Anyone have bolt issues with GRP rods ?

Discussion in 'InsideTopAlcohol.com Tech Questions' started by turbo69camaro, May 6, 2019.

  1. hydrotherapy

    hydrotherapy Member

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    We back up in high gear and when we start moving foward thats when we put in low gear ,because when we tried to back up in low gear the brakes wouldn't stop the car because of gear ratio
     
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  2. Mike Canter

    Mike Canter Top Dragster
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    Yes, everything else is normal operation.
     
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  3. Bjs344

    Bjs344 Member

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    I went about 103 on 1/2 a set of mgp. The front 4 were replaced around 60 after a crank failure. I sent them to mgp at about 80 runs and they said keep going. I had a pin move in one of the caps at 100, made 1 more race, and pulled them.

    BBC mid to high 30s on boost, turned around 8000 most of the time, sometimes 8300-8400

    MGP told me to throw away my stretch gauge so that’s what I did.
     
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  4. Mike Canter

    Mike Canter Top Dragster
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    You are not going to get away with that on a Promod Hemi that is shifting at 9000+ making over 30 lbs of boost.
     
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  5. dragster156

    dragster156 Member

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    I could never do that for piece of mind. Even with the nitrous motors I would put new in every year regardless of runs. 40, 50 or 70 every year motor gets new rods. Just my way, I could be wrong.
    As said with the hemi now I will not go over 35- 40 max. To me it's only a grand and as said, much better piece of mind ;-)
     
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  6. sean70ss

    sean70ss Member

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    Quit using GRP a years ago same issues as op. MGP/BM or RR
     
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  7. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Steve Jackson seems to be doing alright with the GRP's in a legal Pro Mod.

    I fail to see how a converter is harder on rods than clutch cars? If a clutch is locked up, it jerks the motor down on acceleration on the gear shifts harder than a converter. It's like my dad explained to me years ago it's the difference on yanking on something with a rope or a chain. There's more give in the rope.

    Most converter cars have some sort of dump to go back into low and let the motor 'neutral' and not decel the car with the crank. I would think the cap has more stress on it under acceleration.

    I'm not calling anyone out and saying anyone on here is wrong, but as hard as you have to push a legal pro mod to be competitive, there's no chance some failures are due to detonation? You also can't say all rod failures in Pro Mods are GRP's.
     
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  8. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    I'll add that a clutch car will decel against the engine until the engine rpm drops to a point the driver can get the clutch depressed. That point is roughly equivalent to the launch rpm.

    Many rod failures in shutdown are due to no oil pressure. Many cars lose oil pressure after the chutes hit and it runs the oil to the front of the tank or pan, away from the pick up. Not to mention a lot of the oil is up in the valley.

    Also if you beat on them hard enough, they let go when you step off of it too.
     
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  9. Mike Canter

    Mike Canter Top Dragster
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    Not really talking about rod failure or bad bearings. Talking about the bolts becoming lose. Yes if you don’t check them you will get a rod failure but the bolts lose torque after one or two runs. We never needed an air dump on the Lenco solenoids with a clutch but do with a converter. The Liberty transmission free wheels when you let up and same with the Rossler 400. Worst problems seem to be with the Lenco and converter combination. Having a converter with a Lenco also requires you to install that special washer to hold in the snap ring on the sun gear but never had to do that with a clutch car
     
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    Last edited: May 16, 2019
  10. TOL

    TOL Active Member

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    Interesting discussion. Perhaps worthy of its own thread? Why would a converter be more problematic on the rods than a clutch? It has less mass, is inherently more balanced at all times, and when unlocked is kinda sorta a hydraulic dampening device. Weird! I don't have any answers, just questions :)..........
     
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    Last edited: May 16, 2019
  11. Mike Canter

    Mike Canter Top Dragster
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    TOL I did explain it in a previous post. Yes the switch dumps the air out of all pods. And yes you still do the burnout like you did before
     
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  12. turbo69camaro

    turbo69camaro Member

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    I talked to a top fuel team owner he said they stopped using them because on the spare motors that were stored a month or more they had issues.so it was a practice to back off the bolts until the day before the motor is needed
     
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  13. go green

    go green New Member

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    I have had a broken bolt in two separate engine failures , do bolts brake during rod failure, or is a broken bolt a smoking gun ? GRP in both cases.
     
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  14. Mike Canter

    Mike Canter Top Dragster
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    Did you have aluminum thread from the rod embedded in the threads of the bolts. Most likely the bolt failure was due to the bolts losing torque and backing out then being broken
     
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  15. GTPerf

    GTPerf Member

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    Had rod bolt failure twice last year on GRP rods happened the first time we got talked in to the better bolt. had been running L19 bolts never had a problem. First time was with 12 passes. the 2nd time with 9 runs on the rods we really looked things over, after 2 passes we retorqued the rods went to a race made 6 passes came home pulled the pan checked the bearings all were good but bolts seemed not to be tight noticed a sliver of aluminum under the head of several bolts, torqued it back next pass broke a bolt and killed the engine. GRP said that sliver wasn't from the thread as I was thinking but it was from under the washer, so now I'm thinking the cap or washer must not have been machined properly or the washer not bottomed in the cap if after being stretched and torqued twice the washer moved enough to give me a sliver of aluminum when it moved lower in the cap. we really check that now and went back to the L19 bolt so far no problems . just thought the sliver and washer comment was interesting. Something to think about
     
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  16. Brent

    Brent Member

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    Does anyone use a go no-go gauge on their rods? I had read a post from an engine builder that said you would be surprised at how many rods that he returns because they won't pass the go no-go gauge test.
     
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  17. Mike Canter

    Mike Canter Top Dragster
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    GTPerf, that is exactly the problem. You should switch rods.

    Brent, that go-nogo reveals the problem as to what is happening. The problem is with the GRP rods you can’t stop it from stretching. That is why I recommend switching to something like R&R rods with the custom big bolts.
     
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  18. jay70cuda

    jay70cuda Active Member

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    Mike I was thinking that same thing. Why risk it? If weird anomalies are taking place then why not just switch rods. Mgp and R&R are prolly the top 2 companies. I don’t know of anyone using grp anymore. Not even my nos friends. And I got a lot of them.
     
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  19. go green

    go green New Member

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    What is the cost of the CA625 bolt upgrade on the R&R rods ?
     
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  20. turbo69camaro

    turbo69camaro Member

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    We switched to the BME rod with the bolt that goes to 125 FT LBS dropped pan after one run then every 2 and the torque stayed put .motor has 25 !/4 mile runs no issues
     
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