To cog or not to cog...

**Mitch Peoples** · 03-25-2003, 09:09 AM

that is the question. I just had a little accident with the new T-trim (blower pulley bolt backed out). Blower pulley shaft isn't damaged, but the bolt, washer and key are gone and the inside of the pulley took the brunt of the grinding.

I'm fixing the situation, but it seems that a switch to cogs could be a good alternative. The car will never be raced in a rib-only class, so what the hey? :D

I see some advantages like not having to torque down on the belt to prevent slippage, which means less load on blower and #1 main bearings.

How do I size cogged pulleys to match my current setup of a 7" crank pulley and a 2.95" blower pulley? Will there be any clearance issues with the water pump pulley? How much further out (towards the radiator) will a cogged crank pulley protrude vs an 8 rib setup?

Thanks!

**BK Meyers** · 03-25-2003, 09:34 PM

You can compare your existing serpentine set-up with a cog set-up by using the impeller speed calculations. Where you would normally input the sizes of the crank pulley and compressor pulley (such as 7" and 2.95") simply input the number of teeth on the crank pulley and compressor pulley (exa: 73 tooth crank and 30 tooth compressor).

Clearance at the crank does not become a real issue until you go to a 77-tooth crank pulley, and it really depends on your fan set-up. The 35mm cog belt is about the same width as your 8-rib now, maybe just a little wider. One of the biggest things to watch for is pulley alignment. The cog belt is not as forgiving as the serpentine in this area, though I have been luck y and b=never had a problem with either.

Hope this helps,
BK Meyers

**Mitch Peoples** · 03-26-2003, 09:07 AM

Thanks for the info BK. I found a nearly identical key at Lowes hardware and got everything back on last night. I will prolly stay with the ribbed belt unless I have another issue with the pulley.

The cost of going to cogs could be better spent replacing my 2 year old Hoosier QT Pro DOTs!

Good luck this year!

**BK Meyers** · 03-26-2003, 10:54 AM

Be cautious of a normal hardware store "key" (I cannot think of the proper name for them). You need to make sure that it is hardened steel so that it will resist bending.

BK

**BK Meyers** · 03-26-2003, 10:58 AM

You also mentioned that your blower pulley bolt backed out. I ws ablt to find a stud at a local auto parts store that was fine thread on one end and course on the other. This allowed me to have a stud in the drive snout and then have a larger nut and lockwasher holding the pulley in place than the normal Vortech arrangement. Using this stud I also did not have to worry so much about using and possibly damaging the snout threads by trying to tighten the pulley bolt so much.

Later,
BK