350 no compression

[dumbucket1]

I swapped my 882 heads for vortec 062 castings. I bought these vortec heads used and did nothing to them but put them on. I also changed the cam to comp 270h along with lifters timing chain. I went to start the motor and it acted like it didnt have any spark. So I verified it does indeed have spark. then I double checked it was in time. It is in time.

Next I do a compression test, my tester goes up to 30 then drops back to 0. Then with both valves closed I pumped compressed air into the cylinder. It won't hold air and the compressed air is going out the tail pipe. I back off the rockers to make sure the weren't overtightened and no change.

What can be causing this? I have never come across this before. Thanks

[VileZambonie]

So in all cylinders with the rockers completely loose you're blowing air from the cylinder out the tailpipe? That means bent/burnt/cracked exhaust valves.

[dumbucket1]

yes unfortunately every cylinder. I looked at all the valves before I put the heads on and they looked good   

[HAULIN IT]

A couple things to talk about now that the horse is out of the barn. The 270h has .470 lift, this installed correctly could not have piston to valve clearance problems on an engine that was running with 882's. Something else was the problem. One thing that in my opinion is MANDATORY is to vacuum check a cylinder head before installing them on the engine. I have found several NEW valve jobs (a couple by "GOOD" performance builders) that would not pass a vacuum test, yes the engines wouldn't be like yours & not run, but sealing is a key step in a properly running engine. What do you know about the heads? Were they just pulled from a running Vortec engine or were they on "performance engine" of some sort?
 At this point, you don't know if you installed heads with bent exhaust valves or you did something to bend the valves. That being said, I think you better look at the cam timing. Is your's a multi-keyway sprocket set-up of some sort?
 Another thing is priming the engine with a drill to get the lifters fully pumped up & then crank the engine over by hand (in the same direction as running) several revolutions. If the valves hit the pistons enough to bend all of them before you started the engine...you would have felt this while cranking by hand. Good Luck with it! Sorry if I made you feel like you were just scolded by a parent for something   Keep us posted on your findings, Lorne     

[dumbucket1]

I found the problem. Lorne you pretty well hit it on the nose, I put the crank gear on the square key instead of the rounded key and then line up the timing gears dot to dot.

Could have I bent valves by making this mistake? Thanks, Jeremy

[HAULIN IT]

ABSOLUTLY! My guess is this had the camshaft closing late from the correct location & the valves were still hanging open when the piston came up to tdc. Sorry to hear that, but that was my hunch. Lorne

[dumbucket1]

well I put the timing chain on correct this time, reapplied my assembly lube to the cam. Reset my valve lash, dropped the distributor in and it fired right up with a tap of the key so I went ahead and broke in the cam

After break in the idle was just right and boy does that comp 270h sound good, has a nice little lope but not bad enough to where it sounds like it's going to die out on me.

Tomorrow I will recheck the compression to make sure everything is ok

[VileZambonie]

Regardless of where your cam timing was you said the rockers were completely loose. You should not have air escaping from the exhaust valves if they're shut. Are you sure you had the rockers loose when you did the test?

[dumbucket1]

yep took the rockers completely off. Not exactly sure what the deal was.