Header flange thickness. I have a question.
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Safety Car
Joined: Oct 1999
Posts: 3,514
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Header flange thickness. I have a question.
Let's assume for a moment I was having a custom set of stainless headers made. The standard flange was 1/4" but if I wanted to pay an extra $100 I could get 5/16" or even 3/8" flanges. Do you think it's worth it going to 3/8". Personally I think so.
Any thoughts?
[Modified by CRUZMISL, 9:14 AM 4/18/2002]
Any thoughts?
[Modified by CRUZMISL, 9:14 AM 4/18/2002]
Burning Brakes
Joined: Oct 2001
Posts: 1,054
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From: Cape Coral Florida
Re: Header flange thickness. I have a question. (C5Noir)
I asked Lou at LGM about flange thickness and he claims with
stainless 1/4 " is all that is needed. I hope he's right because
I bought a set of his headers and that's all they are.
stainless 1/4 " is all that is needed. I hope he's right because
I bought a set of his headers and that's all they are.
Le Mans Master
Joined: Apr 1999
Posts: 7,820
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From: Burlington ON
Cruise-In I, II, III, IV & V Veteran
CI-I & II Auto-X Champ
Re: Header flange thickness. I have a question. (CRUZMISL)
If the headers are supported at another location than just the head, then 1/4" should be fine. However, if where the headers bolt to the head is the only support for the headers, and basically the whole exhaust system all the way back to the mufflers, then I would definitely go with the 3/8".
My TTS headers have 3/8" flanges where they bolt to the head, and on the collector.
[Modified by MattG, 11:18 AM 4/19/2002]
My TTS headers have 3/8" flanges where they bolt to the head, and on the collector.
[Modified by MattG, 11:18 AM 4/19/2002]
Premium Supporting Vendor
Joined: Oct 2001
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From: Dallas Tx
St. Jude Vendor Donor '03-'04-'05-'06-'07-'08-'09-'10-'11
Re: Header flange thickness. I have a question. (MattG)
Hi Guy,
Here is the issue. It is the 1300 to 1500 degrees that the header flange sees that is the problem. Mild steel has less capacity to withstand that temprature. So there is a need to be thicker. Stainless steel, especially 304 alloy, can take those temps without any distortion, and thus requires less thickness.
The stainless also can be cherry red and not loose the characteristics that the 304 alloy was made to exhibit. The mild steel goes through structural changes to a much greater degree, and to maintain it's shape must be thicker.
Now, after saying all that, I would say that it can't hurt to go with a 5/16" flange, even with Stainless, but it is not necessary.
Thanks,
Lou Gigliotti LG Motorspsorts
Racer
Joined: Feb 2001
Posts: 286
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From: Bayville NJ
Re: Header flange thickness. I have a question. (CRUZMISL)
It's got nothing to do with support. I have made inserts for the last two Chevy motors I built, filling the 3/8-16 holes and using 1/4-20 bolts to attach the headers. A 1/4 flange is plenty strong enough to support the exhaust system.
It's got nothing to do with heat. Mild steel (or any other kind) is not going to droop at 1300°F. This is one of the funniest answers I've ever read on this BB.
It's a function of one thing alone - clamping load support. With a soft composition header gaskets like found on cars for decades, the header flange must be thick enough to resist distortion due to clamp loads at the bolts and pressure from the gasket between the bolts. This tends to warp the flange into a wavy shape. The stainless steel gaskets on the LS-1 are a positive lock type. There is a ridged "o-ring" stamped into the gasket. When compressed, it's flat. The clamp load cannot squish the gasket out like the old soft gasket arrangement. This requires much less flange than older styles. If your using the OEM gasket (which you should for this reason and others that I don't have time to get into), I think 3/16 is enough flange, 1/4 is plenty. If using soft aftermarket gaskets, make them at least 3/8 (7/16 would be better).
It's got nothing to do with heat. Mild steel (or any other kind) is not going to droop at 1300°F. This is one of the funniest answers I've ever read on this BB.
It's a function of one thing alone - clamping load support. With a soft composition header gaskets like found on cars for decades, the header flange must be thick enough to resist distortion due to clamp loads at the bolts and pressure from the gasket between the bolts. This tends to warp the flange into a wavy shape. The stainless steel gaskets on the LS-1 are a positive lock type. There is a ridged "o-ring" stamped into the gasket. When compressed, it's flat. The clamp load cannot squish the gasket out like the old soft gasket arrangement. This requires much less flange than older styles. If your using the OEM gasket (which you should for this reason and others that I don't have time to get into), I think 3/16 is enough flange, 1/4 is plenty. If using soft aftermarket gaskets, make them at least 3/8 (7/16 would be better).
