I got my 383 running yesterday on my '95 camaro and today I readjusted the valves and went for a short drive, I adjusted them with 1/4 turn from zero lash. I think I had them a little too tight initially since it didn't run right at low rpm's, even though I only did a 1/2 turn from zero lash.

I was accelerating from an intersection at just under half throttle when I heard a series of "pop's" from what felt like the intake, but I could be mistaken, then heard the engine start ticking pretty loud. I pulled the car over and took the passenger side valve cover off and found the cylinder #4 intake pushrod bent into a question mark and slid into the little pushrod hole in the head gasket. When I was replacing that pushrod, I noticed the spring retainer was scratched up on the exhaust side of cylinder #4 and the "self aligning" tabs on the rocker arm was damaged, heres a picture of the rocker arm.

I put a stock pushrod back on the intake side of #4 and started it up and it sounded fine, no ticking, no poping out of the exhaust or intake. The idle sounded great and it revved up just fine. It was late and raining, so I just left the car where it was at and I'm gonna pick it up in the morning and have someone follow me home. I plan to do a compression check to make sure theres no bent valves

I'm using comp cams 850-16 lifters, 7808-16 7.2" pushrods and comp pro magnum 1.6 SA 3/8" stud rocker arms without guideplates. I'm using a standard base circle cam with a stock replacement headgasket. The cam specs are .565/.556 lift (1.6 rockers), 286/292 adv duration, 230/236 @ .050, 112 LSA. Intake opens 7 BTDC, closes 43ABDC -- exhaust opens 54 BBDC, closes 2 ATDC. I'm not sure what brand the springs are, but they're duel springs with 10 degree locks and titanium retainers.

My first guess is that my valve geometry is off, but I didn't think just changing rocker arms would require different length pushrods? I listed all the details on my valve train, if anyone has any insight as what could have caused the damage to these 2 valves please let me know. I'm hoping someone here has run into this problem before.

 

I guess the main problem is your running too much comp stuff.

But definity check your pushrod lengh, and the stock lifters are propably better than the comps.

Always check everything at least twice.
-b

 

I went to pick it up this morning and within 500 feet it started ticking again. I haven't looked at it, but it looks like I bent another pushrod

Can the piston really be hitting the valve with a cam that small? I have 18cc dished SRP pistons with valve reliefs

 

I'm not sure what your problem is and I hope it's an easy fix. But why did you decide to use 3/8s studs and SA rockers? That might be part of your problem.

 

I didn't think SA rockers would be a problem, but I bet whats happening is since I adjusted them a bit loser, the rocker is just jumping off the valve. I'm gonna order some new studs and guide plates and go back to my 1/2 turn past zero lash adjustment. As far as 3/8 vs 7/16, if I'm not building an insane amount of power, 3/8" should be plenty strong enough, right? I did a considerable amount of research when ordering parts, but it looks like I missed the ball on some stuff

This morning I had a problem with the #5 cylinder, same senario. The intake side pushrod was bent like a question mark and the exhaust side had the damaged rocker arm SA tabs and marks on the spring retainer where it made contact. I also noticed the poly lock on the exhaust side was loose.

I did a compression test and showed 170psi on #5 and I also tested a cylinder I wasn't having problems with, #1 and got 175psi so I think that rules out piston-valve contact.

Any ideas why the exhaust side would damage the rocker and intake side damage the pushrod, consistantly? or could it just be a coincidence that it was the intake side again?

I've bent pushrods before, but the fact that the adjacent rocker is getting damaged but not hurting the pushrod is confusing the heck out of me.

Thanks for the responses.

 

If you go with guideplates, you will need NSA rockers. You don't want to use SA rockers with guidelplates.

You might want to check for coil bind.

 

With the amount of money that you probably have in that set-up, it would be wise to switch out some parts and make it right. You need some ARP 7/16 studs, NSA 7/16 rockers, proper guideplates, and some decent chromoly pushrods. The SA rocker in your picture is trash now, might as well do it right.

 

Just curious, if I grind off the SA tabs on these rockers, can I use them with guide plates? It's my understanding that the reason you dont use SA rockers with guide plates is the 2 pushrod centering methods are fighting each other, so if I file off the tabs on the rockers, then this shouldn't be an issue anymore, right?

I learned that SA rockers aren't meant for cam lifts higher than .550, so I will order some studs/guide plates on monday, but I'd like to salvage my rockers if I can.

 

What preload does the lifter's manufacture recommend? From the way you are bending pushrods, it sounds to me like you are making piston to valve contact.

Also, it may not be the best setup. But, I've been running a 605/622 lift camshaft for two years with SA rockers.

 

I already did a compression check to rule out piston-valve contact. I will do a check on the #4 cylinder sometime today, but I've already tested #5 and had 170psi where one of the cylinders that didn't have any pushrod problems had 175psi. I could be wrong, but I think any damaged caused by piston contact would cause compression issues.

Here's a picture of the pushrods. The left end of the pushrod in the pictures is what contacted the rocker arm, so the bend took place under the head. You can see the rubbing marks where it looks like the pushrod was getting bound up inside the head and forced into a question mark shape. This is what lead me to believe the rocker is just getting knocked out of place.

I'm not sure what the recomended preload is, I was 99% sure it was a half turn past zero lash, but the car didn't feel right when I did it that way. At 1/4 turn past zero lash it felt great, no low rpm hesitation at all.

 

Chris, in an earlier version of my engine I had a valvetrain problem that caused piston to valve contact. The contact was verified with a borascope. Luckily it just bent the pushrod and the valve was fine. Compression also checked out normal.

 

you didn't rule out PtoV contact, just bent valves

get a hold of a borescope and look in through the spark plug hole for a witness mark on the piston top

 

You should find out what kind of valve springs they are, and if there up to the task, besides the other things mentioned.

 

You have probably got Piston to valve contact or coil bind or retainer hitting guide.
Was all of this checked at assy.
Ditch the SA rockers.

 

How do you find zero lash?
Are you testing compression with the throttle blocked open?

The compression looks low too me.