NO COMPRESSION....wtf?????
Originally Posted by V6 Bird
Then if thats the case it would be electrical....The bendix on the starter may not be engaging...but he says he has fire....That means the starter is engaging and the crank sensor is triggered to give fire. on whatever cylinder it is he is checking for fire.
Guys there seem to be some questions out there as to what we've done. Its not electrical...I'd bet my car on it. Unless the valves are electronically controlled. At the risk of lashing out, which I'm not trying to do, just making it clear. We did use a compression guage, it didnt flinch after turning the motor over several times. Even without the guage you can tell its not compressing the air. The engine sounds like if you were to try and start it with the plugs out. I even left the compression hose attached to the spark plug hole and with the piston near top dead center blew a lung full of air into the cylinder and I could hear it either going into the header or intake
Launching!
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You say you hear air like it is flowing into the intake manifold or exhaust right? Maybe you have a wide open vacuum leak, maybe a large crack on the underside of the intake manifold? If you could pull codes from the computer you would get a code for MAP pressure low if this were the case. On these engine I don't think it would be the cause but on my old 4.3 V6 with trottle body injection I had an internal vacuum leak. This was caused by the trottle body gasket it blew out on the inside between the 2 bores. You couldn't find it until you took the TB off. The car would start and then just die out. you might want to check that gasket for the heck off it. I have been in your position many times before sometimes it is good to have a friend look over the car with you sometimes they might see something you missed. Good Luck
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How would a vacuum leak be the cause of no compression?
Originally Posted by StickSS
You say you hear air like it is flowing into the intake manifold or exhaust right? Maybe you have a wide open vacuum leak, maybe a large crack on the underside of the intake manifold? If you could pull codes from the computer you would get a code for MAP pressure low if this were the case. On these engine I don't think it would be the cause but on my old 4.3 V6 with trottle body injection I had an internal vacuum leak. This was caused by the trottle body gasket it blew out on the inside between the 2 bores. You couldn't find it until you took the TB off. The car would start and then just die out. you might want to check that gasket for the heck off it. I have been in your position many times before sometimes it is good to have a friend look over the car with you sometimes they might see something you missed. Good Luck
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Originally Posted by wicked_95z
Guys there seem to be some questions out there as to what we've done. Its not electrical...I'd bet my car on it. Unless the valves are electronically controlled. At the risk of lashing out, which I'm not trying to do, just making it clear. We did use a compression guage, it didnt flinch after turning the motor over several times. Even without the guage you can tell its not compressing the air. The engine sounds like if you were to try and start it with the plugs out. I even left the compression hose attached to the spark plug hole and with the piston near top dead center blew a lung full of air into the cylinder and I could hear it either going into the header or intake
Originally Posted by TS6
Rockers (if adjustable) too tight, holding valves open? Seen that before.....
Or pushrods too long, same difference.
Or pushrods too long, same difference.
Like I said in the FIRST POST.
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go get a leak down tester like that was mentioned earlier. It will give you the answer were the air is going. You can't do a compression test with the rockers off cause if the intake valve isn't opening there is no air to compress.
Or loosen the rockers(I AND E) on one cylinder and set to zero lash(just so you can feel tension on the pushrod while turning it) then check the compression on that cylinder.
Or loosen the rockers(I AND E) on one cylinder and set to zero lash(just so you can feel tension on the pushrod while turning it) then check the compression on that cylinder.
Give me some credit ... 
We did the compression check with everything assembled. Only when we didnt get any compression did we take the rockers off and blew into the cylinder. I have a leak down guage just no compressor to use
We did the compression check with everything assembled. Only when we didnt get any compression did we take the rockers off and blew into the cylinder. I have a leak down guage just no compressor to use Launching!
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Hi: I would see if you could borrow or rent a small compressor so you can see whats going on in the cylinders. If like you said you blew some air into that cylinder with the rockers off and you could hear it escaping it is not your valves or camshaft or rockers. The valve springs would be holding your valves closed and you know that the valve seats are good because a machine shop check your heads out. I really think it is your head gasket not sealing right. Check the block deck for warpage before you put the head back on. Even if it is a brand new block from GM it could be severlly warped. I am not sure whats going on with your head bolts? If you broke off 2 head bolts in the block you should really try to extract the broken bolts. The head gasket will not seal properlly with out all the bolts in the block. You have a difficult problem and you should go slow and check everything as you go. wiif
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From: Franklin MASS
Yeah, I got my *** kicked by 2 head bolts.....but I did have it repaired...JBA in San Diego put a heli coil in the block. I took it to their machine shop, where they build race engines, so I really think that they did the job right.
Originally Posted by wicked_95z
Give me some credit ... We did the compression check with everything assembled. Only when we didnt get any compression did we take the rockers off and blew into the cylinder. I have a leak down guage just no compressor to use
We did the compression check with everything assembled. Only when we didnt get any compression did we take the rockers off and blew into the cylinder. I have a leak down guage just no compressor to useHow did you blow air into the cylinder with no compressor? Also, the cylinder is going to leak some air, its normal.
Your rings are going to have to be SHOT for this problem to happen, so bad you would have noticed when the motor was apart.
I know you have stock pushrods, that doesn't mean ****. Your heads could be milled enough to make them too long.
I can't belive how difficult you guys are making this........
So you pulled the heads off and they said that they were ok? I thought you said that the exhaust valves were bent. If your not getting compression with the rockers off then you either have bent valves or bad head gasket. Even if you had blow by on the pistons it would still read some compression. You should really buy an adjustable pushrod to measure what length pushrods you need rather than assuming stock length would work. I think I asked you before whether you were running a rollmaster double chain. They have two dots on the timing gear and only one works.
Its been said over and over. If there is 0 compresson the valves are either bent or open. You say they are not bent so they are open during compression stoke plain and simple. You either have pushrods too long, a set of lifters that were machined not deep enough or a cam with too big of a base circle. I have never heard of the last two so I will be willing to bet a large chunk of $$ its the push rods. Loosen the rockers way off and do the compression test again. When the gage moves you have found your problem.
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Originally Posted by gearheads78
Its been said over and over. If there is 0 compresson the valves are either bent or open. You say they are not bent so they are open during compression stoke plain and simple. You either have pushrods too long, a set of lifters that were machined not deep enough or a cam with too big of a base circle. I have never heard of the last two so I will be willing to bet a large chunk of $$ its the push rods. Loosen the rockers way off and do the compression test again. When the gage moves you have found your problem.
Originally Posted by CBX
Just remove the rockers altogether and try it that way. If the valves are seated, which they would have to be, and you still don't have any compression, then I would also agree that the head is not seated properly. You should be able to hear air coming out of the head at the gasket. Try a few cylinders, not just one.