Re: 5000CSQT head mods...

[DeWitt Harrison <de@aztek-eng.com>]

On Tue, 23 Sep 1997 01:02:32 -0600, Bruce Bel wrote:

>> If bigger valves are going to be installed what is the largest head
>>diameter
>> for intake/exhaust???
>> As far as porting goes where can the largest gains be made, the intake
>>ports
>> or the exhaust ports???
>>[ ... ]
>I'm curious, as I don't ever remember this coming up in any discussions on
>this list.  I know several of you have had your heads ported and polished,
>even extrude honed. what did you folks do with the exhaust ports?  

No grinding, but maybe bigger exhaust valves. Extrude honing won't hurt
either.  Bigger intake valves may improve things at the top end, as may
a bigger cam, but both hurt the bottom end. QSHIP, Ned and now
Corky Bell's book advocate staying stock on the intake valves and
relying on boost to cram in the air.  (Caveat: the extra air needs to be
cool.) Mr. Bell argues this from the standpoint of driveability, i.e. low
end torque. Ned argues from the standpoint of best performance gain
comes from freer exhaust side. A couple more psi and a much better
intercooler would produce much more gain for less money than head
work even if you plan to drive a lot above 8000 rpm.

DeWitt Harrison     de@aztek-eng.com
Boulder, CO
88 5kcstq