0 compression in two cylinders
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Senior User
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From: Joyce, WA
0 compression in two cylinders
Early '70s 360 has no compression in front two cylinders on pass. side. Head gasket right? That is what I thought. Just came in from replacing both head gaskets and I still have no compression in front tow cylinders on pass. side. Engine is tired and worn. 90psi in other cylinders before and after headgaskets. Valves are opening and closing. Is it possible that they may not be seating? I put all pushrods back in some order. Tightened down rockershaft.
Where do I go from here? Pull rockershaft off completley and stick finger over plug hole and feel if she sucks and blows?
Any and all questions, comments and suggestions are welcome.
Where do I go from here? Pull rockershaft off completley and stick finger over plug hole and feel if she sucks and blows?
Any and all questions, comments and suggestions are welcome.
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From: Newbury Park Ca.
Or worse.......? Wow, he just had the heads off, what did the valves look like? Valves are working, are the pistons going up and down? Not alot left to contribute to the problem. I sure would've looked those heads over, at least a solvent test in the ports.. Zero, ziltch means something is WIDE open in there. A bad valve will usually show something, low, but something..Even broken rings show something....Strange....aMP
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Joined: Mar 2004
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From: Union, Washington
When you had the head off, did you look at the valves and determine if they were good. Did you check the cylinder walls for major scoring and the pistons for having a hole in them or the piston edge melted down into the rings?
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From: Mddl A MexCans
Did yo screw the freeking compression checker in correctly ? Had to.... I just had that one on an outboard yesterday was bummed for 2 sec LOL.... Ok no really back to you, if you have a compressor run a po boy leakdown unless you have the real thing.
Remove all plugs, rad cap, dipstick, Remove the valve stem from your compression tester screw it in #1 with the engine at TDC, remove the gauge from the other end and connect the compressor hose to compression tester hose. Listen for aire comiung from (exh, dip stk tube, rad mouth, carb) if air is coming out #2 hole guess what!
Remove all plugs, rad cap, dipstick, Remove the valve stem from your compression tester screw it in #1 with the engine at TDC, remove the gauge from the other end and connect the compressor hose to compression tester hose. Listen for aire comiung from (exh, dip stk tube, rad mouth, carb) if air is coming out #2 hole guess what!
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From: Joyce, WA
Guys. I looked the piston and cylinders over carefully. They actually look very good. Better than expected. Valves also looked good. No obvious crack or holes anywhere. I just came in from another go at her. Put shims under rocker pedastels to give PLENTY of clearance between rockers and valves to make sure valves were seating. Still 0 compression. Pumped oil into both cylinders. Still nothing. Put tester in back two holes. Yep tester works. Only 90psi but at least its something. If I put my thumb over the first two holes I can feel it blow and suck, not a lot but some.
Engine ran fine. Then I noticed a drop in vacumm. That led me to finding the two dead cylinders. 360 minus two cylinders is a 270. Not enough power to move a 8000 pound truck.
Any ideas? Any questions? Any aspirin?
Engine ran fine. Then I noticed a drop in vacumm. That led me to finding the two dead cylinders. 360 minus two cylinders is a 270. Not enough power to move a 8000 pound truck.
Any ideas? Any questions? Any aspirin?
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From: Mddl A MexCans
Leak down or did I stutter.. Your to the point that it may be the only thing that find the issue.
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From: Joyce, WA
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Post Fiend
Joined: Mar 2004
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From: Union, Washington
Did you look for cracks in the block or head? Did you check both for being level? If they ain't flat, the won't seal.
If he has "0" psi on compression check, how the hell you gonna run a leak down when it won't hold any pressure?
If he has "0" psi on compression check, how the hell you gonna run a leak down when it won't hold any pressure?
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From: Joyce, WA
Good point about the leakdown test. The head gasket that came off looked good. If it was a warpage issue I would think some sort of evidence would have shown. I am leaning now towards cracks in the head being the culprit. Is that fairly common?
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From: Union, Washington
Originally Posted by Redmanbob
at least you'll know where tthe air is going, it's the point of a leak down.
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From: Newbury Park Ca.
Any chance, any chance at all, that there is a shop towel in the intake???..Looking back, looking ahead, there is nothing that would cause what you're seeing.....A crack certainly wouldn't do it, bad valve and/or ring, even a small hole in a piston will show something, BUT you looked at all that!!!!! The only thing I can come up with is there is no air entering the cylinder to compress. If the valves are working then something is jammed in the intake runners???????????? Hey, try this.......Does your compression gauge have a schrader type release on it? If it does, hold it open and let some air in to compress and see if the needle moves at all during the compression stroke........Gotta be some blockage in the intake...........aMP
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From: fargo, nd
good thought moneypit. one other thing you could do though is take the shaft rocker off the side thats giving you troubles, then pressurize one of those cylinders thats giving you troubles, and see if it holds air... and where its leaking from if it doesnt. if it does then you know youve got a good sealing head gasket, and good sealing valves. if it doesnt, then you know something is wrong there- that way you dont have to take the heads off again if theres nothing wrong there... id be checking the pushrod length and pulling the lifters and checking them out if the cylinder checks out. something would have to be keeping the valves open.