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Old 09-02-2012, 09:13 PM
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oil pressure drop

Originally Posted by JimS View Post
My friend, a very experienced hotrodder who has built several very high hp engines over the years going back to 1960, recently built a Merlin 540" engine.

He first fired it up about 8 weeks ago and all seemed good. Oil pressure was at about 50lbs. He first drove the car about 2 weeks ago and pressure during the 5 mile ride was at about 50 lbs but when he slowed down to turn the corner the red light flickered and pressure had dropped to about 20 lbs.

He increased rpms to about 2k and pressure went back up to normal.

He's running a Crane solid roller, Brodix heads and a high volume oil pump. The short block was put together with extreme attention to detail. Crane says not to do anything to restrict oil flow and consequently increase pressure. He can't for the life of him figure out why this drop in pressure is happening or what he can do about it.

He's figuring on tearing the car down for more mods this winter and of course wants to fix this oil pressure problem. He asked me to check with you folks in hopes that you might have some ideas of what he should be looking for as he tears the engine down.

Any ideas as to why this would occur? What clues should he be looking for? Any ideas I can pass on to him?

Thanks, Jim
Jim sounds like the spring broke in your oil pump. I find it hard to believe but new part quality is falling fast I turned a bearing in a fresh buit 400 chevy with eagle rotating assemble it had a new milling high vol. oil pump thinking my
oil gauge was incorrect

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Old 09-02-2012, 09:45 PM
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Originally Posted by all service View Post
Jim sounds like the spring broke in your oil pump. I find it hard to believe but new part quality is falling fast I turned a bearing in a fresh buit 400 chevy with eagle rotating assemble it had a new milling high vol. oil pump thinking my
oil gauge was incorrect
You responded to a thread from 2005.
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Old 09-03-2012, 11:16 AM
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Oil Pressure Drop at Idle

That 20w-50 oil might have something to do with it too. Using high viscosity oil is old school. He might want to try a 10w-40 oil. For years now GM has been recommending 5-30w in all the newer engines. GM crate motors recommend 10w30 or 10w-40 oil. On a 454 I rebuilt with new rotating assembly, correct bearing clearances and a high volume oil pump my pressure was 80lbs. cold and 60lbs. hot with 20w50. I called my machinist and talk with him about it. He told me to drain it and use 10w40. He said they haven't used 20w50 in years. BTW after I changed to 10w-40 my cold pressure was 60 and hot pressure was 40-45. Another thing I tried using in my motorcycle was 20w50 synthetic. In the mornings with a outside temp of 40-45 and the motorcycle at operating temp. I was going to work and rounded a curve on a bridge at 45 mph. The oil light started flashing. I pulled to the side of the road after getting off the bridge. I cut it off and restarted, revved it a couple of times with no light. It did it again the next time I was riding. I bought it back home changed the oil to a 10w-40 synthetic and never had anymore problems. The motorcycle was new with less than 3000 mile on it.
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