wrist pin clip issues
 

On a 632 Chev , 14.5 engine, we found some pieces of wrist pin clips in the oil change. They are 2- .042 spirolocks.(per side) They were not excessively stretched when installed.My first thought was a bad batch of heat treated clips. I was told that because he hit the chip in the water box, this will cause this kind of problem. Engine had about 60- 75 hits on it. He (the driver) also pedals it in the top end. car is a dragster, about 2100 lbs . I was told that this also might contribute to this problem. I get my info from drag racers that have 40 years in the game & I respect their knowledge. Any input or experiences that I can learn / understand whats going on ? His last engine pounded out the clip grooves to about .030-.035 end play. Same basic engine.Same car . Thanks guys

Re: wrist pin clip issues
 

There is something else going on here. Everybody in the country runs double spirolox ( which is way overkill) and doesn't have a problem and he pounds them out of 2 motors in a row? Something is way wrong.

Re: wrist pin clip issues
 

yea I know somethings very wrong, but the" fun" ? here is how to avoid it next time.The driver won't listen to me & thinks it's the engine builders fault...isn't it always? LOL

Re: wrist pin clip issues
 

I've seen before when an engine is detonated hard enough it will bow the pins and push hard on the spirolox - overrev will do it also.

Re: wrist pin clip issues
 

spark plugs would show signs of detonation?

Re: wrist pin clip issues
 

I haven't seen the plugs, but I was told that it's hard to see signs of detonation from alcohol engines. I don't know this, only going from what I was told. The driver / tuner would see this , I think he would know about this. I keep suspecting , on the chip in the water box. Thanks for the input guys.

Re: wrist pin clip issues
 

His alky tune up or his on & off throttle foot could be flooding the engine at some time in the run and never show up on the plugs. I'm still saying you have the combination of an abusive driver and a slightly off Alky tune up. I don't mean off at WOT. I mean off in the "Fuel Curve" when the foot is on and off the throttle.

Re: wrist pin clip issues
 

Have you torn it down yet to inspect for damage?

Is the damage worse on one bank vs the other? Any specific cylinders consistently worse than the others?

On the non failed clips, do they or the piston grooves show any unusual signs of wear, like four corner wear vs even wear, etc?

Re: wrist pin clip issues
 

Hi all, 1st post here !
With this wrist pin damage issue, what are the rod pin bushings looking like?
Bush brand/material?
Coated pins?
AND pin/rod clearance?
I have seen where the pin clearance is too small and the pin nips in the rod, then any side movement of the piston is forcing on the pin clip and damages the clip and/or piston.

Re: wrist pin clip issues
 

Re: wrist pin clip issues
 

Ron,
You are going to have to trust me on this, and all the "experts" on here are going to piss and moan.
You need to have more pin end play. The reason the other engine opened up to .035" is because that's what it wanted. The pistons deflect from gas pressure and the pin bosses flex inward. We built a fixture and we put 1500 psi nitrogen on top of a room temperature piston just to prove this fact. Lost numerous cup engines and a few IRL engines as well, with too tight of wristpin end play.
Wristpin end play is like bearing clearance, too much and you know about it, too little and everybody knows about it.

See you at the races,
Wayne Kerr

Re: wrist pin clip issues
 

What would be the desired amount of end play on a medium performance engine 150 wall 153 gram, and 545 gram piston, 3.385 stroke? I have .027 right now

Re: wrist pin clip issues
 

Good morning Jeff,
There are certainly many factors that are in play here. The first is piston design, the new "Box bridge design" pistons are reinforced in the pin boss area and can run less wristpin end clearance. .025" would be adequate for that type of piston while the old full round pistons like a Venolia, I would like to see .040"+
Bore size will play a role as well, bigger bore, more piston deflection.

See you at the races,
Wayne Kerr

Re: wrist pin clip issues
 

Wayne what is èasy best way to check this..? Thanks

Re: wrist pin clip issues
 

Simple question.. how much vacuum are you pulling??.. too much vacuum will affect oiling to the wrist pins, and possible damage... just an idea..

Re: wrist pin clip issues
 

Just use a regular one inch travel dial indicator, with an extension. Welding rod for the extension will suffice.

See you at the races,
Wayne Kerr

Re: wrist pin clip issues
 

Wayne,
I'm not squirming or pissing and moaning. I agree with you on clearance, but too much makes the pin act like a battering ram on the clips. most applications I deal with .002 to .006 is plenty. But first Get the alky tune up correct where it won't flood when the driver is pedaling it and the pistons and pins won't deflect so much they need more clearance. I do agree pins need end play, but most pistons grow outward at the pin boss when the engine heats up making more pin end play. Flooding it with the alky is probably keeping piston temp down = no piston growth & more deflection of the pin and piston. I have seen the very same thing in Dirt engines with 4" bores. It bothers me to see a driver that has abusive habits. Some times those DT cars have drivers that are real harsh with the loud pedal, too.
There could be multiple issues with this one. It could even be a set of pins that are not up to handling the load the alky puts on them. Pin deflection can be a real serious issue on high cylinder pressure applications. Good luck fixing it.