Header size?

Posted By: gss

Header size? - 10/23/14 04:50 AM

I have a mild 400, .528 solid cam, old DC Stage 4 heads. I can get a good deal on a set of headers with 2 1/8 primaries. What would I be giving up it terms of torque and horsepower using these headers vs a 1 3/4" primary? Full exhaust street car. Thank you

Posted By: BradH

Re: Header size? - 10/23/14 05:46 AM

Stick with the 1-3/4", or 1-7/8" at most, for what you described.

Posted By: StealthWedge67

Re: Header size? - 10/23/14 06:57 AM

Quote:

I have a mild 400, .528 solid cam, old DC Stage 4 heads. I can get a good deal on a set of headers with 2 1/8 primaries. What would I be giving up it terms of torque and horsepower using these headers vs a 1 3/4" primary? Full exhaust street car. Thank you

If you can get a good deal on them, I'd consider buying them and see if you can sell them to a racer, or trade them for some 1-3/4" primary headers. They'd cost a ton of torque on that combo.

Posted By: gss

Re: Header size? - 10/23/14 07:16 AM

I understand all that. I just want to know the difference in horsepower and torque. There has to be countless dyno tests and dragstrip tests.

Posted By: Mr.Yuck

Re: Header size? - 10/23/14 01:11 PM

I went from 1 3/4 to 2" and only picked up 1.5mph. But I have a little more motor than you. 2 1/8 are huge and might be a pain to deal with. You can get a brand new set of 1 3/4 from Summit for $150 or less.

Posted By: an8sec70cuda

Re: Header size? - 10/23/14 02:18 PM

gss...I agree 100% w/ what was said already, a 1 3/4" or 1 7/8" header is what you need. Those 2 1/8" headers will kill the lowend on your motor.

Posted By: 1320Dart

Re: Header size? - 10/23/14 02:25 PM

How do you guys come up with header sizes? Is there a formula that you use?

Posted By: tubtar

Re: Header size? - 10/23/14 02:47 PM

Quote:

How do you guys come up with header sizes? Is there a formula that you use?

Yeah........it's called Mr. Peabody.

He has a program ( pipemax ? )and was very generous in his assistance with mine and many others.
The Wallace calculator can give you a good baseline too.
http://www.wallaceracing.com/header_length.php

Posted By: 1320Dart

Re: Header size? - 10/23/14 03:31 PM

Quote:

Quote:

How do you guys come up with header sizes? Is there a formula that you use?

Yeah........it's called Mr. Peabody.
He has a program ( pipemax ? )and was very generous in his assistance with mine and many others.
The Wallace calculator can give you a good baseline too.
http://www.wallaceracing.com/header_length.php

Thank you tubtar

Posted By: BradH

Re: Header size? - 10/23/14 03:51 PM

Quote:

I understand all that. I just want to know the difference in horsepower and torque. There has to be countless dyno tests and dragstrip tests.

I'm sure there are some magazine tests done on header sizes that will give you a reasonable idea. Google can probably turn up a few.

Regardless, a header way too big for any given combination kills the torque curve... and the combination you described can't afford to give up torque with only 400 cubes.

Posted By: Dunnuck Racing

Re: Header size? - 10/23/14 04:09 PM

Regardless, a header way too big for any given combination kills the torque curve... and the combination you described can't afford to give up torque with only 400 cubes.

Exactly!!! I will post some tests I ran and show you. Too large a header basically leaves a huge hole in the torque curve right where you will need it.
Keith

Posted By: MR_P_BODY

Re: Header size? - 11/03/14 08:32 PM

Quote:

I have a mild 400, .528 solid cam, old DC Stage 4 heads. I can get a good deal on a set of headers with 2 1/8 primaries. What would I be giving up it terms of torque and horsepower using these headers vs a 1 3/4" primary? Full exhaust street car. Thank you

For your mild street car you would be giving up a lot
of torque with 2 1/8 pri. and mainly where you would
need it... 1 3/4 would work great for the street..
if you can.. set the collector length to about 18"
from the end of the primaries.. also measure the distance
to the front wall of the muffs... they should hopefully
be in multiples of that 18"(as in 18" 36" an so on)
for the best torque... in most cases(if not all) the
pri length is too long and the collector is to small
in dia and length).. if its 3" dia a 3.5" is normally
better but being a street car I wouldnt worry about it

Posted By: 383man

Re: Header size? - 11/03/14 09:27 PM

I agree you dont want that big a tube header on your combo. I used 1-3/4 on my old mild 440 combo and it dipped in the 11.40's with a full exh when it was in my 63. You can get Hedman 1-3/4 for a good price as thats all you need for your combo as like everyone says the large tubes will hurt the low end torque alot. Ron

Posted By: 440Jim

Re: Header size? - 11/04/14 04:51 AM

Quote:

I have a mild 400, .528 solid cam, old DC Stage 4 heads. I can get a good deal on a set of headers with 2 1/8 primaries. What would I be giving up it terms of torque and horsepower using these headers vs a 1 3/4" primary? Full exhaust street car. Thank you

As others have said, you would get killed in torque below 5500 rpm. And below 4000 rpm would be really bad. There is no way I would run a header that big in dia in your combo.

Posted By: Mopar-Al

Re: Header size? - 11/04/14 06:17 PM

With a full exhaust system i don't see a problem myself. Racing is a different story for diameter

Posted By: gss

Re: Header size? - 11/04/14 08:53 PM

A little more information: These are high end custom fenderwell headers with a custom exhaust system. Cost to replace would be around $3000. It would be nice if they were a little smaller, but I think I will eventually build more cubic inches so hopefully it will be fine.

Posted By: Cheatham

Re: Header size? - 11/05/14 04:18 AM

yep buyem and grow into them