Carb jet size


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By redbirdman - 10 Years Ago
I'm using a Ford 4bbl carb. from a 1969 390 on a 312 engine with a VERY mild Dempsy Wilson camshaft. It has #48 main jets. It idles so rich it will burn your eyes. Runs fine otherwise. I have double checked the timing, point dwell, etc. I have had the float level at several levels. Seems to do the best at the correct setting. It has been like this for years, I'm finally getting tired of it!! Any thoughts on jet size. Thanks

Jack..

1977 T'bird
1955 T'bird
1946 Ford
1971 Torino
2004 Taurus
2010 Range
1977 Mustang Cobra 11
By charliemccraney - 10 Years Ago
Which carb?  What are the specs on the "very mild" cam?  Jets should have nothing to do with idle.
By Oldmics - 10 Years Ago
If your sure that the float levels are correct, then I would hazard a guess that your idle bleed circuits are clogged in some fashion which would allow less air into the circuit causing it to run rich.
Cure - ???????????   Rebuild it !   Making sure all of the passage ways are clean and open everywhere. Make sure you also check the needle screw valves on the metering blocks for any wear.

Oldmics
By PF Arcand - 10 Years Ago
To clarify, is that carb a model 1.08 or 1.12 ?  Apparently the 1.08 seem to suite our Y-Blocks better. Also, I read that some of the models used on 390s & so on, were designed for use on anti smog engines, so there may be some significant tuning issues.. 
By slumlord444 - 10 Years Ago

Had a carb off a 390 on a 302 for some time. Never could get it to idle right. Finally had a small holley rebuilt and works much better. Try smaller primary jets.
By redbirdman - 10 Years Ago
Thanks for your interest. I ordered #46 jets yesterday.