I just installed a 150 Amp Powermaster "stock appearing" alternator on my soon-to-be-installed BBB. It was necessary for me to re-clock the alternator but everything else looked good until I installed a new Gates XL 7490 (13/32" x 49 - 5/8") fan belt on it. As you can tell from the attached photos, the belt sits high on the alternator pulley.... So high that the cords in the belt are outside of the pulley groove. The belt fits deeper (but not quite down to flush with the edges of the grooves) of the WP and balancer pulleys, but flush with the edges of the PS pump pulley. The new belt measures 13/32" wide at the top but the groove in the installed alternator pulley measures only a hair wider than 12/32" at the top. The new belt fits the grooves of the pulleys on the SBB in my car, and the grooves of two OE-type alt. pulleys in my Buick parts stash, correctly. I'm concerned that there's a risk of throwing the alternator belt at high RPM. Time for me to pull the stock pulley off of the old alternator and replace the pulley on the new alternator with it (assuming ID, OD and the offset of the old pulley matches the new one)??? Thanks in advance for your help.
Is the diameter of the stk pulley the same if so just swap them. I'm sure power master has a deeper pulley too
Thanks for your response, Bens99gtp. It's not the depth of the pulley (which is one of their "deep" pulleys), but the width. The Powermaster catalog does show alternate diameter pulleys, but I didn't see anything regarding wider pulleys. I'll contact their tech department regarding alternate widths before doing anything rash, tho.
deeper width is what I ment.....not deeper like how tall the walls are. Guess I should had worded thst better......in my mind I knew what I was trying to say
As long as you have good side engagement - the "V" angle of the belt matches the pulley - I'd say you're good to go - unless you just don't like the look of the belt that high. Pulleys interchange, and depending on your needs, a smaller or larger diameter pulley might be better suited. Have you done the math? https://www.powermastermotorsports.com/power_pulleys_a.html
What is the need for such a big alternator? I use 70A (originally on a 5.7L diesel engine) which is OK, belt slip becomes more and more of a problem with big alternators. Bruce Roe
mine is 100 amp My electric fuel pump pulls just under 20amps 2 electric fans that each pull 25 on start up and go down some when running Never measured my water pump All 3 of which see more run time with out the motor running than with. Plus msd ignition But I can race all weekend without fear of needing a recharge
Thanks for your responses gentlemen. I appreciate you taking the time. Bens99gtp - I will most likely R&R the Powermaster pulley with one of the pulleys in my stash of old Buick OEM parts. They're the same diameter, which results in about a 1:3 ratio compared the the crank pulley (as Powermaster recommends for street driven cars). Besides I plan on having a few of the unpainted parts under my hood bright-white Cad plated to match what was found on late-60's/early-70s... Parts like the alternator pulley, fan and upper adjustment arm, throttle cable bracket, etc. Dave - Yup, I did the math. See my response to Bens99gtp above. Bruce - Since I have to replace my 70's- era Oldsmobile 85-AMP alternator anyway, I'm planning on a worse case scenario: Electric fan/fans, FI, stereo, etc. A 100-Amp Powermaster may have been a better choice, but we'll see what happens. Thanks again.
