How big of a header works on SBC ?
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How big of a header works on SBC ?
I was told 15 years ago headers over 1 7/8 don't help. Alot has changed since then. What about now? Oldhead
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Re: How big of a header works on SBC ?
sort of an open ended question.... on a 9:1 327, no. on a 12:1 434, probably!
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Re: How big of a header works on SBC ?
A 2.5 inch header would "work". Might not make any power though. But, the exhaust gasses would certainly get out. But, yes, I have used 2 inch and even 2 1/8 inch header on small blocks. Its more about how much total power is being made. I had a road race 327 pick up 65 hp and 38 ft/lbs going from a 1 5/8 with 3 inch collector, to a 1 7/8 with a 3.5 collector, with a dual plane intake to boot. Totally bas akwards.
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Re: How big of a header works on SBC ?
Yet that same header combo on a restricted 2bb engine looses with larger header about that same amount.Frankshaft wrote: ↑Sat Nov 11, 2017 5:59 pm A 2.5 inch header would "work". Might not make any power though. But, the exhaust gasses would certainly get out. But, yes, I have used 2 inch and even 2 1/8 inch header on small blocks. Its more about how much total power is being made. I had a road race 327 pick up 65 hp and 38 ft/lbs going from a 1 5/8 with 3 inch collector, to a 1 7/8 with a 3.5 collector, with a dual plane intake to boot. Totally bas akwards.
The options for stepped or high velocity headers when going from 1 3/4' TO 1 7/8" builds more power then a straight tube set depending on the heads and cam choice. The extra scavenging of the stepped headers helps in a smaller carb as well as a big carb engine. Just depends on the RPM range you run.
Some guys find very good luck with a 1 3/4" header and while the info is available they never go bigger because of the work involved to fit them in the chassis thus loosing out on potential gains.
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Re: How big of a header works on SBC ?
Frankshaft wrote: ↑Sat Nov 11, 2017 5:59 pm A 2.5 inch header would "work". Might not make any power though. But, the exhaust gasses would certainly get out. But, yes, I have used 2 inch and even 2 1/8 inch header on small blocks. Its more about how much total power is being made. I had a road race 327 pick up 65 hp and 38 ft/lbs going from a 1 5/8 with 3 inch collector, to a 1 7/8 with a 3.5 collector, with a dual plane intake to boot. Totally bas akwards.
I've found the same results.
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Re: How big of a header works on SBC ?
A 900hp 410 sprint car uses 1 7/8 - 2
And on some tracks the wing cars run 1 3/4" headers.
I think the extra high compression has something to do with the small headers
And on some tracks the wing cars run 1 3/4" headers.
I think the extra high compression has something to do with the small headers
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Re: How big of a header works on SBC ?
850hp Cup motors run 1 7/8” off the head. Not really a compression thing, just that most people have waaayyyyyy too large of a header. Darin Morgan shared that the Cup cars like a little bigger exhaust port than you would find on a drag car at an equal power level due to the full exhaust requirement. Just another data point to suggest most headers are way too big.englertracing wrote: ↑Sat Nov 11, 2017 8:48 pm A 900hp 410 sprint car uses 1 7/8 - 2
And on some tracks the wing cars run 1 3/4" headers.
I think the extra high compression has something to do with the small headers
The sky is the limit in header size for a SBC (literally). Lol
-Bob
Re: How big of a header works on SBC ?
I think frankshaft had a point, total power is what matters. 1200 hp creates the same waste gas regardless of displacement. The rest of the system is part of the equation as well.
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Re: How big of a header works on SBC ?
Is this supercharged?
Should be running port sized headers, then stepping from there.
Should be running port sized headers, then stepping from there.
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Re: How big of a header works on SBC ?
I see a trend in higher cr and earlier evo engines with relatively smaller headers as of latehoffman900 wrote: ↑Sat Nov 11, 2017 9:32 pm850hp Cup motors run 1 7/8” off the head. Not really a compression thing, just that most people have waaayyyyyy too large of a header. Darin Morgan shared that the Cup cars like a little bigger exhaust port than you would find on a drag car at an equal power level due to the full exhaust requirement. Just another data point to suggest most headers are way too big.englertracing wrote: ↑Sat Nov 11, 2017 8:48 pm A 900hp 410 sprint car uses 1 7/8 - 2
And on some tracks the wing cars run 1 3/4" headers.
I think the extra high compression has something to do with the small headers
The sky is the limit in header size for a SBC (literally). Lol
Like mentioned world of outlaws tuning a 1.75" header
And street cars with low cr late evo wanting relitavely larger headers
Like some 450hp thing wanting a 1.625 or 1.75" header.
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Re: How big of a header works on SBC ?
Eh, still not sure. You see engines with that power in prep restricted classes running 1.5” tubing off the head. I’m talking 2bbl circle track engines and the “stock” type drag classes. Of course, this is a custom built header following everything Calvin preaches in terms of flow.englertracing wrote: ↑Sun Nov 12, 2017 2:20 amI see a trend in higher cr and earlier evo engines with relatively smaller headers as of latehoffman900 wrote: ↑Sat Nov 11, 2017 9:32 pm850hp Cup motors run 1 7/8” off the head. Not really a compression thing, just that most people have waaayyyyyy too large of a header. Darin Morgan shared that the Cup cars like a little bigger exhaust port than you would find on a drag car at an equal power level due to the full exhaust requirement. Just another data point to suggest most headers are way too big.englertracing wrote: ↑Sat Nov 11, 2017 8:48 pm A 900hp 410 sprint car uses 1 7/8 - 2
And on some tracks the wing cars run 1 3/4" headers.
I think the extra high compression has something to do with the small headers
The sky is the limit in header size for a SBC (literally). Lol
Like mentioned world of outlaws tuning a 1.75" header
And street cars with low cr late evo wanting relitavely larger headers
Like some 450hp thing wanting a 1.625 or 1.75" header.
As Calvin has pretty much said here before, most headers are so bad, that bigger tubing works because you’re really just trying to minimize pumping losses at that point.
I’ve seen Calvin’s headers support ~60hp/cyl with 1 3/8” tubing off the head, and ~75hp/cyl with 1 5/8” tubing off the head.
-Bob
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Re: How big of a header works on SBC ?
That’s true, but assuming the same VE in both cases, for the same hp a large capacity engine would turn proportionally lower revs and push out an inversely larger slug of exhaust each cycle.
Re: How big of a header works on SBC ?
Larger slug but more time to get rid of it
Bigger duration can use a smaller pipe just like with itb you can make more hp with smaller runner diameter if the cam duration is higher.
The higher the rpm the shorter the pipe the smaller it can be for the same losses.
Bigger duration can use a smaller pipe just like with itb you can make more hp with smaller runner diameter if the cam duration is higher.
The higher the rpm the shorter the pipe the smaller it can be for the same losses.