I just fried my 402 on the test stand and it has 75 psi at idle and 100 psi at about 2000 rpm. That is when the motor is hot. Tried two different gages with same results. Any thoughts?

Originally posted by y72ss:
I just fried my 402 on the test stand and it has 75 psi at idle and 100 psi at about 2000 rpm. That is when the motor is hot. Tried two different gages with same results. Any thoughts? =
Yes,,,, My thoughts are the oil pressure is too high :D

What pump? Did some "expert" shim the the spring?

Likely it is WAY too high for everything to be in proper shape. What oil is in there? I have had engines that pinned the guage when cold but came back to reasonable levels after a few minutes. Do you have some sort of Speed Racer hot rod goodie oil pump in there? Never liked that stuff even a little bit always use the tock Hi Perf. Gm pumps in my engines. If you have a stock GM pump I fear something is wrong.

It's a dynagear high volume pump.I think the pump was shimed wrong at the factory.I've never had a pump with that much pressure. I have 10w40 oil in it.

Don't know about Dynagear but I do know when we were kids we would stretch the relief spring or stick a heftier spring in the pump to push up the oil pressure.

I read a lot here and post a moderate amount BUT whenever I see Oil Pressure issues and there is a non GM pump in the engine I start to think. I have seen it over and over and over. Most of the aftermarket pumps have all this go fast special config stuff and I ask myself..."If it was needed why didn't GM put it in from the get go?" Also I ask myslelf "MILLIONS of GM High Perf engines survived TERRIFIC abuse with stock pumps so why is this backyard engineering companies pump gonna be better"?

Just my two cents

Melling, Dynagear,, same pump & there is just no reason for a hi vol pump in a rat in almost any application.

You cannot force more oil through an engine unless you create more leaks somewhere or raise the pressure.
If your engine builder or whoever did the engine insists on bearing clearances you can drive a truck through than it may indeed need a hi vol pump to keep up. ;)

That said, there is probably something wrong with the bypass if you actually have 100PSI.
Or you may have very good clearances & the bypass can't handle the extra volume of a pump that doesn't belong on there in the first place,,, :rolleyes:

Mike,
This happened to me on my 505, nice tight blueprinted bottom end, Melling M77HV. I used the HV because of the Crower Hippo's bleeding oil...and my front oil gallery plugs with the .030" hole.

Didn't need it...

I had 100 psi cold with 10-30W, and ~75-80 hot idling.

I just got it back together with a M77..

I with mike on this one we have always used the std. volume pump on any of the big blocks we have built and the oil pressure always has been very good.

With that much pressure your taking a chance on tearing up the distibutor gear and the cam gear on the back of the cam.

I agree with cnc blocks,that much pressure puts lots of strain on the dist drive and cam gear---as well as the pump---67rat

What are the opinions on a high volume pump in a small block? Same, use a stock one?

Yes, use use the stock one with the higher pressure relief spring. it'll get you up to about 60 or at cruise. It's the same size pump, not a HV type.

Tom