[DeTomaso] Exhaust Port Plates for conversion to 2bbl heads with

[JDeRyke at aol.com]

In a message dated 7/26/08 12:03:33 AM, dyogi at hawaii.rr.com writes:

> When I removed the 4v set, you could see the mismatch of the heads/headers 
> due to the port/header size imprinted on the gaskets but the gaskets held up 
> great.  I don’t know how much performance difference loss there is due to the 
> mismatch but they didn’t leak and worked. 
> 
4V headers are larger in dia at the port and this acts as a sort of 
anti-reversion step. The exhaust flows out unrestricted but when the reflected 
ram-pulse returns from the collector, it catches on the 'step' at the head and doesn't 
make it all the way into the combustion chamber to dilute the incoming intake 
mixture; sort of like a check-valve. This increases the torque at some point 
in the mid-range, where most street driving is done. Much the same thing 
happens when installing a 2V intake on 4-V heads. The limiting factor is the 
diameter of the 2V portion which limits upper rpm gas flows (either intake or 
exhaust) and resulting power. You pay extra for such things when tuning an engine 
for midrange.... FWIW- J Deryke



**************
Get fantasy football with free live scoring. Sign up for 
FanHouse Fantasy Football today.
      
(http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020)