3.1 Fresh top end, now zero compression. Help

gwmed · #1 07-01-2006, 10:09 PM

I just did a top end on my 3.1. New head gaskets intakes and reassemble. Zero compression. Here are the steps I have checked.
1. Loosen all rockers. Good compression
now I know it is in the valve driveline somehow. I removed all rockers and pushrods on the front bank just to triple check they were in the right place. That is a yes. I am at a loss. Is it possible I screwed up the lifters? I removed them one at a time, cleaned out with air and put oil in and on and replaced. Any insight would be helpful.

tblake · #2 07-01-2006, 11:46 PM

yeah, lifters may be the culprit. I dont think they should ever be completly dried of oil. may want to take them out and leave them soak in oil overnight. reasemble and try it again, or just replace them.

Blue Bowtie · #3 07-02-2006, 08:24 AM

Check to make sure that you did not mix intake and exhaust push rods. They are different lengths, by about 3/4".

maxwedge · #4 07-02-2006, 10:26 AM

Quote:

Originally Posted by Blue Bowtie

Check to make sure that you did not mix intake and exhaust push rods. They are different lengths, by about 3/4".

Seconded, common mistake, symptoms match.

jeffcoslacker · #5 07-02-2006, 10:28 AM

Or cam is clocked 180 out...

Blue Bowtie · #6 07-02-2006, 10:51 AM

¿Cam out 180°?

That means only the ignition would be off phase with the cycle. The engine would still produce compression during a cranking test. And since the CMP is triggered by the camshaft on most later models, it really wouldn't matter at all. Picture the system, and you'll understand what I mean.

jeffcoslacker · #7 07-02-2006, 11:14 AM

Quote:

Originally Posted by Blue Bowtie

¿Cam out 180°?

That means only the ignition would be off phase with the cycle. The engine would still produce compression during a cranking test. And since the CMP is triggered by the camshaft on most later models, it really wouldn't matter at all. Picture the system, and you'll understand what I mean.

So, I got intakes opening on a compression stroke, and you say I'll have compression? Better rethink that...

tblake · #8 07-02-2006, 12:04 PM

its a pushrod style motor, athough im not doubting you jeff, but why would he have to take the timing chain off to just overhaul the top end? Its not an overhead cam style motor. (at least i hope not)

tblake · #9 07-02-2006, 12:10 PM

Ha, just a side note. A guy brought in his grand am with the 3.1 V6 in it to our shop. It needed intake gaskets, but the guys who did it did head gaskets also. It had chocolate milk oil. They got it all backtogether, and it ran good (from what i heard). The next day the owner came to pick it up, left it idleing out side while he went in to pay the bill, came out and it had stalled, and would not restart. It was pushed back in, and a few techs later, someone finally did a compression test on it. Cylinders 1 and 2 hade adaquate compression, all the rest had none. Turnes out he drove it so long with coolant in the oil, that the cam bearing siezed up and snapped the cam right in half. One could see only half the rocker arms opening with the valve covers off. It was hard convinciening him that he needed a new motor in his car. LOL

jeffcoslacker · #10 07-02-2006, 12:33 PM

Quote:

Originally Posted by tblake

its a pushrod style motor, athough im not doubting you jeff, but why would he have to take the timing chain off to just overhaul the top end? Its not an overhead cam style motor. (at least i hope not)

He wouldn't...I'm confused today...I thought it said new timing chain in the post...getting mixed up with something else I'm reading ...

Blue Bowtie · #11 07-02-2006, 12:36 PM

Quote:

Originally Posted by jeffcoslacker

So, I got intakes opening on a compression stroke, and you say I'll have compression? Better rethink that...

If the intake valve is open on the "compression" stroke (not the downward stroke) the cam timing is NOT 180° off (with respect to crankshaft rotation) but something less than that, like 90°. You'd have to be a real Rhodes' Scholar to install a timing set a 12 O'clock / 3 O'clock.... If you meant 180° out on the crank sprocket, that would be different.

If the cam is in fact installed 180° from where it might have been before (with respect to crankshaft degrees) the "compression" stroke has just become the "exhaust" stroke. the crank, rods, pistons, and pins don't care. The engine is "programmed" by the cam timing, and so long as it is in 180° increments, it won't matter. It would matter if it had a conventional distributor for an ignition system, but that's not the case.

jeffcoslacker · #12 07-02-2006, 12:42 PM

Quote:

Originally Posted by Blue Bowtie

If the intake valve is open on the "compression" stroke (not the downward stroke) the cam timing is NOT 180° off (with respect to crankshaft rotation) but something less than that, like 90°. You'd have to be a real Rhodes' Scholar to install a timing set a 12 O'clock / 3 O'clock....

If the cam is in fact installed 180° from where it might have been before (with respect to crankshaft degrees) the "compression" stroke has just become the "exhaust" stroke. the crank, rods, pistons, and pins don't care. The engine is "programmed" by the cam timing, and so long as it is in 180° increments, it won't matter. It would matter if it had a conventional distributor for an ignition system, but that's not the case.

You're right...I apologize...I'm having severe brain spasms today...think I drank too much last night...

Blue Bowtie · #13 07-02-2006, 12:51 PM

I was almost certain you knew that. I figured it was probably a little pre-4th warmup.

I'm holding off until tomorrow to work on getting really "faced" (it's raining here).

gwmed · #14 07-02-2006, 01:10 PM

Thanks for the replies. More info. The timing was not touched. all rockers are functional. I removed the lifters one at a time, blew them out w/ air re-oiled them and reinstalled thm. None were mixed up. All pushrods were re-checked, the exaust are the longer ones. I am wondering if the air somehow "locked" the lifters at full legnth and the aren't retracting, hence the long pushrod symptom. IE valves staying open. I have not pulled the rear valve cover as I had the assembly complete. I dont want to jerk the whole thing down because something "might" be the cause. However, I will do what ever it takes to get my son back on the road. when i removed the rockers and pushrods on the front bank I have great compression. As always, thanks in advance. I will keep the boarb informed.

Blue Bowtie · #15 07-02-2006, 01:30 PM

Disable the ignition at the coil pack. Reinstall one pair of pushrods and rockers. Crank the engine and observe the valve action. If it seems normal, add the rest of the push rods and rockers, and crank/observe again. Compare the relative lifts of the valves.

Obviously, the pistons, rings, and valves are intact, or you would not have compression with the rockers removed.

If necessary to establish some cranking compression with the valve train assembled, back off the rocker arm nuts a few turns and see if compression is restored. (I'm thinking pumped-up lifters or sticking lifters).

If you can create compression by backing off the rockers a few turns, AND you feel lucky, reconnect the coil packs and try starting. If you can get it to run, try slowly torquing down the rocker nuts slowly to force oil from the lifter bodies. If they are pumped-up to the locking clips (full extension) they should bleed down along with the right (rear) bank of cylinders as the valve train is exercised.

Be absolutely certain you don't have any piston/valve interference before starting the engine in this manner.

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