L-72 distributor questions

[Joe L.]

Re: L-72 distributor questions

The parts house is wrong. The 201 was OE on all '63 engines and L-71, but not the others you listed.

If you don't convert to full time vacuum advance - but why on earth would anyone not do this given the benefits - you can use just about any VAC with 16 deg. or less advance because the Two-Inch Rule doesn't apply since there is no vacuum advance at idle, which is why such engines will run hot and get lousy intown fuel economy.

Regarding Joe's post, I've got the "B10" penciled into Lars Grimsrud's list - 0 @ 7" , 12 @ 12", so this may be an exact replacement for the L-72 OE 360 VAC.

My hand hand written notes that show a NAPA part number of VC-1765SP, but I don't know the source of this data.

On a note of caution, some specs list distributor degrees and some crank degrees. In not sure if the "12" is dist or crank. If it's distributor, the crank advance is 24 deg., which is way too much. Someone is going to have to buy one and test it.

All of the specs in Lar's list are DISTRIBUTOR degrees.

Duke-----

I think the embossment on all original GM Delco-Remy distributor vacuum controls referred to maximum crankshaft degrees of advance.

[Glen C.]

Re: L-72 distributor questions

Glen -- any chance your '66 L72 is a late production car, with (maybe) an original 360_12 can ? There was some discussion yesterday or so that this distributor 1111093 had more than one vac advance number factory installed over the production life of 1965 and 1966.

P.S. does your lower shaft cast housing have the partially filed and machined oil annulus, as shown on the left in the pic below ?

My lower housing looks like the one shown on the left, but my gear (angle of the teeth) looks more like the one shown on the right, but without the center groove around the circumference. This, and other clues, make me think that the dist. may have originally been for a 67 390 or 400. Most engine dates show Sept. Oct. 65

[Steven S.]

Re: L-72 distributor questions

Partial groove would be correct for the 1111093 distributor, the one Wayne has pictured is probably one of the ball bearing reverse rotation over the counter units.

Steve

[Glen C.]

Re: L-72 distributor questions

Partial groove would be correct for the 1111093 distributor, the one Wayne has pictured is probably one of the ball bearing reverse rotation over the counter units.

Steve

Are the grooves or the divot in the gear an identifier used to signify a part#, BB vs. SB, manufacture, or some other factor? Does no groove vs. one groove, vs. two grooves mean anything? Like the Muncie M20, M21, M22 input shaft grooves? Just a thought. Reguarding the divot was this a way to balance the shaft assembly? No one has mentioned the #171 shaft or the #542 cam, that I mentioned in my initial post. Is there a listing some where that breaks down these #'s to specific dist part numbers?

[Duke W.]

Re: L-72 distributor questions

Duke-----

I think the embossment on all original GM Delco-Remy distributor vacuum controls referred to maximum crankshaft degrees of advance.

Yes, but some specifications list distributor degrees and most guys don't read the footnotes.

Duke

[Steven S.]

Re: L-72 distributor questions

Are the grooves or the divot in the gear an identifier used to signify a part#, BB vs. SB, manufacture, or some other factor? Does no groove vs. one groove, vs. two grooves mean anything? Like the Muncie M20, M21, M22 input shaft grooves? Just a thought. Reguarding the divot was this a way to balance the shaft assembly? No one has mentioned the #171 shaft or the #542 cam, that I mentioned in my initial post. Is there a listing some where that breaks down these #'s to specific dist part numbers?

Not that I'm aware of, the divot as far as I know is just for correct orientation of the gear to the rotor. Joe might be able to help with your questions on the specific component part numbers.

Steve

[Wayne M.]

Re: L-72 distributor questions

Partial groove would be correct for the 1111093 distributor, the one Wayne has pictured is probably one of the ball bearing reverse rotation over the counter units.

Steve

Correct; the one on the left is on my 1111263 racing distributor for gear driven camshafts --- should'a mentioned it in my post.

So if Glen's 360_12 vac can is original to the distributor, and if it is a 1111093 (missing its band), the other engine dates he describes indicate early '66 production (if not a later but over-the-counter distrib, ie. if the '093' was ever a service unit as well). Can't pin it down without knowing the original car it came in.

[Glen C.]

Re: L-72 distributor questions

I've been looking through my grease/lube collection, and found some Solder Seal plumber's heat proof grease. It is used for hot water and steam applications Part# GR-1. This grease has the color and consistency, [kind of a paste] of the old 40+ year old grease removed from the top bushing cavity of my TI dist. I'm going to use it & see what happens. Anyone else ever use this stuff?

[Timothy B.]

Re: L-72 distributor questions

Glen,

Just use a piece of gauze saturated in light weight motor oil and lightly pack the cavity. Install the plastic seal and it's done.

[Joe L.]

Re: L-72 distributor questions

Not that I'm aware of, the divot as far as I know is just for correct orientation of the gear to the rotor. Joe might be able to help with your questions on the specific component part numbers.

Steve

Steve and Glen------


The dimple on the distributor drive gear is for orientation with the tip on the rotor. For the most part, this is only important on Corvette applications to ensure that the distributor ends up in a position that is suitable for the tach drive and suitable for clearance of the vacuum control with distributor shield supports.

As far as the numbers on the distributor cam and auto cam attached to the top of the main shaft, I don't think these numbers are derivative of any part number. They are some other coding system for the parts and I don't have any table correlating these numbers to finished part numbers. I've been looking for such a reference for years and I'm still looking.

The distributor drive gear used from 1965 to 1985 is GM #1958599. There were several other part numbers used prior to that time but all are interchangeable with the 1958599.

[Glen C.]

Re: L-72 distributor questions

The lube is generally available on the Internet Flea Market, in Delco containers (one will last a lifetime) Original distributors did not use a thrust bushing on the crossgear, and if your housing shows no wear in the pocket where the crossgear rides then none is necessary. There are some tricks to installing the bushing so it is not detectable, email me if that becomes a necessity. The "goop" from Delco surrounds the upper bushing and provides some lube thru the porus bronze.

Bill, I'm not sure if I should add the brass button on the tach cross shaft. I know this can be a problem area. Both my gear and housing are shiny where contact is made, but not discolored or gauled. By the way, one of the Vette suppliers indicates that their brass gear button is a "service replacement as original button was plastic". Maybe this item was added later in production or on service replacements??

[Glen C.]

Re: L-72 distributor questions

Glen,

Just use a piece of gauze saturated in light weight motor oil and lightly pack the cavity. Install the plastic seal and it's done.

Thanks for the tip. Sounds easier than my solution!

[John H.]

Re: L-72 distributor questions

Glen,

Just use a piece of gauze saturated in light weight motor oil and lightly pack the cavity. Install the plastic seal and it's done.

That's what I've always used - pieces of gauze bandage packed in the cavity and oil. Don't forget to oil the felt washer that goes on top of the plastic seal before you install the breaker plate.

[Timothy B.]

Re: L-72 distributor questions

Glen,

The brass button is a aftermarket fix. I believe in 1970-71 GM started using a nylon button and the distributor housing has a small hole drilled completely through the distributor where the cross gear rides for the nylon button to clip in.

If you have the brass button and want to install it, locate the hole to be drilled be installing the screw in bushing and get a 5/16" (I think) drill bit that fits snug in the bushing hole and use it as a pilot to give a drill start for the hole. This will locate the center where the gear rides. Check the brass button shaft for the hole size and stay just under so it's a press fit. Make sure you drill through straight but it's not rocket science :-)

After you drill the pilot hole have the distributor milled 1/2" diameter 1/16" deep (I forget the name of the drill bit for this) so the button sits flat inside the housing. This is necessary for the gear alignment to the main shaft.. Cut approx. 1/8" of the brass button shaft so it does not stick through the distributor and fill this small hole with JB weld. Let it harden and get a razor blade and shave it flat. Paint and you will never know it's there... Also, if you have to reduce the diameter of the brass button to fit inside the 1/2 hole you milled just chuck it in a drill and spin it against a file to reduce it a bit..

[John H.]

Re: L-72 distributor questions

By the way, one of the Vette suppliers indicates that their brass gear button is a "service replacement as original button was plastic". Maybe this item was added later in production or on service replacements??

Glen -

Don't believe everything you read in vendor catalogs - the button wasn't added until the early 70's.