Zoomie Lengths

Are there any real rules of thumb for the length and diameter of a zoomie primary tube on a supercharged motor? For instance, shorter for higher RPM or bigger diameter for more displacement, etc....? Is there any sort of intent being made to generates a suitable reflected exhaust pulse, or is all of that irrelevant since there's 40+ PSI waiting behind the intake valve? Has anyone messed with stepped diameter zoomies?

Or is it more just a matter of what "looks right" for a given application, and get the exhaust out as quickly and smoothly as possible?

 

As I recall, Dave Archer, http://www.dynobill.com/, did a back to back of 2.25 diameter vs 2.50 on his HH8 BBCs and the smaller picked up 15 ft lbs.

This was published in "The Puller" magazine some years ago if someone were to have the article.

 

I watched Rick Santos and Grimes try a zoomie and then a collector header on back to back runs ------ no difference in ET -----I was always wondered what bottom end meant vrs top end when a blown motor goes 8000 rpm at the hit ------ ??

 

Header length

Hi,

For what its worth I had a friend with a screw blown TAD that did dyno and track testing with 3 sets of headers in what I believe were 2" increments. He said the only thing that changed was the weight of the car.

Best wishes,
Trev

 

header lenght

we have a vprc chassis and tried to hook headers back to firewall and put a lot of bends in them the egts went crazy , we also had a problem splitting the seam in the bends , also made way more power when we put conventional zoomies
on the car