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Author Topic:   400 pontiac oil pressure problems.
stevenm
Dirt Full Roller

Total posts: 43
posted August 08, 2005 05:13 PM  
My friend has a car 77 grand prix running in the cruiser class 1/4 mile with a 400 pontiac engine.

The motor looses oil pressure down to 0 after the engine gets about 210 degrees but as long as he gives it gas it has good oil pressure over 60 pounds.If he lets it idle after it gets above 200 degrees it has no oil pressure at idle.

When the engine is cold it has perfect oil pressure at idle but as the temp rises the oil pressure drops until you gas the engine.

The engine was built with by a good engine builder that is no longer around for questions.It was built as a street car but turned into a cruiser dirt car and the engine never had oil pressure problems after running the heck out of it on the street.

The engine was run saturday night and it sucked the spring in the lower radiator hose up into the hose and it was sucking shut and running on the warm side [240] in the heat and after it cooled down and got ready for the feature the lifters were very noisy until he made a few laps and they quit ticking but no oil pressure if he lugs the engine in the pits or if he lets it idle so he had to keep the rpms up to keep oil pressure up.

What could be happening with the oil pressure by dropping after heated?

Thank you for any info.

Steven.


btennant
Dirt Full Roller

Total posts: 28
posted August 08, 2005 09:01 PM  
I would guess that the oil is cooked an no longer has viscosity change it with valvoline 20w50 and if that doesnt work add some kind of engine honey disconect the oil pressue gauge and drive er till she drops. seriously though if it got hot and lost oil pressure the damage is done your clearances opened up somewhere try heavier oil and a new pump. Otherwise pull her out and start over.

stevenm
Dirt Full Roller

Total posts: 43
posted August 08, 2005 09:11 PM  
The oil my friend runs is Castrol 20w 50.The engine has good oil pressure even while hot as long as he keeps the rpms up around 1800-2000 rpms.

When the engine is cold it holds beautiful oil pressure as long as it stays under 200 degrees but once it gets over 200 degrees the oil pressure drops to 0 when at idle but goes over 60 pounds when giving it gas.

It is a mystery so far.

Thanks for anymore advice.

Steven.

btennant
Dirt Full Roller

Total posts: 28
posted August 09, 2005 04:24 PM  
Id try a different brand of oil and maybe even a synthetic also have you changed the oil since it was overheated?

stevenm
Dirt Full Roller

Total posts: 43
posted August 09, 2005 05:04 PM  
My friend is going to change the oil to a different brand oil synthetic heavy weight.

I do hope it solves the problem because the engine was a hoss on the street.

Thanks for the replies.

Steven.

wetwolfone
Dirt Full Roller

Total posts: 51
posted August 10, 2005 06:56 AM  
Maybe try straight 50 wt.


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