Bruce, quick question.

[Jefferson S Creech]

Message text written by INTERNET:diy_efi at efi332.eng.ohio-state.edu
>I am not bruce, but I think I have some useful data.


It depends on what you define as later.  The LT1's have a 3" tpi
runner, and are good for top-end.  I believe the LS1 have 14" and I
thought the earlier TPI (<93) had 24".    I guess to know you would
need to know how long the crossfire had, less than 24" would probably
mean it has better top end.   I am sure bruce can add tho this.

                                Roger

On Thu, 10 Dec 1998 ECMnut at aol.com wrote:

> Are the runners in the cross fire manifold better for 
> top end boogie than the later TPI units?
> They look l-o-n-g on the TPI..<

I'm not Bruce either , but I have a little tidbit that might be of use to
you as well . Back in the '60's , a man named Dick Maxwell came up with a
formula for the relationship between runner lengths and the power curve on
an engine . Wet and dry manifolds have different formulas .

Wet Manifolds : 75,000 / complete runner length (in inches) = horsepower
peak
Dry Manifolds : 100,000/ complete runner length (in inches) = horsepower
peak

This doesn't account for port velocity influences , and refers to complete
runner length - from butterflies ( or carb base ) to the valve seat , as
measured through the center of the port . Also , keep in mind that bigger
plenums reduce the vacuum signal , which results in lost pressure wave
action ( cylinder packing ) . In other words , short runner , big plenum ,
needs higher compression to utilize  the manifold at low rpm's . The
Engineer types that frequent this list can elaborate on this better than my
hi - skule drupoff butt can .