What size header tube for BB? - Chevelle Tech
Headers and Exhaust Discussion related to Exhaust systems and headers.

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post #1 of 13 (permalink) Old Feb 10th, 20, 10:25 PM Thread Starter
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What size header tube for BB?

Engine is a 454 (460), 590 hp/590 ft lbs., 4L80 (manual shift), 3.31 rear, healthy hydraulic roller cam. Heads are GMPP bow tie oval (2.19/1.88) ported by a certain builder we all know in CO. Going into 3” exhaust.

Basically, is 1 7/8” enough, or should I go to 2”?
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post #2 of 13 (permalink) Old Feb 11th, 20, 8:35 AM
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Re: What size header tube for BB?

2 inch is the way to go. You need like 700 hp or so to begin to see any real delta worth the extra hassle and cost and fitment of the 2 1/8 inch. Most have a 3.5 inch collector then you would go to your 3 inch exhaust which is great for your motor. Breakpoint for the 2.5 to 3 inch exhaust is about 500 hp. A 1 7/8 might work well also some guys might chime in that have dealt with this size.
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post #3 of 13 (permalink) Old Feb 17th, 20, 5:31 AM
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Re: What size header tube for BB?

I'd run the 1&7/8. bigger is not better.

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post #4 of 13 (permalink) Old Feb 17th, 20, 6:06 AM
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OLIVER
 
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Re: What size header tube for BB?

I ve seen an improvement at the track with a 2 over 1 and 3/4 - pn Hedman 66002
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1969 396 SS monaco orange (72)
468 Vortecpro 585 HP back to street cruiser
M20 4 speed - 3.31
Prosystems 1000
BEST ET 11.62 (with 4.10)
BEST MPH 121
BEST 60 FT 1.64
4000 lbs street car


1969 El Camino Street Strip
467 Vortecpro Tunnel ram 730+ hp TH400
BEST ET 10.67 @ 127 1.56 60FT
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post #5 of 13 (permalink) Old Feb 17th, 20, 2:19 PM
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Re: What size header tube for BB?

Oliver has a pretty gnarly Vortecpro (Mark Jones ) in his car in Italy. It's very unlikely you need those big headers.

Alternatively, you could ask Mark since you are already a customer of his. his recommendation will be dead on. Mark is the real deal.
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post #6 of 13 (permalink) Old Feb 17th, 20, 6:47 PM Thread Starter
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Re: What size header tube for BB?

I did speak to Mark about it right after the dyno run, and he said 1 7/8", but 2" would be fine also. My initial thought was indeed 1 7/8", but I thought I'd ask here just to get additional opinions - not that I don't trust Mark's implicitly. My plan was to go with Doug's headers and have them coated at Jet Hot Coatings. The engine pulled 588 foot/lbs. at 4,200, and 588 horsepower at 6,000. He and I both think it has a little more in it at my elevation (near Maple Grove). Using a Holley Terminator on top.


My first inclination was to stay at 1 7/8", if for anything to get just a tad more clearance. Will be running 3" X-pipe, and very likely 2˝" out of the mufflers.
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post #7 of 13 (permalink) Old Feb 17th, 20, 7:41 PM
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Re: What size header tube for BB?

I have a 454 around 580hp, had 2" then changed to 1 7/8". Seems to have more torque and hp feels the same as before.
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post #8 of 13 (permalink) Old Feb 18th, 20, 11:32 AM
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Re: What size header tube for BB?

Mark told me to use 2” headers when I was at his shop dynoing and picking up my engine, 467 all roller, 600/600. I bought some uncoated hedman’s and had them ceramic coated in Joplin.
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post #9 of 13 (permalink) Old Feb 18th, 20, 12:35 PM
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Gene
 
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Re: What size header tube for BB?

Bronze 68, I was there when we dyno'd that engine! all BLACK and SILVER! Glad it made it "home" ok!

Either will work fine. Look PEAK HEADER TORQUE is a minor measurement which tells you were peak "port torque" occurs in the primaries given the bore area. smaller will give you more 3000 rpm boost, larger more after 4500. That's all it is, no more, no less. So its a"secondary" optimization equation, not a primary.

I thought about "optimizing" mine to 1.875", but Mark said 2" are fine, actually preferred FOR MY APP ( maybe as it's a clutch, no stall) So i had my 2" Hookers coated a "TURD" time! In White! Smaller coated Hedmans NEW would have been cheaper.

I cant speak to lack of TQ, as you cant go WOT on street rubber with an MJ mill. Not with my race Holley, maybe with EFI you can.

They actually use the math in this article;; Math dont lie, PEOPLE do! The Correct-Sized Headers Will Give You the Best Performance

Based on that 2" works for an MJ468. Smaller only means you'll shred more rubber, earlier. But if you already had 1.875"; I'd run 'em. No headers yet - WHATEVER FITS BEST! I 'd say. But at least using the math in the article, you can bust out a calculator ( I'm not an engineer, but a numbers guy) and know where the 2" versus the 1.87" put their peak header TQ ( approximately 4500 and 3900 respectively on a 468).

Your engine likely shows peak TQ at 4400, as mine did with the same cam. So, given the math, you can dial in the headers to give you peak HEADER TQ right above the engine ( as I did, as I'll drop the clutch at 5200 to HOOK up at 4200...) or to come in just under the engine's 4400 rpm peak TQ at 3800. ( if for example you were using a 3500 or less rpm stall, flashing to the peak pipe TQ - this makes sense)

So, as Mark said, either will work, the math shows what you might expect from an A/B test.


PS I had my system pro -designed ( Dr Gas engineer), the 2" hookers feed into a 3.5" collector; then thru a 3.5" to 3" Dr Gas X pipe to 3" head pipes and 3" Magnaflow 12578s. 2.5" Torque tech ( not in biz anymore) tails finish off an engineered system for 500-700 hp, meaning it should run same with open headers.

Gene
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Be big, be a 'builder'!

Last edited by 427L88; Feb 18th, 20 at 1:03 PM.
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post #10 of 13 (permalink) Old Feb 18th, 20, 1:06 PM
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Re: What size header tube for BB?

Quote:
Originally Posted by oliver69 View Post
I ve seen an improvement at the track with a 2 over 1 and 3/4 - pn Hedman 66002
Just curious... how much of an improvement? What size exhaust behind the header?
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post #11 of 13 (permalink) Old Feb 18th, 20, 1:26 PM
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Gary
 
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Re: What size header tube for BB?

With your gear and where you're going to be driving that thing 1 7/8 is plenty and I would rather have 1 and 3/4 over 2 in. Let's put it this way if the header is you test against each other have identical Dimensions other than the primary diameter it will make as much horsepower with the 1 and 7/8 headers as it does with the 2inch headers but it will pick up torque especially down low where you are driving 90% of the time
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post #12 of 13 (permalink) Old Feb 18th, 20, 6:04 PM
 
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Re: What size header tube for BB?

heres a good video to watch that compares the 1-3/4 - 2-1/8 headers

https://youtu.be/O1bXPNy1Yn4
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post #13 of 13 (permalink) Old Feb 18th, 20, 6:19 PM
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Re: What size header tube for BB?

Quote:
Originally Posted by novadude View Post
Just curious... how much of an improvement? What size exhaust behind the header?
i ve run them both with a 18 inch collector extension ... all the exhaust and mufflers removed at the track

the collector extension is 3 inch diameter and 18inch long

I went from 115 /116 mph to 119/121 mph ( which was my best mph )
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1969 396 SS monaco orange (72)
468 Vortecpro 585 HP back to street cruiser
M20 4 speed - 3.31
Prosystems 1000
BEST ET 11.62 (with 4.10)
BEST MPH 121
BEST 60 FT 1.64
4000 lbs street car


1969 El Camino Street Strip
467 Vortecpro Tunnel ram 730+ hp TH400
BEST ET 10.67 @ 127 1.56 60FT
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