back-firing 24-35

[Guest rwolf]

Can someone tell me what (if any) dist. caps are interchangable with the '24 4cyl. The car is doing a lot of back-firing. I've changed the condenser and the carb. She'll idle fine all day but on the road that's another story. I've just started to chase this problem and it just seems the next logical step to replace the cap. If it's not the cap maybe the coil is breaking down under load?

[D Binger]

Have you checked to see if any of your valve cages have turned?

[The Old Guy]

If your Buick has the condenser encased in a tin box, that may be the problem, even though it is new. My friend's 25 had the same problem, and we finally put a later style condenser in, and that cured the trouble.

[Guest rwolf]

The condenser I added is the modern type , round metal, the microfarad rating may not be correct but I doubt if it is breaking down.

I checked the valve adjustment and it is correct. I don't know what you are refering to as a valve cage?

Thanks for the interest and advice

[Brian_Heil]

You have a 24-35, you don't have valve cages. 1923 was the last year for valve cages and then only on the six. If you're running a stock marvel carb. I'd guess it's out of adjustment. Keeping track of where the air screw is on the carb. (that's the large knob on the top) to start with. Crank it in a couple of turns to lean it out and see what happens or go the other way if that makes it better. You only have four cylinders, if you had a miss fire due to ignition, you'd be seeing it at idle too.

[Guest rwolf]

Brian,

Thanks for the input. I couldn't find the right size heater tubes for the Marvel so I replaced it temporarily with an updraft carb I had. The carb worked fine on my 6cyl Willys-Knight. Do you think it could be some kind of a valve problem-like weak springs, or maybe they get sticky under load?

[Brian_Heil]

Heater tubes with today's fuels are a problem. 1920's fuel due to it's low reed vapor pressure (RVP) needed the exhaust heat in Winter to make it ignite, today'd fuels don't need the heat and the tubes/heat can lead to vapor lock problems in Summer. This tube system really worked well and I think was a big reason Buicks sold so well in the North and in Canada but today it can really ruin a hot days tour/fun/parade. If you want the tubes so you look authentic, that's fine but plug them so none of the exhaust gas can get to the carb. Take the butterfly out of the exhaust valve too for better performance. Only you and I will know its in a cigar box for the next owner and that the tubes have a small freeze plug stuck in them on both ends. I took my tubes off all together. They transmit heat by conduction like the devil himself.

Don't know much about the carb you cobbled in. If it worked on the other car well, it should here too. Have you checked all the other things? Fuel clean? Plugs, wires, cap, rotor, points?

I had a miss once that drove me nuts. It was a failed ballast resistor wire that would vibrate like a broken light bulb filament sometimes making contact and sometimes not. Also Buicks are famous for shorting the plug to the sheetmetal sparkplug cover with today's longer plugs. The original plugs were short little devils and it wasn't a problem. I've added sparkplug boots.

[Guest rwolf]

Brian,

Thanks for the information on the tubes, very interesting. I suspect I have something breaking down in the ignition system. Problem is it only happens under load. It will idle all day with no problem, when I drive it that's the problem. When there's no more snow and the weather is warmer in N.Y. I will leave sunny Florida and figure it out.