GRP Rods

[steve hurt]

Just lost a set of GRP rods last Sunday...the #8 Rod bolt backed out and pulled the threads out (hence causing catosrophic throughout engine)..
I found three more bolts that had lost torque upon tearing down, this was the 10th pass on the motor....Rods were properly torqued and stretched...
Has anyone else heard of any issues with these rods??? If you Run GRP what is your procedure for stretch and torque? What lubrication do you use on threads and under shoulder of bolt? Just curious. thanks


Steve

[Ed-vancedEngines]

I use just regular 30 weight oil as is perscribed to be used. I have seen numerous reports of guys having bolts back out of aluminum rods of all brands including the GRP. I think I have seen more reports about the GRP though, because there are more builders probably using them. That is my guess. In all cases I have heard about the bolts were properly torqued with a torque wrench.

The huge problem with that is that most people do not really understand what being properly torqued is really meaning. The torque specs given by rod mfg are torque specs after the threads are burnished and the bolts have been cycled several times. Even the bolt stretch specs are after the threads are burnished in by a first torquing.

I use GRP exclusively and will likley never change, but have also not had any problems associated with them. I do burnish in my bolts first and do cycle them a few times before I bring them to bolt stretch. I do use only bolt stretch using an ARP bolt stretch guage to do it with, but I do check them with other methods to be certain. I have an engine in here now that is a heavy nitrous engine of over 2,000 hp that has run 8,600 rpm and when I pulled it apart for inspection, the bolts took quite a lot of break away torque to break them loose.

Last year when this rumor was circulating against the GRP rods, my pal Vinnie Budano decided to check them for ultimate destruction byt increasing torque on them until something broke. What broke was one of the rod bolts at many multiples of torque than was recommended. The other bolt was then removed and the threads of the bolt and the rod, were thoroughly examined for any negative signs and they found none. Next they intentionally over torqued a set or rods to a little above the max recommended bolt stretch and ran the engine hard at high rpm on the dyno, hitting it with N2o and doing all they could to stress the rod while on the dyno. After tear down they found no problems. They are still using the GRP rods in the serious engines and on Vinnie's personal engines.

So if your rod bolts were correctly torque stretched to bolt stretch specs, I have no idea what may have caused your problems. I hope that you have called to Brian and talked with him about this.

Ed

[Pitbull]

My engine lost a rod at 8100 rpm , on its 1st Nitrous pass.
And all the rod bolt were still tight and in place.
Also 1 of the rods just plain incinerated for no good reason.
The bearings are all intact and no signs of being burnt.