waterpump pulley '65

[Twan B.]

my fan was out of ballance so i decide to take the fan and pulley off. Regarding the technical manual it is the correct one for my L75.
When i was inspecting the pulley (it was ok) i notice that there are the numbers 3850680-- stamped in.
Is this pulley a rep.?
Twan
#44079

[Jack H.]

Re: waterpump pulley '65

It's pretty common for GM to emboss pulleys for visual ID/verification. Your copy of the AIM cites what was factory original and the water pump pulley changed with engine configuration/options.

The base and L75 engines share the same pulley (3744043) which differs from what was used on L76/84 and L78. I did a quick check of my Parts and Accessory manuals (1972 and 1982) and didn't find the 3850680 pulley you cite listed as being a service replacement item.

That doesn't mean the part wasn't considered 'correct' in periods before or after the two time snapshots I looked up. Our friend Joe Lucia can probably recite nice and correctly what's up with the pulley part number you have in-hand...

[Mike G.]

Do you have air conditioning?

If so, that is the correct 2-groove water pump pulley.

If not, take it off and sell it for no less than $100. Rare piece (ask me how I know).

[Joe L.]

Re: waterpump pulley '65

my fan was out of ballance so i decide to take the fan and pulley off. Regarding the technical manual it is the correct one for my L75.
When i was inspecting the pulley (it was ok) i notice that there are the numbers 3850680-- stamped in.
Is this pulley a rep.?
Twan
#44079

Twan-----


Is this car an original C-60 equipped car, whether it is now, or not? If so, the GM #3850680 is the correct pulley. It's also quite a rare pulley since it was used only for 1964-E66 applications and was replaced by GM #3890419 for late 1966 PRODUCTION and for SERVICE in June, 1966.

The GM #3850680 pulley was also used for several other 64-66 passenger car applications but all of these were rather uncommon.

[Twan B.]

Re: waterpump pulley '65

Thanks for the respons, Jack and Mike, it is a 2 groove stamped steel pulley regarding the NCRS manual it is correct for my non air L75 Corvette. The cars with air do have a 1 groove pulley (regarding the manual).

[Twan B.]

Re: waterpump pulley '65

Thanks Joe, This is the reason a joined the NCRS, people know what they talking about!
Gr. Twan

[Mike G.]

Twan - where are you getting that info?

A non-A/C '65 L75 has a single groove WP pulley, p/n 3790356. There's no need for a second groove unless there's an A/C compressor on the engine.

That double groove pulley that you have is for an A/C car. It's called out in the AIM under option C60.

What NCRS manual are you referring to? If it says that 3850680 is for a non-A/C car, then it is wrong.

The good news is that you have a very hard-to-find pulley that's worth a few bucks.

[Twan B.]

Re: waterpump pulley '65

Hi Mike!
Regarding to the 1965 NCRS Technical Information manual page 117, Fifth Edition, Small block water pump pulley: Base Engine and L75 300HP: The standard water pump pulley is stamped steel with a double belt groove. there are no ### regarding to the manual.
Gr. Twan

[Joe L.]

Re: waterpump pulley '65

Hi Mike!
Regarding to the 1965 NCRS Technical Information manual page 117, Fifth Edition, Small block water pump pulley: Base Engine and L75 300HP: The standard water pump pulley is stamped steel with a double belt groove. there are no ### regarding to the manual.
Gr. Twan

Twan-----


GM says that the waterpump pulley used for 1965 base and L-75 engines without C-60 was GM #3790356. I have conflicting information on the groove count of this pulley, though. The AIM depicts a single groove pulley. GMSPO says it was a double groove pulley. I don't know why a double groove pulley would have been required for this application, though, and GM rarely used pullies in PRODUCTION with unused grooves.

[Mike G.]

Photos in Dobbins and Adams show

a 2 groove pulley on non A/C L75's, both 1964 and 1965. Aft groove is unused.

So as long as your belts all line up --looks like you're "money"!

Cheers! Mike

[William G.]

Re: waterpump pulley '65

I have a 65 300hp with air and looking in garage to find.
Could someone post a picture of 3850680 water pump
pully
Thanks
BILL

[Jack H.]

Re: waterpump pulley '65

I think the thread was focused on the PULLEY that attached to the water pump and not on the water pump itself with respect to embossed PN...

[Mike G.]

Re: waterpump pulley '65



Here it is. OD is 6.25". 3850680

[Joe L.]

Re: waterpump pulley '65

Does anyone have a GM #3790356 they could post a photo(s) of?

[Wayne M.]

Re: waterpump pulley '65

Twan-----


GM says that the waterpump pulley used for 1965 base and L-75 engines without C-60 was GM #3790356. I have conflicting information on the groove count of this pulley, though. The AIM depicts a single groove pulley. GMSPO says it was a double groove pulley. I don't know why a double groove pulley would have been required for this application, though, and GM rarely used pullies in PRODUCTION with unused grooves.

Joe -- a little more on the GM P&A info on this '356' pulley: my Rev. July 1 1965 does not mention groove count but shows that it is used on a TON of Chevrolet vehicles.

In my Rev 1 Jan 1970 P&A30B catalog, it shows for '63-6 Corvette exc. Sp.H/Perf, or air. It is described as DOUBLE groove, 7_3/32" OD, and (is supposedly) stamped with the part #.

1970 Catalog says also used for '66 Corvette w/A.I.R. (327) exc. C.A.C., Sp. H/Per.