Autolite 4100 Carburetor 1.12 to 1.08 bore adapters
Sometimes at idle there is a hesitation under initial acceleration. This is one of the few flaws in the otherwise excellent Ford Autolite Model 4100 4 barrel carburetor with the larger 1.12" ventures.
This DIY option shows you how to make is two copper sleeves to size down the primary bores of a 1.12 Autolite 4100 carburetor for improved throttle response. They reduce the intake area of the primary venturi to the same size as on a 1.08 carb but keep the extra diameter once the air leaves the opening and mixes with gas to keep the ratio correct. This will not turn your carb into a 1.08 unit as it will still have the larger throttle plates and 1.12 boosters.
The install is straight forward . You put the sleeves in your freezer for about 15 minutes and them press them in the venturi openings by hand (after removing the primary cluster). They will expand and be a tight fit. Do to tolerance in manufacturing in the 60s some slight fitting may be required. I had one customer (the first quote below) that the adapter was loose in one of his two bores (issue with the manufacturing of his carburetor) but the sleeves still functioned flawlessly. As in that example if the sleeves should ever come loose, there is no danger of them falling into the carburetor because they are too big to fit through and they will continue to function as designed.
You only need to make one set as they are not required for the secondary ventures
If you want a 1.12 carburetor to function exactly like a 1.08 carburetor you would need to install these sleeves, change the jets to meet your engine specs AND change/modify the boosters.
What these sleeves WILL do without any other modification is improve throttle response and make it easier to install a big block 4100 on to a small block
Quotes from customers who are running these sleeves:
"Instant difference in throttle response and almost completely eliminated the hesitation off of idle, very impressed."
"The Venturi reducers have been installed and I am very pleased in how the car is running."
When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission.
Affiliate links to items in this video:
Ball Bearing amzn.to/3FI6YnB