[DeTomaso] Cleveland 2v vs 4v heads

[Daniel C Jones]

> Looking at the Intake Port of the 351C 2V, you will see that it is larger
> than the 390, 428 and some 427's and 460's (multiply the two dimensions).

I've never measured this but it sure doesn't look that way to my naked
eye, comparing 2V to 427 LR and 428CJ.

> the 351C looks more like a standard 427 or 428 head!

Looks completely different to me.

> The 2v heads actually work better on the street than 4v heads do

Sometimes they do, sometimes they don't.

>I was wonder what the thoughts were between the 2v heads or the 4v heads
>for a Pantera?

There's no single answer to this question.  It depends upon what you want
to do (what RPM range you want to operate in), what you are starting with,
how big your budget is, whether or not you want a low profile intake that
will fit under the stock engine screen, etc.  It's the combination that
makes the power and cylinder head choice is but a single variable, albeit
an important one.  If you're starting with an open chamber 351C-4V with
dished pistons and want to use a relatively mild cam, the closed chamber
Aussie 2V's make a nice upgrade.  With flat tops and more cam, closed
chamber 4V's may work better.  For a big inch stroker, 4V's are the way
to go.  It's also quite easy to choke off any advantage a 4V head may have
with restrictive mufflers and a poor intake manifold choice.

> Does anyone know about a serious test using 2 vs 4V heads?
> This could have been done in four ways.
> 1. Exactely the same engine, and exhaust, carb, cam etc.
> 2. The enine is built to suit the heads.
> Both example should use the same rpm field, say 5000 rpm hp.
> Then a slightley hotter version for say 6500 rpm hp.

Goran, I'm not sure if you are aware of the list/forum dyno project I
started but I intend to test exactly what you describe (and much more).
We'll have a mild cam and a hotter one, along with tests of open vs
closed chamber heads and ported and unported 2V and 4V closed chamber
heads all on the same basic engine.  A variety of intake manifolds will
be available.

> I have been driving a 2V hed equipped Pantera using a 240 @050 cam
> and Hall big bore headers and a 750 Holley, and I was not that impressed
> by the performance at any rpm even if not bad. On the strip it managed
> 14.5 sec.

With the RPM range that 240 degrees duration @ 0.050" puts you in, I'd be
looking at 4V heads.  If it's running a Performer intake, the intake is
a limiting factor.

> Aside from this I should like the 2V heads to have located the ports
> at the height of the top of the 4V heads, not at their bottoms.

That's sort of the idea behind the 3V heads.  Smaller ports shifted
up and to the side.

> They are also machined for mechanical cams as delivered while only the
> Boss version of the 4Vs are machined that way as-stock.

and the 351 HO.

> Only early Aussie Clevelands had the desirable siamesed bores. Later castings
> were the same as the U.S. version, with 5000 miles of shipping expenses added
> on.

Two batches of XE192540 race blocks were cast at the Geelong foundry in
Australia.  The first batch of XE blocks were manufactured in 1975 and were
available over the counter, if you knew enough to ask for the right part
number and had the cash.  They were listed under the catalog part number
D1ZZ-6010-T and were quite expensive for the time, about $1500 in 1976.
The blocks were completely machined, except for the cylinder bores which
were semi-finished, being rough-bored at 3.990".  A number of these blocks
were shipped to Holman and Moody and Gapp and Roush.  Holman and Moody used
to list these blocks under the part number D6HM-6010-1.

A second batch was commissioned when Ford (U.S.) decided to get back into
racing in the early 1980's with the formation of the SVO program.  These
were manufactured duing 1982 and 1983.  There were quite a few of the second
batch that didn't meet minimum specs with respect to core shift and other
defects.  Some of these blocks were subsequently transferred to the standard
machining production line and were sometimes fitted with two bolt main bearing
caps (depending on when they were discovered to be defective) for use in a
standard passenger car engine.  The blocks that passed inspection were
originally listed in the U.S. SVO catalog under the part number M-6015-A3
with a price of around $900.

I've had one of each of these blocks.  One had a 5M2 date code (December 2,
1975) and a 1975 in a circle and the other had a "24C2" date code which would
indicate it was cast on 24 March, 1982.  Neither had Siamese bores but they
did have thicker, non-contoured main bearing webs, a thicker non-sculpted
block skirt (oil pan rail), beefier high nodular iron four bolt main caps,
and thicker (0.165 inch minimum thickness) cylinder walls.  The only 351C
blocks that I've seen with Siamese bores were SK blocks which oddly had the
thinner lower end of a standard production 351C block.  Both of my blocks
carried the XE192540 part number but I've seen XE182540 part numbers as well.

Dan Jones