[cabhop]

I'm missing the medium length head bolts for a budget 350 build. I'm guessing that the factory bolts aren't anything special and I could use grade 8 bolts from Tractor Supply for the 4 that are missing. Does anyone see any issues doing this? Thanks

[Schurkey]

That's better than generic Grade 5 bolts, or leaving those four bolts out.

GM head bolts and main-cap bolts are high-quality items. I would find another set of used-but-usable OEM bolts in preference to buying cheap-junk Chinese "Grade 8" stuff. (But ya gotta do what ya gotta do.)

My GM "Standard Parts Catalog" says the GM headbolts and main bolts are made of 300M steel--good stuff indeed. The Catalog doesn't specify if the threads are rolled before or after heat-treat, or what sort of heat-treat is used. That's an advantage of ARP.

[tom s]

But they are something special!Most 1/2in grade 8 bolts are like .498 full length.Factory head bolts are smaller diameter .447.It can effect the yield of the bolt with could effect the clamping force.FWIW,Tom

[Schurkey]

Originally Posted by tom s

But they are something special!Most 1/2in grade 8 bolts are like .498 full length.Factory head bolts are smaller diameter .447.It can effect the yield of the bolt with could effect the clamping force.FWIW,Tom

Triple-important on short bolts, to promote shank stretch.

[4dblnkldude]

I could send you them. How long do they measure?

[steve25]

The factory bolts neck down under the bolt head such that they stretch and load the same amount dispite there differing length with the same 95 ft lb adjustment.
A off the self grade 5 or 8 bolt will not do that!

[61-63]

For $80 or so ARP makes a high performance headbolt kit for Pontiac engines.

[Cliff R]

The Tough Shi# Charlie's grade 8 bolts are NOT to be trusted for such things. They will not have the consistencies required to provide adequate clamping force when torqued to spec. They are fine for holding down intakes, timing covers, valve covers, etc, but I would NEVER use or recommend using them to replace main cap or head bolts.......FWIW......Cliff

[STEELCITYFIREBIRD]

Get the correct bolts!!

[dataway]

You could get quality grade 8 US made bolts ... but they would probably cost you more than used originals. (BTW .. what's the same of that US company Chromo? something like that?)
There are tons of guys on here that could send you some used OEM bolts within a few days for very easy money .... that's how I got the bolts I needed.

[HWYSTR455]

Isn't there also something specific about the head of OE head bolts? My understanding is that you can't just use 'any ol' grade 8 bolt'.

.

[dataway]

OEM head bolts have a machined surface on the bottom of the head (at least on the heads that don't use washers), that seats on a machined surface on the head.

[Bermuda Blue]

Originally Posted by dataway

You could get quality grade 8 US made bolts ... but they would probably cost you more than used originals. (BTW .. what's the same of that US company Chromo? something like that?)
There are tons of guys on here that could send you some used OEM bolts within a few days for very easy money .... that's how I got the bolts I needed.

Holo-Krome. They make some of the best fasteners available. Not cheap. .

https://www.holo-krome.com/

[Sirrotica]

In the late 70s I bought a set of 1971 #197 455 HO heads and installed them on my 1973 T/A 455 D port engine. The D port head bolts were too short so I went to the bolt and fastener store and got the right length hardened bolts with hardened washers and installed the heads with the new bolts and washers.

Now the heads were stock as was the short block so the compression ratio was advertised at 8.4 to 1 so there wasn't a ton of compression with the setup. I had no problems with sealing because I didn't know any better at the time I thought I was doing the right thing. Those heads remained on that block for over 35 years without issue.

Would I do it again today? Probably not. I realize that in the overall scheme I didn't do the correct thing, but it did work and never had any ill effects in all that time. No head gasket failure, leaks, stripped holes in the block, etc. It wasn't a race engine, although I did run it in autocross and street duty, not like it was in a grocery getter station wagon.

In the end was it correct? No it wasn't. Did it work? worked for 35 plus years, albeit with low compression.

[Skip Fix]

Not sure where HO Racing used to get their kits looked like regular grade 8 but been a few years since I built the RAIV 400 to see under the head.

So weird deal about ARP head bolts and different lengths. Edelbrock heads use ARP bolts and the early heads used different torque for different length bolts. Same kit from ARP all bolts get torqued to same setting! So who is correct.?

[cabhop]

Originally Posted by 4dblnkldude

I could send you them. How long do they measure?

Thank you for the offer! I'm sure I have them, just buried somewhere in storage. Tractor Supply was going to be the path of least resistance vs digging out a storage unit...LOL

[Scott Thelander]

4 for 20 shipped

Scott in Lacey

be there friday

[PAUL K]

Originally Posted by Skip Fix

Not sure where HO Racing used to get their kits looked like regular grade 8 but been a few years since I built the RAIV 400 to see under the head.

So weird deal about ARP head bolts and different lengths. Edelbrock heads use ARP bolts and the early heads used different torque for different length bolts. Same kit from ARP all bolts get torqued to same setting! So who is correct.?

Agree about the H-O bolts and I've used their head bolt and main bolt kits on several engines over the years, without issues.
As far as the change in torque values, according to ARP their new lube that comes in the blue packets requires the higher torque values compared to the paste that's in the white package.
If you recall the rod bolts that came with the white colored packets of paste used to have instructions to torque the bolt and back it off three times. Now with the blue lube you not longer need to do that..... according to ARP.

[pfilean]

Not really meaning to hijack the thread but all this talk has me rethinking a project.
I'm trying to add a A/C to my 61 using original compressor bracket. That requires having extra length bolts that of course didn't come with my salvage yard bracket. Like most of us I have a lot of left over bolts from old projects but no head bolts of the correct length. I have GR8 but the nearest length is 4 1/2 which could be a little shy on thread engagement. Per parts book I should have 1/2-13x4 5/8. Even if I bought a rebuild set I doubt that would be a length included..
Anyone know where individual head bolts in that length are available? I can even get by without the stud-on-head bolt that Pontiac sometimes used.

[Skip Fix]

I still think it is weird the same ARP bolts in an Edelbrock box had two different torque values vs the straight ARP bolts.