Pushrod question-what causes them to bend?

[Eliteman76]

I'm sitting here right now, just come in from the garage, setting up for my road trip, and I have a batch of pushrods that came with a 351c that was in pieces when I got it...cam was out, one piston is out, pulled to check bearings and the kid dropped it and broke the skirt on the very bottom, cheapie cast POS pistons...and I had set some of the pushrods that I am assuming came from that engine...and noticed the are bent...like all of them are bent.
Cam that was in the engine looks pretty fresh, lifters from it arn't mushroomed or anything as far as I can tell...I basically just losely bolted the heads, intake and such back on the block for storage sake and to keep the bores from rusting at all.

I'm just curious is all, someone over revved it? I can say that the bearing on the rod...010 bearing, and it's worn.

I keep thinking back to a buddy years back, 70 1/2 RS camaro, his kid took it out and hurt the engine screwing around, and when he pulled the engine apart, the push rods on the 350 were damn near S shaped.

Andy

[cantvalve16]

That is what I would think. Over revved and floated the valves until..... bang bang bang. I kinda think of the pushrod as the "fuse" of the valvetrain. It's the first thing to go. The weakest link.

[BlackoutSteve]

That is what I would think. Over revved and floated the valves until..... bang bang bang. I kinda think of the pushrod as the "fuse" of the valvetrain. It's the first thing to go. The weakest link.

A valve is not really connected to the pushrod when floating, so the valve contacting the piston would generally not bend the pushrod. It would bend the valve though.

However, a valve that has floated will rapidly take up slack in the valvetrain when closing and slam the rocker arm against the pushrod when it seats, that could cause it to bend.

Also, I have heard of poor spring harmonics causing pushrods to bend. When a bad spring occilates excessively at certain rpms, it requires an incredible amount of force to compress it. Sometimes the pushrod just can't push that hard.

Excessive clearance in the valvetrain is another, where the pushrod is belting the rocker arm at every opening. The start of the ramps on the cam lobes are very subtle and too much slack will not allow them to gradually open the valves as designed..

I'm sure there are several other reasons too.

[milner351]

the only time I ever bent a pushrod in a clevo was when I over revved it - easy to do with those big valves on the 4v heads.

Sounds like you're putting together quite an arsenal of clevo parts!

[Eliteman76]

Milner, I keep having this torino crack habit problem, it's called I keep finding cars the have clevelands... ;)

I had another post about a '73 GTS with the head off on the pass side, rust in the bore.
Debating about seeing if it would be worth bothering screwing what's left of the two engines for a cheap runner...I have a sick idea...dropping a 4v 351c with a C4 in a gutted ford contour...cut out the back floor pan and buy a 4 link kit and weld in a spare 9" off a Torino I have, or go nuts and do a channel job with a spare Torino frame that I will soon end up having.
Like I don't have enough crap to mess with right now.

Andy

[milner351]

it's probably a good thing for our wives we don't live within easy weekend driving distance!

My first car had a clevo and I'll always have at least one around. I know they are a "thin wall" casting - but after watching a friend of mine put literally a cleaned up home rebuilt junkyard clevo 4v into a back halfed pinto with a c4, cam, intake, and headers - still running the single point dizzy, stamped steel rockers, etc.... that car had a throttle stop to run 12.0 and stay in sportsman bracket. He rarely broke anything.

I think these old engines (all of them not just clevo's) will run pretty well without the optimal dream machine shop megabucks rebuild most of us would like to do...

[Caveman]

There's another possible cause:

Installing the cam upside down.

Ask me how I know.

[BlackoutSteve]

Up side down? You mean back to front??

[Caveman]

nope. like aligning BOTH of the timing dots at 12 o'clock, instead of 6 & 12.

stupidstupidstupidstupidstupid.

[Caddyman]

Most of the bent pushrods I've seen are from interference.
Too little valve-to-piston clearance=interference
Float a valve=interference
Timing chain failure=interference
Rod bearing or piston failure=interference