Steve Kistler

All I have written about on carb ,choke and everything in between ,I got some answers. I found out my engine guy sent me a 480/288 cam and I did a compression check and am just over 100# per cylinder. The original heads have too large of CCs for this size cam. I did get it to idle and run decent with a high curb idle until I buy some aluminum heads with smaller chambers and runners. I am assuming there are no other ways of increasing compression?Thanks

MelWff

What engine, BB , SB, CID?
Exactly what size heads?
What kind of cam, hydraulic, solid, flat tappet, roller?
What manufacturer and number cam?

Steve Kistler

1979 L82 bored .060 over Everything stock except Engitech 480/288 cam. No emissions and full dual 2” exhaust without cats.no a/c.

MelWff

I come up with nothing as Engitech being a camshaft manufacturer?
Are you sure that is the name and correctly spelled?
Is this a hydraulic, mechanical, flat tappet or roller camshaft?
Boring the engine actually should raise the compression readings since you are forcing more air into the same size cylinder head.
Are you sure the valves are correctly adjusted?
You ran the compression test with the carburetor throttle held wide open?

Steve Kistler

I do not know the brand of the camshaft I was just told what the lift/duration was. It is a hydraulic flat tappet cam shaft. I did the compression test with all of the spark plugs pulled and spun it up for several seconds to get maximum compression and each one of them came up just over 100 #. The machinist of 40 plus years engine building did the heads and I set the rockers by the book so to speak. I am always surprised by the amount of information that differ. The local hot rod guy says this size cam with stock CI heads makes way less vacuum. He is a retired GM factory mechanic.

MelWff

You didnt answer the part of the question as to whether you had the throttle wide open when doing the test.

MelWff

Setting the rockers by the book may not work depending on which procedure you used and whether the camshaft characteristics ensure that the lifter is on the base circle when you adjusted it.
What is the number of turns of preload you used?

Easy Mike

Are you having vacuum issues? You don't say you are. Headlights open and close?

Steve Kistler

I am not near capable of answering the melwff questions other than stating what I did. I took out the plugs and cranked the engine for a few seconds with the distributor unhooked and all plugs removed. As far as setting the rockers I put the rockers on and tightened them as I stated you the Haynes manual. I did not go back and reset them after the cam break in. My headlights do not open or close

Steve Kistler

I didn’t know you had to hold the throttle open, learn something new every time from people who know stuff....lol I believe I will go back through the rockers and do the compression properly and see what happens

HeadsU.P.

It really doesn't make any difference. The "test" cylinder gets all the air it needs from a closed throttle just like it was idling, but you are only cranking at 60-70 RPMS instead of 600-700.
The other cylinders have plugs removed and receive plenty of air. A battery's capacity has more impact on compression test than a open throttle.

Even with large combustion chambers you should be getting more than 100 lbs. A fresh engine with 8:1 C.R would still have 130-150 lbs.
Somethings not healthy in your shortblock or valve heads.

Steve Kistler

I will pull the valve covers tomorrow and see if there’s anything obviously wrong. I am a little hard of hearing and am hoping it is something I can fix. Thanks for input

HeadsU.P.

And for what its worth: a 288 / 480 cam likes lots of compression, loose torque convertor and tall gears in the back

Steve Kistler

I pulled the valve covers and set to TDC on compression stroke. Almost every pushrod can be turned with slight pressure. Can this be the compression and vacuum problem? I read conflicting information about whether or not I can readjust on a cold engine. I do understand that at operating temperature the metal components will expand and tighten. I also read that too tight causes the compression loss. Because most were at the rotate between thumb and forefinger stage and some not could be relevant.Thanks in advance

7t9l82

something isn't right,you shouldn't be able to turn all the pushrods . Some should have pressure on them for being open or partially open.
gm factory mechanic?

Steve Kistler

He said he retired from GM and worked on the engines and carburetors. That’s all I know about it and I believe he owns the local NAPA store. Actually I said almost all of them not all of them intake on 3and4 and exhaust on 5and7 are tight

MelWff

When you adjusted the valves using the Hanes book, did you start with the #1 cylinder on TDC and then adjusted cylinders Exhaust 1, 3, 4 ,8 and Intake 1, 2, 5, 7?
Did you then turn the engine one complete revolution so that you were at #6 cylinder TDC and then adjusted cylinders Exhaust 2, 5, 6, 7 and Intake 3, 4, 6, 8?
How many turns did you use to adjust them from from zero clearance, 1/2? or 1?

Steve Kistler

I did and from zero I went a quarter turn. I was reluctant to do the 1/2 in case they were too tight. I will get my leak down gauge tomorrow and see what it shows. I want to pursue every avenue before pulling the engine and draining all my fluids. I don’t even have 50 miles on the engine. I actually followed the Haynes book and tightened valves in firing order

HeadsU.P.

For what its worth, some of those compression tests and compression testers can be off by 20, 30 lbs just by how the hose was attached to the head. I know its difficult to get the tester hose in correctly and usually very little room to snug it with a wrench. What I am getting at is maybe your compression is higher by error. If not, you have some serious issues with piston rings and / or head gasket. A Leak-Down Test will help here.

In my opinion, let the valvelash go for now. Its not going to change your compression results unless a valve is NOT allowed to close fully. But with all your pushrods able to spin, that's not the issue here.

I would be curious to know what pistons were installed with your 60 overbore. Somebody just slapped a fairly aggressive cam in there without other modifications to compensate the low compression. It just doesn't work.

Steve Kistler

They were single relief flat tops. I did the engine rebuild and the machinist bought the rebuild kit so he could put in the cam bearings and freeze plugs. I told him I planned to use aluminum heads with my original intake and Qjet. I also have plans to install headers. As a retired teacher I have limited resources and plan to add those components over the next few months. I figured I could drive it while waiting. I just read an article stating low compression and low vacuum are synonymous