I have a JayCee crank pulley. It is 7", not 6.75". I thought it would be good to get a little more cooling.
I did sell my semi-hemi heads when I went from 1776 to 2110. My compression went from about 6.9 to 9.
Think of this like a multi-speed bicycle. A bigger ring up front and a smaller gear out back means you go faster, but it takes more power to push the gear.
The crank pulley is like the big ring on the bike. A smaller pulley means the fan turns more slowly. A larger pulley means it turns faster.
The fan/alternator pulley is like the gears in the cassette on the bicycle's rear wheel. A smaller pulley means the fan spins faster, a bigger one means it turns more slowly.
The only way to overdrive the VW fan is to put a stock diameter pulley on the crank, and the smaller 356 fan pulley on the alternator. I wouldn't do this without a welded and balanced fan. Even then, I wouldn't spin my engine over 6500 RPM or so.
Most people want no more fan speed than they absolutely need. Spinning the fan more slowly means there is more power available for motive power. That's why this arrangement is called a "power pulley". There are many different combinations to play with.
Good Morning to some and Good Afternoon to others.
this pulley thing is simple...stock gen/alternator is 4 1/4" OD, but found some early pulleys measured 4 3/16" OD
CB performance billet pulley measures 4 1/4" OD
356 porsche is 3 3/4" OD.
stock steel crank pulley [with grooves and no seal] measures 6 7/8" OD
JC measures 7" OD with or without grooves for a seal.
Scat alum pulley measures 6 3/4" OD either with grooves or without for seal.
aftermarket "power pulleys" measure 5 1/4" and were designed to clear dry sump pumps and slow the fan speed and resistance at higher rpm's.
The popular trick of the days past was to use the 356 pulley to speed up the fan speed at lower rpm's. of course it also increased fan speed overall but the negative point was the fans would come apart.
Overall I have ran all these combo's and they were suited for each situation. there's not one correct application unless it's 100% stock. Same logic goes for the seal no seal topic. what ever works for your application. several people feel they need a seal at the front pulley to eliminate oil leaks. Most cases your oil leaks are due to TOO Much Crankcase pressure.
Hope everyone is doing well with all the things going on. no better time to work on that classic.......just think of it as a job and when you walk out to garage for 8 hours you won't hear your other half ask " what are you doing" every 10 minutes
DannyP posted:Stan, we need to first get rid of all the semi-hemi low compression Berg BS. Then we'll have made some progress.
;-P
Stan Galat posted:Think of this like a multi-speed bicycle. A bigger ring up front and a smaller gear out back means you go faster, but it takes more power to push the gear.
The crank pulley is like the big ring on the bike. A smaller pulley means the fan turns more slowly. A larger pulley means it turns faster.
The fan/alternator pulley is like the gears in the cassette on the bicycle's rear wheel. A smaller pulley means the fan spins faster, a bigger one means it turns more slowly.
The only way to overdrive the VW fan is to put a stock diameter pulley on the crank, and the smaller 356 fan pulley on the alternator. I wouldn't do this without a welded and balanced fan. Even then, I wouldn't spin my engine over 6500 RPM or so.
Most people want no more fan speed than they absolutely need. Spinning the fan more slowly means there is more power available for motive power. That's why this arrangement is called a "power pulley". There are many different combinations to play with.
Absolutely; I later switched to a welded and balanced fan with my 356 pulley. VS shipped them with the 356 pulleys but with regular stock fans.
Thanks, Danny. I just got out from under there trying to take pics of my oil pump and it appears that I've got the sand seal type. I'll post two pics on the other thread of my pump. You really can't see much.