cuisinartvette

For those that have, how many had bent valves to go along with it?
piston damage?

Were they intake or exhaust.


Just bent a whole slew of them in mine, mainly intake valves, brand new motor too.


Just curious....probably going to tear it out just to inspect and be on the safe side.

After over 20 yrs about time I had a breakage I suppose.

AlkyIROC

Bent pushrods is never good

Bent valves - Very probably. With the rockers off, leak test the cylinders.
Damaged pistons - Maybe but probably just some marks in the tops
Bent con rods - Maybe if OEM rods. With the heads off, make sure the pistons all reach the same height in the cylinders.

You either have too little piston to valve clearance or you floated the valves. Either way, something is wrong and needs to be corrected.

paulo57509

Bent pushrods? Try broken ones.



1968 RS/Z-28, 302CID was on the way to Stockton from San Jose. Pulled into Livermore and the engine wouldn't idle. Twisted the distributor around and got it to idle and drove the rest of the way.

Next day, tore it down to replace the timing chain and drove back to the Bay Area. Would cruise OK on the flats, but no power going over Altamont Pass and Mission Grade. Once home, pulled the manifold and found what you see here. It was running on three cylinders. Pulled the heads, but no bent valves. Domed pistons smacked the valve heads square.

Talk about low oil pressure. Yes, the car is still around.

Guest

I bent two and had no other damage. Lucky me.

sofakingdom

iTrader: (1)

I've had both...

Think of whatever part is weakest, as acting like a "fuse", thereby protecting the stronger parts around them by failing.

Stock push rods are pretty weak. They bend EASY, before stock valves will, for the most part.

High-strength push rods with stock valves, kiss the valves goodbye.

Good push rods and good valves, kiss pistons goodbye, and cams and lifters; and maybe even rods.

When they bend, if the motor keeps running, then they bend back and forth every time they get operated; think about what happens to a coat hanger when you bend it back and forth real quick a bunch of times, the results on a push rod aren't much different.

I hope you get out of it without too much grief. You might but who knows. One of the times that has happened to me, a 454 stripped the plastic teeth off the chinesium gums of the cam sprocket. Stock push rods. I had a friend who was working at Comp at the time buy me a timing set that evening and bring it home, and I stuck it on right quick. It didn't ever really run right. But next day I had to drive it about 200 miles for work anyway, and by the time I made it about 30 miles, it was running REALLY TERRIBLE. I babied it and tried to keep the RPMs below 2500 or sothe rest of the trip, but it kept getting worse; by the time I made it back home, 3 int PRs were broken. The motor looked about like Paulo's 302 up there; of course all 8 intakes had got hit, it being a big block. Called my friend again, had him bring a set of PRs and a set of 1400 series rockers home for me, slapped them on that evening. That was in about 1990. The car still runs today. So it's not necessarily the end of the world.

cuisinartvette

Sheesh...has good pushrods (or had lol), shaft rockers solid rollers forged pistons. Was tuning with the LM1 and had to get a reading on the secondary side. Couldnt have been much above 5k less than 6 thought I head/felt something slight..Let off the gas seemed Ok so got back on and the exhaust pitch changed
dramatically so I knew something was wrong, limped it few hundred yards back home, sounded terrible like the motor was going to fall out of the car like it was running on a few cyls. Used Nextek springs, good rods pistons etc.
Surprised actually.
Im tearing the motor out tonight and praying for a sound bottom end but its all coming apart anyway too much in this one to risk it.
Either this cam wasnt degreed in right or to little p to v clearance...im betting degreed in wrong.
I only cracked the secs a few times and it felt way flat, on the primary side felt strong . Guess things must have been close til some rpm got it and things started moving around. Ugh
Ill get some photos of the carnage of course.

skinny z

One bent exhaust valve and one pushrod. Missed shift on Vortec headed 350 (7000 rpm!).
New valve (lapped in) and one pushrod later, put another 60 000 on it before it was pulled to be rebuilt.

AlkyIROC

When I blew up my old 383, I don't know what failed first. Either a rod let go or a piston disintegrated. Lots of carnage. When I pulled the heads off, there were 5 visibly bent valves. I still have the heads. I never did pull them apart to see if any more valves were bent.

I went to a BBC after that.

cuisinartvette

Long afternoon but motor and trans are out. cant pull one without the other.

Tuned headers + scattershield+hood on and 7 qt pan....oh yeah no extra hands and the picker wanting to pull itself towards the grille.

But got it out managed a 1 in scratch inside the hood, so much for fresh paint.

Hopefully know why this happened next week sometime. had to resist the urge to tear it down myself and let the machinist do it as he insisted.

This time around it better come out right...if Im not super impressed it will all get sold top to bottom and Ill piece together a BBC so far this just isnt cutting it. Something was way wrong though so I dont want to speak too soon.

AlkyIROC

When I pull the engine, I take off the hood. It's only 4 bolts on the hinges. The nose of my car can also easily be removed to allow the engine hoist to reach in farther from the front. Can't pull an engine with the hoist off the side of the car.

After breaking many engines in the past, my last rebuild had the machine shop do a lot of it. After I got the rotating assembly balanced, I had the machine shop put the rotating assembly together in the block. That way all the bearing tolerances etc were checked. I had a private engine builder redo my heads. I did the rest of the assembly.

It's just all those close tolerances and corrections I can't do properly.

That was 3 years ago and I haven't had a problem with the engine since.

cuisinartvette

My hood is a little on the heavy side so I coudnt do it myself had to hope for the best.

This is the first motor Ive had that I had someone else assemble/blueprint etc.
Was meant to be spun up fairly high so they probably know a few lil tricks to putting one together that will live at high rpms so I paid the dough and let them. Guess if I hadnt Id be up the creek right now, SO far hes offering some type of goodwill.

Not pointing fingers though its anyones guess what caused the problem originally. Ill know something next week.

Thats hot rodding for you, sometimes things just happen.

Gus58

bent pushrods means valve to piston clearance has been comprimised, this has got to be be due to valve timing slipping, check timing chain when motor is down....

Air_Adam

I bent 9 from my big block last summer.... I had the heads on the floor standing on-end, with the pushrods beside them. One head tipped over and crushed/bent alot of them. So I upgraded from 3/8 to 7/16 and will never worry about it again

skinny z

Quote:
Originally Posted by Gus58
bent pushrods means valve to piston clearance has been comprimised, this has got to be be due to valve timing slipping, check timing chain when motor is down....

..or pushing the valvetrain past it's ability to keep things under control. ie. valve float.

skinny z

...or this! Ouch.

Gus58

would that bend all like in the pics though? It would have to be pulling some revs...

cuisinartvette

Well no damage to the motor tore it down anyway for piece of mind.

Pushrods werent up to the task of the springs, just need a better rod thats all.

No piston to valve contact, whew!

Word of advice, buy the BEST pushrod you can, overkill is good.

AlkyIROC

Stock pushrods are good for stock valve springs

cuisinartvette

Supposed to be a Manley 1 piece, apparently thats not what got in there.

Springs just overwhelmed them...wonder how much power I was losing with them flexing around all the time?

Dyno Don

iTrader: (7)

As many years as I have been building motors, I would look further for the cause.
Pushrods don't just bend without some reason.

cuisinartvette

THe pistons and valves are mint, plenty of clearance.

We tested the prods and they checked out at 58 rockwell hardness.

however we stuck one in a vice and putting any pressure at all against them bent/broke immediately. They were .080 wall alright but the metal inside you could practically scoop out it seemed like, really poor quality. I put this together in 03 and just started it a few monts ago Im betting I got some early Chinese knockoff that was **** poor quality. Springs are only 200/500ish.

Cant see any interference issue anywhere, no bad springs, coil bind nothing.


All I can say is it seemed to run good normal driving but dip into the secondaries some and although it wanted to grab rpm it went reeeeal flat!! It should be pulling like a rocket...as if the motor lost 100hp, that bad. No misses stutters or anything either. Carter 172 mech pump 1/2 line all the way to the tank pickup.