ucc2ic65

Can someone explain why the 365hp motor (and other larger hp engines) had a wider machined pulley on the alternator versus what came with the smaller hp engines?

Thanks

Nowhere Man

The combination of the deep grove pulleys and what grove the alt belt runs on

68hemi

Made to keep the belts from rolling over and/or flipping off. They are referred to as "deep groove pulleys."

ucc2ic65

So was it effectively a like a spacer?

ucc2ic65

Got it. Thanks.

Nowhere Man

The alt belt runs on the outer grove of the double grove pulley

ucc2ic65

Thanks.

Easy Rhino

The larger diameter allows the alternator to turn more slowly, avoiding over-speeding it.

The deep groove helps prevent throwing the belt at high rpm or when quickly changing speed.

The thickness allows it to align with the outer belt, as the SHP engines came with the inner belt that used the idler pulley.

63 340HP

For whatever reason the 340 and 365 hp alternators pulley groove is spaced out away from the alternator (possibly, as mentioned, to provide alignment with room for the deep grooves in the crank and water pump pulleys).




In a pinch a dual groove alternator pulley aligns the belt in the outer groove.

68hemi

Corvette Central shows this alternator pulley as correct for 1965 350-365 h.p. and A/C. but I doubt that it was the case OEM but is in fact a catch-all pulley. The 350 and 365 should be different since one used and idler (tensioner) pulley and one did not, PS was available with 350 and not with the 365. A/C and PS were available together with the 350. There were a lot of different crank, WP, PS, A/C and alternator pulley combinations on C2s

https://www.corvettecentral.com/c3-6...ey%26count%3d9

More pulley info in this thread.

https://www.corvetteforum.com/forums...ng-belt-3.html

SWCDuke

IIRC the Delco specified max rotor speed for their alternators is 18,000 RPM. So in order to avoid exceeding this speed with the high redline mechanical lifter engines the pulley effective diameter had to be larger to slow it down, and given the higher idle speed of mechanical lifter engines, it provided sufficient speed/amps at idle speed.

Given the relatively low volume of these SHP/FI engines it was probably cheaper to machine these pulleys than tool up to make the two piece stamped pulley used on most engines, so what you got was something that was a bit heavy, but bulletproof.

Duke

Avispa

Yep, check out the two different alternator pulleys for L36 (hydraulic lifters) and L72 (solid lifters) big blocks with power steering. They're both have a belt groove spaced away from the alternator, and the L72 pulley is smaller diameter

L76_Cpar

Hi Duke,

I found your post from late last year on alternator pulleys. You may recall, you helped me tune / time my 65 L76 last month and it runs great now. Thanks again!

I am now looking to correct a few incorrect parts on the car and am working on restoring the correct 37 amp 1100693 alternator for the car . Do you know the part number for the correct 3 5/8 deep grove pulley? Is it 3829387 AI by chance? Is there a pn for the fan?

Chuck