Stretch con rod bolts.

[mattcfish]

My vanagon motor with only 20,000 miles on it just exploded. I through two rods simultaniously because of snapped stretch style con rod bolts. All Vanagon rebuilders warn against using them, because this is the end result. Early 1.9L vans used a non-stretch bolt that doesn't snap.
Here's some good reading and frightening pictures.
http://www.thesamba.com/vw/forum/viewto ... sc&start=0
Needless to say, this is going to delay my 1000cc Power Kit upgrade/valve train upgrade on my 90/6. I've got the parts, but I won't have the time for awhile.
My question is...why are stretch bolts used on BMW cranks, and why don't they have the same kind of failures that the Vanagons have? Is there a fool proof method for installing them so they aren't over stressed?

[Garnet]

BMW seems to use better rod bolts and never has had much of a problem with them. Even in the cars they where never an isue.

On your Vanagon check out Gowesty. They have custom rod bolts made by ARP. They use them on all their engines including thier 2.5L strocker. They had a lot of problems with the stock VW ones.

[Frog]

My vanagon motor with only 20,000 miles on it just exploded. I through two rods simultaniously because of snapped stretch style con rod bolts. All Vanagon rebuilders warn against using them, because this is the end result. Early 1.9L vans used a non-stretch bolt that doesn't snap.
Here's some good reading and frightening pictures.
http://www.thesamba.com/vw/forum/viewto ... sc&start=0
Needless to say, this is going to delay my 1000cc Power Kit upgrade/valve train upgrade on my 90/6. I've got the parts, but I won't have the time for awhile.
My question is...why are stretch bolts used on BMW cranks, and why don't they have the same kind of failures that the Vanagons have? Is there a fool proof method for installing them so they aren't over stressed?

Sorry to hear.

If it makes you feel any better, reading your post made me go buy new bolts...today. I was planning to put my engine back together tonight....and had not planned to replace them. I am now going to.

Thank you

[Garnet]

Back to your orirginal question "why are strectch boltsd used?" I don't know, I'm not enough of an engineer (heck I can't even spell).

I do remeber mechanics asking for rod bolts for BMW cars back in the 70s "cause you can't reuse them", and thought that was stupid because we reused rod bolts all the time on other engines. But I never saw them fail.

I reused the rod bolts on my R100/7 in about 1980 and put another 35,000 miles on it before I sold it. I now understand what happens to stretch bolts or commonly called "torque to yeild" bolts and repace them as required.

PS:don't read my post about drive shaft bolts in "Oh the Horror"

[Chuey]

Man, you'd think rod bolts would be something that is just plain "worked out".

GoWesty engine working fine with forty thousand miles on it. A couple of guys at GoWesty have airheads. They ride mountain bikes too. It's fun for me to go there; like minded souls.

Chuey

[vanzen]

No problem with my V-dub rods ... or any BMW ones.
Mountain bicycles will still be too dangerous for me –
even if there aren't any mountains around these parts :o

[ME 109]

I'm a mountain bicycle man. I love mount'n bicycle women.

[Major Softie]

I'm a mountain bicycle man. I love mount'n bicycle women.

As a friend mumbled as we passed a particularly attractive bicycle woman: "Oh, to be a bicycle seat..."

[ME 109]

As a friend mumbled as we passed a particularly attractive bicycle woman: "Oh, to be a bicycle seat..."

The vast majority of bicycle seats are damned to a life of hell!

[Major Softie]

As a friend mumbled as we passed a particularly attractive bicycle woman: "Oh, to be a bicycle seat..."

The vast majority of bicycle seats are damned to a life of hell!

That possibility dawned on me as well.