DeTomaso Mailing List: February 98, Message #40
     



From: 	"Mary Taphorn" <marytaphorn@email.msn.com>

Subject: Fw: Fw: FPP 4145 update

Date: 	Sun, 1 Feb 1998 20:24:08 +0000





-----Original Message-----

From: Andy Poling <andy@globalauctions.com>

To: Multiple recipients of list <detomaso@realbig.com>

Date: Sunday, February 01, 1998 12:12 PM

Subject: Re: Fw: FPP 4145 update





>I'll readily admit that my knowledge of performance Murcan V-8's is thin

>(having wrenched on furrin cars with furrin motors all my life).  I've been

>doing some reading though.  (I heard those groans!)

>

>My understanding of conventional wisdom is that dual-plane manifolds

>have smaller, longer runners than a single-plane manifold, and that they

>therefore work better at the low-end at the expense of top-end power.

>

>But I hear folks here saying that the comparisons they cited showed the

>dual-plane manifold producing better top-end power.

>

>Can someone 'splain to me how this can be?



>>I am certain others are more qualified, but I'll take a stab.  Part of the

debate is clouded in semantics.  What is your definition of top end power.

While I'm new to this Forum and thus clueless on  general understandings the

group may have reached before, I'm not shy so I'll toss in my opinion.  Due

to design limitations, i.e. oiling, rods, etc., it takes significant

modifications to get a cleveland to run reliably over 6500 RPM.  I don't

think you will find much arguement that a single plane makes more power at

high RPM (>6000) than a dual plane.  Dyno tests in past articles don't

evidence any advantage until you exceed 6000RPM and I don't believe it was a

significant advantage until you reached the other side of 6500RPM.  The

advantage increases demonstrably above 6500RPM. However, the price you pay

is a GREAT loss of torque and horsepower throughout RPM range under 6000.

This has been documented on a dyno in an article that had been published

years ago. So the question is, what do you define as your engine's high end?

For most Pantera owners it is probably 6000RPM and they are better served by

a dual plane.  As one who races SCCA(Not my Pantera), I'd wager that if your

displacement is still <360CI and you've spent the big bucks building an

engine that can survive trips to 7500RPM, you would still be quicker on a

race track with a dual plane in a Pantera.  The reason is the gear ratios in

the gearbox are too widely spaced to allow to to stay in the 6000 - 7500 RPM

range enough of the time.  With the dual plane, you would have superior

drivability and a wider torque range .  Now for our fringe element

membership with the ultra high buck engines that live near Michigan Speedway

or dream of the Silverstate and can run the engine in that narow range - My

hats off to them.  Otherwise, while those engines are great for Dyno

bragging rights, please move offline coming out of the corner's apex because

you are in my way.



John T.

>

>-Andy

>#3822

>

>72 Pantera - Rocky         91 Miata - Steve (bionic)            96 A4Q -

Rudolf

>80 928 - Phantom               97 Miata - Nadia                84 RZ350 -

Sting

>

>

>