Weber 48 IDF Carbs Options

[914 Monster]

Can anybody please inform me about the 48 IDF weber carbs and which IDF weber carb provides more top performance?

[Al Meredith]

I had 40MMs on my 2056 when I built it . My Son wanted to see how it would perform with 44's. We installed EMPI's 44's and he says he can feel the improvement at high RPM. I know it is running rich but it is cold in Atlanta and I don't want to rejet until it gets warmer. The flat spot at about 3000 RPM is gone with the EMPIs , that could be the rich mixture. Oh! at the Dyno it does show rich now. I'll have a better responce whenit gets warmer.

[r_towle]

I had 40MMs on my 2056 when I built it . My Son wanted to see how it would perform with 44's. We installed EMPI's 44's and he says he can feel the improvement at high RPM. I know it is running rich but it is cold in Atlanta and I don't want to rejet until it gets warmer. The flat spot at about 3000 RPM is gone with the EMPIs , that could be the rich mixture. Oh! at the Dyno it does show rich now. I'll have a better responce whenit gets warmer.

Drive the car.
Define upper end for yourself. At our age its probably lower than what your son feels. You can put in a rev limiting rotor to save the motor from your son...I did and he never knew.

Big valves and big carbs will only kick in from 4500-5500 rpm and then your valves start to float...unless you have stiffer valve springs, lighter valves, etc etc.
Track car, living at those RPM's for 20 minutes...you bet.
Street car that stops and goes...never.

I have tried both...the 40mm carb, properly jetted is really a nice match for these motors under 2.2 liter...that seems to be about the limit.

Intake air speed in the lower range is terrible with big valves and big carbs...or one of those alone..even worse. Then the air/fuel mixture stands a good chance of deatomizing with the fuel returning to a liquid..then fouled plugs are the result.

Rich