rod bolt problems

What would cause a rod bolt to be bent when I pulled rods and pistons out I found a bent rod bolt in #1 ..any thoughts would help.thanks Dave

 

Was the cap loose.....

If so, you just got really luck that it didnt kick the rod. We had that happen twice this year, hopefully solved for next season. Going to MGP, I think they have all the best features.

 

Ken it appeared to be tight, but that to me is the only way it would have gotten bent.Dave

 

rods

MGP the best hands down the man knows rods. Kosky racing

 

yes very lucky..no DAMN LUCKY.Dave

 

Rod bolts can bend if the other (opposite) bolt is loose. It would expect signs of movement on the serrated parts of rod and cap though. Normally the loose bolt will fracture (impact / fatigue load) and the remaining bolt will bend or shear in one go.
Don't keep the other bolt for spares if you ever considered it, it may be on it's way as well.

 

How much was it bent ??

I have heard lately that some guys are finding bent rod bolts---- they are attributed to high rpms with long strokes and high bob weight setups .

It might be that more torque is needed ?
Of course that's between you and the rod maker---- is your torque wrench accurate ?

Using the right assembly lube ?

Do you pull them apart and re torque while they are hot ??

Is somebody new doing the bottom end ???

 

I've had this exact thing happen more than once.

I've also had bent rod bolts that came out of my biggest stroke engine, it had a lot of runs on it and had a couple over rev situations. I could tell upon dissassembly that something was wrong because it wasn't easy to remove them, there was drag. I put a machinist square along the side of them and they were bent, not much, but they weren't straight.

 

If bolts show permanent deformation (bent) then they have been stressed beyond the yield point. If this happens with two bolts which are known to be tight it suggests forces are too high, so higher tightening torque will not help. Too low tightening torque would normally lead to fatigue fractures which is definitely not a bent bolt, but nothing is quite normal in our engines.
When you see bent bolts is the big end bore in the rod still round or is it oval and do you see signs of wear on the bearings near the parting line? Just wondering if you're stressing the rods and caps up to the point that they become oval-shaped. During this process there will be additional bending stress in the bolts as well, which may explain the bent bolts. Definitely a risk related to heavy rods / pistons and very high speeds.

 

Which way are they bent, out at the bottom?

 

Are you sure the washer had the undercut facing the the bolt head?

 

hi Mark, I do my own bottom end as for torque wrench I use only snap on and I own my own calibrate tester for my torque wrenches, to the naked eye I could see it bent but I put it in my lathe and spun it and it really showed then, always use oil and lots of it on the rod bolts, as for rpm's the last to races we went up on the rev limiter two times that is when we loaded up and came home also I might add that the crank bolt was loose and I use the one that Bob auto (automan) sells the torque spec is 400 foot#. thanks for all the GREAT replys.Dave

 

Dave, look at your PM.

 

Can i ask what the rod bolt material was?

 

rod bolts were the ones that they used in the brooks b2..
and yes the washers were facing the rite way.Dave

 

I hate to sound like a a#@ hole...but I was going to ask several post ago if it was a Brooks....sorry but those are sh#%!! Put MGP in and be worry free

 

Tim
I just was sure you might remember and comment on those
john

 

AFC357..I have to say in 20 yrs. I only kick 2 rods out one time being our fault I have ran Jerry's rod all that time and when I was working on tom hoovers fuel funny car that is all he was running..it's race car parts they all break it is just (when) Dave

 

I certainly lack the experience of most here on blower deals. However I have seen the same brooks rods where a major mistake was made (not by me ;-) and on inspection the wrist pin was egg shaped and the rod beam was severly bent.. but... did not break, some may say this is due to soft material but every bearing was paper thin by 300ft and the rest of the rods were fine so IMHO the rods did a pretty good job.