Losing oil pressure when it gets warm...

[GsxrMike]

My buddy and I "slapped" together a motor and everything was working great until he started losing oil pressure so we changed the oil pump tonight and everything was great. I was following him in my K5 to our inlaws and when we got there he said he had to keep the thing over 2000rpm to maintain 20psi oil pressure. Basicly the motor starts out with 40psi oil pressure and drops to 0 when it gets warm. I read a couple of other treads about this but I don't see any of those things being the problem. I think we might try a heavier oil because we don't think this is going to be a high milage motor anyways. Any other suggestions?

 

[Jason4x4]

My buddy and I "slapped" together a motor. Any other suggestions?

I think you answered it.

I would imagine that bearing clearances are incorrect, and therefore causing your problems.

 

[SRSGSXR1000]

x2 on the bearing clearances, who installed the cam bearings? when i worked in a machine shop it was common for sbc engines to have cam bearing clearance issues. Most people just drive the bearings in, and shave them till the cam fits. Really shouldn't cause an issue, i've seen tons of sbc engines that only ran 3 or 4 lbs of pressure at idle then jump to 20 above 2000 rpm's. i say run 20/50 oil and run the piss out of it. If it was a critical bearing, "rod, main" well you would know by now.

 

[4X4HIGH]

What did i tell you in the "slapped together" thread?

 

[SRSGSXR1000]

What did i tell you in the "slapped together" thread?

But thats the beauty of the SBC engine, you literally can "slap" them together and they will usually live.

 

[GsxrMike]

What did i tell you in the "slapped together" thread?

Yes I know!

The cam bearings are reused bearings. The motor didn't have these issues before so what would cause these issues now? I am kinda thinking bearing clearences too but is there anything we can do about it to make it live for a little while? I pulled a valve cover yesterday and all the rockers were full of oil so I know some oil is getting up there. I was thinking of running 20/50 like what was mentioned before. I guess we will try that and see what happens. What is the least amount of oil pressure the motor will live on?

 

[GsxrMike]

Anybody know where I can find an oil flow chart for the 350? Google didn't come up with anything useful.

 

[rcamacho]

Ditto on clearances. Sounds like you are bleeding too much oil past the bearings.