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Old 02-08-2012, 06:14 PM
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Originally Posted by chrisinestes
I'm building a hot rod from the frame up. I'll be using a Pontiac OHC 6 for power. I thought it would look sweet having 6 MC carbs on it. I've done a ton of Googling on the subject and it's been done, but it's a tricky thing. Nobody I've talked to has actually done it themselves, they just have seen it done succesfully by somebody else. It seems the main problem is MC carbs don't have accelerater pumps and aren't designed to run with much fuel pressure at all. It's a budget build, so I can't just go buy 6 new Mikuni Harley Davidson carbs at $500 each.

Has anybody here done this, or know somebody who has? Any Ideas? They wouldn't have to be MC carbs, I'd just want 6 1 BBL carbs.

Ak Miller did this on 6 cylinder Mustangs back in the 1960's. Problem then was finding M/C carbs with enough venturi area to support a cylinder. These days with 40 plus mm carbs that's less of a problem.

Like you said 6 Mikuni flat slides for a Harley would set you back about 3000 dollars. that would get you carbs with accelerating pumps. However when the carb is mounted up close to the head an accelerating pump is less necessary.

The carbs don't have to be logged together, there is no need to balance cylinder to cylinder vacuum except to run vacuum accessories like power brakes. Still if you log them you can somewhat take advantage of all the venturi area per cylinder. Note Yamaha's Ex-Up system that opens all the carbs to a log at high revs so any cylinder can breath through all, this system was used on the V-Max.

The fuel pressure can be managed with a regulator to get the pressure down to a couple pounds. The best way to do this is either a bypass regulator or two regulators one between the pump and a reservoir than another to the carbs feed from a fuel log. Either of these takes the pump pulses out which makes the carbs usually fed by gravity a lot happier.

The throttle linkage gets complicated as each carb has to be actuated and adjusted individually, you'll be using a lot of small Heim joints with ball bearing supported shafts for smooth operation.

For this kind of money you could put individual runner EFI on it which would be less trouble in service and look every bit as cool. you colud build this around the system off a junkyard Chevy Colorado with the inline 6.

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