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Re: Adjusting C-1 carb idle
Sounds like you have a 56 carb on the front. That extra screw on the side should be shut all the way tight. It was originally used for idle speed, but was omitted in later models. The front carbs can probably be shut almost all the way if not completely. Try starting out with them shut and adjust the rear carb first. Then if you need a bit more air, open the fronts just a little. The car will likely idle too rich no matter what you do. It seems to be the nature of the beast. -
Re: Adjusting C-1 carb idle
As Ed noted, turn the screw on the linkage side of the base in all the way. Adjust the idle mixture screws on both carbs to get highest vacuum reading; the front carb needs to be part of the idle equation so fuel flows through it - otherwise the needle and seat and idle passages will get gummed-up from stagnant fuel. Good post further down from Jim Frakes on this, including keeping a long 1/4" open-end wrench handy for occasional "touch-ups". Just part of having 2x4's - they look good, but need more attention than a single carb; and, as Ed points out, they have always run (and idled) on the rich side - mixture distribution from the rear carb to the front cylinders is poor, so they're jetted on the rich side to keep the front cylinders from leaning out during normal (rear carb-only) operation.Comment
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Re: Adjusting C-1 carb idle
John is right, of course, (as usual)concerning the front idle jets. HOWEVER, on the 61 I had that was equipped with 2 fours, the only way I could ever get it to idle without spitting raw gas out the exhausts was to nearly close the front screws. If yours will idle decently with the fronts adjusted the way they were ment to be, by all means you should do so. But, if you see black spots in your driveway underneatht eh pipes, close the fronts a little. Not so much the the engine idles rough, just a lot less than the rear. Maybe you'll see what I mean. Hope you don't have the problem. Also, many folks find that increasing the idle speed a bit past the factory specs makes for a better idle with the 2X4's.Comment
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Re: Adjusting C-1 carb idle
Good point, Ed - mine idles very nicely at 900-950 rpm, and remains stable - not so well at 800-850 rpm.Comment
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Re: Adjusting C-1 carb idle
If I remember correctly mine would idle pretty well about 800. It was a hydraulic lifter/mild cam, and should have idled at 5-600. Your 270, of course, and would need a few more turns. My fuelie also needs about 950 to idle properly, though the factory spec is 800-850. In either case it seems that somewhere around 150 RPM more than the spec for the particular engine is what it takes.Comment
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