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'95 LT1 throwing rocker arms ?!?!?


Maro

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Hey guys... about three weeks ago, I was cruising into work at ~62 with the cruise control on and all of the sudden, I lose a cylinder. Car starts chugging badly under load and blowing oil smoke out the exhaust (pulling it past the rings on the dead cylinder).

 

Limp it home and start pulling it apart to find that the #4 intake rocker arm is 90 deg. out of position and that the pushrod is bouncing around and hitting the valve cover. Anyhow... can't figure it out. Pushrod isn't bent, rocker isn't bent/cracked, and the lifter appears to be be fine.

 

So, I pull the valve train and heads and everything else looks good. Put it back together with a new lifter, pushrod, and rocker assy. for #4 intake.

 

Runs fine for 3 weeks, then all of the sudden, getting off of I-270 last night, it starts ticking pretty badly. The cylinders are still all firing, but it doesn't sound good.

 

SO, I pulled her apart tonight and find that #4 EXHAUST rocker is cocked off of the valve stem and is pushing down on the valve spring retainer! Luckily the retainers stayed steated and the spring stayed put....

 

Mind you, this is the other valve on #4. :eek:

 

Anybody have a clue? :mad: Running ~40-45 psi oil pressure.

 

[ 09. July 2004, 10:24 AM: Message edited by: Maro ]

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Originally posted by desperado:

Hmmm, sounds like you are pulling out the press in studs. Jegs sells a pinning kit if you don't feel like going ot the trouble of tapping and facing the heads for screw in studs. But that is my best guess.

LT1 heads use screw-in studds stock. That can't be it.

 

LT1's are hydro-rollers. I can't recall if the 95's have factory hardended pushrods or not. I know the 92-94 motors have them, the 96-97 don't. Of course they are stamped steel rocker arms.

 

Which leads to my next question. Is the valvetrain stock?? Are you running stock studds, stock rockers, stock springs, pushrods, etc.?

 

Also, has there been any valvetrain work in the past couple thousand miles before this first incident?? Any motor problems just prior to this happening?

 

I've had a roller rocker turn on me from not being tight enough, but that was during adjusting the rockers, so that wasn't a big deal at all.

 

Does it look like the rocker nut came loose? What is the condition of the rocker studds?

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LT1's don't have pressed in rocker studs. The rockers are self aligning,you might want to look and see if the groove at the tip is messed up. Are you using the stock valvetrain?

 

Vinny, yes they're hydraulic rollers.

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Stock valvetrain. Hydraulic roller tappets, hardened pushrods, stock stamped rockers, screw in studs, etc. Motor was never opened prior to the first problem.

 

Haven't found any studs backed out or any rocker nut's backed off. Pushrods have not been found to be bent (not even slightly) and the rocker tip on #4 exhaust was in good shape 3 weeks ago when I put it back on.

 

Only other suggestion I have gotten is that the lifters might be colapsing slightly on occasion, allowing the pushrod and rocker to "float" and come back down off the valve stem.

 

Oil pressure has always been ~ 40 psi while cruising, so I don't think it could be oil pressure related. Do you?

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Just thought of something... might be nothing.

Aren't the exhaust and intake lifters per cylinder connected by a bar to keep them facing the correct way on the cam? Since you've had 2 issues, and they were on the same cylinder, maybe that connecting bar has a problem? Bent or dirty?

Just a thought.

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Good thought, Nurk...

 

The tie bar is a seperate piece on the LT1 and it kind of looks like a dogbone with two semi-rectangular slots in it. It isn't really hooked to the lifters.... just keeps them square on the cam.

 

Anyhow, the bar was fine. Flat and straight....

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Originally posted by Maro:

My $$ is on your second comment... lifters are just wearing out....

Yup.. just remembered a friend had the same thing happen to his 95 LT1. His was a 383, but he'd left the stock lifters in when he built the engine. At SLP day in Columbus it started chattering like crazy and he only got one run in..
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Originally posted by Maro:

The Camshaft is fine. Lobes all look good and the lifts match up. My $$ is on your second comment... lifters are just wearing out....

+1

 

dang, I sold a set of brand new Comp Cam lifters about a month ago... too bad it didn't have the problem earlier... I could have given you a hell of a deal.

 

Also, just a thought... are you sure you are setting the valve lash properly on your car? I had that problem when I put my first cam in... those stock stamped rockers are a pain in the butt to get set right. Now would be a good time to upgrade to some Crane Gold 1.6 self aligning rockers when you get the new lifters.... a little extra power and allot easier installation :D

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