MY SS is toast...

[getarz4u15ster]

Originally Posted by Dave Coyle

You said that you checked and all the rockers were fine, did you roll the motor over and see if they were all moving? I have never been inside one of these motors yet but have built many "old school" motors and in the past when I had a problem like yours, the timing gear and chain had failed. It may be that your bolt has come loose and has slipped on the cam and the cam is no longer in time with the crank which will cause the "no compression" problem you have. Also, the crank timing mark should always be @ 12 o'clock and the cam can be @ 12 or 6 o'clock and you will be fine. If you do have spark and fuel then most likely you will find the problem once you get the front cover off. Keep us posted with what you find!!! Good luck.

That's exactly what i'm thinking.. I did crank over the motor several times with my dad (who's been a mechanic now for 30 year building hot rods) and confirmed as well all the rockers are moving, and completely shutting. So like you said once i get the timing cover off and see what happened there i'll know for sure. I Also, i think the timing chain jumped the gear. I just went ahead and ordered the katech C5-R chain and and the LS2 tensioner.. along with everything else.. i'll keep you all posted. I'll try and take some pics as well.

[Russell James]

I would think if the chain jumped that far to not allow any running or even firing or backfiring, that some of the valves would have hit the pistons. If they are all closing normally now, seems like they didn't hit the pistons.

Check the oil, is it really stinky with gas? Like you mentioned before, the cylinders could be washed down with gas and showing little compression.

If you find the timing marks still lined up, I'd look at some of the wiring and connectors. I've seen the cam sensor cause very strange no start problems without a trouble code. If they messed with one of the main harness/connectors before, that would be an area of suspicion.

[f5journal]

I am having a hard time understanding this. The LS engine must be really unlike the old small blocks. You would never even turn the engine over if the cam was not moving in correct unison with the crank.

Just like if you had just built the engine and were hand adjusting the valves and hand turning the crank for the first time, you would find out in a heartbeat if you had screwed anything up

[getarz4u15ster]

Originally Posted by Russell James

I would think if the chain jumped that far to not allow any running or even firing or backfiring, that some of the valves would have hit the pistons. If they are all closing normally now, seems like they didn't hit the pistons.

Check the oil, is it really stinky with gas? Like you mentioned before, the cylinders could be washed down with gas and showing little compression.

If you find the timing marks still lined up, I'd look at some of the wiring and connectors. I've seen the cam sensor cause very strange no start problems without a trouble code. If they messed with one of the main harness/connectors before, that would be an area of suspicion.

So I checked the oil last night.. there's no sign of any gas in the oil pan which is good... I'm going to be dropping it anyway to get the oil pump off and replace the chain with something better. Once i verify or don't that the timing of the motor is correct, I'll do another compression test which will then tell me if any of the valves are bent or not, which i not believe they are because when the rockers are off of lobe lift, there is play in the rocker arms (remember they hydrolic lifters) which tells me they are fully seated. I"M TRYING TO STAY POSITIVE HERE haha. However if the valves are bent, I guess I'll just be getting both heads port and polished while there off, no point in not i guess.

[Russell James]

Originally Posted by f5journal

I am having a hard time understanding this. The LS engine must be really unlike the old small blocks. You would never even turn the engine over if the cam was not moving in correct unison with the crank.

Just like if you had just built the engine and were hand adjusting the valves and hand turning the crank for the first time, you would find out in a heartbeat if you had screwed anything up

That's why I'm thinking the timing chain may be fine. If it were way off, I believe the valves would have hit the pistons. Probably also would have heard quite a racket in the front cover area when it was stalling, and now cranking.

Did you happen to notice if it has oil pressure while cranking?

[f5journal]

This would be a real lesson if the posted who mentioned Onstar disable turns out to be right

[tjbusa]

[getarz4u15ster]

We'll see... I just called Onstar and verified again that the disable feature WAS NOT engaged and they confirmed. Wish it was that easy....

[ackeight]

Good luck. Sorry you had to be the Guinea pig in this situation but you may help other people out later on with their cam builds and repairs. I may have missed your answer but did you upgrade to the 3 bolt?

[getarz4u15ster]

Originally Posted by ackeight

Good luck. Sorry you had to be the Guinea pig in this situation but you may help other people out later on with their cam builds and repairs. I may have missed your answer but did you upgrade to the 3 bolt?

No i did not go with a three bolt, stayed with a single bolt...

[Orange Krate]

Originally Posted by Russell James

That's why I'm thinking the timing chain may be fine. If it were way off, I believe the valves would have hit the pistons. Probably also would have heard quite a racket in the front cover area when it was stalling, and now cranking.

Did you happen to notice if it has oil pressure while cranking?

I have to agree with Russ... in every compression loss situation dealing with a timing gear and chain, there is usually some sort of audible noise up front whether it is a timing chain/gear or gear drive unit. I always replaced my timing chains with Cloyes and never had a problem. Always used new cam bolts too with thread locker for the express reason of not wanting them to back out. As for compression loss... I cannot believe that you have lost all 8 cylinders, at least from something cataclysmic in the bores. I have rebuilt numerous upper ends and not even had to touch the bottom end and that was with thousands of miles on the bottom end. Wishing you the best and hope to read the outcome. PLEASE post some photos of any strange discoveries so that we all might learn! Good luck again

PS-When I went to an industrial repair school (36 years ago) I learned that "90% of all mechanical problems are electrical".

[getarz4u15ster]

Originally Posted by Orange Krate

I have to agree with Russ... in every compression loss situation dealing with a timing gear and chain, there is usually some sort of audible noise up front whether it is a timing chain/gear or gear drive unit. I always replaced my timing chains with Cloyes and never had a problem. Always used new cam bolts too with thread locker for the express reason of not wanting them to back out. As for compression loss... I cannot believe that you have lost all 8 cylinders, at least from something cataclysmic in the bores. I have rebuilt numerous upper ends and not even had to touch the bottom end and that was with thousands of miles on the bottom end. Wishing you the best and hope to read the outcome. PLEASE post some photos of any strange discoveries so that we all might learn! Good luck again

PS-When I went to an industrial repair school (36 years ago) I learned that "90% of all mechanical problems are electrical".

So i have an explanation as to why there was no compression... partly.

I got home and started the tear down.. I got off all the usual pieces (water pump, hoses, serpentine belt, moved the alternator out of the way, and FINALLY got all nervous and pulled the Timing Chain Cover. "What do my wondering eyes should appear a full and complete timing chain and gear" right? I stood back for a minute and thought to my self "Self" what in the world is going on here... And my mind went back to a previous thought i had to day while sitting at work. I WONDER.... I USED A SINGLE BOLT CAM, and the on those cams they have a pin that is formed into the cam that helps align the timing gear... are you getting where i'm going with this... Yep you guessed it.. the pin sheered completely off the cam and stayed stuck in the timing gear. The only reason the cam was spinning when i was cranking the motor over with the ratchet was because the cam bolt was holding the gear tight enough to actually spin over the cam and move the valves. So basically as soon as the pin broke the motor shut down because of a loss of compression on all cylinders because nothing was moving at all! except the pistons of course. THANK GOD I WAS AT IDLE and there is no piston to valve problems! And the pictures you all have been waiting for are below... Needless to say a three bolt camshaft, gear and LS2 tensioner is going back in there to solve that problem. All you single bolt cam thinkers... THINK AGAIN and don't do it.. go with the three bolt!

Cam gear with PIN still in it


inside of cam gear, pin still in it




Cam with pin sheered off


Let the questions/beatings begin

[steeleshark2]

What would have been the best way to prevent this from happening? I am looking into getting a cam here in about 6 months and figuring what all should I get done with the cam job instead of just springs and rods to get the build right?

[cmore]

Sounds like u may have dodged the bullet! Congratulations!