Good Morning, I have to replace my power booster (again). I am thinking of doing an aftermarket one like the one linked. I am curious about the different diameter sizes. Most seem either 8 inches or 9 inches. What difference would the diameter make....

I should add, I will most likely need to add a vacuum pump, with my cam I only get about 10-11 inches of vacuum.

Thank you.... :-) Timothy

https://www.summitracing.com/parts/l...=true#overview

 

Timothy,
The power of the booster is determined by the area of the diaphragm.
So, compared to a factory 11" booster, the 9" has a third less power and the 8" has 47% less power.
If you need a smaller booster for clearance, some use a dual-diaphragm 8" which has about the same power that the 11" does. That looks like the one you linked.
Gary

 

Ditch the vacuum pump and booster and get a hydroboost. Running off the PS pump pressure makes this insensitive to engine vacuum and it's much smaller.

 

Love to do that Joe, but “eeck” that is way out of my budget….

 

Which one are you looking at? This one is $475.



If you want to spend a little fabrication and scrounging effort, you can adapt a common hydroboost from a GM one ton pickup using these brackets.

 

Oh wow - that is definitely reasonable. I was looking at some on Summit that were starting at $ 850 and up.