Anyone have bolt issues with GRP rods ?

We have had some bolt failers with the 90 ft and 120 ft lb bolts .Torque wrenches check good .pan gets dropped after one run and re torqued then after 2-3 runs after. Seams to take a few runs to get the torque stay the same..this is a NHRA hemi pro mod car 10,000 rpm max .We have in the past gone 40-50 laps with zero issues This started happing mid last year

 

are you not stretching the bolts?? just relying on your torque wrench??

 

I’ve been running the GRP 5550 rods with the L-19 1/2” hemi bolt ,rod bolts torqued to 100-115 ft lbs for 4 years and no retorque ever on a 555 bbc making around 2500 hp 8100 rpm and even lots of street driving with no issues! Finally decided it was time to change them so I ordered a new set?

 

Have you discussed this with GRP?

 

Thanks for the info glad its not us have the re torqing issues lol crazy that you have to do that .I remember the R&R rod issue think the rod bolts were bottoming out on the threads .I have had bolt issues on my personal car with GRP 6 runs on a new set and broken bolt But I did not know about the re torque protocol.I sent the remains to them and of course there reply was it was something on my end .The car owner is sending the broken bolts off to a professional metallurgist for a full failure and chemical analyses. Also big difference bbc @ 8100 and hemi @ 10,000 plus I got 80 runs on my GRP SBC rods @ 8500 The team I am working for is switching to BME rods

 

I remember a nhra blown team bending a grp rod in the shape of an S after 3 runs. Switched over to mgp and have never seen any issues since. The rnr rod with the metric bolts are very nice pieces. Seen a promod car put the cap on backwards and run it for couple runs before they caught it. Turned the cap around and kept racing lol

 

We have been running GRP rods since late 90s/00s cant remember exactly when . The first thing is the correct way to torque rods is by stretch we torque to 90lbs and after 2or3 runs the torque is down to 85lbs when measuring stretch. You can buy a gauge for this from GRP .I have run them in my TAFC since 2009 with no issues.
On my first 5.40 run in TAD I bent a rod into an S shape I keep it in the trailer to show how good the rods are the reason it bent was the engine was on the limiter and hydraulic,d but it didn't break!!!

 

I guess the age old question has to be asked... how many runs on a set of rods before changing them or would new bolts be a consideration

 

I hear some TD and TS guys are putting 70-80 runs on their rods?? Obviously we don't have the strain of a pro mod or TAFC engine so that plays a part.

I personally would not go that far - I will stick to the 30-35 range.

Just my opinion.

 

I thought the same as well. I believe a few had some aluminum exit stage left - lol.
I would anything above 40 would be playing with fire even in our applications. ie under 8500 rpm without a ton of boost and/or overdrive. I could be wrong though

 

Curious why the converter would aggravate the situation?.....

 

If it's a Lenco drive put it low gear 'then it will free wheel,we use the air parachute for this and release the presure from the pod .
We also have a switch in the rear of car that shuts the air off when making the burn out so the driver can hit the air button release the air and not throw the chutes.
I have not had a problem with sprags ,been doing this for 2 years,alot easyer on bearings and rods.

 

What would you recommend in the case of a lockup Quikdrive and a 3-speed CS2 Lenco ?.........

 

The parachute lever switch dumps both pods? Do you dump pressure at the end of the burnout like Hydrotherapy describes above?