Too much compression??
 

I bought this 276 CI that had been in storage for at least 15 years. It came with Edelbrock heads and a 4 duce Sharpe intake. I stripped it down to a short block, had Skip rebuild the pumps, put a Rochester 2gc on a merc 4 bolt and a set of EAB heads. Used the rolled up aluminum foil check for clearance. On my test stand it ran fine and sounded strong. Ran it on and off over a week sometimes for close to an hour. Only thing I noticed not perfect was a little blue smoke if I jazzed the gas. After my last run I checked compression while it was still warm.
5---142 160---1
6---131 155---2
7---121 151---3
8---143 152---4
How does that compression look to you guys??
Thanks
Pete

Re: Too much compression??
 

I can't speak for others it doesn't seem right. It is my understanding the variation between the highest and the lowest readings shouldn't be more than 10%. Several cylinders don't fit the rule.

Tom

Re: Too much compression??
 

Yep, don't look right. Rule thumb--"As a rule, most engines should have 140 to 160 lbs. of cranking compression with no more than 10% difference between any of the cylinders."

Re: Too much compression??
 

Put some oil in the low cylinders and see if the compression comes up a little. Could be some stuck rings from sitting so long. Personally, I'd put it in a car a drive the H--- out of it.

Re: Too much compression??
 

I could be wrong here but I'm sure I read that some heads inc eddies have different chamber sizes for left and right, I see one side up and one side down. Walt, John?

Re: Too much compression??
 

If it's running on all eight, put it in something and pull a load with it. At least it's hitting on all eight and all the compressions are above 120 psi. Marvel Mystery Oil in the low ones might loosen the rings & valves a bit. Put some in the fuel tank too.

Re: Too much compression??
 

new engine, with the slight blue smoke, maybe has not completly seated the rings? revv up and let off--revv up let off--etc--do this for awhile trying to seat the rings, when you check compression check, wide open throttle and put a squirt of oil in each cylinder as you check compression-as when it is running oil is splashing the lower end of cylinder bore

Re: Too much compression??
 

Until there's a load on it, you're just wearing the rings out to run it.

Re: Too much compression??
 

Looks to me that the drivers side head has a larger combustion chamber, or the pass side has been milled.

Re: Too much compression??
 

flatjack9>>> I'd put it in a car a drive the H--- out of it. >>>
Ross-F1>>>Until there's a load on it, you're just wearing the rings out to run it.
>>>

Yup. You can come back after about 1-2K miles and tell us what the numbers are then.

Jack E/NJ

Re: Too much compression??
 

you actually wear the rings to seat them-don't you???

Re: Too much compression??
 

It is normal for one bank to have slightly higher pressure when both heads have similar volumes. No, the compression is not too high.

I appreciate what Flatjack said and second the motion.

Re: Too much compression??
 

This engine was built in 1989 and ran in a 48 coupe up untill it was swaped out for a CXXX crate engine in 1999. It looks to be the best candidate for my AV8. I am going to take Flatjack and JWL advice and run it hard.
Pete

Re: Too much compression??
 

Did you fabricate your jack stands/rollers? Neat.

Re: Too much compression??
 

So what's gonna happen to the Edelbrock heads and Sharp 4 pot intake? You are putting them back on arnt you? If not stick um in a box and I'll look after them.
Martin.

Re: Too much compression??
 

Lawson check out http://www.backyardbuddy.com/ I love them safe and easy to setup and move.
The heads are wall art. One had a crack that I think could be fixed by welding but for now I put them aside. I sold the intake to help cover the cost of buying the engine. I have enough problems running two carbs on my 40 panel.
Pete

Re: Too much compression??
 

Why would that be?

Asking to learn.

Re: Too much compression??
 

Pete, I did wonder why you took them off, makes sence.
Mike, the valves are at different angles either side of the engine, the eyebrow reliefs that the valves sit in on the deck surface are a slightly different shape and volume. This leads to different total combustion chamber volume, intern leading to different compression between each side.
Some heads account for this, having a left and right head. Basic part #6050 and #6049. One is left and one is right. But can't remember at the mo, which is which. These heads were ment to have slightly different chamber sizes to correct the compression ratio.
Hope that's clear.
Martin.

Re: Too much compression??
 

Mike B.--- because the valve locations and associated height, block, and seat topography are different from bank to bank. In other words, the volume differs before the heads are installed.

Re: Too much compression??
 

Is that the same for ALL blocks ?