ARP rod bolt problem

X

xCountryGuy04x

I FIX CATS!!!!!!!
I know a lot of you have arp rod bolts installed. Well, I just got off of the phone with the machine shop. He said the arp bolts lack enough thread to tighten down on the cap. 1/16'' he says. And wasn't just 1 rod, they tried on all of them. I spoke with an arp rep, and he seemed very arrogant, like they never make a mistake. He is supposed to call me with their dimensions of what they are supposed to be. But I haven't heard from him yet. Another wrench in my already tight deadline. Anybody else ever ran into or heard of this? Rods are stock common rail fracture cap rods if it matters......
 
Well. There are two different rod bolts.
3900919 are for the older rods. They measure MJ11 X 1.25 X 26
4891179 are for the cracked cap rods. I can't find the size on those.
 
I just thought it would be cheap insurance. Not worth the investment? Arp lists them to fit 89-07. Plus, instead of buying new, 1 time use torque to yield bolts, i would buy something i Could use a few times.
 
xCountryGuy04x said:
I just thought it would be cheap insurance. Not worth the investment? Arp lists them to fit 89-07. Plus, instead of buying new, 1 time use torque to yield bolts, i would buy something i Could use a few times.
Click to expand...

It's a nice thought, but how often are you taking your rod caps off?
 
Snedge said:
Well. There are two different rod bolts.
3900919 are for the older rods. They measure MJ11 X 1.25 X 26
4891179 are for the cracked cap rods. I can't find the size on those.
Click to expand...

4891179's are 57mm

the 3900919's I have in my hand are 58mm........
 
Arp did call me a little bit ago. He said the R&D dept said that the rod they designed them for was a machined cap rod, not fractured. So, I guess, thats where the problem lies. He said R&D was ordering 2 fractured cap rods as we speak. 1 to measure, and another for destructive testing, to see if they are worth making bolts for.
 
xCountryGuy04x said:
I just thought it would be cheap insurance. Not worth the investment? Arp lists them to fit 89-07. Plus, instead of buying new, 1 time use torque to yield bolts, i would buy something i Could use a few times.
Click to expand...

I've reused rod bolts on every CR I've rebuilt. Never had a problem.
 
xCountryGuy04x said:
I did make mention that they were weaker than the 12 valve rods. Might as well as told him in pig latin




I have reused a lot of torque to yield bolts too. But reusing them in a rotating assembly, I don't think i could ever bring myself to do.
Click to expand...

Just finished another one yesterday.
 
Every single b series engine ever built has "used" tty
Bolts in it. They were torqued once to machine the rod, and a second time to assemble a engine. Most don't realize that bolts are stronger the second time they are torqued than the first time around. We've been on that fine line, where the bolts torqued once pulled apart, and the ones that were cycled and re torqued held up.
 
xCountryGuy04x said:
I did make mention that they were weaker than the 12 valve rods. Might as well as told him in pig latin




I have reused a lot of torque to yield bolts too. But reusing them in a rotating assembly, I don't think i could ever bring myself to do.
Click to expand...


Show me a stamping on the bolt that indicates they are TTY. Just because its tq+angle doesn't mean its TTY.

When I was at CTC we reused mains/rods/head bolts all the time, and trust me, those engines don't live easy lives.
 
9724VF350 said:
Every single b series engine ever built has "used" tty
Bolts in it. They were torqued once to machine the rod, and a second time to assemble a engine. Most don't realize that bolts are stronger the second time they are torqued than the first time around. We've been on that fine line, where the bolts torqued once pulled apart, and the ones that were cycled and re torqued held up.
Click to expand...

Agreed, but it's barely more. If a bolt is rated at 100ksi, you might get it up to around ~104ksi. Plus if you go past the yield stress, it drops off really quick and you get failure even if you anneal it.

07.gif



EDIT: To explain the chart. Linear Elastic means bolt stretch that will 100% return to stock when the pressure is let up. Plastic Deformation means that the bolt will stay stretched after pressure is let up, but will still spring back a little. Plastic deformation can strengthen the bolt, but just barely, and going too far is easy and will cause failure.
 
Last edited:
I also agree, but it made the difference between spitting a rod out on a 100% new ULSS tractor on 1 hole, and the other 5 staying hooked to the crank. No, we should have not been that close to the edge anyhow.
 
9724VF350 said:
I also agree, but it made the difference between spitting a rod out on a 100% new ULSS tractor on 1 hole, and the other 5 staying hooked to the crank. No, we should have not been that close to the edge anyhow.
Click to expand...

That's fair. If it works, it works! Just sharing what I know.
 
You must log in or register to reply here.
Back
Top