Help! - Rocker Arm Stud Question

[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.

[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??

[ckrobins]

approx 100 miles west of here

[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]

found a picture of what I had on ebay

[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!

[1988GTU]

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

Everyone makes mistakes.

[ckrobins]

exactly why I was shopping for new ones

[bszopi]

Ahh, that would definately explain the broken stud. I would definately make sure to check the rest of the studs before I got everything buttoned up. Wouldn't want something to happen a few miles down the road.

Edit...

REALLY?!?! If you have a digital camera, I'd love to see what they gave you as a replacement!!

[ckrobins]

FYI - the nut in 1988GTU's last post looks like the new ones they're trying to sell me. The old nuts have a shoulder cap on the bottom

[ckrobins]

Thanks for confirming the torque spec, Brad. I have the Grand Am's GM shop manual and both of those numbers - 18 ft-lbs for the nut, 47 ft-lbs for the stud - agree.

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....

[bszopi]

Yes, the nut is 18ft-lbs and the stud into the head is 47ft-lbs.

[1988GTU]

So 17.7ft/lbs for ?

[torq455]

The pictures show exactly the old stud and old rocker arms that I have. Right on. The new parts I have don't match these, and the dealer claims I can't get the old ones any longer from them. Am I just asking for the wrong things or are these really that hard to get?

89 inch-pounds is more like 7 ft-pounds, isn't it? That might explain how we broke the old one.... :sheepish:

Yeah, more like 7.4 ft/lbs. I torqued my rocker studs to 25 ft/lbs. I didn't have that degree tool, so I estimated. I estimated 35 ft/lbs origionally and broke the threads in the head--pulled them clean out. Had to heli-coil. Been over 2 years and still ok. lucky me! Not sure as to why you broke a stud.

[bszopi]

I was looking at my All-Data account, and it actually lists 24Nm (18ft-lbs). That seems a far cry from 10 Nm+30º. And I just checked my 94 GM Service Manual, and it also lists 24Nm. So I guess diregard my previous spec, and I'll have to update the specs page.

The stud is 64Nm (47ft-lbs) for when you go to torque that down.