'67 L79 alternator pulley

[Wayne M.]

Re: '67 L79 alternator pulley

....When I compared my measurement (2-10/16th" or 2.625") to your measurement (2.725"),....

Scott -- sorry it's taken me so long to get back on this. The difference in the above is that I was measuring from the front (outboard) face of the bracket to the forward of the two manifold bolt holes, whereas you measured from the rear (outboard) face to the rearward manifold bolt hole [the one at the center dump of the exh. manifold]. But doing the add/subtract on your nice pic, [6.8125+2.625-6.75] gives 2.688" to compare with my 2.725 (which I rechecked and now get 2.709 to 2.717; I had to use a fine pencil and lined paper as my caliper maxes out at 6.0"). So we're only talking 22 to 38 thou difference, which may just be our measuring or manufacturing tolerance, or both . Have to conclude that with the switch from the '64-5 "696" to the '66-7 "222" that they did NOT move the compressor mount eyelets forward to compensate for the spacer-washers of the earlier bracket, when deep groove pulleys were called out.

Thanks for your effort.

[William F.]

Re: '67 L79 alternator pulley

Guess I got this started. Maybe I have adult ADD, but after all this-"Just the facts, ma'am." Best answer to "which ALTERNATOR pulley for '67 L79 with AC but nothing else sems to be apulleu slightly biggger OD than 3"' using 3/8" belt. Where do I get closest thing to this (from a ready source) and what do I ask for?

[Gary B.]

Re: '67 L79 alternator pulley

William,

Call John Pirkle. I think he will have whatever Corvette pulley you could ever need.

Gary

[Joe R.]

Re: '67 L79 alternator pulley

Guess I got this started. Maybe I have adult ADD, but after all this-"Just the facts, ma'am." Best answer to "which ALTERNATOR pulley for '67 L79 with AC but nothing else sems to be apulleu slightly biggger OD than 3"' using 3/8" belt. Where do I get closest thing to this (from a ready source) and what do I ask for?

Hi William:

You need the 3846180 pulley. Paragon sells a reproduction:

https://www.paragonreproductions.com/p-351777-alternator-pulley-3-od.aspx

[Scott S.]

Re: '67 L79 alternator pulley

Update on pulley set-up survey for 1967 L79 with C60 and no power steering, "HT" engine suffix:









Width of both grooves at top of pulley: .4 (where top of belt will travel)

[Joe L.]

Re: '67 L79 alternator pulley

Update on pulley set-up survey for 1967 L79 with C60 and no power steering, "HT" engine suffix:









Width of both grooves at top of pulley: .4 (where top of belt will travel)

Scott------


No pulley of GM #389041 EVER existed. However, a pulley of GM #3890419 did exist. In fact, that waterpump pulley was used for 1967 L-79 with C-60.

No 1967 Corvette EVER originally used a GM #3995643 waterpump pulley. Absolutely NONE. Period. The GM #3995643 pulley did not even exist in 1967 (or, 1968, 1969, or 1970). As far as Corvette goes, the GM #3995643 pulley is a SERVICE-ONLY pulley which replaced the GM #3890419 in December, 1971.

The crankshaft pulley that is usually used with the 3890419 (and 3995643 replacement) was a GM #3850838 and it was used for the 1967 L-79 with C-60 application. However, it was discontinued without supercession in January, 1988.

[Scott S.]

Re: '67 L79 alternator pulley

Scott------


No pulley of GM #389041 EVER existed. However, a pulley of GM #3890419 did exist. In fact, that waterpump pulley was used for 1967 L-79 with C-60.

No 1967 Corvette EVER originally used a GM #3995643 waterpump pulley. Absolutely NONE. Period. The GM #3995643 pulley did not even exist in 1967 (or, 1968, 1969, or 1970). As far as Corvette goes, the GM #3995643 pulley is a SERVICE-ONLY pulley which replaced the GM #3890419 in December, 1971.

The crankshaft pulley that is usually used with the 3890419 (and 3995643 replacement) was a GM #3850838 and it was used for the 1967 L-79 with C-60 application. However, it was discontinued without supercession in January, 1988.

Hi Joe,

Thanks for the clarification, I'm reporting the replies as received. I recognized that "389041" was one digit short, but forgot to look it up to figure out what the last digit should be before posting.

[Mark G.]

Re: '67 L79 alternator pulley













Mark

[Joe L.]

Re: '67 L79 alternator pulley

Mark

Mark------


The GM #3848904 pulley was replaced by the GM #3995641 in late 1971. The 3995641 remains available from GM to this day.

[Scott S.]

Re: '67 L79 alternator pulley

Hi Mark,

This is great news!

Confirmation that the deep-groove pulley set-up for L79 with C60-only (no N40) is factory original after all! Hopefully this info will be included in the next 1967 Judging Guide. Also, it would be great to have a published recognition of the "HT" engine suffix for L79 with C60-only (no N-40), since this configuration/designation is not mentioned in any of the other books.

[John H.]

Re: '67 L79 alternator pulley

Also, it would be great to have a published recognition of the "HT" engine suffix for L79 with C60-only (no N-40), since this configuration/designation is not mentioned in any of the other books.

Scott -

As a corollary to the "HT" suffix issue you noted, has anyone come forth so far with a theory on why the "HP" suffix is shown for an L-79 with A/C and power steering (and the "KH" suffix for the same combination with K-19)?

I can find no Engineering reason whatsoever to assign a unique suffix to either of those combinations; as far as I can determine, the 1967 engine assembly as shipped from Flint V-8 was exactly the same for a no-option L-79, L-79 with only A/C, L-79 with only power steering, or L-79 with A/C and power steering.

[Scott S.]

Re: '67 L79 alternator pulley

Scott -

As a corollary to the "HT" suffix issue you noted, has anyone come forth so far with a theory on why the "HP" suffix is shown for an L-79 with A/C and power steering (and the "KH" suffix for the same combination with K-19)?

I can find no Engineering reason whatsoever to assign a unique suffix to either of those combinations; as far as I can determine, the 1967 engine assembly as shipped from Flint V-8 was exactly the same for a no-option L-79, L-79 with only A/C, L-79 with only power steering, or L-79 with A/C and power steering.

Hi John,

The only theory related to this that I recall reading was Joe Randolph's:

Regarding your reference to having an HT code on your 1967 block, that makes sense to me if the 3848904 water pump pulley was used for that configuration. If deep-groove pulleys were used for the L79 when equipped with only A/C, there would be no need for a special engine code. As far as Flint was concerned, there would be absolutely no difference between an L79 engine that St. Louis would configure for any of the following:

1) L79 without A/C, PS, or AIR
2) L79 with A/C only
3) L79 with PS only

Since Flint installed the water pump and St. Louis installed the pulleys, there would be no need for Flint to use a different engine code for any of the above configurations.

The situation changed when a 1967 L79 was equipped with both A/C and PS. In this case St. Louis installed the standard-groove pulley set, and the water pump hub spacing needed to be 5-9/16 inches (for standard-groove pulleys) instead of 5-11/16 inches (for deep-groove pulleys). In this case, the water pump installed at Flint was different, and a different engine code was needed to distinguish that configuration.

My theory is that the HP code was used for this one configuration only, when the L79 was configured with A/C *and* PS.

[Mark G.]

Re: '67 L79 alternator pulley









Mark

[Joe L.]

Re: '67 L79 alternator pulley

Mark

Mark------

For many years small block short leg waterpumps were only available from GM in SERVICE with a single hub spacing. As described in the instruction sheet, for certain applications the hub had to be driven 1/8" further onto the shaft. Corvette was one of the applications, but, just as you infer, I don't think that all Corvette applications required this. In PRODUCTION there must have been 2 different waterpump part numbers each reflecting the different hub spacing.

Finally, in late 1972, GM made available TWO different waterpumps for 1955-70 SERVICE. One, GM #3998206, had a hub spacing of 1/4" from the rear of the hub to the end of the snout. The other, GM #3998207, had a hub spacing of 3/8" from the hub to the snout. In actual practice I have observed that there is a slightly greater distance from the hub to the snout, but there was still a 1/8" difference between the 2 pump part numbers. The actual hub spacing specification is from the block mounting surface to the forward face of the hub. Measurements from the rear of the hub to the end of the snout can be very inaccurate.

All of the GM #3998206 and 3998207 waterpumps I have ever seen used the 3839175 or 3859326 castings with 3/4" NPT upper bypass fitting.

[John H.]

Re: '67 L79 alternator pulley

Mark

Mark -

The engine block was suffix-coded (on the side of the block, with a paint stick) when it was upside-down in the bore air-gaging station, the first station on the engine assembly line. That's what everyone on the rest of the line looked at to tell them what innards to install in/on the block, and that's what the machine code stamper looked at to select the correct gang-holder to stamp the front pad after the engine was rotated right-side-up and the cylinder heads went on.

Flint V-8 machined the raw pump casting and assembled the 326 water pump in-house, so they must have produced at least three versions of that pump:

1. The truck version with the 3/4" NPT bypass hole

2. The Corvette version with the 1/2" NPT bypass hole, for non-A/C cars.

3. The Corvette version with the 1/2" NPT bypass hole, with the hub pressed 1/8" differently for A/C cars.

Corvette engines weren't suffix-coded uniquely for A/C until 1964, so there must have been two unique hub-press dimensions for both the 608 pump (250 and 300hp engines) and for the 326 pumps (350/365hp engines) from '64-up.

Interesting stuff - apparently the unique suffix for A/C engines was the difference in the water pump hub-press dimension.