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Discussion Starter #1 (Edited)
Until I get some headers, I'd like to replace the stock manifold bolts. I remember way back, there was a set of grade 8 manifold bolts to replace the stock bolts that are prone to breaking. Wondering if anyone has a set.
 

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You should be able to get the bolts at any major screw supplier. You only need the diameter, thread pitch, and length. You could even take one of the originals with you.
 

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I got my last set at ACE Hdwe. Pretty EDIT: black phosphate. Now even the big box places have GR8s in the last few years. Be very sure to reuse all the cast steel thermo lateral spacers, except 4 in the centers which use thinner ones. Even though front bolts don't have a reputation for snapping as the rears, I've used extra long ones and jamb nuts for the PS alt bracket(s).

Overall configuration:
https://i10.photobucket.com/albums/a115/FTSS/Header%20Bolts_zpsvjkcsokm.jpg
 

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If you can hold on for a few days, I'd recommend getting flange headed bolts for this application.

I recently bought some to work with my 1998 Tahoe engine, and like to use the flange head a lot where I can.

I'd go with a zinc plated steel screw. I'm not sure on the length required offhand if they just 1" long and some use the round spacers.

I used to have a picture on Photobucket, but I think they all went away when they made it a pay service.

Anyway it's 3/8"-16, and possibly 1" long. You can probably find the information thru threads here.

Tractor supply is a great local source for fasteners, but I'm not sure if they have flange head screws.

The alternative is McMaster Carr, which you can have in your hands in 4 days.

Looking at 1" long screws, there's two choices available, one with a serrated head, Zinc Plated and the other being flat, and it's black oxide. I typically like Zinc plated as they're typically cheaper. In this application I would see no harm in using the serrated head screws, P/N: 94239A114/QTY: 10

 

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I'd be leery of serrated flange heads not allowing the the freest lateral slip of the cast collars. All lengths are 1 1/2" (IIRC), except the center 4 at 1". There was at least one account in the murky past here that someone's 1 1/2 bottomed out in the head. Then you're hunting 1 1/4", so just check and match what you remove.



But you're right there's scads of threads on this.
 

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The grade 8 bolts will be marked. Do not use standard bolts. Head type is not important as long as you can install and remove it.

Header bolts are usually shorter than OEM manifold bolts. They are usually 3/4 inch to 1 inch. The OEM bolts may be 1 1/2 inches long. The OEM manifold is about 3/4 of an inch thick. Headers have a 1/4~3/8 inch flange, and use shorter bolts. Measure your bolts for the correct length.
 

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I'm a big fan of stainless hardware, it's similar in strength to grade 8 and it won't rust. And you can definitely find flanged stainless hardware, though maybe not in local hardware stores. If you're planning on doing headers down the road though, I probably wouldn't spend the money on it since they'll require different hardware.


Edit: now that I think about it, I think stainless normally falls somewhere between grade 5 and grade 8 for strength. I still think it's probably strong enough, it's completely fine with headers, but I wonder if the different thermal properties of the stainless and cast iron could cause enough of an issue to break them with repeated heating and cooling cycles if you used them with factory manifolds. I kind of doubt it, but I'm not a metallurgist either.
 

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I do use stainless steel on my exhaust ... because it is stainless steel..

I do not recommend any stainless bolts in the exhaust manifold ... steel to steel is IMO what to use .... stainless is an alloy metal ..
 

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I'm a big fan of stainless hardware, it's similar in strength to grade 8 and it won't rust. And you can definitely find flanged stainless hardware, though maybe not in local hardware stores. If you're planning on doing headers down the road though, I probably wouldn't spend the money on it since they'll require different hardware.


Edit: now that I think about it, I think stainless normally falls somewhere between grade 5 and grade 8 for strength. I still think it's probably strong enough, it's completely fine with headers, but I wonder if the different thermal properties of the stainless and cast iron could cause enough of an issue to break them with repeated heating and cooling cycles if you used them with factory manifolds. I kind of doubt it, but I'm not a metallurgist either.

The stainless hardware found in hardware stores sometimes isn't even grade 5. I wouldn't use anything stainless unless you get it from a reputable source like ARP (or totally stainless, which seems to mainly source from ARP). With that said, those brands have stainless hardware that exceeds grade 8 specifications and is safe to use on all sorts of applications that hardware store stainless would never be safe for, like brake and suspension parts. I hear of marine engine guys using them all the time in exhaust manifolds, but those guys will also caution you not to use any sub par stainless or you will run into fatigue issues causing the bolts to eventually fail after multiple retightenings as they stretch.
 

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Henry 06, just go to your local hardware store buy identical as oem but in grade 8. That's all I did.

You'll need 3/8-16 black flange head in grade 8.I reused the original pair of stud bolts on pass side.The alternator mounting brackets go to them is why I chose to reuse them.

There's also one stud bolt on driver side but it's not used as a stud bolt so I replaced it with a regular bolt.

If you're going to do it this way here's the bolts to buy.

PAS SIDE: buy 3 in 1 1/2" length and 1 in 1" length. (reuse the 2 stock stud bolts).

DRIVER SIDE: buy 4 of the 1 1/2" length and 2 of the 1" length(assuming you're eliminating the stock unused stud bolt).

Here's couple pics of the stock bolts and spacers as removed from engine for reference if it helps to round'em up before diving into yours.

Jim
 

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The stainless hardware found in hardware stores sometimes isn't even grade 5. I wouldn't use anything stainless unless you get it from a reputable source like ARP (or totally stainless, which seems to mainly source from ARP). With that said, those brands have stainless hardware that exceeds grade 8 specifications and is safe to use on all sorts of applications that hardware store stainless would never be safe for, like brake and suspension parts. I hear of marine engine guys using them all the time in exhaust manifolds, but those guys will also caution you not to use any sub par stainless or you will run into fatigue issues causing the bolts to eventually fail after multiple retightenings as they stretch.

The stainless stuff I find is generally stamped 403, which if memory serves is a perfectly adequate grade for most stuff, but it is likely made in China so I wouldn't trust anything critical with it. For any internal engine fasteners and other safety critical applications I fully support ARP as a first choice. I currently have a list of hardware written down that I need to order from them one of these days.
 

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I ran grade 5 exhaust manifold bolts for years on my B-bodies, just changed them out every few years and never had a problem.

While you have your manifolds off, check them for flatness. On a set I'm working on right now, the outer two ports have warped away from the head. I'm having the manifolds milled flat before I reinstall them, and that should significantly help the outer bolt longevity as well.
 

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I ran grade 5 exhaust manifold bolts for years on my B-bodies, just changed them out every few years and never had a

[SNIP]
I never thought of that, just outright changing them every few years. That would pretty much solve the problem. Just making sure you install a quality replacement, and use some anti-seize on the threads as well.

+1 on the recommendation!
 

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I never thought of that, just outright changing them every few years. That would pretty much solve the problem. Just making sure you install a quality replacement, and use some anti-seize on the threads as well.

+1 on the recommendation!
using grade 5 bolts that is why you do the changing every few years IMO not good idea.

use the GM spec grade 8 steel . also GM shop manual , use a med loctite ..on the bolts .. anti seize will cause them to loosen then the gasket and converter can get messed up due to leaks.
 

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True, but it's easier to drill out a grade 5 than a grade 8 if it came to that. And if you live in a rust-prone area, it's cheap insurance to change them out every few years so you have bolts and not nubs to deal with.

Agreed on the loctite!
 
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