LT1Falcon

iTrader: (3)

well i FINALLY got the falcon back together yesterday after 5 months and the new 6 speed. everything was fine except for one thing. there was a strange knocking noise coming from the motor. it was fairly loud and only audible at low rpms. didnt know if it was just the sound of the the new roller rockers or what. seamed a little loud to be that. i had replaced rockers (cc promags), valve seals, lt4 springs, retainers, and seats, tr55 plugs, msd cap and rotor, new rear main seal, and of course the whole t56 swap. well i could not diagnose it. and the bad part was that my new fabricated aluminum valve covers cant come off without pulling the motor or the intake manifold. so i figured i would pull the manifold tonight. got it off and a pushrod was laying diagonal underneath. got the pass. side valve cover off, and the rocker was laying on its side. it sheared the stud right off. so im hoping it was just a defective stud? gonna order all new arp ones tonight. what do you all think, just a bad stud?

Razor_Blade

iTrader: (8)

Check your valve train geometry.

LT1Falcon

iTrader: (3)

everything looks good. and its not like im pioneering some new part. how many guys have put roller rockers on our motor with lt4 valve springs? quite a few ide say. so its not like im pushing the limits or anything

Razor_Blade

iTrader: (8)

If I'm not mistaken you're the one who asked for opinions here, so no need to get snippy when some offers a suggestion. If you're that confident that all is well, throw another stud in and hope it doesn't happen again instead of asking what people think.

I've had a few studs break over the years and there was always an underlying problem with the valve train.

Good Luck!

Alex94TAGT

Where did the stud shear off? Is it going to be easy to remove?

The problem is that our factory studs are 7/16" on the bottom (screwing into the head), and 3/8" on the top for the rocker. I know ARP makes full 7/16" rocker studs (I use them and would recommend them), but I'm not sure if ARP sells studs with the factory mismatch -- you'll have to check. To be clear, 7/16" studs won't work with your 3/8" rocker arms.

Further, you should take that loose pushrod and roll it on a glass table. Use a flashlight. See if it's bent.

I take it you know your way around setting valve lash and whatnot...

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[EDIT] Unless you've milled the heads, decked the block, or something along those lines, your valvetrain geometry should be "ok". I wouldn't assume that to be the problem, but it's easy enough to check since you're in there. We can explain the process if you've not done it before. Just need a sharpie marker.

Z284U2TRY

iTrader: (5)

tq on the rocker studs? Easy out the stud and replace and check results what does the lifter look like? Pushrod? Have you over revved it? Seen this before in ls1's.

LT1Falcon

iTrader: (3)

didnt mean to sound "snippy", i appreciate any advice. ive already ordered some new arp studs, 7/16 on the bottom and 3/8 on top. it sheared off right below the nut on the stud, so basically there was nothing sticking out of the head. i just took a center punch and a hammer and went around the edge of the stud and tapped it out. pushrod looks good but i decided to get some new chromemoly ones while i was ordering. i talked to an experience engine builder and he said that moving the exhaust studs to the intake side can cause it to crack sometimes. i had removed them all in order to grind a smooth surface on the end for the poly lock to seat good, and just stuck them back in any hole. so maybe that was the problem. regardless, i just hope it was the stud and nothing else got binded up or anything.