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  Mustangsandmore Forum Archive
  The Exotic Fords
  Cam and converter selection for DeTomaso Longchamp Coupe with 351C/C6

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Author Topic:   Cam and converter selection for DeTomaso Longchamp Coupe with 351C/C6
Daniel Jones
Gearhead

Posts: 972
From: St. Louis, MO
Registered: Aug 99

posted 04-22-2003 11:09 AM     Click Here to See the Profile for Daniel Jones        Reply w/Quote
I was recently contacted by a guy from Sweden who's looking for some
guidance on cam and converter selection for his 1984 DeTomaso Longchamp.
The Longchamp is a front-engined 2 door coupe that designed to be a
competitor to Mercedes 450 and Jaguar XJS coupes and is powered by a
351C Ford with either a C6 3 speed automatic or a ZF 5 speed manual.
If you've never seen one, here are a few a picture of a Longchamp:

http://www.panteraclub.com/longcham.htm
http://www.carsonline.com.au/212htm.jpg

Bjorn's looking to perk up the performance without taking a huge hit
on economy (gas is expensive in Sweden and he takes long trips in
the car). The transmission is a C6 automatic and the engine is an
Australian-sourced 351C with open chamber 2V heads and a Holley Street
Dominator intake (economy type single plane with smaller than 2V ports).
Pistons are 0.030" over flat top Keith Black hypereutectics so I'd
guess compresion is in the 9.0:1 to 9.5:1 region. Vehicle weight is
around 3800 lbs and tire size is 295/50/15's but the final drive ratio
and carb are unknown at this point. I'm also not sure of the exhaust
manifolds. I don't think they are the standard 2V cast iron manifolds
and I don't think they are true headers. If they are like the stock
Pantera parts, they are shaped like a cast iron manifold but made of
steel tubing with no collector (each tube intersects the horizontal
tube in a separate place).

The Holley Street Dominator isn't much of an intake. Another guy in
the club with a Longchamp replaced his with an Offenhauser Dual Port
2V and was pleased. I like the Weiand Xcelerator 2V for 2V heads but
my experience is with lighter cars with 5 speeds. An Edelbrock Performer
2V might be better choice for the relatively heavy Longchamp, particulary
with a low stall speed converter.

Bjorn emailed Comp Cams and got a recommendation on a 260H (260 degrees
advertised duration, 110 LSA, and 0.484" lift) but thought that seemed
too mild. Steve L., didn't you run a 351C-powered pickup with a Comp
268H? What sort of stall speed converter did it need? Think a 270H
would be a better choice with a bit of stall speed? He's got the stock
rockers at this point and I'm having him check to see if he has aluminum
sled fulcrums. If so, I'll suggest switching to the steel 4V parts, if
not upgrading to roller rockers. Bjorn's rebuilding the C6 and is looking
for a converter recommendation. He's looking at the Summit catalog and
wondering if something like a Summit SUM-G2706 (1,600-2,000 rpm stall
speed) or a B&M BMM-40427 would be a good choice. I suggested he consider
swapping the C6 out for an AOD or AOD-E but that's more than he wants to
take on at this point. He bought the car in parts and wants to get it on
the road soon.

Any help on cam and converter selection greatly appreciated.

Thanks Much,
Dan Jones

SteveLaRiviere
Administrator

Posts: 48752
From: Saco, Maine
Registered: May 99

posted 04-22-2003 11:16 AM     Click Here to See the Profile for SteveLaRiviere        Reply w/Quote
The 268H ran great with the stock six cylinder C6 converter in my truck.

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Moneymaker
Administrator

Posts: 29200
From: Lyons, IL, USA
Registered: May 99

posted 04-22-2003 12:06 PM     Click Here to See the Profile for Moneymaker        Reply w/Quote
351 CJ style converter replica from JPT.
Nice and tight for top end, yet just enough slippage to get it moving off the line.
268H is a nice 351C cam for street use.

------------------
Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
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Professional Manwhore
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Quote #1: "I never met a magazine mechanic I liked."
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Daniel Jones
Gearhead

Posts: 972
From: St. Louis, MO
Registered: Aug 99

posted 04-23-2003 01:59 PM     Click Here to See the Profile for Daniel Jones        Reply w/Quote
I called JPT and passed the info on to Bjorn who has to verify the
flexplate tooth count and converter circle. Bjorn sent along pictures
of his exhaust manifolds. They don't look too bad, better than an iron
manifold but not as good as a long tube. Also, Bjorn's heads are stock
so no adjustable valvetrain. Shouldn't be a problem with the 268H which
has lift close to a CJ cam, though.

Thanks for the input,
Dan Jones

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