Rebuilt my Autolite 2100 but have a float level question ?

Dougsters

Member
Jun 30, 2010
77
3
9
Temecula Calif.
Set my 2100 carb. wet float level per specs. runs much better but my question is--after shut down and car sits for a while I rechecked level and it dropped an 1/8th." restarted up rechecked and back up to correct level.Is gas flowing backwards for a second until neddle seats(new needle/seat) or is it seeping out venturis, cann't see any gas dripping but can smell fuel down throat. So is this drop in gas level normal? And a surge back up 1/8th" due to pumping action? Thanks for your help.
 
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Dougsters

Member
Jun 30, 2010
77
3
9
Temecula Calif.
Realmongo thanks for info but on same topic >

Most likely it is evaporating off the hot engine through the vents.

Yea evaporation makes sense--- another question thu ,do you know if it really matter's about venturi size I have a 66 289 C code C4 2100 on for 15 years.Called Pony Carbs and they said my 1.23 vent. size and carb. no.C4MF is for a 390 C.I. engine and should have .054 jets. Is it really worth it to go to the 1.13 venturi size for the 289 whats the upside if any? Better milage etc. ? When I rebuilt never checked jet size. BTW plug inspection looks good and runs OK other then 10 MPG in city. Thanks Much.
 

Dougsters

Member
Jun 30, 2010
77
3
9
Temecula Calif.
Forgot to mention ,it's a calif. car and had all smog equip.on

Yea evaporation makes sense--- another question thu ,do you know if it really matter's about venturi size I have a 66 289 C code C4 2100 on for 15 years.Called Pony Carbs and they said my 1.23 vent. size and carb. no.C4MF is for a 390 C.I. engine and should have .054 jets. Is it really worth it to go to the 1.13 venturi size for the 289 whats the upside if any? Better milage etc. ? When I rebuilt never checked jet size. BTW plug inspection looks good and runs OK other then 10 MPG in city. Thanks Much.

when I bought it last summer.Since removed smog pump etc. A mustang shop put motor together 16 yrs. ago when it had to pass smog,maybe they downsized the jets anyhow will pull and see. Thanks.
 

Realmongo

I prefer to be called "Evil Genius"
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Oct 10, 2001
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The original 1966 289 2V C6DF-A, B, E, or F carb with its 1.14" venturi was rated at about 300 CFM, where the 1964 Mercury "Special" C4MF-A, D, or E with its 1.33" venturi was rated at about 400 CFM, which will allow your engine to rev higher. You can always have it dyno-tuned to get the A/F ratio just right.