Author
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Topic: Cam and converter selection for DeTomaso Longchamp Coupe with 351C/C6
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Daniel Jones Gearhead Posts: 972 From: St. Louis, MO Registered: Aug 99
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posted 04-22-2003 11:09 AM
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
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SteveLaRiviere Administrator Posts: 48752 From: Saco, Maine Registered: May 99
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posted 04-22-2003 11:16 AM
The 268H ran great with the stock six cylinder C6 converter in my truck.------------------ '70 Mustang Mach 1 - '72 Mustang Sprint - '94 F-150 Please remember our sponsors, Mustangs Plus, NPD, Osborn Reproductions, MyFordPerformance.com, and FordRamAir.com
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Moneymaker Administrator Posts: 29200 From: Lyons, IL, USA Registered: May 99
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posted 04-22-2003 12:06 PM
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 Fleet of FoMoCo products including 88 ASC McLaren Mustang #28 Professional Manwhore The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked." Quote #2: "Make sure brain is in gear before engaging mouth!" Quote #3: "If you can't run with the big dogs, stay on the porch!" www.moneymakerracing.com
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Daniel Jones Gearhead Posts: 972 From: St. Louis, MO Registered: Aug 99
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posted 04-23-2003 01:59 PM
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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