engine and drivetrain STRETCH BOLTS, cont'd & a simple question . . .

[TimNC]

OK, I just got through the wealth of info. about stretch bolts in the recent post below . . . But as I am into my first basic M10 engine rebuild the $100 questions is (literally) . . . do I need to replace the crank main bearing bolts and/or the head bolts when I put my M10 engine back together? If so what are the bolt specs and best source? Thanks in advance to the experts for their advice. TC

[Pierre]

(nt)

[TimNC]

What about the 10 bolts that attach the crank main bearing casings to the block, can they be reused?

[c.d.iesel]

having a motor apart and asking if one should reuse 30

year old abused hardware is .........???? .

Like wondering if the old oil pump should be re-used also?

A hack can elect to use any questionable parts in a rebuild

and the value, reliability, power, and safety are in the toilet.

A trained technician will not reuse old stretched, over tightened, rusty,

weak threaded, oxidized, out of true, overheated, 30 year old

parts. It's just not right. It's clearly spelled out in any factory repair manual not to reuse critical high stress hardware.

have fun

[mikekoch]

OK, OK. We know that the concensus seems to be that you should not reuse the main bolts, but who has them?

I just called a local parts house and they said all they can get is a set special order from ARP for 107.99. I doubt this place even knew what I was talking about, they are easily confused when I say "1971" and "2002" in the same sentence.

So, I called Rasmussen BMW in Portland and was told that the two longer ones are NLA, but that I could get the remaining 8 for a total of 23.20 including washers. Their mechanic who specializes in the older engines said that the main bolts could be reused.

Kuni BMW in Beaverton confirmed the NLA status of the two center bolts. I was quoted 1.40 each for the other 8, without washers.

Is anyone aware of any parts places with online ordering that stock the bolts that we need? Any other sources?

Thanks

Mike

[TimNC]

Mike, just like you, I have discussed the issue of recycling components when tearing into these M10 engines and I have gotten varying and even conflicting opinions from "those who know". Which is why, after seeing the "stretch bolt" essay, I posted the question about recycling the head and crank bolts in the first place . . . and immediately two conflicting opinions surfaced. One said it is OK to reuse head bolts and the other said throw everything away and buy all new stuff. But from what I am learning, both are probably correct in their thinking . . . . to C.D.'s point you certainly want to replace things like a thirty year old oil pumps and timing chains. But as for things like hardened steel head bolts and crank cap bolts on these stock M10 engines, the more opinions I get the more I hear it is OK to put the same bolts back where they came from unless there is some visible damage or signs of real abuse. So, I am replacing the oil pump/chain, timing components, etc., but I am recycling the head bolts and crank cap & connecting rod bolts. If you need new bolts, Bavarian Autosport, 2002AD and others sell'em on line.

[Guest Anonymous]

Given the NLA status of the middle middle bolts I was planning on recycling those anyway, and will probably order the other 8 from BMW. I've been to both bavauto.com and 2002ad and didn't see main bolts. Have checked bimmerpartswholesale, autohausaz, ireland, racetep and others as well with no luck. That's more or less why I am asking if anyone else knew of an online source as I am sure there are resource I am not aware of. Again, that is for main, not head bolts. I'll be replacing the head bolts.

When this is said and done I'll be more into engine parts than what I spent on the car, if not there already! No surprises there though. Wait, I bought pistons and a new Schrick 292, defintely well beyond it right now with all the Ireland stuff. Still have to pay the machine shop. Ouch

My wife is getting wary of all the boxes arriving at the house. I just remind her how much fun it will be... no really.

Mike

[Guest Anonymous]

As for vendors with parts not listed on the web sites . . . call'em on the phone. Usually one or the other will have'em. And don't worry too much about explaining the boxes arriving at your door step . . . it could be worse, a lot worse, you could be out "with the boys" drinking, gambling and chasin' women, right? That's the way I'd spin it.

[TobyB]

unless something bad has happened.

Think about it. It's just NOT crap, they are very good bolts that aren't overstressed. Even in a race car.

In 1973 Hans torqued the main bearings up. NOTHING HAS MOVED SINCE! The bolts were put into elastic tension, and there they have remained!

They're probably in better shape than the NOS bolts that have been banged around in a bag in the back of Schultz's Speed shop...

That's even true of the rod bolts- but they're a lot closer to the elastic limit than the mains or head bolts- and also easily obtainable- so there, I agree, spend the $40.

Now, if there's galling, bottoming and especially rust (usually on the head bolts) then it's worth changing them.

For perspective, look at the hardware on the average small block Chebby. Even assuming that the metallurgy is the same, there are an equal number of SMALLER fasteners holding that Chebby together. And they usually DO hold together.

So if you're super- paranoid, sure, spend the extra bucks. Me, I'd rather spend that money on a good dynamic balance instead. Or heck, a set of ARP studs, which DO have some merit...

that's me.

t