Philm

Could have that high of compression if your lifters are leaked down. Did you run the engine before doing your compression check?

ckin62

The motors are 8.5-1 CR. I spray a little WD40 in the cylinder prior to doing the compression test. So, that will increase the number a bit. Experience tells me that dry compression is 175psi (no WD40). I did not run the motors before the compression test.

The break in ive always do is....run motor to operating temp (usually 10 min.) Let it cool to ambient. Run motor 15 mins at 2000 to 2500 rpm, let cool again. then run motor 20 mins at varying rpm with some quick increases and decreases but never idle. Let cool and your ready to run or dyno. there are alot of theories on break in. I have always had good results from this one.

ckin62

ttt

ckin62

I did a leak down and the most I saw was 10% at 100psi. Most cylinders were at 8 or so. I pulled the vavle covers and added a large breather to each one. I cleaned the motor compartment and went out for another run. Seems to have very little blow-by at all now. BUT, one motor now has a low oil pressure issue. Starting up it is fine 50psi or so then when it warms up it slowly decreases to about 20psi when above idle and at idle it is darn close to zero. So, as soon as I saw the pressure below 20 I shut it off. Does this sound like a oil pump failure? I tested the oil pressure sender it checks fine. I pulled the oil filter and it looks normal and i spun the motor over with an open oil line and it does pump volume. I'm now wondering if the bypass in the pump has been damaged.

blue thunder

Did you chisel the oil filter open to look for bearing material between the pleats?

ckin62

No but I plan to. I am pulling the motor and gonna go with new anyways. It is cheap insurance and I know it ran for a bit with very little oil pressure. I just dont understand what the problem is and want to figure it out before I rebuild. If I dont I am certain to have this issue again.

blue thunder

I just finished a job last night replacing the oil pressure sender on my sb engine. It was reading low OP. 20psi at wot. Cut open the filter and all was good. Put on mech gage and had 75psi at wot. So it is possible you have nothing wrong. Also, it is common to get some blowby on force induction engines. Mine with superchargers are pretty good but a lot of guys have to run large oil catching breathers to manage the blowby/oil spray. Do a search on breathers and you will see a lot of talk in that regard.

ckin62

I tried a different pressure sender and it gave me the same read pattern. I also have 2 other pressure switches (one for a dash light and the other an alarm). When I was test test running they never indicated an issue, but in the driveway at idle they do. So, I don't think it is an easy fix.

blue thunder

The oil filter will tell the story. But it sound like you are correct unless there is some sort of electrical problem.

Budman II

iTrader: (1)

You need to throw a mechanical gauge on it - the electrical gauge might have an issue. But it is suspect that it is suddenly reading low.