Another possibility is a worn or otherwise sloppy oil pump itself. This gives the same results on the gauge as sloppy bearings do.

An oil cooler may well help if you determine that this oil pressure is purely the result of overheated oil, but you should know why your oil is getting so hot. A street driven Spitfire engine shouldn't get its oil so hot, especially on highway drives.

Be carefull going with extremely high viscosity oils, particularly as the weather gets cooler. High viscosity oils do not flow well. So while you may have higher pressure, you may not have lubrication, especially up into areas like the valvetrain. High viscosity oils experience more shear in use, breaking down faster and more severely. High viscosity oils are more prone to cavitating at the oil pump, particularly on cold mornings. They are also known to snap oil pump shafts.

Using a t-block to install the sending unit and capilary tube for the gauge is not a danger in my opinion. These blocks are quite stout and not prone to fatigue failure from the minute loads placed on them by the sending unit. Using a cobbed up bit of brass tubing and compressing fittings would be a different story.

If you should lose oil pressure, you've got more then adequate time to shut the engine down. It's also a simple matter to hook up a buzzer or strobe to the oil pressure sensor wire under the dash.


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Voda2000
Member since Oct-31-01
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Oct-21-03, 03:21 PM (PST)
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26. "RE: Cautiously optimistic resolution"
In response to message #25
 
I agree with Foxtrapper that you would have time to shut do not an engine if the oil pressure was lost, assuming you see it quickly. I have been told that drag racers sometimes make their last run with and empty oil pan to increase their times. You are only talking about a 10 second run but under very high stress.

Has anyone one ever though of wiring some sort of fail safe in that if the oil pressure dropped to low the engine would stop automatically?

Andrew
1978 1500 Spitfire
"ERTW"


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76
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27. "RE: Cautiously optimistic resolution"
In response to message #26
 
Andrew - There are fuel pump cut off switches operated by oil pressure. Drag racers are also known to rebuild their engines in- between runs.

Brian B. Ready
76 Spit (aka Little Blue)
94 Stratocaster (aka #2)
http://www.angelfire.com/blues2/spitfire/


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Voda2000
Member since Oct-31-01
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Oct-21-03, 05:11 PM (PST)
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28. "RE: Cautiously optimistic resolution"
In response to message #27
 
Brian,

Good point about the drag racing never really considered that.

The shut off switch would be a good idea if you have an electric fuel pump. Could you use the existing oil pressure switch to ground the coil till the pressure build up enough to allow the motor to start and if the pressure dropped cause the coil to cut out?

Just a thought.

Andrew
1978 1500 Spitfire
"ERTW"


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Lance
Member since Jul-17-03
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Oct-21-03, 05:53 PM (PST)
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29. "RE: Cautiously optimistic resolution"
In response to message #28
 
   The only problem with the fuel pump cut is that the engine would still have time to run off the fuel in the floatbowl of the carb. I think cutting the spark would be the way to go.


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foxtrapper
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Oct-22-03, 03:19 AM (PST)
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31. "RE: Cautiously optimistic resolution"
In response to message #26
 
   You don't want to ever have an engine shut off automatically due to loss of oil pressure. Murphy's law would have it happening at horribly inopportune moments, like crossing a train track, or pulling out into heavy traffic. An indicator telling you of the problem and then having you respond promtly when it is safe is far better.

The time for running an engine without oil before damage results is in the several minutes category. I've personally run engines without oil for hours before they seize. In fact, I've had one that never did seize, it simply quit running when the camshaft wore down through the cylinder head into the combustion chamber, eliminating compression.

The one that does result in quick failure is loss of coolant. Even then it takes a few minutes, but only a few. Loss of coolant results in more severe damage, and at a much quicker rate.


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76
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20. "RE: Alarmingly low oil pressure at idle"
In response to message #0
 
Jeff - Triumph did not install oil pressure gauges in the Spitfire so their owners wouldn't have a heart attack when they looked at the gauge at idle!

Again, 10psi at idle on a well worn engine may not be cause for concern. I myself would not be comfortable with that on a newly rebuilt one such as yours (or mine).

On changing gauges from Autometer to Smiths (late model TR6 to match the others) I had a 10% drop in pressure. I agree with previous post that said try another gauge.

Also, it apparently has been HOT! out there. I would, and am, considering an oil cooler. When it's 90's out here and I've been on the highway for 1/2 hour or so I see considerably less oil pressure than when driving the back roads for the same amount of time. 20psi, which I fiqure is almost 25 due to the low reading on the gauge.

Here's hoping either of these will get you back to 20-25psi at idle!

Brian B. Ready
76 Spit (aka Little Blue)
94 Stratocaster (aka #2)
http://www.angelfire.com/blues2/spitfire/


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Bill A
Member since Dec-8-01
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Oct-20-03, 07:15 PM (PST)
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23. "RE: Alarmingly low oil pressure at idle"
In response to message #20
 
   Jeff and all,

About two years ago before I installed an oil preassure gauge, while driving down the highway the oil preassure sending unit blew out spraying the oil out in seconds. Because of the top being down and the sun shining I didn't see the idiot light come on. I did see the oily mist rising from the left side though and headed for the side of the road. Luckily I was within walking distance of a gas station. After plugging the hole and buying some oil I went on my way. I was sure I fried the engine but two years later it's running better than ever. These are tough little engines. Before it left the garage again though it had an oil preassure gauge. Even an inaccurate Smiths gauge is better than the idiot light.

Bill Allison
74 Spitfire
69 GT6
65 Jag XKE
70 VW Karmann Ghia


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Jeff McNealadmin
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24. "RE: Alarmingly low oil pressure at idle"
In response to message #23
 
Just curious, Bill. Did you retain the idiot light, given that the pressure switch failure is what caused you all the grief to begin with?

Or are you just relying on the gauge now?

After a lengthy drive this evening, I'm getting 20 lbs at 1,000 RPM, and about half that at 600-700 RPM (I know, my idle is set a bit too low at present).

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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Bill A
Member since Dec-8-01
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Oct-21-03, 06:49 PM (PST)
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30. "RE: Alarmingly low oil pressure at idle"
In response to message #24
 
   Jeff,

Since the wiring was already there I just put a t fitting on and installed a new sending unit along with the line for the gauge. I've never read a post here or anywhere else of a sending unit failing like this so I think I just had a freak occurance.

Bill Allison
74 Spitfire
69 GT6
65 Jag XKE
70 VW Karmann Ghia


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clshoreteam
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Oct-25-03, 10:09 AM (PST)
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32. "RE: Alarmingly low oil pressure at idle"
In response to message #30
 
   Actually,
I've had 3 oil pressure senders fail, (see archives).
And yes, long brass fittings *will* snap off eventually. Not one of mine, since I took the advice of the seasoned successful racer who advised me to 'fix it or lose it'. You can websearch yourself if you want to, plenty of forums like this, of folks that it did happen to. (Why would they lie about it?)

It's been stated on this thread that engines can run 'for hours' with no oil, and that drag racers 'do it all the time'.

Were these Spitfire engines? And was that with 'no oil' or 'not much oil left in the sump'? And what is meant by 'running'?

A Spit motor with a completely spun #3 conrod bearing will startup and 'run'. Sure, there's an awful noise, the motor shake like mad, won't turn over 3,000 RPM, lot's of smelly smoke, plus the bearing shell is melted, the crank journal scored beyond repair, and the conrod ruined, but hey, it 'runs'.

As a Spitfire owner for 35 years, and an ex-racer, I've had, and seen, my share of motor blow-ups. I never had a 'magic Spitfire' that would run without oil.

And as for drag racers, let's see, they run about 1/4 mile, then routinely tear down the motor, right? And their crank journals are nitrided too? And replacing engine components is standard weekly (daily) procedure?

C'mon folks, get real. If you lose your oil in a Spitfire, then you are looking at a teardown. Minor if you catch it right away, major otherwise. For most of us, that's a PITA and expense, to be avoided.

At 3,000 RPM, the linear velocity at the conrod journal is about 20 ft/sec. The conrod bearing, flattened out, is a strip of metal about 3/4" wide x 5" long. So imagine dipping this strip in motor oil, placing 250 lbs weight on it, and then dragging it accross a smooth flat steel surface at 20 ft/sec. Oh yeah, and heat it to 250 F first.

Got the picture? How long do you think that strip will last without damage?

So do what you can, to avoid losing your oil:

Capillary tubing from the block to a remote T fitting is just as reliable as the same type of capillary tube direct to the oil pressure guage. The difference is, such a fitting won't break off and spill out *all* your oil.

And as for being 'too complicated' or 'extra work', well, you gotta make that call yourself. I consider unexpectedly breaking down on the road, and having to rebuild my motor as 'complicated extra work'.

I'd much rather spend my time and money doing modifications to my car.

YMMV,

Carter


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Jeff McNealadmin
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Oct-25-03, 10:33 PM (PST)
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33. "RE: Alarmingly low oil pressure at idle"
In response to message #32
 
I believe in erring on the side of caution whenever practical and whenever possible. Even more so when it comes with Spitfire engines, which seem to have a long and distinguished history of something short of longevity when run in anything less than optimum conditions.

To tell you the truth, after reading everything, I'm almost tempted to forego the oil light, and the brass "T" fitting all together, and simply connect the capillary for the gauge straight to the engine block. I'm in the habit of visually scanning the gauges and I'm not really sure if that little green light would grab my attention anyway, unless I was driving at night, perhaps. It seems that either the oil pressure sender unit or brass "T" connector failing are two of the main reasons one would experience a sudden drop in oil pressure at least insofar as catastrophic and sudden volume loss are concerned.

By the way, I think that either conditions are deplorable and whoever is manufacturing those pressure senders and "T" fittings should be ashamed of their products. There's no excuse for that kind of failure, IMHO.

I'm curious about the core plug in the block that's fitted right below the oil filter. If feasible, it seems like a nice place to fit an adapter to connect the oil sender, perhaps, while using the current oil sender opening to install the gauge. That way, the "T" fitting could be eliminated all together. Would that be a viable option?

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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rowsinski
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Oct-26-03, 07:39 AM (PST)
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34. "RE: Alarmingly low oil pressure at idle"
In response to message #33
 
Jeff,

I like a pressure gauge as well. I just replaced my combo Smiths Temp/Oil Pressure gauge (only one hole). The gaugeguys.com have them with the actual temp degrees verus green/yellow/red. ($125 I think) Details on other tread. The only disadvantage is that the temp gauge uses a capilary tube that must not be kinked ( the reason for the replacement- mercury filled). When I checked the temp reading against a digital temp gauge it was right on.

PS: The oil pressure reading is now higher with the new gauge (existing sender). So different gauges... High is fell over 60 low after hot at idle @20+.

Bob Owsinski
76 Spitfire
Dearborn Hts. MI
http://mywebpages.comcast.net/rowsinski


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foxtrapper
Member since Feb-27-02
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Oct-26-03, 07:15 PM (PST)
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35. "RE: Alarmingly low oil pressure at idle"
In response to message #32
 
   If you lose oil pressure and blithely drive it home anyways, yes, you are looking at a teardown and rebuild. If you see the oil pressure light turn on, pull over and shut the engine off, you're not looking at a rebuild. The Spitfire engine is no more sensitive to loss of oil pressure as any other babbet bearing engine is. Every one of these engines is run regularly without oil pressure with no damage. They are started up without oil pressure, and after an oil change go without oil pressure until the dry filter is filled. True, it's only a matter of a few seconds, but it's no different then losing oil pressure when driving. Instantaneous damage does not result.

In fact, oil pressure is irrelivant to engine life. Oil film is, and that's not a function of pressure from an oil pump. As long as the film is there, the lubrication protection is there. Pressure from the oil pump is merely a means of flowing replacement oil into the bearings. There is no pressure from the pump in the bearings, and if there were, it wouldn't be enough to protect them against the much higher pressures seen coming down the connecting rod from the combustion process, or even the compression stroke for that matter.

It's never a good thing to lose oil pressure, but one needn't get hysterical over it.


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vagt6
Member since Oct-7-03
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Oct-27-03, 07:26 AM (PST)
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36. "RE: Alarmingly low oil pressure at idle"
In response to message #35
 
I posted earlier in this thread about my GT6 exhibiting the same low oil pressure at low rpm. Well, after reading a lot of posts on the web, most notably one from John Kippling, I decided to switch to synthetic oil (Mobil 1 0w40).

I then drove about 45 miles, City & highway, and the oil pressure gauge never dropped below 15 or so. It was hovering around 5-10 with non-synthetic oil. The car also seemed to run slightly cooler, but I need to drive more to verify that.

I think it may have been the lower viscosity (from 10w-30 to 0w-40) that did the trick. Any comments?

Mark K. Brown, Charlottesville


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Richard & Daffy
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Oct-27-03, 07:34 AM (PST)
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37. "RE: Alarmingly low oil pressure at idle"
In response to message #36
 
Look carefully at the oil ratings. The first number represents viscosity when the oil is cold, the second when the oil is warm. Therefore 0W-40 is lower viscosity than 10W-30 when cold (0 rather than 10), but higher viscosity when warm (40 rather than 30). This should explain why you are getting higher oil pressure readings - lower viscosity will, generally give you a lower pressure. Still, I'm a little surprised that it makes that much difference (although to be fair I'm no expert on this subject!!).

Richard & Daffy


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Jeff McNealadmin
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Oct-27-03, 08:23 AM (PST)
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38. "RE: Alarmingly low oil pressure at idle"
In response to message #36
 
I suspect that you would see the same results by switching to 20w50 mineral oil for the same reasons that Richard states regarding the viscosity index.

I've seen a lot of debate on synthetic versus mineral oil for these engines, and came to the personal decision to stick with mineral oil for now. It has more to do with the difference in manufacturing tolerances between modern engines versus what we're driving more than anything else, I think. I know that John Kipping is a well-respected guy, but I've also seen input from other well respected guys that led me to my decision.

I like the results you're reporting though. Please keep us posted.

Best wishes,

Jeff
San Diego, California
'68 Spitfire Mk3 aka "Mrs. Jones" FD 21032 L


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tonymrfixitteam
Member since Dec-25-02
2633 posts (A TTN governor, governor)
Oct-27-03, 12:29 PM (PST)
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39. "RE: Alarmingly low oil pressure at idle"
In response to message #38
 
Jeff, you could plug in your O/P sending unit, or O/P gauge anywhere along the oil gallery. If you can't see the O/P warning light you could wire 'in line' a small Buzzer or Peeper, I bought one of these from Radio Shack for about $2 to hook up to my turn signal light, because with my 13" steering wheel I could not see the turn signal flashing light on the dash.
With regards Oil, I have a great respect for John Kipping, but I dissagree with his strong views that all 1500 engines need oil coolers. Having had a very expensive cooler failier in the past and wondering about the detrimental effects of too cool engine oil, I contacted oil industry chemists at both Penzoil and Texaco/Chevron to ask advice on the heat ranges of regular v synthetic oils with the Idea that the Higher heat tolerance of a synthetic would do away with the need of an oil cooler altogether. the information i recived was consistant, in that up to an oil pan Temp of 300 deg F * this was a temperature estimated from the much higher temperatures at the bearing sufaces* Regular oil would suitable, and that synthetic oils 'came into their own in high temperature Heat Sink situations such as in Torbo charged engines. *or engines with no oil in the pan?*
Based on this information, I installed an oil temp sending unit in the cars oil pan. To date, I have never seen temps over 270 F.
I run with name brand 20w-50 oil, my hot oil temp is 60 psi at 3000 rpm 20 psi at 850 rpm. I do have an auxillery oil feed to the head, with a 30 thou restricter.

Tony M
74 Spitfire 1500
84 Toyota Pickup
03 VW Golf


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