[DeTomaso] 351 C Building Advice for Forced AIr and EFI

[John Bentley (jab)]

Ahhhh, an informed reply....  Thanks Dan.

Clay, as far as pistons go, I'd recommend you talk to whoever is going
to supply your pistons or whoever is going to build your engine.  After
talks I've had with Randy at JE Pistons, he has a slightly different
spin from Dan on quench design for a force-fed engine.  His take is the
offset "D" design is not ideal and shorter rods (like stock length)
reduce the time the piston is high in the bore and thinks that's a good
thing due to higher than normal cylinder pressures.  To each, his own.
If you ask 10 people about how to make a Cleveland sing, you will for
sure get 10 different answers!

The other side of that is you can pretty-much take Dan's word on
anything engine related and do well.  

JB






-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com]
On Behalf Of Daniel C Jones
Sent: Friday, November 16, 2007 12:03 PM
To: detomaso at realbig.com
Subject: Re: [DeTomaso] 351 C Building Advice for Forced AIr and EFI

> Should I get an aussie block for higher nickel content? Does that even

> matter?

I've not been able to independently verify the claim the standard Aussie
blocks have more nickel content than U.S. blocks.  In any event, extra
nickel doesn't make the block stronger, though it may improve surface
wear.  The standard Aussie blocks are 2 bolt main.  I'd certainly go
with a U.S. 4 bolt main block over a 2 bolt main Aussie block.  The
Aussie XE 4 bolt main race block (which is thicker all over the block)
would be the one to get but they are very rare and much more expensive.
In this case, 4 bolt mains are worth the extra cost assuming the block
passes sonic check.

For a given power level, a supercharger is generally easier on an engine
because you need to spin a normally aspirated engine to a higher RPM and
loads on the bottom end increase with square of RPM.  However, there are
places where a supercharger is not so easy on the engine.  With a crank
driven supercharger, loads at the crankshaft snout can be very high and
any typ of compressor increases thermal loads.

> If I am to use forced air induction should I use 4V heads?

The 4V iron heads would work well, particularly wioth some short side
radius work, offering little restriction to the supercharger.  The
bigger ports are beneficial for turbo/supercharged applications where
the impellor defines the flow rate.  Even better would be the Ford
Motorsport A3 aluminum high port heads.  The intake ports are better
than a 4V's and the exhaust ports are particularly well suited to a
turbocharger or nitrous.  Assuming you convert a tunnel ram to EFI for
the intake, the A3's will match on 3 sides, needing only the tunnel ram
port floor raised to match.  Assuming you want to run pump gas, I'd run
closed chamber heads with either a mirror image dish or D-dish pistons.
You want to get your compression down in the 8 to 8.5:1 range while
preserving the quench effect (you want a flat part on the piston to come
near the flat part of the combustion chamber opposite the spark plug).
You also want a blower specific forged piston design with a thicker
crown and lands.  Also, consider inconel valves (particularly on the
exhaust side), an ignition controller that pulls timing in proportion to
boost (e.g. MSD-6BTM) and/or water/alcohol injection.
Run a longer rod to reduce side wall loading under boost.  With a
standard stroke, you have plenty of room for 6" to 6.2" rod with Chevy
journal.  With the connecting rods, you'll be concerned with buckling
under pressure so you'd want something with a larger cross- section like
a forged steel H-beam design or even aluminum rods from someone like
BME.  You'll probably want a custom cam but Crower lists a 351C
hydraulic flat tappet blower cam with wide lobe separation angle.
Specs are 246 degrees @ 0.050", 0.548" lift, 114 degrees LSA with power
band between 2400 and 6700 RPM.  Makes a nice nitrous cam, as well.
Compression means lots of heat so don't skimp on the cooling system.  An
Edelbrock water pump, larger radiator and better fans, along with an
increased capacity road race Pantera oil pan (Armondo or Aviad), along
with oil temperature and boost gauges.  Look at Victor Rienz for the
head gaksets.

> The more I read about different heads the more it is confusing on 
> which ones to buy.

Ones like the CHI 3V's will limit your intake choices to a very tall
single plane or a dual plane, neither of hich will be well suited to you
application.  CHI will open the ports up on a 3V to match 4V intake
manifolds, however.  Don't even consider the 2V heads.  If doing a
positive displacement supercharger, the Offy 360 intake is often used as
a base, thouh there were 351C-4V blower manifold available at one time.

A word about boost.  Boost isn't necessarily proportional to power.
You can make a bunch of boost on a restrictive induction system but not
that much power.  Install a less restrictive induction system and you'll
make less boost but more power.  B&M's supercharger catalog used to have
a strong warning against using stock 302/351W heads with their Roots
style superchargers because the OEM Windsor heads are too restrictive.
They'd make lots of boost but not that much power and would actually
overheat.  Pick a power level and let the boost work out to what it
needs to be, not the other way around.

> It appears turbos are easier to position in the engine bay but I would

> prefer a supercharger although I cannot perform the maneuvers Dave has

> done myself.

By maneuvers, do you mean fabrication?  Either way, you are looking at
custom fabrication and the turbos will package better in a Pantera.
There isn't much room between the bulkhead and front of the motor for
crank driven superchargers.  It can be done, however.  Contact Fred
Terry on what he did for his crank driven supercharger.

Dick Koch, Dave Doddeck, and Pat Mical all have twin turbo Panteras.
Here's a picture of Dick's engine:

 http://www.panteraplace.com/ICD/2004/ICD%202004%2020.jpg

If considering turbos, you might want to contact Dave or Dick.  Dick
originally had a blow through carb set-up with larger twin turbos.
I think he is much happier with his smaller turbo EFI set-up.  His basic
engine isn't anything exotic, just open chamber 4V heads on a standard
351C block with mild cam but under boost it makes plenty of power.

If I were doing one for my own self, I'd pick Ford Motorsport A3 high
port heads and an XE.  Hmmm, come to think of it I have an XE block
fitted with an XH1 forged steel crank and Carrillo rods.  That would
make a very nice blower foundation.

> It seems like everyone else in the automotive community (outside the 
> Pantera community) is doing really well with supercharged and 
> turbocharged street/race engines.

I know the 5.0L Mustangs guys are doing really well at splitting the
5.0L blocks right down the middle under boost :-)

> I'd definitely go with the aussie block which should have siamesed 
> bores and much stronger main bearing mounts (not just the caps!).
> Be careful- not all blocks from australia are 'aussie-cast' blocks!

Exceedingly few of the Aussie blocks are the XE race blocks.  Ford only
made 2 batches of them with a few hundred blocks in each batch.
The guys selling Aussie blocks on the web are trying to fool people into
believing their blocks are the stronger XE blocks.  They are not.
The typical Aussie 2 bolt main block weighs and sonic checks no
different than U.S. 2 bolt main blocks.  The XE block is completely
different with thicker main webs, main caps, walls, deck and valley.

Dan Jones
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