Lethal Farce

"Inherited" a 63 with supposedly a new motor. Only thing I noticed at first was a very noticable clicking from the valve train. It started rough one afternoon and had noticable smoke from one side. Long story short- Broken push rod. If I could get the piece out, can I just put in a new one and re-adjust. Provided the bottom end of the broken piece is clean without chips / shavings, etc?
Thanks, LF

midyearvette

yes, you can replace one pushrod. however, you may have a clearance issue as to why it broke in the first place.....

Lethal Farce

Thanks. My experience with setting valve lash is limited to motorcycles. I am worried about getting over my head and not being able to identify the problem.
LF

Westlotorn

First verify that the Rocker Arm retaining nut is still adjusted like the other nuts in the valve train. If it backed off while running a new nut is in order. The number of threads visible above the top of the nut should be pretty similar on all the rocker arms. If it was still tight and not the source of your loose push rod the cam may have lost a lobe, when it wears down enough your push rod can jump loose and break. I have never seen one just break all on its own. ( Except in over revved big blocks )
A push rod is cheap so deffinately put a new one in and see how it runs but you most likely have a hidden issue.

Lethal Farce

Thanks. Tried to use a magnet to pull the bottom piece out, and I had it almost out and it fell, and now I cant get to it with the magnet. Crap.
LF

Westlotorn

You can buy mechanics magnets, extendable, 2 foot long with a decent magnet attached, they are narrow and can go into a push rod hole.

It is possible that debree got into the lifter under this failed push rod, a lifter can bleed down leaving the push rod loose if it has failed. I keep hoping it is not your cam.

Lethal Farce

I towed it to a local shop with a bore scope. He found the broken piece and also the lifter had come out of the lifter bore. Cam looked good. We are replacing all pushrods as many were also bent. Looks like I was heading for a major problem. I hate to think what would have happened if I really spun it up.
The root cause in his opinion, is that the pushrod guide plates were the wrong ones. They were for 3/8" dia push rods and allowed too much side to side movement with the narrow pushrods. I should be running in time for the rugrat to take it to the Prom on Saturday.
LF

Westlotorn

Multiple bent push rods would normally mean you have coil bind, when you rev it high the cam may be lifting the push rods more than the springs allow. When a spring reaches the end of its travel, fully compressed, it is in a coil bind. If this is true it usually leaves marks on the springs where the coils have touched in coil bind. Look for the shinny lines on the springs where they may have hit in coil bind.
The cause is too much cam for the springs to handle.
If your set up is very close to coil bind it may work under 5,000 RPM and bend push rods at 6,000 RPM because the weight of the valve train makes the valves open a little more at High RPM. For this reason machinist will leave a measured amount of safety room before coil bind can happen in a engine.
Have you had this engine into the high atmosphere recently? Above your normal RPM range?
In cases with coil bind it can also break valve springs.
Glad the cam looks good.

Lethal Farce

Thanks for everyones help. New rocker arms, pushrods & guide plates, 4 studs, and it is running like a top.
LF

Westlotorn

That is good news.

jasonwku

Can you tell me the approximate price for all of this work. I am going to need one new pushrod, new rocker arms, and one stud.

mhanley

I put all new Comp Cam Magnum ( RP1412-16 ) pushrods and roller tip rockers ( they fit under stock valve covers ) and one stud ( standard size ) in my L79 for about $255. Are you going with a oversize stud order standard ? I hammered mine ( using a special tool ) and used Loctite 640. I haven't had any problems what so ever.

Mike

Kerrmudgeon

I had a tank of bad gas once, and the motor kept backfiring trying to fire up. After about a dozen backfires it started but ran like crap. I took the covers off and it had blown two rockers off the rods, and the rods were one bent, one broken. Replaced them, and it's still running good, and a piece of pushrod has been in the motor for about a 100K kilometers!

jasonwku

It is for a 355 stroker motor. One of the push rods broke. One piece was found up top but the other piece hopefully is in the oil pan. The stud is 7/16. This is taking away from the power which I definitely would like.

Avispa

They can even be the right ones, but you still need to check clearances. I had two different exhaust guide forks break off my pushrod guides, causing the rockers to rotate and push the spring retainers of. Only my teflon guide seals saved me dropping the valves into the motor. I was totally stumped, until I noticed that the base of each guide fork was worn shiny. Manley made the guide plates incorrectly so that there was no clearance at the base of the guide fork. Moral of the story; check EVERYTHING yourself. Don't assume the parts were made correctly.

jasonwku

Thanks everyone. I will let you know how it turns out. I know right now I'm not getting the full benefits of the engine. I'm not trying to race it or anything but just want to reap the complete benefits the engine has to offer.