'66 Belts and Pulleys 427/425

[Scott S.]

Welcome from the frozen north. My fan to crankshaft belt seems too short. The belt measures 34 inches and pulleys measure 6 5/8 on the crank and 7 1/8 on the water pump. Does anyone have the correct pulley and belt numbers? Joe Lucia are you out there? Thank you in advance for your help.
Scott Sinclair #2379

[Wayne M.]

Re: '66 Belts and Pulleys 427/425

Scott -- sounds like your pulley diameters (outer rim dimension) are correct. Measured my 396 but the '66 are the same. Your problem is in the belt. Should be # 3837810 and 34-3/8" long (not 34"). Your upper pulley # should be 3864480, later changed to 3906656 (undoubtably same dia.). Your lower cast iron pulley is # 3863108.

Have you unbolted the w/p pulley to set the belt in the groove, before bolting back up to the hub ?

Wayne -- warm winds blowing in the north west.

[Dan A.]

[Joe L.]

Re: '66 Belts and Pulleys 427/425

Scott-----

I agree with the information provided by Wayne and Dan. The belt you need was originally of the GM # mentioned. GM says that belt GM #9433722 will replace that belt and SERVICE your application. It's 34-3/8" long. What's more, it's still available from GM.

These captive belt situations require a precise length belt since there's absolutely no adjustment. Your other option would be to order the reproduction belt from Quanta. This would, theoretically, give you both correct length and correct configuration.

[Scott S.]

Re: '66 Belts and Pulleys 427/425

Thank You, Wayne, Dan and Joe. You have been a great help.
Happy Corvetting
Scott Sinclair

[R N.]

Re: '66 Belts and Pulleys 427/425

Hi Scott,

I just went thru the same thing. I ended up trying 4 different belts (same item from Quanta) before I got one to fit. Quanta offers a short version (34.4") and a long version (34.8") of belt # 3837810. The first two belts from Quanta measured 34-1/8" and 34-3/16" both didn't fit, the long version measured 34-5/8" and was way too big.

Quanta went thru their stock and the longest belt they could send me was 34-1/4" (not the 34.4" they state). At first I didn't think it would fit. I installed the belt around the lower pulley and then around the W/P pulley while it if off the W/P. I then got it far enough onto the water pump as to were I could get 2 bolts started.

As there is very little clearance if any between these two pulleys when installed, I very carefully pried (in the v-grooves of the pulleys from the side) with a larger screw-driver to get enough space for the W/P pulley to clear the lower pulley.

Working it a bit I got it on the W/P, after this I then tighten the W/P pullyey with the attaching bolts and everything fit AOK. Once everything was aligned I removed the bolts again and then reinstalled the bolts with the fan in palce.

As others have said, you need an "exact" lenght belt. In my case 34.250" was enough, but tight. Hope it helps Scott.

Regards,

Kurt