recarbing/sparking - MC 350/260

[fasteddy]

'78 19' Cobalt dv with a MC Alpha 350/260. Qjet carb with choke stove, mech secondaries, vac choke pulloff. Looks like the original carb with the MC tag still on it.

I've got a bog at 3200 that really impairs planeoff. I've toyed with mpi and tbi dreams, but the practical side says stick with a carb that fits all the other hardware, instead of hack wiring and reprogramming an efi system (at least for this season...).

I've found several vendors, and most offer a generic 350 Qjet replacement that has 'lectron choke and vac secondaries, both of which I like for around 250 without a core.

Question A: What's the best ign switched engine mounted power source for the choke wire, and should I rig a timer circuit that resets at ign off?

Q. B.: The secondaries are tunable by changing the secondary vacuum diaphragm spring. What secondary kick in is likely best for a heavy old Cobalt to snap it up on plane? Fast or slow open?

This motor also has stinkin' ign points/condenser. I had to beat the spider webs off my Heathkit dwellmeter to tune that thing. And steal my wife's diamond nail file to clean up the points, since the point screw is so chewed up it's gonna take a drill to get it out. Aftermarket distributors or hack in an HEI? Since I don't care about spark fade above 4800 on a 4600redline motor..

I'd like to hear direct experience with ease of install, tuning, longevity.

[kenJ]

Have you tried rebuilding what you have? Carbs don't usually fail, they get gummed up. Good cleaning may solve your problems. I'd spend the money for a breakerless distributer. It's hard enough to adjust points in the driveway. Would hate to try in a rolling boat.

[fasteddy]

It's a 30yr old oem casting, with sloppy shafts and worn linkages and overall corrosion and crud. My time is more valuable doing something else besides voodooing in a new carb. And I believe that vac secondaries are better in this app than mech secondaries with a manifold that needs high velocity flows for efficient cylinder filling and mixture homogenizing. The secondaries only open as much as the engine demands air, regulated by manifold vacuum. This means that the position of the mixture needles on the secondaries more closely matches actual air flow, and that air flow is at the most efficient rate for fuel flow from the secondary jet. Mech secondaries bog. The sound of "the four barrel" kicking in is really a short bog. I like snap, not bog. Electric chokes don't get hung up by a floating choke stove housing or a rusted bimetal spring or a mud dauber nest on the stove or a missing clip. One wire. Simple and elegant.