Main bearing cap bolts - ZR-1 Net Registry Forums

tpepmeie · 05-10-2009

Howdy gents,

Reading the FSM, it appears that the main cap bolts are Torque to Yield, and are recommended to be replaced after use. Is this, in fact, the case?

If so, where is the best place to get replacement bolts (2-bolt motor)? Are there any upgraded bolts or studs? I know Bill K used to sell the stud kit, but I think it required some machining of the block and loss of the alignment dowels.

Thanks in advance,

Todd

93 #411

phrogs · 05-10-2009

good luck finding some.

I have been searching for a while for my spare motor, try kurt he has some of them but I am missing the washers as well and he doesnt have those I think he might have the main cap bolts.

I don't think they must be replaced

Polo-1 · 05-10-2009

Sent you a pm

flyin ryan · 05-11-2009

Quote:

Originally Posted by Polo-1

Sent you a pm

This will be good

A26B · 05-11-2009

Todd,
I had this very discussion with Graham last year at BG. You were there too, sure wish you had been there for the talk-about.

Summary: Torque to yield doesn't actually mean the bolt exceeded yield strength and suffered permenant deformation which would occur if yield had been exceeded. The differential thermal expansion rates of steel & aluminum would however, place additional longitudinal stress on the bolts, for which no empirical data was ever obtained. It could be calculated but would probably assume "0" deformation under the bolt head or through the thread engagement.

Bottom line: Graham didn't think there would be any adverse results from reusing them. FWIW, this same line of thinking also applied to the head bolts.

He also went on to say that he was opposed to increasing the main bolt dia because of the possibility of encountering casting porosity during the bolt thread enlargement. It would be difficult to determine and would result in potentially catastrophic results.

Having said all of this, I feel confident that Graham was probably thinking along the lines of a stock or mild rebuild. Considering what you are doing, this bit of info probably doesn't have much value to you, except for the larger main bolts/studs.

flyin ryan · 05-11-2009

Quote:

Originally Posted by A26B

He also went on to say that he was opposed to increasing the main bolt dia because of the possibility of encountering casting porosity during the bolt thread enlargement. It would be difficult to determine and would result in potentially catastrophic results.

I agree, need to have the meat in the casting first. If the surrounding material isn't there...

tpepmeie · 05-11-2009

Quote:

Originally Posted by Polo-1

Sent you a pm

Kevin, thanks.

rkreigh · 05-11-2009

Quote:

Originally Posted by A26B

Todd,
I had this very discussion with Graham last year at BG. You were there too, sure wish you had been there for the talk-about.

Summary: Torque to yield doesn't actually mean the bolt exceeded yield strength and suffered permenant deformation which would occur if yield had been exceeded. The differential thermal expansion rates of steel & aluminum would however, place additional longitudinal stress on the bolts, for which no empirical data was ever obtained. It could be calculated but would probably assume "0" deformation under the bolt head or through the thread engagement.

Bottom line: Graham didn't think there would be any adverse results from reusing them. FWIW, this same line of thinking also applied to the head bolts.

He also went on to say that he was opposed to increasing the main bolt dia because of the possibility of encountering casting porosity during the bolt thread enlargement. It would be difficult to determine and would result in potentially catastrophic results.

Having said all of this, I feel confident that Graham was probably thinking along the lines of a stock or mild rebuild. Considering what you are doing, this bit of info probably doesn't have much value to you, except for the larger main bolts/studs.

I was there and overheard this discuss at JVDs. graham is the man. he also didn't think studs were all that hot either as the bottom end is plenty beefy.

you can magnaflux the bolts, but I would chase the threads, lube em up and reused them. you should be fine.

Polo-1 · 05-11-2009

Quote:

Originally Posted by A26B

He also went on to say that he was opposed to increasing the main bolt dia because of the possibility of encountering casting porosity during the bolt thread enlargement. It would be difficult to determine and would result in potentially catastrophic results.

Quote:

Originally Posted by flyin ryan

I agree, need to have the meat in the casting first. If the surrounding material isn't there...

Also these are " formed " or " rolled " threads NOT cut threads. The blocks are threaded to the bottom of the holes.

10-10-2009

So how many folks have done a rebuild with old bolts and how many folks with new bolts only? I have never had issues in the past with SBC or BBC rebuilds using the old bolts.

05-10-2009	#1
tpepmeie Join Date: Aug 2005 Location: Fishers, IN Posts: 815	Main bearing cap bolts Howdy gents, Reading the FSM, it appears that the main cap bolts are Torque to Yield, and are recommended to be replaced after use. Is this, in fact, the case? If so, where is the best place to get replacement bolts (2-bolt motor)? Are there any upgraded bolts or studs? I know Bill K used to sell the stud kit, but I think it required some machining of the block and loss of the alignment dowels. Thanks in advance, Todd 93 #411

05-10-2009	#2
phrogs Join Date: Jul 2004 Location: Kalamazoo MI Posts: 1,753	Re: Main bearing cap bolts good luck finding some. I have been searching for a while for my spare motor, try kurt he has some of them but I am missing the washers as well and he doesnt have those I think he might have the main cap bolts. I don't think they must be replaced __________________ JOHNNY P Currently own 90 ZR-1 #845 DRM 500 engine package 90 #226 Parts car Hit me up if you need anything.

05-10-2009	#3
Polo-1 Join Date: Sep 2005 Location: Washington Posts: 955	Re: Main bearing cap bolts Sent you a pm

05-11-2009	#5
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,394	Re: Main bearing cap bolts Todd, I had this very discussion with Graham last year at BG. You were there too, sure wish you had been there for the talk-about. Summary: Torque to yield doesn't actually mean the bolt exceeded yield strength and suffered permenant deformation which would occur if yield had been exceeded. The differential thermal expansion rates of steel & aluminum would however, place additional longitudinal stress on the bolts, for which no empirical data was ever obtained. It could be calculated but would probably assume "0" deformation under the bolt head or through the thread engagement. Bottom line: Graham didn't think there would be any adverse results from reusing them. FWIW, this same line of thinking also applied to the head bolts. He also went on to say that he was opposed to increasing the main bolt dia because of the possibility of encountering casting porosity during the bolt thread enlargement. It would be difficult to determine and would result in potentially catastrophic results. Having said all of this, I feel confident that Graham was probably thinking along the lines of a stock or mild rebuild. Considering what you are doing, this bit of info probably doesn't have much value to you, except for the larger main bolts/studs. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

10-10-2009	#10
HAWAIIZR-1 Guest Posts: n/a	Re: Main bearing cap bolts So how many folks have done a rebuild with old bolts and how many folks with new bolts only? I have never had issues in the past with SBC or BBC rebuilds using the old bolts.