Have a Look. What Would You Do?

[Don L.]

Hello all.

I am in the process of completing a complete cylinder head refurb/valve job on my 1972 L48 engine this winter. The machine work is complete and I'm preparing to re-assemble the engine. I've been advised by some to re-use my original head bolts. I'm not so sure.

The back story:
I bought this car in 2005 as a body-off restored car. I've successfully campaigned it as a National Top Flight car. I have receipts showing it had an engine rebuild and valve job in 1999-2000. Based on observation, the bolts look to be re-used originals. I'm now faced with either using these bolts again or buying new bolts. See the attached photo of one of the bolt's threads. This photo is quite indicative of the rest of the set. Considering that they've likely been re-torqued once already, and considering that the threads at the end of each bolt is somewhat compromised, I have considered replacing the bolts this time. What concerns me is that because I am interested in replicating factory appearance as much as I can, I consider reproduction bolts from one of the reproduction parts houses that we all know. Should I trust these replacement bolts as true high quality grade 8 bolts? Should I re-use the original bolts? Should I buy known quality bolts like ARP, realizing/accepting they won't be typical for normal GM production? I prefer the reproduction bolts, however, I worry about their true quality and performance.

Inputs and/or ideas will be most appreciated. Thanks in advance.

[Rick R.]

Re: Have a Look. What Would You Do?

I'd use the ARP bolts.

[Gary R.]

Re: Have a Look. What Would You Do?

I'd use the ARP bolts.

I wouldn't use that bolt and would also go with ARP

[Bob W.]

Re: Have a Look. What Would You Do?

Don, I to would go with the ARP bolts . They are the best.

Bob

[Steven B.]

Re: Have a Look. What Would You Do?

I've done my 2X4 and L-82 both with ARP.

[Patrick H.]

Re: Have a Look. What Would You Do?

You could always contact Paragon, see if they actually have the bolts manufactured for them (as opposed to buying them from another vendor) and what specs they use, if you really want new original-appearing bolts. IF they have them made, I suspect they use original specs.

[Don L.]

Re: Have a Look. What Would You Do?

You could always contact Paragon, see if they actually have the bolts manufactured for them (as opposed to buying them from another vendor) and what specs they use, if you really want new original-appearing bolts. IF they have them made, I suspect they use original specs.

Had considered that but wanted to solicit the minds here first. I'd want to talk to one of the techs there though vs. the sales people. I also plan to talk to my local Chevy dealer. Who knows, they may still be available there...

[Edward J.]

Re: Have a Look. What Would You Do?

Don, I would not use this bolt, I do not know if this is the only bolt you need but if it is let me know I am sure I can find one or more in my shop, let me know the length and Pm me your address and I can send .

[Patrick H.]

Re: Have a Look. What Would You Do?

If you stop by a facility that does engine rebuilds, odds are you can find bolts with original headmarks in far better condition laying around in their scrap pile. GM only made millions of these things yearly.

[Duke W.]

Re: Have a Look. What Would You Do?

Hello all.

Considering that they've likely been re-torqued once already, and considering that the threads at the end of each bolt is somewhat compromised, I have considered replacing the bolts this time..

It looks like corrosion damage to me. Some of the SB head bolts penetrate the cooling jacket and should be installed with a sealer, so the first couple of threads are not stressed, but are subject to corrosion if cooling system maintenance, namely periodic antifreeze replacement, is poor.

Duke

[Mark E.]

Re: Have a Look. What Would You Do?

If you stop by a facility that does engine rebuilds, odds are you can find bolts with original headmarks in far better condition laying around in their scrap pile. GM only made millions of these things yearly.

Be careful with used head bolts. They are designed to stretch when torqued, and may be compromised (deformed) if over torqued or reused.

[Gary R.]

Re: Have a Look. What Would You Do?

Be careful with used head bolts. They are designed to stretch when torqued, and may be compromised (deformed) if over torqued or reused.

I am moving my shop now and just a week or so came across some original head bolts that appeared to be good- probably why I kept them but I tossed them for the reason Mark mentions. They were most likely fine but I figure when I go through the 350 going into my 69 I am not going to use old bolts. To me I would rather have a known proven part over a possibly lesser part that looks correct. I know I am going against the grain but that's how I have always built my cars.

[Duke W.]

Re: Have a Look. What Would You Do?

Be careful with used head bolts. They are designed to stretch when torqued, and may be compromised (deformed) if over torqued or reused.

All bolts stretch when torqued. It's a matter of whether the elongation is in the elastic or inelastic range. Vintage small block head bolts stretch within the elastic range, and can be reused if not damaged. Some modern engine head bolts elongate into the inelastic range, but may be reused as long as the elongation does not exceed maximum specification.

Duke

[Don L.]

Re: Have a Look. What Would You Do?

Don, I would not use this bolt, I do not know if this is the only bolt you need but if it is let me know I am sure I can find one or more in my shop, let me know the length and Pm me your address and I can send .

Thanks! You've got mail...

[Patrick B.]