I bought one of the manifolds for the front 3 cylinders and planned on using the cut off rear manifold. My engine builder hates this idea and thought I should use other dutra on the rear. What do you think about this? I'd like to hear your thoughts about HP gains if any. I looks to me that the Dutra manifold I bought should flow very well. Is the cut rear manifold going to kill me on the dyno? Does a 2nd Dutra fit on the rear a still clear the starter and kick down? (I am likey going to the Lokar cable anyway and have the mini starter)
Keep in mind that I am building a 260 stroker and doing all the head work available, cam, 4 barrel, ect. How much HP will be lost by not using a 2nd Dutra manifold? I am really just looking for an educated guess here. 5HP, 10HP or alot more?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

http://www.dutra.org/doug/doug-sl6-exha ... -duals.htm

There is some work involved in doing this as the link outlines.

I think their are more horses to be lost in not properly designing the system after the manifolds.

I dont know that any testing has been done to indicate the HP differece between the factory rear and the rear Dutra. I think 5 HP sounds reasonable.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

You will have some clearance issues between the rear Dutra and the starter. I have the full Dutra duals, and a mini starter, and still had to do some grinding on the exhaust flange to get clearance. I wrapped the starter for heat, but eventually the wrap fell off, and I never replaced. It has not been a problem, but the wiring is very close to the rear manifold as well. There really is not anything wrong with using the front Dutra, and rear modified stock unit. You have carb heat with that as well, which gives better cold start drivability.

I had the rear stock unit for several years before I went to the turbo. It was the turbo that prompted me to get the rear Dutra. When I started planning the turbo project was when I purchased the rear unit. It was a year or so before I actually used it, and the entire project took almost a year to fabricate and get running. If Lou Madsen hadn't made a charity run up from North Carolina(he's now in VA) it might still be just sitting there.

My point is, once it is done one way, it is a big deal to change it. And, it probably does not make much difference. Don't let your machinist scare you. He most likely does not know the slant world, and its slanted engenuity.
Sam

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If you're driving on the street, the front Dutra/rear cutoff setup will be considerably less hassle. Your machinist probably isn't really familiar with the setup and is just going off the pictures in his head.

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Too many people who were born on third base actually believe they've hit a triple.

Howdy,

Looking foward to time trials on that stroker! Gotta agree with the other guys, that cut off rear will work just fine and work readily easily....as in bolt on. The advantages of having my 4bbl heated, an easy fit up and coming close to maximizing breathing with a large exhaust have never made me regret my installation. Also, while I used an older exhaust manifold if I had it to do again (and I AM starting another project) I will use a newer exhaust manifold with the round weight and better ribs. The wiring was not a problem for me because I used AndyF's brackets to move a GM alternator to the driver side down low, then completely rewired the whole harness to use relays and switches everywhere. This let me islolate wiring, use high temp wiring of lower gage number than stock and insulate it from engine heat.

rock
'64d100