Reply to "Dyno Questions from a novice"

> Attached is printout from the dyno.

Would you email me that directly? The attached one is too small for me to read.

> Dan your prize is in the mail for guessing the closest.

I have an unfair advantage. With the Dynomation simulation program and the
data collected on the flow bench along with the testing on the 351C dyno mule,
Glen Hartog's 408C, Mike Drew's 408C and Orville Burg's 393C I can make very
accurate predictions.

> interested in talking with you about cams.

Sure thing. I should be home from Saudi Arabia very soon and would be happy
to talk.

> I think I will pursue an upgraded exhaust (Maybe the GTS headers and mufflers)
> and that should get me over the 300HP mark.

The GTS headers are fine but the GTS mufflers are not much better than the OEM
ANSA. We lost 50 HP on those on a 408C. Mike Drew's modifed versions (cans
gutted and filled with a perforated Y-pipe so no baffles) lost 38 HP on a 351C
versus 50 HP for the unmodified versions. We suspect that the internal diameter
of the tips is the biggest remaining restriction, though it could also have a
reflection off the y pipe.

Steve Wilkinson had a prototype set of 4-into-1 headers and mufflers that will
be available in either mild steel or stainless steel at a very good price (IIRC
$1200 for the stainless set of headers and mufflers). By the constuction (the
super thick flange is the tip off), I believe OBX is manufucaturer. The mufflers
look externally like ANSA's but are modified internally and have a larger ID in
the tips. Steve said they picked up something like 25 HP over the ANSA's. He
seemed willing to lend a set for dyno evaluation once they are in production so
I hope to test them.

On most Pantera headers, the collector internal diameter is only 2 1/4" and is
very short. I expected this to be a major restriction but the dyno has shown
it's not that bad. Testing against a set of long tube headers with 3" diameter
collectors has shown the Pantera headers do give up some power in the lower RPM
ranges (due to the short primary lengths) but the horsepower difference at the
top end is small. As I've mentioned before, the mufflers are the major
restriction. We've been testing 3" inlet/outlet straight through Magnaflow
mufflers with a 3" diameter intermediate pipe clamped or bolted (depending upon
the headers used) to the headers. I'd like to also test 2.5" intermediate pipes.
I suspect those will not show much of a penalty compared to the 3" diameter since
the collector diameter is smaller. Then I'd like to test the 3" inlet, dual
2 1/2" outlet Magnaflows to see if they work as well as the 3" inlet/3" single
outlet vesions. THere is a possibility there is an adverse reflection off the
internal Y-pipe. If that's the case, I'd expect to see dips at particular RPM's
but not across the entire RPM band. 2 1/2" inlet mufflers might even be
acceptable but I'll have to contact the muffler manufacturers for pressure drop
info to know for sure. My guess is that a 2 1/2" intermediate pipe feeding a 3"
inlet muffler would not lose any power the a 3" intermediate pipe. I run similar
Magnaflows on my daily driver '87 Mustang and like them quite a lot.

Flowmasters have a reflection problem that makes them sensitive to placement
(distance to from the collector to the muffler). Closer tends to be better so
maybe not a big problem in a Pantera.

Mike McDougal has posted on the Cherry Bombs he uses. I didn't get a chance
to dyno those but Mike reports they made a noticeable difference.

Dan Jones