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Kirkham Motorsports

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  • 2 Post By DanEC
  • 2 Post By Jerry Clayton
  • 2 Post By cycleguy55

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  #1 (permalink)  
Old 08-26-2018, 01:45 PM
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Default Oil Pressure in FE 427

Dear Cobra Lovers,

i need your advise in a case. I have got the pleasure to get a Kirkham 427 SC with FE Engine (Shelby block, 526 cui stroker, approx. 8'00m mls).

Today i recognised that i have kind of strange behaviour in my oil pressure:

- the oil pressure at idle did not went below 6 bar (normal was 4,5) and under rpm not under 8 (normal was 6) with oil temprature of 80 Celsius / 180 F
- in addition the engine was not accelerating as usual (still enough but felt wise a bit less)
- at idle the engine was running smoth and without any additional noise or indications
- the color of the oil was honey brown, no suspicious smell or anything

What can be the reason for this? Is it a blocked oil filter or a blocked oil valve?

What could be the impact on the engine and what you recommend for further diagnosis?

Oil i use is 10w60, oil level correct, last oil and filter change approx 2'000 mls ago.
In general the engine runs a bit fat, this is on fixing list....

Thank you for recommendations for further diagnosis.. I dont want to kill the engine so far

Greetings from Germany

/Marco
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Old 08-26-2018, 02:37 PM
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Possible cause of high oil pressure is blockage in the oil delivery.
Malfunctioning oil pump can restrict oil flow and cause high oil pressure indication.
Of course you can never rule out a bad gauge either but I doubt this is your problem.

Oil pressure is measured as the flow resistance between oil pump and bearings in the crankshaft.
If it is actually too high, could mean you are not getting enough oil through the bearings to keep your engine from self destructing.

Last edited by Unique427; 08-26-2018 at 02:40 PM..
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Old 08-26-2018, 06:37 PM
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I would advise verifying the oil pressure with a known good mechanical gauge connected to the same spot as the sending unit for the dash gauge is connected.

Always verify that there is a real problem before you start looking for one. Otherwise you may find things to fix that might actually cause a real problem.

An incorrect gauge reading, in my opinion, is more likely than an engine problem that causes the oil pressure to go high at both warm idle and at rpm.

The oil pump pressure relief valve should not be open at warm idle, so you can rule that out.

A chunk of some broken part, such as roller lifters, should not get past the oil pump screen nor would it go through the pump without something bad, so a chunk of something blocking the oil system is not likely.

A spun bearing where the oil hole is blocked off can cause an increase in oil pressure and loss in power from friction increase. That friction increase and no oil flow in a rod bearing should have caused catastrophic failure rather quickly. I doubt this has happened. An FE cam bearing maybe, but that should have made something rattle somewhere up top. I still suspect the reading is false.
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Old 01-24-2019, 08:16 AM
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I have had similar issues to the OP on my newly re-built 428 ... once I had converted Bar to psi

...and I still have to some extent.

- are you using a mechanical or electrical gauge? - the latter notoriously inaccurate.

I found that my engine takes quite a while to properly warm up, and that I was/do hit >100psi (6.9 Bar) at initial start-up, according to my unverified mechanical gauge. After a few mins this falls to 85-90 psi at idle tickover. If the engine continues to idle and warm up, this then slowly falls. However once properly warmed up, the relief valve opens and the gauge falls rapidly down to 20 psi or less at idle. During the summer heat this was quite quick. Now in the winter it can take a while to heat up sufficiently, so perhaps your engine is not warmed up sufficiently?

I still don't like the current high pressure when cold, but will do an oil change over shortly, as i don't know what grade of oil the engine was supplied with.
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Last edited by KevinW; 01-24-2019 at 08:23 AM..
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Old 01-25-2019, 04:46 AM
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It sounds like your bypass is not working properly or has a really stiff spring in it. It shouldn't have anything to do with lowering your idle pressure as the engine warms up. It's purpose is to open only above a certain psi level (cold or hot engine) which the engine usually hits on a cold start or at high revs. The high pressure won't hurt your engine but it can contribute to some leaks or possibly even rupturing a cheap filter = if the throttle is winged after a cold start up - and I would use a good quality oil filter like a Wix.
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Old 01-25-2019, 04:49 AM
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Thanks Dan. I think I should be able to access this if I drop the sump?
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Old 01-25-2019, 08:02 AM
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10w60 ????? why??????

Ford FE engines have the oil relief valve at the end of the oil galley and because of that do have high pressure issues when oil is not up to operating temps----
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Old 01-25-2019, 09:01 AM
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Marco,

Your oil pressure is controlled by your oil pressure relief valve, nothing else. Oil pressure is normally high at cold start and as engine temp comes up, the oil pressure goes down. The high oil pressure at cold start and 'normal' oil pressure once warmed up has to do with oil viscosity when cold at first start and oil viscosity once warmed up.

I am on the same page as Jerry. 10W60 is not the right oil viscosity. You should be running something like a 10 or 15W 40 max in the winter and 20W 40 or 50 max in the summer depending on how hot it gets where you live and how hard you work the engine.

If it is a racing application you ought to be using a racing oil in the 40 or 50 weight range. 60 weight oils are usually fount in drag race applications running alcohol with a blower on top. You aren't doing that and you don't need those oil weights.

Your observation,

Quote:
Originally Posted by Lord.BIX View Post
... - the oil pressure at idle did not went below 6 bar (normal was 4,5) and under rpm not under 8 (normal was 6) with oil temprature of 80 Celsius / 180 F
did not make sense to me. If, as you say, the oil pressure at idle did not go below 6 bar how then was it normally 4.5 bar?

Similarily, if it did not go below 8 bar under rpm how then was it normally 6?

Did you mean to say the oil pressure had been normally 4 to 5 bar but now was 6 bar?


Ed


p.s. Your oil coloration is caused by a rich idle and possibly rich intermediate and wide open throttle mixtures. Oil with fuel in it does not lubricate as well as oil w/o fuel in it. You should fix the problem
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Last edited by eschaider; 01-25-2019 at 09:06 AM.. Reason: Added PostScript
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Old 01-25-2019, 09:36 AM
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10W60? I'm with others here, that's WAY too high, even with your previously stated 4.5 bar at idle and 6 bar at speed. Keep in mind thinner oil actually lubricates better, as flows better (particularly when cold) and is better able to work it's way through tight clearances.

I'd try 5W40, probably even 5W30. As long as you're maintaining 10 PSI/1,000 RPM (0.7 bar/1,000 RPM) your engine will be fine. IOW, at 5,000 RPM 3.5 bar (50 PSI) is sufficient for a long and healthy life.
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