General engine tech -- Drag Racing to Circle Track
I have a set of Carrillo rods with SPS CARR rod bolts. I normally change out my typical ARP bolts every two or three rebuilds, but they cost about $125 a set for four rods. SPS CARR are going to cost me just about $400 for four rods (I'm in Canada, we have exchange, duty, shipping charges, etc, that you guys may not have). I hate to toss them just because I have a habit of changing rod bolts.
I went to the Carrillo web site and they say this:
Under racing conditions, we suggest that the H11 bolts be changed periodically. In comparison, the Multiphase® bolt (SPS-CARR) is designed to be a non-replacement type fastener.
I don't know the original pre-install length of these bolts. If the threads are perfect, if they stretch what they should at the right torque, how long can you use these for? This is a vintage race Cooper S engine that is turned to 7500 rpm.
When using these bolts in oval track or endurance engines I have replaced them after 1,000 hours of running time. They all still maged good but, it was just that I didn't wish to trust them after that.
Check and record the free length now. Then stretch and relax them...if any bolt stays +.001"from the free state length i would replace the entire set...
Bottm line is can you live with a chance of a catastrophic failure, over $400 worth of bolts????? If so then go for it..
“If I hit you with this you’re going to be numb, that’s why they call them numb-chucks “Si Robertson
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- Joined: Mon Oct 04, 2004 1:17 pm
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Thanks guys. These bolts have way less than 100 hours on them, so if 1,000 hours is a guideline that gives me a little confidence.
I'm happy to spend $400 on bolts if it gives me something. But I look at changing things as a risk also. I've put new parts in an engine just to have the new parts fail - then I have to ask myself if I had left the old parts in what would have happened?
Thanks for the advice about stretching them and relaxing them. I'll do that. In the end, I'll probably end up replacing them, but where do you stop? You can't just replace everything in the engine every time you have it apart. Well, you can, but then you aren't refreshing, you're building a new engine.
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