Header size vs torque make a difference?

[DocDirk]

Reviewing my dyno report on my BB 533 stroker Ford engine I find that it was run with 1.75" OD headers and measuring my current ones that came with my kit, they're 2.00" OD. I've heard or read somewhere that a smaller headers would result in higher torque - would a change as above result in a noticeable difference? I know there are many ways to optimize low end torque, but I'm wondering, all other things being equal, if the header diameter is a significant contributing factor or not.

Thanks!

Dirk

[kitcarbp]

Dirk, In general yes, the diameter of the primary pipes will affect peak torque value and what rpm that peak torque occurs at. Exhaust gas velocity increases as diameter decreases, but flow rate(cfm) decreases as dia decreases. For street driven rpms most advise 1.75-1.875 inch pipes is fine for big cube motors. There are software packages the pros use to simulate best header designs when it comes to racing.
Here is the owner of Sanderson Headers take on affects with data for a small block engine. The 533 cubic inch monster has plenty of torque in any case whether 1.75 or 2.0 inch primarys are used. There are other ref out there as well

http://www.sandersonheaders.com/tech_get_technical.php

[vector1]

i'm thinkng the 1.75 would bee too small, 2" would be more appropriate and those stovepipes look intimidating.

[CobraEd]

Everyone knows that the diameter and length of the primary pipes affects the amout of torque and where peak torque occurs. But I can't remember if the numbers are significant. It seems to me that the differences are small.


.

[CarsByCarl]

2.00" would be the minimum for your application in my opinion.

[mdross1]

With all those cubes at hand you would not feel the difference.My 460 headers were built at Tubular Automotive in Mass.They are racing headers 2" pri to 3 1/2" col.This thing hits hard right off idle,with a scaled suspension.

[Jerry Clayton]

the differences might be small between the 1.75 and 2 headers on an engine that size---but if you would actually put a header on of the size the engine needed, you would see a more pronounced differance-----On that engine I would at least run a 2.25 and preferably a 2.375 header

[mdross1]

When my headers were being sized up for the 460,2" was the biggest pipe they could fit around everything.