Do you really need a blow thru carb when used in a procharger box.Isn't the pressure equal unlike when you use a blow thru hat. JOHN SR

That's what I was told, regular carb inside the Procharger box.

C&S and prosystems will run lines from the hat, to the throttle shafts, to keep them pressurized under boost. So you can run a hat and not have fuel leaking past the shafts.

but they have to modify the throtle plates and install seals so when its under pressure the installed hos's willl expand the throttle shaft seals..

Fenderack,,no matter what you will need to modify the carb and make it a blow through carb.(the carb is always under pressure and the boost pressure is forcing fuel out of it).you will need jet extensions on the rear metering block,you will need notched solid floats..i run .150 needle and seats,the holes behind the power valves need to be opened up to flow more fuel..i run the jets square and also open all 4 barrels at once to get equal distribution of fuel to all the cylinders..

the answer is yes,the boost is being blown through the carb instead of sucked through,big difference in the power valve system.

If your box is charged at lets say 12psi That means that you have 12 psi around the carb and in the carb down to the throttle plates correct so all that being equal it seems like if any the you would only need seals on the throttle shaft.With a blow thru hat you have 12psi in the hat and down to the throttle plates but atmospheric pressure on the outside.Just trying to get his figured out in my head. Because I was also told I do not have to run a blow thru in the box. I want to make sure what's correct.Thanks for any input. JOHN SR

john,like i said earlier,there are things that are different on a blow through carb,more than throttle shaft issue.i have a buddy with a m3 setup with a pro systems carb in the box,nothing is done to the throttle shaft bushings and he gets some fuel in the box that he drains every now&then but it is not a lot.pro systems makes a deal that goes under the carb for not in a box blow through setup and works in conjunction with modification that they do with the throttle shafts.if you call patrick from pro systems he can explain how it works much better than i can.some will say that the plate&modifications are not necessary but do you want fuel leaking from the throttle shafts while under boost in a closed engine hatch,the possibility of a fire and the liability issues is why the carb is in a box in marine application,but not in a car.i am by no means a pro charger expert but i do have experience with them both in and not in a box.