WTB Grade 8 manifold bolts - Chevy Impala SS Forum
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post #1 of 18 (permalink) Old 11-30-2018, 08:59 AM Thread Starter
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WTB Grade 8 manifold bolts

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.

1995 9c1 Impala Clone

Last edited by Henry '06; 11-30-2018 at 09:07 AM.
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post #2 of 18 (permalink) Old 11-30-2018, 09:05 AM
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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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post #3 of 18 (permalink) Old 11-30-2018, 09:27 AM
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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).

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https://i10.photobucket.com/albums/a...psvjkcsokm.jpg

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!

Last edited by 96 Black; 11-30-2018 at 10:16 AM. Reason: I saw it below
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post #4 of 18 (permalink) Old 11-30-2018, 09:54 AM
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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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post #5 of 18 (permalink) Old 11-30-2018, 10:13 AM
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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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\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!
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post #6 of 18 (permalink) Old 11-30-2018, 10:18 AM
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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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1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check https://www.impalassforum.com/vBulle...ion-parts.html
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post #7 of 18 (permalink) Old 11-30-2018, 08:56 PM
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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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Last edited by schlicky13; 11-30-2018 at 09:00 PM.
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post #8 of 18 (permalink) Old 12-01-2018, 08:37 AM
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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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post #9 of 18 (permalink) Old 12-01-2018, 10:11 AM
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Quote:
Originally Posted by schlicky13 View Post
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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post #10 of 18 (permalink) Old 12-01-2018, 11:40 AM
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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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