bent pushrod 94 Burb 383

[LVJJJ]

Had this stupid knock (maybe piston slap or worse) for a long time. Coming home from camping trip towing travel trailer it really started knocking, luckily it started getting really loud just as we were getting home. Took it to local dealer turns out it was a bent pushrod. No idea how that happened. So rocker ruined top of valve (#2 intake). Now waiting for dealer to locate a GM valve and to put it back together. Probably still going to still nock cause I think it is the lifter, but mechanic says if he replaces that lifter he'll have to replace the cam???? That true?

 

[PlayingWithTBI]

I think it is the lifter, but mechanic says if he replaces that lifter he'll have to replace the cam???? That true?

Nope, not with a roller cam. You need to take an oil sample and send it in for analysis to see how much metal was scattered throughout the system.

 

[Schurkey]

Had this stupid knock (maybe piston slap or worse) for a long time. Coming home from camping trip towing travel trailer it really started knocking, luckily it started getting really loud just as we were getting home.

What's in this "383"? Roller cam? Flat tappet? Non-stock rockers? Are they the RIGHT KIND of rockers? (self-aligning vs. non-self-aligning)

What heads? Pushrod guideplates?

What has the oil pressure been, at idle, in gear, engine fully warm?

Took it to local dealer turns out it was a bent pushrod. No idea how that happened. So rocker ruined top of valve (#2 intake). Now waiting for dealer to locate a GM valve and to put it back together.

Why do you need a "GM valve"? Is this a GM crate engine? Still under warranty?

Are the retainer/keepers damaged? Valve spring? Valve stem seal?

Probably still going to still nock cause I think it is the lifter, but mechanic says if he replaces that lifter he'll have to replace the cam???? That true?

Seems very unlikely. Maybe that's GM "official procedure".

 

[tayto]

the push rod bent because something is binding. not to sound like a broken record but was your rocker geometry checked. you really need to post more info. the dealership will replace parts but they wont know how to fix your problem if it is an assembly error

 

[LVJJJ]

Thanks all of you, I think you have hit on several things. My mechanic is very good, known him since the early nineties, has done a great job on all my cars. But...........

The engine is a remanufactured 383 from S&J Engines in Spokane. Had that little knock from the beginning but went away when engine heated up, but has gotten worse. It's a roller cam with correct lifters. It has stock rockers and push rods. I think Shurkey nailed it. The stock rocker must have got a little off center, somehow bent the push rod, the push rod then egged out the guide hole in the head, and the rocker got way off center and pounded the heck out of the top of the valve. I ordered a special rocker that has a square area where it hits the valve to stay centered. Probably should replace all of them with this special rocker. Makes sense what you all have said. Thanks.

As for a GM valve, its a Chevy dealer and they order parts thru GM. It still ain't here yet and we've missed two days of our vacation. A RockAuto valve ought to do just fine. How many GM 350's are out there? so why aren't valves readily available??

 

[Schurkey]

What heads? Pushrod guideplates?

You haven't said what kind of cylinder heads this engine has, or whether it's got pushrod guideplates.

TBI heads, and Vortec heads MUST have self-aligning rocker arms. Sixteen of 'em. The cylinder heads have round holes where the pushrods pass through, the iron of the head does not guide the pushrod.

Cylinder heads with pushrod guideplates MUST NOT have self-aligning rocker arms.

Cylinder heads that have oval holes that are tight to the pushrods MUST NOT have self-aligning rocker arms. The iron of the head guides the pushrod.

 

[Hipster]

This mechanic needs to get to the root of the problem. If the roller on the lifter failed then yes, it might need a canshaft as well. Pushrods don't normally just bend. over revved, a valve seizing in the guide , a cam lobe/ lifter roller that's been damaged by the valve train pounding from the get go. Parts ran out of room for some reason and it seems, why?, has yet to be determined. Good at stock stuff and being familiar with HP type stuff doesn't always go hand in hand and I hope it's not the mechanic suggesting you run self aligning rockers and guideplates together if that's the case.

 

[Schurkey]

Edit to my above post: I'm hearing that a few early TBI heads did not use self-aligning rockers.

VERIFY WHAT YOU HAVE. There's multiple methods for keeping the rocker arms aligned, but SOMETHING has to guide the rocker.

 

[LVJJJ]

Has oval hole in the head to guide the rocker, bent pushrod egged out a very little bit. So now have some metal in the oil pan? I think the rockers and pushrods are as stock as can be.

Don't think I've revved it over 4,000. We do climb Steven's pass in second at about 3700, probably 15 minutes to get to the top of the real steep 6% grade. I think the computer limits RPM's to 4200

Thinking about changing to roller rockers, shoulda done that in the first place.