LP carburetors.

M.Genrich

Member
Im getting ready to convert my old single block U to LP. Im new to propane and my question is this. The engine is a little 403 with a 11.5 static compression ratio running at 10% over factory high idle. I don't figure I need a giant carb. I have a new 100 impco and a century that I believe came off of a 705. From what I have been told the impco is the better carb but the century looks like it will flow air a whole bunch better. any thoughts???
 
The century carb should have a spray bar in it. If the carb is too big for the engine you won't develop enough vacuum to draw in enough fuel for full power. Need 1" vacuum at WOT for it to work properly. Exhaust analyzer is the proper way to set them. I put sleeves in some of them around the spray bar to create a venturi effect. The impco won't have that problem as the air flow determines the fuel flow.
 
I have almost the same set-up as you do. I have a 403 with 10a4213 heads, custom ground cam for 10% over, but I am using the ensign carb and regulator, which I am looking into replacing because I cannot make the regulator work right.
 
Impco flows about 190 cfm. That's more than the 670 lp manifold can flow and more than a 4232 can flow I'd use an impco E regulator.
 

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