lucky131969

I've been troubleshooting a low oil pressure problem, that existed before I owned the car.

History: Engine rebuilt before I owned the car, oil pressure known to be an issue after the rebuild.

The symptoms:

50 psi on startup, as the engine reaches operating temp, the oil pressure drops to 20 psi. The oil pressure does not increase with RPM. Engine is quiet, no valve train noise, etc.

I changed the pump(std volume melling), also inspected for the plug above the main bearing cap. The pump changed nothing..same issue. Since the engine was a rebuild, I pulled the timing cover to see if the three galley plugs were installed, and they were. I pulled the pan again today to check the main bearings, and noticed the brand new oil I had just put in(with a total run time of 10 minutes) was very dark...like it was not being filtered.

I pulled the canister, and removed the bypass valve, to discover there is no gasket between the bypass valve and the block.

So the question is: does anyone know what the outcome of not having that gasket installed is? Other than all the oil not going through the filter, is it possible to affect the oil pressure?

lucky131969

ttt

Powershift

Effect should be minimal. Most folks don't use/install.

I do have one on my 1967 327/350 HP. Purchased from DR REBUILD a few years back.

You have other issues than this.

Larry

lucky131969

Famous last words.

rongold

I think John Z once said that the above mentioned gasket never went into production and never appeared on any cars. If you want to get one, LICS sells them. I really don't think it will make a difference as Powershift said above.

MikeM

There was no gasket on production engines.

Have you verified the oil pressure reading with another gauge?

BLOCKMAN

Surely a clearance issue of some sort and if the above the rear cap was left out it should not affect oil pressure as most people beleive.http://speedtalk.com/forum/viewtopic...er=asc&start=0

Its got to be a bearing clearance issue or maybe a cam bearing issue,I have seen guys not get the rear cam bearing in far enough and cause a bleed off issue causing low oil pressure.

Here are some links to look over on Jackfits 365 horse enigne his engine with a standard volume/high pressure pump idles at appox.50 and runs about 70 at the higher rpms.

http://forums.corvetteforum.com/c1-a...blem-saga.html

http://forums.corvetteforum.com/c1-a...ga-update.html

If you ever find the problem let us know!!

Jacks issue with dirty oil was a ring seal problem as it leaked down up to 40% because the block was not plate honed. Since we corrected the problem the oil stays alot cleaner now.

lucky131969

Absolutely.

lucky131969

Thanks for the links. I've read over them already, which led me to look for the three plugs behind the cam gear. Yep, my block has been bored over .060, which certainly has me concerned if the torque block was not used......

Thanks....

BLOCKMAN

Do a leak down test at TDC as that will tell the story. Thats how we found Jacks Problem!!!

Good luck

lucky131969

I pulled off the main caps, and below is what I found. From what info I have, it is a 10/10 crank. I verified the bearings are stamped .010. I did plastigage the mains, and found them to be .0015 - .002 (not counting what did not crush because of the grooves). I know the wear is abnormal, but I do not look at engine bearings everyday, so I could use an expert eye/opinion please.

BLOCKMAN

Looks like a lot of trash went through the engine and by the looks the block needs a line which is not un common that why there is more wear on one side of the bearing and not the other.

There should be a press in plug up near the drivers side on the rear or the block where the head would set on does it look like its been repalced with a threaded plug???

Alot of guys over look this area but the plug has to come to clean that oil galley if not up on start up it will push trash right into the bearings, Also I beleive in plugging the bypass so all the oil is filter before reaching the bearings.

Good luck with your build

Carl

lucky131969

Thanks Carl. Sent you a PM.