Author Topic: connecting rod bolt- replace every time?  (Read 1268 times)

Offline jachenbach

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connecting rod bolt- replace every time?
« on: 09.12. 2014 13:24 »
I have 2 engines to go through and one apparently new set of rod bolts/nuts. Although I'm a BMW master tech and certified on Ducati, I am very much a novice on the A10, so forgive an amateurish question: Are A10 rod bolts one time use or can they be re-used? BMW has a very specific procedure on the S1000RR= clean, torque, remove, clean, reinstall and torque to spec; some Ducatis state how many times they can be used. I haven't seen any specifies on the A10. I figured on replacing, but I'm on a tight budget. Looked them up and they're going for $90 US. Gasket set and crankshaft plugs another $100. Don't want to throw a rod due to pinching pennies, but neither do I need to spend money unnecessarily.

Online a101960

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Re: connecting rod bolt- replace every time?
« Reply #1 on: 09.12. 2014 18:00 »
Quote
Are A10 rod bolts one time use or can they be re-used?
Strictly one time use, and make sure that the replacement bolts are the right specification. They must be forged bolts with a rolled thread. Be careful because there are cut thread bolts out there, and you don't want to be using those.
John

Offline muskrat

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Re: connecting rod bolt- replace every time?
« Reply #2 on: 09.12. 2014 19:06 »
That may be technically correct but! I used the original 1957 rods and bolts in the A7SS racer and re-used them many times (at least 10 times). I had cranks snap and barrels come adrift but never a big end bolt problem. *dunno*
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Online RichardL

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Re: connecting rod bolt- replace every time?
« Reply #3 on: 09.12. 2014 23:34 »
If you use ARP rod bolts, the preferred measure of tightness is the length of the bolt. You record the length of each bolt before it is tightened. When you remove them you measure them again. If they have not stretched by 0.001" or more, then they can be reused (I'm just quoting the manufacturer). Here is the page from the ARP catalog:

http://arpcatalog.com/?src=home#29/z

My own inclination would be to believe that you could apply the same theory to non-ARP bolts and things would be fine, but I'm not an authority on the subject (or, it seems, any subject). I have billet rods with ARP bolts. The torque spec is way beyond that for normal bolts and it would be ridiculous if I had to replace the bolts just to run a Plastigage test.

Richard L.
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Re: connecting rod bolt- replace every time?
« Reply #4 on: 10.12. 2014 11:11 »
The first A series engine I rebuilt ( plunger going into small journal s/w arm cases ) still had bolts with castellated nuts and split pins , needed my old mans input has to how to get torque/ pin hole linned but that engine was bullet proof  plus I didn't know better . Nowadays i always replace the bolts ,Bob.
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Offline BSA500

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Re: connecting rod bolt- replace every time?
« Reply #5 on: 10.12. 2014 13:30 »
That may be technically correct but! I used the original 1957 rods and bolts in the A7SS racer and re-used them many times (at least 10 times). I had cranks snap and barrels come adrift but never a big end bolt problem. *dunno*
Cheers
I've had my A7 20+ years and the engine apart approx five times and I am still using the conrod bolts. The nuts on mine are  a self locking type and everytime they are undone they are still the same tightness. I don't like the look of the ARP nuts. They just look like ordinary nuts with no security to prevent them undoing(I'm sure they are fine), but if my bolts look in good condition etc I will still use them

Offline edboy

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Re: connecting rod bolt- replace every time?
« Reply #6 on: 10.12. 2014 18:53 »
personally speaking , if the rod caps come off and on nicely so the bolts are not bent i would reuse bolts. the critical part of assembly for me is if the conrods dont bind up on the crank when torqued. as already stated the snapped conrod bolt is the penultimate final stage of a process that usually begins with lubrication failure and ends with half a conrod waving to you through your drive side crankcases