View single post by discogodfather
 Posted: 07-06-2020 07:44 am
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discogodfather



Joined: 09-17-2007
Location: San Francisco, California USA
Posts: 221
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 Did another round of tuning, this time concentrating on transition (4000 and up) and high speed throttle response and high speed ratios, including fast throttle and WOT pulls: in my original setup I had:

38mm chokes
4.5 Aux Venturis
120 main
F4 emulsion
170 air
55f9 idles
45 pump jets

I went and tried some other combinations:

F2 and F16 Emulsions - bad breakups, not smooth progression

Tried 50 f11 idle jets - not able to get the engine to run without lots of throttle or using the cold choke.

She seems to love 55F9 and won't run well on practically anything else, 3.5 turns for seated on the mixture screws. Around 13.5 to 1 on the wideband after set for max manifold vacuum.

She simply loves the F4 emulsion as much as the 55F9 idles. The F4 is a strange emulsion tube, it's listed in some of the books as a racing tube designed for alchohol? Some descriptions seem to suggest it has "fuel and air mixing at all rpm's and keeps fuel in reserve", whatever that means. The tube has holes in all of the areas- top middle and bottom. This is really the only emulsion tube I have which allows for smooth transition.

I was still experiencing popping on decel and as soon as I really got my foot into the throttle, doing quick WOT pulls, it was bogging and running very rich, like below 10 to 1 on the WB especially at 4000+.

So I decided to go to 36mm chokes to kind of try and get the air moving faster thinking it was related to some large quantities of air and fuel kind of lagging. Funny enough it made little difference and I was back to using the same jetting setup after some substitutions, but now throttle response was a little crisper and transition was better, and no more popping. Hard on throttle or on quick throttle, still running very rich and breaking up.

Got to the place where I felt like an even leaner main jet and a leaner pump jet is the way to go, at least to see some differences. I feel like at WOT the ratio should be around 10 to 11 to 1, with a cruising of 13 to 1. Ordered some 110 and 100 mains and 35 pump jets.

Last edited on 07-06-2020 07:47 am by discogodfather