Supercharger Pullies 14 mm or 8 mm

What is the better size pullies to run with on a BAE 521 ci with PSI Screw blower in a TA/FC.
Engine came with 14 mm pullies , but i want to change the overdrive ratios, so should i stick with the 14 mm or change to 8 mm pullies as i only have the one top and bottom pullies at present. What length belt should i also start with as I dont have any at the moment.

And is there a good size bottom pulley that you start with, that allows you to change the overdrives with only changing the top pullies. If so would appreciate some information for the 14 mm and 8 mm setups, what would be a good overdrive to start at.

Also has someone got any pullies for sale.

Regards Greg.
ph 0016478234401

 

Total tooth count, & center to center distance off the chart will tell you what length belt you need.

As far as the pulleys go...run what the other guys run. That way when you need to borrow a pulley, everyone is able to help (and the other way around)

http://www.rcdengineering.com/belt_chart.html

 

You see alot of broken 8mm belts and fewer broken 14's

8mm belts are okay for those that change them all the time.

 

If you're going to run TA/FC you 100% need to use 8mm. The smaller top pulley combined with 14mm makes it hard for the belt to....make the turn so to speak. The 8mm PS "purple belts" are the best that you can buy. Most using that application change them at 6-8 runs. You would want to be at 1.92 over or 92% blower o.d.. As far as belt length, I would assume you'd use the 8mm-1600-75PS belt.

Brandon Booher
NHRA TAD #323

 

Supercharger pullies and overdrive.

Thanks guys to the response so far, Current pullies that came on the engine where 14 mm with bottom pulley being a 45 tooth pulley and the top pulley being a 25 tooth, giving it 80 % overdrive, The Car is brand new and the driver is new to a TA/FC and will this be a good enought starting point, looking to only run low six's at first. til he gets comfortable with the car.

 

If you buy a 14 mm# 48 you will have 92%

if you buy an 86 and an 45 8mm you will have 91.1% no 8mm pullys will give you 92 %, I'm cheap, so i would go with the 8mm so the belts will last longer if theres a belt that long.

 

really? i used to put 10 to 15 runs on them and change them for general purpose on the funny car, then i had put as many as 20 runs on one with the pro mod. also i learned along time ago that belts just don't break on their own. belts break mainly due to detonation. plus 90 percent of all f/c's with a screw run an 8mm

 

Most run 1610 8mm and YES..detonation BREAKS belts! If we bang a panel, we change the belt

 

i ran 14mm 52 btm 24 top. use the largest bottom you can, it will help by slowing the belt speed down. if you do not have a raised cam block, the pulley gets real close to your pump drive. we milled the bottom of the extention to clear.