I've got a hypothetical question about the damage that could come from missing a shift in a manual car, like shifting from the top of third down to second instead of up to fourth.

If you were at the top of third gear and you shifted down to second by accident would it be possible to bend pushrods by just overreving the engine alone, or would the engine need to reach valve float before it would bend pushrods?

Would an effective rev limiter help slow down the rate of rpm climb at all in such a situation?

And lastly, have you guys ever experienced someone bending pushrods by missing a shift like that?

Thanks,
Brendan

If its a BB, absolutely. Push rods and probably break a couple of valve springs. Small blocks aren't quite as prone, but can also cause damage. And rev limiter does nothing in this situation. And lastly, I've bent pushrods and NOT missed a shift.

Originally posted by SemiHemi:

If you were at the top of third gear and you shifted down to second by accident would it be possible to bend pushrods by just overreving the engine alone, or would the engine need to reach valve float before it would bend pushrods?

Would an effective rev limiter help slow down the rate of rpm climb at all in such a situation?

And lastly, have you guys ever experienced someone bending pushrods by missing a shift like that?

Thanks,
Brendan BTDT - just as described. Going into second at 5700 on the tach. Had pushrods that resembled candy canes after that.

All cause a buddy asked me to get on it as I went by him so he could hear the new pipes. Boy did I look goofy when I missed the shift, but I played it off and told him I did it on purpose so he could really get a feel for how the exhaust sounded.....at 7500 smile.gif Then I limped home.

I was hauling ass one day on the highway and ran up on a van way to fast. The only way I had to keep from hitting him was to down shift to 3rd from 4th at 90MHP. Needless to say the rearend jumped up and down off the ground, but I didn't hit the van! Luckly I didn't bend any push rods. Thanks god for fat rods.

I find it almost impossible to cross the gate backwards when you're powershifting if the shift rods are precisely adjusted.

Am I missing something?

I dont know but it seems to me that a push rod..unless it's really poorly made wont bend unless you have some sort of mechanical interference.If you were to expirence severe valve train seperation and then slamming back together then that would certinally qualify as mechanical interference.The combination of seperation ( clearance where there shouldnt be ), deflection , movement , springs bouncing , valves bouncing and everything that was seperated slamming back together say up the flank where you should NEVER have seperation.....Oh that hurts just thinking of it.

Assuming of course that one doesnt have 5/16's pushrods and 340 lbs on the seat and 800 lbs open..
and a .750 lift cam...That could kill a misapplied part...But if the proper parts are used then it seems some sort of interference would bee needed to kill it.

Originally posted by d1_bradley:
And rev limiter does nothing in this situation. Is that true? I was getting ready to get a rev limiter for that very reason... in case I missed a gear at high rpm. I also agree with 427L88 never went to 2nd when trying to go for 4th. Missing 3rd from 2nd now that's another story graemlins/clonk.gif

a rev limiter won't do any good because it disrupts the ignition system to prevent the engine from pulling beyond a set rpm range. in this accidental downshift situation, the over-revving is caused by mechanical force. the car is moving forward at a speed that produces a given rpm in a given gear. if you are in a gear that is too low, you will get an rpm that is too high :eek: :eek:

I have never missed a gear like this in a big block, but my friend was being a designated driver in my Z28 one day with me riding shotgun. he went from the top of third to second gear at about 90 mph. the small block floated and died. we figured the worst, but just turned the key to start it and ran it about another 20000 miles with no problem.