decided to upgrade to a Borgenson P/S setup
and Vintage Air . Trying to determine pulleys required
seems stock arangement was
2 grove pulley on water pump (short shaft)
3 grove pulley ( 2 piece ) on crankshaft
single grove for Alernator, P/S pump and Air Compressor
would like to use stock setup
any help in finding the pulleys (part no.s , similiar type replacements etc.)
thanks
Steve Fiore

 

Hi Steve:

Welcome to Corvette Forum. I can't quite tell what year your car is, so I'll just describe the '66-'67 L79 setup that I am most familiar with.

It's important to understand that when a '66-'67 Corvette small block had BOTH power steering and factory air, the pulley set used on the L79 was the same as the pulley set used on the 300 HP base engine. This was a "standard groove" pulley set rather than the "deep groove" pulleys used on other versions of the L79.

I believe the reason was that the wider deep-groove pulley set would push the PS pump pulley too far forward to guarantee clearance from the frame. For small blocks that had both PS and A/C, the PS belt rode in the outermost, third groove of the crank pulley. This brought the PS pump pulley very close to the frame rail. Here are the factory parts for an L79 with both PS and A/C:

Water pump pulley: 2-groove, part number 3890419
Crank pulley: 2-groove, part number 3850838
Crank add-on PS pulley: part number 3751232
PS pump pulley: 1-groove, part number 3770509
Alternator pulley: 1-groove, part number 3909817

These are all "standard-groove" pulleys that require a slightly smaller offset on the water pump hub than the 350 HP L79 engine. When that offset is correct, the crank pulley and the water pump pulley will be perfectly aligned.

The inside groove on the crank drives the water pump and alternator. The middle groove on the crank drives the water pump and A/C compressor. The outside groove on the crank drives the PS pump.

If you are using the stock GM power steering pump, this pulley set should line up fine. Note that some attention may be needed for aligning the non-stock Vintage Air compressor, but whatever setting they use for the 300 HP base engine will be correct for this pulley set.

If, by any chance, you plan to regularly run your engine to 6000+ rpm, you will have some risk of tossing the long A/C belt and/or alternator belt. Be sure to keep them properly tensioned. In general, GM used deep-groove pulleys on the L79 to help keep the belts from getting tossed at high rpm.

While GM did not use deep-groove pulleys when the L79 had both power steering and A/C, it is possible to assemble a deep groove pulley set using pulleys from other GM applications (based on a GTO PS pump pulley). Clearance between the PS pump pulley and the frame is close, but it fits on my car. I can provide details if you are interested in this non-stock option.

 

Steve, welcome and I love all the pictures of your restoration you posted in your album. Very nice!

Looks like you have a ‘67 coupe. Joe’s advice above is spot on, just realize you may need a bit of trial and error to get it right. The VA Sanden compressor requires a unique mounting bracket and they offer a plain steel bracket you can paint to keep the sort of stock look. You can use a stock ‘67 Corvette PS pump with the Borgeson along with the WP and crank pulleys Joe mentioned. Your next issue will be finding the correct length belts, but I usually buy a few different ones, find the correct one and return the rest. Good luck and what color is your coupe?

 

Hi Joe,

Thanks for the response on this one. I'm real interested in this topic because I have a '66 L79 that I added power steering to 2 years ago, and I'm now considering adding Vintage Air as well. However, my research turns up some different part number that are required to make this additional mod . . . and I'm referring to the diagram in the AIM on page F428. In comparison to your part numbers, here is what the AIM says:

Water pump pulley: 2-groove, part number 3890419
Crank pulley: 2-groove, part number 3850838
Crank add-on PS pulley: part number 3751232 - should be part # 3855836
PS pump pulley: 1-groove, part number 3770509 - should be part # 3834720
Alternator pulley: 1-groove, part number 3846180 - should be part # 3875368

My current set up has the a 2-grove upper and lower pulley for the crank and water pump with a belt on the inner groove running the alternator, and the belt on the outer grove running the power steering pump. It appears with the VA, the belt on the outer grove would then run the VA, and I'd need an add on pulley on the crank to run directly to the power steering pump - that would therefore necessitate a new pulley on the power steering pump as it would need to move forward to line up with the new add on pulley? Your thoughts? Thanks!

Tom

 

Hi Tom:

I found one mistake on the alternator pulley, and have edited it. For 1966, I think it was 3879368. For 1967, I think it was 3909817. I'm away from home right now, but I will check my '67 AIM when I get back. However, I'm 99% certain about the other part numbers I provided. Another guy (Mark Gorney, RIP) investigated this topic separately and came up with the same part numbers I provided. I have a '67, but Mark had a '66 and he thought the pulleys were the same for '67.

Does your L79 have the factory pulley set for an L79 with PS but no AC? If so, that would be a deep-groove pulley set. Your PS pump pulley should be cast iron and will line up with the second (most forward) groove on the crank pulley, and the alternator pulley should be machined aluminum.

You are correct that the PS pump is always driven by the forward-most groove on the crank pulley. So, when you install the add-on crank pulley, the PS pump pulley needs to move forward to line up with the new third groove. This where I think GM got spooked by the tight clearance between the PS pump pulley and the frame.

They solved the problem by using the standard-groove pulley set from the 300 HP engine with PS and A/C. Standard-groove pulleys have narrower grooves, so a 3-pulley stack-up of standard-groove pulleys is about 3/8" shorter than a 3-pulley stack-up of deep-groove pulleys.

When I explored converting my '67 with PS and A/C to deep grooves, I found a deep-groove PS pulley from a GTO that had just barely enough frame clearance to work. Then I worked backward through the crank, waterpump, and alternator pulleys to get everything to line up.

If you want to see if the GTO pulley clears the frame on your car, the GM part number is 9786900. I found that the originals had a bit more clearance than the reproductions. These, and all the other part numbers mentioned here show up regularly on ebay. FYI, here is the complete deep-groove pulley set that I installed on my '67 with PS and A/C:

Crankshaft 2-groove: 3858533
Crankshaft add-on 1-groove: 3916385 or 3765947
Water pump 2-groove: 3995641
Alternator 1-groove: 3846180
PS pump 1-groove: 9786900

BTW, if you have a factory L79 2-groove water pump pulley now (part number 3770245), you can keep that and it will fit fine. However, for their air conditioning configurations, GM used a smaller diameter water pump pulley like the 3995641. I suspect that GM wanted the water pump and fan to spin a bit faster when the car had A/C.

 

Hi Joe,

Thanks for the quick reply. YES - I have the standard 2 grove upper and lower pulleys for a 66 L9 . . . my car was built without either PS - or-- AC so the outer pulleys simply ran the "captured" belt. When I added the PS, I used the standard PS pump pulley for the application and am now running the PS off the outer groves. Inerestingly, further reasearch shows that LIC has 2 PS pulleys - one for the AC application which I think is further forward than the cast iron PS pulley I currently have. I may order that one along with an add-on pulley for the crank and see if that gets me to where I need to be! Thanks again!

Tom

 

Hi Tom:

You might want to hold off ordering any pulleys until you have an overall plan. I'll be happy to assist you with evaluating the feasibility of various combinations before you start buying parts. I have samples of almost all of the candidate pulleys and can help you evaluate their compatibility.

GM had two families of pulleys, "standard-groove" and "deep-groove." In general, you cannot combine standard-groove pulleys with deep-groove pulleys. The reason for this may not be obvious until you take into account that each belt track of a deep-groove pulley is about 1/8" wider than a standard-groove pulley. The following photo helps to illustrate the difference. This photo shows a deep-groove pulley on the left and a standard-groove pulley on the right:





For '66-'67 small block Corvettes, GM had only two combinations of PS pump pulley and crank pulley:

DEEP GROOVE, USING THE SECOND GROOVE OF THE CRANK PULLEY:
3834720, single deep-groove (cast iron) PS pump pulley designed to align with the second groove of the deep-groove crank pulley 3858533
(this is what I believe you currently have on your car)

STANDARD-GROOVE, USING THE THIRD GROOVE OF THE (COMBINED) CRANK PULLEY:
3770509, single standard-groove PS pump pulley designed to line up with the third groove created by the standard-groove 3751232 crank add-on pulley
3751232, single standard-groove crank add-on pulley that fits inside the standard-groove crank pulley 3850838

If you try to combine standard-groove pulleys with deep-groove pulleys, you will get misalignment and possibly other fitment problems. One fitment problem is that the 3751232 add-on pulley does not fit inside the deep-groove crank pulley 3858533 that you presently have on your car. And, even if it did fit, it would be about 1/4" forward of the PS pump pulley 3770509.

I think the bottom line is that your pulley set should be either all deep-groove or all standard-groove. For the C2 small block with both PS and A/C, GM used a standard-groove pulley set. If you get all of the pulleys that GM used for this configuration, they will all fit and will line up well. This combination was pre-engineered for you by GM.

If you want deep-groove pulleys (which are only helpful for high-rpm operation), there is no existing pre-engineered GM system for a C2 with PS and A/C. To create a properly aligned deep-groove pulley set, you need to use some traditional hot-rodding techniques and combine parts from different cars. I managed to come up with a working combination by using a GTO power steering pulley and a deep-groove add-on pulley from some other Chevrolet vehicles. There are probably other combinations that would also work.

 

You might want to hold off ordering any pulleys until you have an overall plan. I'll be happy to assist you with evaluating the feasibility of various combinations before you start buying parts. I have samples of almost all of the candidate pulleys and can help you evaluate their compatibility.

Joe . . . too late, I ordered the other PS pulley from LICS yesterday. And, I have a "plan" - to figure out how to use the pulleys I alreazdy have . . . I have no intention of replacing everything I already have. So, may need your help to figure out which add-on crank pulley will work!

Tom

 

Hi Tom:

If you want to keep the deep-groove pulleys that are presently on your car, the only solution I know of is to use the power steering pulleys that I used:

Add-on crank pulley: 3916385 (Camaro) or 3765947 (Chevy truck)
PS pump pulley: 9786900 (Pontiac GTO)

All of these are available used or in reproduction. A quick search on ebay using these part numbers will typically bring up some examples. For the 9786900, I have found that some reproductions are not quite identical to the originals.

The two add-on pulleys nest properly inside the 3858533 crank pulley that you probably have now. While the part numbers are different, they seem to be functionally identical.

The GTO power steering pump pulley fits the stock C2 power steering pump but brings the belt groove forward to line up with the above add-on pulleys. The frame clearance is tight, but it fits on my car,

 

Thanks Joe - as you're well aware by now, when it comes to modifications for my C2, I'm not afraid of "unconventional"! Appreciate the help!

 

you will love the vintage ac set up .you might have to relocate the msd box, but no big deal . and make sure your primary fan can push enough air to cool the condenser.If you need any help the guys at vintage were very helpful .the blower motor really puts out the air.I really like the borgeson steering box as well.I ended up installing a ididit tilt steering wheel while I was at it, I love it.enjoy your ac .