DeTomaso Mailing List: February 98, Message #198
     



From: 	Dan Jones <djones2@mdc.com>

Subject: Them thar' 2V heads, AOD's, etc. - Reply

Date: 	Wed, 4 Feb 1998 12:20:11 +0000





> OK, so the recommendation is a change to the Offy dual plane, right?

> It's on the to-do list.



That's an Offy *Dual Port* manifold.  It's not really a dual plane manifold

but rather a pair of single plane manifolds stacked on top of each other,

one for the primaries and one for the secondaries.  To package this in

a conventional manifold envelope, the plenum is divided fore-and-aft while

the runners are divided top-and-bottom (in roughly a 2/3rds to 1/3rd ratio).

 The primaries feed the longer path, smaller area, bottom section of the

runners and the secondaries feed the shorter path, larger area, top half.

 You cruise around on the small side of the port (keeping the air/fuel

velocity up) and when the airflow demands it, the secondaries open up and

the rest of the port is utilized.  



It's a neat idea and supposedly Ford, AMC, IH, Holley, and the Ethyl 

Corporation all did development work on the concept but Offenhauser is

the only company to bring them to market and their advertisements say they

have the patents.  Some compromises were necessary to package the concept

and top end suffers as a result.  On the plus side, the Offy provides great

low and mid range performance and throttle response, and excellent fuel

economy.  



Dave Williams ran one on a Cleveland and here's what he had to say about

it:



>> also called it Dual-Port (or maybe they were two different things).

>> It was their attempt at a dual-length runner for carbs, but I have no

>> idea how successful it was.



> Worked pretty damned good, actually.  I had one on a 351C-4V. 11.2:1

> CR, 780 Holley, Accel centrifugal-only distributor, C6, 2.70 posi and

11

> inch wide tires in a '70 Torino.  Broke the tires loose any time I

> wanted, and pulled low 20s on 92 octane regular.  (yes, this was a few

> years ago)

>

> Some years ago David Vizard did an intake manifold shootout for PHR.

> He ran the stock manifold, tunnel rams, single planes, dual planes, and

> a Dual Port.  The test engine was a small block Chevy, but the basic

> trends are probably applicable.  The Dual Port was near the bottom for

> peak horsepower, but the powerband - "area under the curve" was 

> very wide, and the BSFC numbers were outasight.  If Iskenderian ever

> decides to ship the damned camshaft, I have a long-rod 416 SBC with >

a Dual Port and a 950 Thermo-Quad gathering dust.

>

> Offy makes a manifold called the 360, which is technically a single

> plane piece.  It's just a box with some short runners, an inch or so

> long, depending on the application.  For the Dual Port, they put a

> divider in the plenum and runners, making two separate manifolds, one

> for the primaries, one for the secondaries.  There are some airflow

> compromises due to the secondary bores dropping down to the lower

> plenum.  Frankly, the Dual Port looks pretty hokey, but throttle

> response is incredible, and they work very well for daily driver/tow

> vehicle class stuff.  Several of my friends have also used them and 

> been happy with them.  But it's not a high performance manifold.  It's



> what the S.P.2.P and others were advertised as, but couldn't deliver.





> The Edelbrock carb is a 1406, so 600cfm. Nicely polished and shiny 

>  looking, but in need of an external cleanup.



If you want to keep the Edelbrock carb, you'll want part number 6110-DP.

For spreadbore carbs, you'll want part number 6111-DP.  PAW lists them

in there catalog for around $220.



> The old cast iron 4bbl manifold is the 'spreadbore' type. Is that good?

> Bad? Or just an info point? I don't plan on using it....



Just different.  The factory 351C spreadbore manifolds used here in the

states were all for 4V heads and will only mount up the mutant Autolite

4300D carb, not the far superior Carter Thermoquad or Rochester Quadrajet

carbs.  The ones used in Australia were reportedly equipped with Qjets

(can you confirm this?).  I've got a couple Thermoquads and a Qjet that

I'd love to try out on something.  If only it were aluminum ...



> Craig suggested I should swap out the C6 in the Longchamp with an 

> AOD.  Interesting idea! Anyone got anymore info on such a swap? Is

> an AOD a 'dropin' replacement for a C6? Driveshaft length, Ujoints...

> That'd be too good to be true, if so...



I've swapped out a C4 in an early Mustang for an AOD and wrote up the details.

 I can email you a copy if you're interested.  Also a friend swapped out

an FMX for an AOD in his '69 Mach 1.   I expect the C6

swap would be similar.

 

> Can I just head off to a junkyard, find a Thunderbird Super Coupe and

> drag the AOD out of it? What other Fords had an AOD in them? 

> Lincolns?



Lots of cars and trucks did and there were many updates along the way.

 Get a late one from a performance car (Tbird SC or 5.0 Mustang).  Also,

be forewarned that there's an AOD-E version with electronic control.



Later,

Dan Jones