34ADF Jetting

[digitech]

I'm trying to improve the overall running of my engine on my '79 spider and I've noticed my plugs are showing the engine is "to the lean side". The engine starts, idles and runs well enough but it feels like it could make more power, like it wants to make more power but "just runs out of gas" if you know what I mean.

I have a indeterminate, higher than stock compression - not too high however, a 40-80 cam on the intake and stock cam on the exhaust, rebuilt stock head and 4-2-1 exhaust manifold with stock exhaust system. The carb is a 34ADF on a single plane intake. My original jetting was Pri. main, 120 with a 170 air bleed and the Sec. main, 130 with a 180 air bleed. I changed the Pri. air bleed to a 160 and the Sec air bleed to a 175. This made a slight improvement to the plug color but not enough; acceleration and high speed running MIGHT be better - hard to say.

I'm thinking the next step would be to go richer by a step or two on the main jets in the float bowl. If anyone has some jetting tips for the 34 ADF, I would greatly appreciate it.

Also, does anyone know how the secondary throttle stop screw is supposed to be set? I can't find any info on how it's supposed to be setup at all. I currently have the screw adjusted to just touch the linkage.

[124JOE]

you could try putting a large fuel filtter up by the carb

[digitech]

So, I changed my pri main jet to a 125 and the pri air bleed to a 165. Plugs are now beginning to come in nicely so I think I'm on the right track. The idle is decent, esp. considering the cam, with the mixture adjusting screw a little over 1 turn out.

The engine is pulling well, all the way through 6500 rpm which is as high as I've rev'ed it and doesn't have any flat spots, from off-idle to throughout the entire range. There IS some pinging from 2000 rpm to about 3200 rpm, on 89 octane - if my research is correct, this indicates a need to change the pri emulsifier tube to a richer one. However, I cannot get the existing tube out so that probably isn't going to happen. Instead, I'll see if the pinging can be controlled with higher octane and the next colder plug.

All in all, I don't know if I can get it to run any better.

[digitech]

Does anyone know if there is a recommended "spread" between main jets and their air correctors? I have been trying to keep a spread of about 40, i.e., my pri main is a 125 and the air corrector is a 165.