BBC 427 header size?

[patrickonb]

OK, so I hadn't started thinking too much about header size/length/etc. until last night.
After reading a couple of articles about it, I've come to the conclusion that it could be
pretty critical for the outcome of the situation. Unfortunately, the only articles I've found
with any real "facts-n-figures" were all dealing with engines that were 500ci and larger.

What I'll be running:

BBC (427 .030+ over)
about 12.5:1 comp.
781 heads
Carb 750 methanol
6500+/- rpm

This will be drag race only, no street driving.

Look forward to your suggestions.

Thanks,
Patrick

[mag2555]

1 7/8" primary tubs 35.5" long and all 4 tubes within 2" of that max lenght.
A good merge collector and a 16" long extension which should be tweaked.

[Bigchief632]

2 inch. For a drag only car, which I'm assuming you will have a reasonable converter and maybe a trans break? But with any reasonable converter and the gear ratio it should have, the extra horsepower at the higher rpm, the slight loss of TQ it'll be faster with the 2 inch. Not earth shattering difference, so either or, whatever you can find that fits the car and your budget. And because it's on methanol, 2 inch without a doubt.

[1980RS]

Hi, welcome to the site. I have one example for you and it dates pretty far back but it relates to your question on headers with a 427 BBC. A good friend of mine years ago who still has his homebuilt L-88 427 that he made from over the counter GM parts. When he got the car done and was in the market for headers he went to Headers by "ED" and Ed got them right for him. Ed made his tubes 1 7/8" and told my buddy that's the biggest you should go on this engine and Ed also use a smallish collector that only used a 3" opening. This 427 Camaro was the car to beat in out town for almost 30 years until the big inch engine guys started to show up and even on the street some of then had their hands full with his car. Sadly one day as my buddy was going to a car show he hit a man hole cover and ripped those headers all to sheet and had to get some new ones. Ed's headers were no longer affordable so he bought a set of 2" Hooker S/C headers with the 3.5" collector. I went for a ride in that car after the header change and his 427 felt like it lost 100lbs. of torque and was down on power. Now he can't change anything on his car without the wife's approval first. Lesson here is always go smaller with headers rather than the other way around. You may make more hp with bigger tube headers but is the tq. loss worth it?

[ClassicComp]

I run a slightly smaller engine than that and a hooker 2”x3.5 collector with 10” ext is good for low 10’s at 3300lbs

[af2]

Hi, welcome to the site. I have one example for you and it dates pretty far back but it relates to your question on headers with a 427 BBC. A good friend of mine years ago who still has his homebuilt L-88 427 that he made from over the counter GM parts. When he got the car done and was in the market for headers he went to Headers by "ED" and Ed got them right for him. Ed made his tubes 1 7/8" and told my buddy that's the biggest you should go on this engine and Ed also use a smallish collector that only used a 3" opening. This 427 Camaro was the car to beat in out town for almost 30 years until the big inch engine guys started to show up and even on the street some of then had their hands full with his car. Sadly one day as my buddy was going to a car show he hit a man hole cover and ripped those headers all to sheet and had to get some new ones. Ed's headers were no longer affordable so he bought a set of 2" Hooker S/C headers with the 3.5" collector. I went for a ride in that car after the header change and his 427 felt like it lost 100lbs. of torque and was down on power. Now he can't change anything on his car without the wife's approval first. Lesson here is always go smaller with headers rather than the other way around. You may make more hp with bigger tube headers but is the tq. loss worth it?

Had to be something else. There is little difference between the two and the 3.5" collector also.
Don't get me wrong about the bigger is better but it shouldn't have been like that.

[ChopperScott]

For reference, I have 1 7/8" X 29" headers with 3.5" collectors in the Camaro. These are 'out of the box' Hooker Super Comps, on an 11:1 434 small block that runs up to 7200 rpm, with a 950 cfm carb. So far, they've been good for 9.80's at 3060#, naturally aspirated on pump gas.

[mag2555]

The 427 exh ports flow no more then 175 in stock form.

[rebelrouser]

If you are serious about your combination buy Pipemax and do the calculations. If you are building a set, a step header should give you the best results and Pipemax can give you the step sizes and lengths. Built several headers using Pipemax and was happy with all of them. If you are buying a set I would go with the 2 inch as you said in your post 6,500 rpm and higher. Mild street and drag cars from my experience like the 1 7/8 With the price of a quality set of headers Pipemax is cheap insurance, plus it is fun to play with as it is a pretty good engine simulation program as well.

[69427]

If you are serious about your combination buy Pipemax and do the calculations. If you are building a set, a step header should give you the best results and Pipemax can give you the step sizes and lengths. Built several headers using Pipemax and was happy with all of them. If you are buying a set I would go with the 2 inch as you said in your post 6,500 rpm and higher. Mild street and drag cars from my experience like the 1 7/8 With the price of a quality set of headers Pipemax is cheap insurance, plus it is fun to play with as it is a pretty good engine simulation program as well.

This.

At 6500 the 2" x 3 1/2 16" would work well for you.

I have used Pipe Max for years for the headers on our 427 69 Camaro. For comparison our methanol injected 3.76 x 4.320 at 7500 uses a set of 2 1/8 ~30+" x 4" 16 Lemons headers. Dan recommended a 2" step to 2 1/8 but the 2" covered the exhaust ports some so I went with the straight 2 1/8". The 2" Headman Hustlers we had would only rev to 6800 - 7000 for us.
I have been building a set of merge collectors with the PM recommendations to try this coming year.

[alotadust]

I was a designer for hooker headers in 68-69.
I bought a L88 crate motor from Bill Thomas ( direct GM parts outlet)
along with header from him, (not sure who made them)
th400, 4.88 gears,2200 stall, 3in exhaust, never uncorked!
they were 1 7/8,x3in
so I made some 2inx 3.5 collector, various lengths. even tried different collectors (slip on)
this was a daily driver, to work, store, and old irwindale raceway,
11.60 @ 114 all day long with bill thomas headers.
and with every configuration of 2in I tried, the ET slowed, MPH was the same .
This car was driven to work ,every day, and to the drags, and back,
I put the Bill Thomas headers back on, then parked the car for 3yrs to go play Army.

later upgraded most everything, same short block, (427/L88)
but was able to track 10.50, using hookers , as RPM was raised beyond what we felt
the 1 7/8 would handle.

[Tom68]

OK, so I hadn't started thinking too much about header size/length/etc. until last night.
After reading a couple of articles about it, I've come to the conclusion that it could be
pretty critical for the outcome of the situation. Unfortunately, the only articles I've found
with any real "facts-n-figures" were all dealing with engines that were 500ci and larger.

What I'll be running:

BBC (427 .030+ over)
about 12.5:1 comp.
781 heads
Carb 750 methanol
6500+/- rpm

This will be drag race only, no street driving.

Look forward to your suggestions.

Thanks,
Patrick

Won't need much exhaust with that little carby.

[1980RS]

Hi, welcome to the site. I have one example for you and it dates pretty far back but it relates to your question on headers with a 427 BBC. A good friend of mine years ago who still has his homebuilt L-88 427 that he made from over the counter GM parts. When he got the car done and was in the market for headers he went to Headers by "ED" and Ed got them right for him. Ed made his tubes 1 7/8" and told my buddy that's the biggest you should go on this engine and Ed also use a smallish collector that only used a 3" opening. This 427 Camaro was the car to beat in out town for almost 30 years until the big inch engine guys started to show up and even on the street some of then had their hands full with his car. Sadly one day as my buddy was going to a car show he hit a man hole cover and ripped those headers all to sheet and had to get some new ones. Ed's headers were no longer affordable so he bought a set of 2" Hooker S/C headers with the 3.5" collector. I went for a ride in that car after the header change and his 427 felt like it lost 100lbs. of torque and was down on power. Now he can't change anything on his car without the wife's approval first. Lesson here is always go smaller with headers rather than the other way around. You may make more hp with bigger tube headers but is the tq. loss worth it?

Had to be something else. There is little difference between the two and the 3.5" collector also.
Don't get me wrong about the bigger is better but it shouldn't have been like that.

Well in my own testing in the last few years my car with the BBC has always gone slower with my 2" super comps vs my 1 3/4" headers. ET slips do not lie.

[Bigchief632]

The 427 exh ports flow no more then 175 in stock form.

He's using 781 heads, and hasn't said if they were ported or not. Generally, the more efficient the exhaust port and cam events are, the smaller the header you need, to a point. There won't be big swings in power when switching between header sizes, the better those 2 are, when the exhaust port is weak, and maybe the cam isn't quite right, you'll see bigger gains with bigger headers on the same combo. Done it many times, back to back to back.

[Dan Timberlake]

"back to back to back"

The re-test of the baseline condition is usually hard to come by. Time, expense, excitement over some positive improvements. But, but really adds some to the confidence in all the test the results.

Some Standards have requirements to test repeatability and record the results as part of some official measuring or balancing procedures.