Technical > Matt Shaff's Engine Shop

Pulled threads on #3 main

(1/4) > >>

H.G. Wells:
Looking for some guidance from those that have experience with this.
Putting new bearings in a cast iron block BBC. Has ARP studs and when I went to torque #3 main one of the outer studs pulled the threads out.  Looks like some of them were already rusty and on their way out.  Thought I would helicoil it till I realized that one went into an oil passage and I did not trust myself to get all the little crunchy parts out if I drilled and tapped it.  I have not disassembled the motor yet.   Thought about stuffing a piece of hose thru the outer galley plug and making sure not to drill into it, but wonder how many other threads are about to go. 

Will a heli coil hold or do I go with a timesert or one of the better pieces?
Pull the whole thing apart and take it to a machine shop and have them check all the holes? One of the inner holes thread did not look so hot either.

This is on a blown 496.

wideopen231:
IMO the best thing you can get will not be enough.Not saying don't repair just go with the very best thing you can get. heil coil would not be my first choise. With the cost of building a motor why skimp on somethine as important as holding the crank in place.

ricardo1967:
That always sucks, even more when the engine is already assembled. It happeded to me a few years ago, when I was assembling a block bought used. It stripped two or three outer threads, the outter (angled) bolts we just too short. It didn't hit oil gallery though. I did prefer Time-Serts, but actually chose Helicoil to expedite the fix. It's working well since. I did replaced the allen bolts to the longest ones that would fit (for more thread engagement). I did torque it with a wrench, but didn't trust the torque reading though, because the Helicoil is more 'grabbing' that the original parent metal (cast iron).

dreracecar:
OK , dont get on me for this, 2 bolt or 4 bolt????

Timeserts offer longer engagment contact in both the block and on the stud threads.

H.G. Wells:
4 bolt factory, not splayed.
I know the correct answer is to strip it, take it to the machine shop and have it and any of the questionable ones redone with good time sert or other aircraft quality fastener  and then flush out the block and not use helicoils. But we have a race the end of May that we would like to make and if we do this there is no way we will make it. Other side says do not risk catching garbage and screwing up a really nice high dollar crank, rods, etc.

Can it be done by hand with the block upside down and the oil passage blocked off somehow and the motor still assembled?
this block has had several of the head bolts helicoiled so I am loosing faith in the integrity of the other threads.

Navigation

[0] Message Index

[#] Next page