DeTomaso Mailing List: March 2000, Message #101

Sure, we can go PUBLIC....<grin>
I can tell you that my 650DP was not enough under 5500...After I stroked the
old engine to 377ci I added a flowed 750 which was +/- 810 and it was
perfect up to 7000 at Silver State...the new engine will be a 393ci....so
the question needs to be asked...will a 1100cfm add value added...HORSEPOWER
GAIN VERSUS GAS MILEAGE LOSS....keep in mind I 20 gallons gotta last 90
miles at full throttle!!! :-)
The old stroker engine with the flowed 750cfm DP used about +/- 17 gallons
to finish the 90 mile course.   
thanks tony
MD  

-----Original Message-----
From: Tony DiGiovanna [mailto:t.digiovanna@mindspring.com]
Sent: Friday, March 03, 2000 2:23 PM
To: Antenucci, Dennis
Subject: Re: 600 or 750? 


I wouldn't mind taking this discussion public.  Up to you:

If your engine is 351 CID & you want max power at 5500RPM & it has pretty
well prepared race-ready heads and all (VE of 1.15) & a single plane
manifold, then your calculated engine CFM is 640.  It is generally
reccomended to size your street carb at 1.3 times this value, or at 833 CFM
or next biggest carb which is 850 CFM.  You are on the right track.

However, if you are buiding a race-prepped car and don't mind sacraficing
the bottom end a bit and spending a more $, properly modified and jetted
race Holleys can run well at 0.5 inch pressure drop instead of the
factory-rated 1.5 inch pressure drop.  Done right, yields 5% more power.
Therefore you would be looking at something closer to a carb that is
normally rated at 1100 CFM prior to custom prepping.

I haven't looked, but it is possible that some of the upper-end carbs, in
the Jegs catalog for example, may be rated at 0.5 inch pressure drop.  I'll
check.

Also please note if you are stroking the CID up, the CFM goes up.  I seem to
recall you were doing that, which is why I asked.  The 850 CFM carb seems
just at the lower limit for high-speed track activity.  You will note most
serious V8 race engines, drag and road, have big Holley Dominators on them,
sometimes two.  This is why.


----- Original Message -----
From: Antenucci, Dennis <AntenucciD@MTA.NET>
To: 'Tony DiGiovanna' <t.digiovanna@mindspring.com>
Sent: Friday, March 03, 2000 9:13 AM
Subject: RE: 600 or 750?


> PROBABLY A 800CFM DP
>
> -----Original Message-----
> From: Tony DiGiovanna [mailto:t.digiovanna@mindspring.com]
> Sent: Friday, March 03, 2000 11:13 AM
> To: Antenucci, Dennis
> Subject: Re: 600 or 750?
>
>
> I can't imagine a dual plane manifold for your intended purpose.
>
> Are you going carb or injection?
>
>
> ----- Original Message -----
> From: Antenucci, Dennis <AntenucciD@MTA.NET>
> To: 'Tony DiGiovanna' <t.digiovanna@mindspring.com>
> Sent: Friday, March 03, 2000 6:59 AM
> Subject: RE: 600 or 750?
>
>
> > Tony,
> > Keeping in mind my engine build has got to make MAX power at 5500-6000
RPM
> > with that 3.5 ring gear do you think there is any benefit of using a
duel
> > plane over single plan with those 302B heads?
> > Hell, I may not even be able to get a duel plane with those heads but
> > thought I'd ask anyway!
> > Thanks
> >
> > -----Original Message-----
> > From: Tony DiGiovanna [mailto:t.digiovanna@mindspring.com]
> > Sent: Friday, March 03, 2000 6:26 AM
> > To: Multiple recipients of list
> > Subject: Re: 600 or 750?
> >
> >
> > I note you don't mention your intended manifold selection.  I highly
> > recommend a dual-plane for street use.  The Pantera gear ratios put you
in
> > the low RPM range a lot on the street.
> >
> > I had a 10:1 with American 4V heads and a single plane Weiand manifold
and
> a
> > similar cam.  A 650 double pumper had crisper throttle response on the
low
> > end, a 750 double pumper had more torque on the mid and upper end.   I
> > attribute the bottom-end "sleepiness" of the 750 to poor atomization of
> fuel
> > due to the single plane and low velocities in the big ports.  The dual
> plane
> > manifold cuts the plenum averaging effect in half, the Aussie heads will
> > have higher port velocities, so this will likely off-set the bottom end
> > effects I saw, so I would heavily lean toward the 750.  I have always
much
> > preferred mechanical secondaries over the vacuum type.
> >
> > I would never put a 600 on a 351 Cleveland.
> >
> >
> > ----- Original Message -----
> > From: <Cars5244@aol.com>
> > To: Multiple recipients of list <detomaso@realbig.com>
> > Sent: Thursday, March 02, 2000 3:50 PM
> > Subject: 600 or 750?
> >
> >
> > > Sorry for all the questions, but you guys have been through this
before.
> I
> > > really do appreciate you input.
> > >
> > > Engine will be 20 over  KB #148 pistons, approx. 10 to 1 using Aussie
> > heads,
> > > Crane cam 524421( 226/230 @ .050, 528/536 110 LC. Will be for street
> use.
> > > Should I use the 600, would that be the 80457S or 750 80508S or is
there
> > > another model for each?
> > > Thanks,
> > >
> > > Skip
> > >
> >