Help! - Rocker Arm Stud Question

[ckrobins]

exactly why I was shopping for new ones

[1988GTU]

So this all came about by installing the wrong pushrods in the wrong spot?

Everyone makes mistakes.

[ckrobins]

All I can say is it must have. I was warned about the pushrods being different lengths. I separated the longs from the shorts. I thought I put the short rods on the intakes. I finished putting the engine together and failed a compression test while cranking. All six intake valves were bent, none of the exhausts were. What else could it be?? I'm sorry, Brad, no camera. The folks at the parts shop accepted the returns, and I'll visit the machine shop tomorrow in search of the right stuff. Thanks!

[ckrobins]

found a picture of what I had on ebay

[bszopi]

Hmm.. wierd.

On a side note, I'm pretty sure there are a couple other members on here from Cedar Rapids. And I have a good friend who lives in Des Moines, although I couldn't tell you how close that is to Cedar Rapids.

[ckrobins]

approx 100 miles west of here

[ckrobins]

Well - I found some used replacement rocker arms and a rocker stud today.
I have replaced the parts that were broken with the original type.
We put it all together again tonight, making sure that the short pushrods went on the intakes and the longs went on the exhausts.
Studs torqued at 47 ft-lbs, nuts torqued at 18 ft-lbs.
I turned the engine over by hand (wrench on the harmonic balancer nut) and it hung up after about a 1/3 of a turn in either clockwise or counterclockwise direction.
I backed off all of the rocker nuts and checked the pushrods - short was on intake, long on exhaust.
I turned the engine through two complete revolutions with no interference. I tightened down the exhaust rocker nut on cyl. 4 and turned it through two full turns - no interference.
I tightened the intake rocker nut on cylinder 4 and the engine turned freely up to the point where the intake valve on cyl 4 began to open and it hung up.
The intake valve is touching the piston & I can't figure out why.
The guys at the machine shop put a new camshaft in the block when they overhauled it - could it have the wrong size lobes on it? The lifters are new - could they be the wrong ones? Everything else is the same as the engine was to begin with - I just don't get it....

Any ideas about what might be wrong??

[bszopi]

Its just #4 hitting? I would suspect either 1/2 or 5/6... I can't remember off the top of my head which side it is, but the valves switch sides on one end. So having an issue in the middle seems odd.

[1988GTU]

I would go to the salvage yard and buy some EXACT year/engine?car? pushrods and a replacement rocker arm assembly kit from the LOCAL parts STORE (about 50 bucks 1 year limited warranty) for your application. If this fails, take off the head(s) to inspect for a bent valve.

.02

[ckrobins]

OOPs! It's cylinder 2 I did this with - not #4. (front side of the engine compartment closest to the passenger side fender) I backed off on all the nuts and only tightened the nut for #2's exhaust first then #2's intake. I left the others backed off for that test. When I first had all of the nuts torqued down it was hanging up on #3 - so I think all of the intakes have the problem - but I haven't tested all the cylinders individually

[1988GTU]

As for why the stud may have broken - the earlier mishap I mentioned was six bent intake valves, six bent or broken pushrods. I knew the pushrods for the intakes were supposed to be the short ones and I still managed to screw up. I showed the broken stud to one mechanic at a motor supply shop and he said he thought the stud had been cracked before we tried to torque the nut on it. I figure if there was enough force involved to bend a valve and break a pushrod, there was probably some stress put on the studs too. Oh yeah, and one of the pushrods was jammed through a rocker arm. The rocker arm and pushrod came out as a unit....

So the engine rebuild was done after you found this out?
If you didn't rebuild it after you found this out, then I am 99.9% positive the valves are bent.

[ckrobins]

Yes - the intake valves were bent. There are new valves - reground and replaced in the heads. I am turning the engine by hand to avoid bending them again. The parts I picked up today are parts from a used engine of exactly the same type as the original

[SappySE107]

I would check the cam timing because it sounds like its not setup properly.

[ckrobins]

OK - so I want to check the cam timing.

First of all, the cam timing gear is indexed to the camshaft with a pin, the crankshaft's timing gear is indexed by the keyway. If the timing is in error, it will be because the timing marks didn't line up properly when the timing chain went on. I did check this when it was going together, but let's say I didn't do it right. I'd like to make this check without pulling the engine, if possible.

I can turn the crankshaft until I get the timing mark on the harmonic balancer lined up on the mark on the timing case. That will be TDC for cylinder 1 or cylinder 4 depending on which cycle of the crankshaft the camshaft is on.
One of the cylinders at TDC (let's say #1) is in between the compression stroke and work stroke. The other cylinder (#4) has just finished the exhaust stroke (exhaust valve just closed) and just starting the intake stroke (intake valve opening)

So if I turn the engine over until I'm just between exhaust valve closing and intake valve opening on #4, then where should I expect to find the timing mark on the harmonic balancer in relation to the mark on the timing case? Maybe a better way to ask the question is: how many degrees off TDC does the exhaust valve close and how many degrees off TDC will the intake open? I can turn the cam till the exhaust closes and measure against the timing marks.

Is the 3.1 (gen 3) an interference engine? If it isn't, should the valve ever be touching a piston even if the cam timing is off?

[Darin]

Yes its an interferance engine, I would suggest just pulling the timing chain cover off and check. I am possitive the cam timing is off.