Couple of distributor questions.

[Mike E.]

While I'm waiting for the machine work to get done on my L76 I've started to rebuild the distributor. The Tach quit about 30 years ago so I knew that I would be replacing the main shaft and the tach drive gear. From what I've read most failures are caused by sloppy lower bushing and sure enough it's pretty loose when compared to the upper. That brings up the first question, should I leave the upper bushing alone if it seems tight? Also how does someone measure clearance on such a part?

LIC sells a main shaft for my application that Joe Ciaravino has verified the "football" for centrifugal advance is installed correctly so I'll be going with that part for the main shaft. I know I should replace the lower bushing but should I also replace the upper? It goes without saying I want to replace all wiring and the grommet because it's dried out and cracking. The ground wire also looks really gnarly and should be replaced. I've attached a photo of the base plate that I would like to save if the wire can be replace and be reliable. It looks as though it might be silver soldered to plate? What methods have other folks used to replace this wire. LIC sells a wire with the terminals attached that looks to be a good part based on the image.

The next question is about cosmetics. The '65 JM doesn't mention paint at all on the distributor housing yet I assume it was painted. My question is was it painted prior to machining or after? If it was painted prior to machining then some raw machining should probably be exposed.





Mike

[Joe L.]

Re: Couple of distributor questions.

Mike-----


Attached find a photo of an NOS distributor. The distributor housing was painted black and the paint was applied after the distributor housing was machined. The external surfaces of the distributor were painted from the very top of the housing to and including the flange that seats on the intake manifold. The rest of the distributor, including internal surfaces and the housing below the flange, were not painted. The paint was a rather thin, semi-gloss black that was on the flat side of semi-gloss.


DSCN2929.jpg

[Timothy B.]

Re: Couple of distributor questions.

Mike,

Attach some pics showing damage on the main shaft and tach gear. From the pics you posted the other day I can't decide if the damage is that great to change the shaft. Keeping the original main shaft should be your first priority, in all cases the brass button needs to be installed inside the distributor where the tach gear inward thrust wears the housing and if you read the archives you can do this yourself. This is the damage that causes mis-alignment of the gear mesh which damages the main shaft gear. The tach gear wears the distributor housing so fine inside the distributor it almost looks like it was made that way but it's not.

I think the ground wires for the coil to distributor and points plate is available at NAPA and you can solder it back on. I personally would not change any bushings unless you find damage, just tighten the end play to about .006+- and let it alone.

I consider myself a purist, but I went ahead and installed the Breakerless SE in place of the points in my 67 300hp distributor. You will be very happy with this upgrade, it uses the stock wire and it's function eliminates worry about wobble from points plate etc. plus you use the stock coil and ballast resistor. Take your time and install it exactly as the directions show and it will take 45 minutes. If you want to use points get the NAPA premium set along with a new condenser, there are part # in the archives.

One other thing I want to offer is about plug wires, consider the NAPA Beldon wire set for you car, the reproduction stuff is just not up to the standard of these these 7mm wires and when the cars sit the secondary ignition parts can cause problems.

[Joe R.]

Re: Couple of distributor questions.

As long as you have the distributor in your hands disassembled why don't you do the rebuild right and replace everything as it's available and relatively low in price. Replace the upper and lower bushing, shaft, tach counter shaft with thrust washer. Just to be on the safe side I drill and tap where the plastic bushing or brass bushing goes and put a set screw there to take out the end play leaving .003-.004 and lube it generously. Then replace the points with some modern breakerless solid state device and never have to fool with the distributor again.

JR

[Joe C.]

Re: Couple of distributor questions.

While I'm waiting for the machine work to get done on my L76 I've started to rebuild the distributor. The Tach quit about 30 years ago so I knew that I would be replacing the main shaft and the tach drive gear. From what I've read most failures are caused by sloppy lower bushing and sure enough it's pretty loose when compared to the upper. That brings up the first question, should I leave the upper bushing alone if it seems tight? Also how does someone measure clearance on such a part? LIC sells a main shaft for my application that Joe Ciaravino has verified the "football" for centrifugal advance is installed correctly so I'll be going with that part for the main shaft. I know I should replace the lower bushing but should I also replace the upper? It goes without saying I want to replace all wiring and the grommet because it's dried out and cracking. The ground wire also looks really gnarly and should be replaced. I've attached a photo of the base plate that I would like to save if the wire can be replace and be reliable. It looks as though it might be silver soldered to plate? What methods have other folks used to replace this wire. LIC sells a wire with the terminals attached that looks to be a good part based on the image. The next question is about cosmetics. The '65 JM doesn't mention paint at all on the distributor housing yet I assume it was painted. My question is was it painted prior to machining or after? If it was painted prior to machining then some raw machining should probably be exposed. Mike

Although the advance cam is now installed correctly in the version that LICS sells, be advised that it is NOT the same as your original. The main concern is that the ramped side that the heels of the advance weights ride on is oriented properly. Many of the parts houses (at least Paragon, that I have verified via photo that they sent me) is still selling shafts with the football installed upside down, with the pins installed upside down as well, which means that it will be "functional" and only close examination reveals the problem. In any event, the advance program with the generic SHP cam will be slightly different from original, but not enough to significantly affect engine operation.

Your shaft failed because the tach drive gear stripped. Be sure to install either a thrust button or a set screw for the driven gear, and keep end play to no more than .008".

Heat the old wire mount on the breaker plate and pry open the wire tabs once the solder has softened. Place the new wire in the open tabs, close them, and then reheat, keeping the heat away from the solder on the plate end. Use a soldering iron to heat the closed tabs and the wire, just enough to allow a small amount of new solder to flow into the joint. Orientation of that wire is CRITICAL, so if removing the old mount clip, remember to place the new one EXACTLY as the old one was. Keep the wire length exactly the same as the old wire as well. Unnecessary to replace the upper bushing, but pack the cavity with fresh grease and install a new nylon cover and new felt washer. Set shaft end play to no more than 0.010", with about 0.005" being ideal.

Properly oriented main shaft cam ("football") is the one shown above the distributor. The installed "football" is upside down:

[John D.]

Re: Couple of distributor questions.

Nice post and pics Joe. Mike if it were my distributor I would send the whole thing to Don Baker and let him restore it. Don is a fanatic on the original footballs, cams, etc. He also has the correct vacuum advances.
Like Joe Ray said though it's best to replace as much as possible (if it needs it) providing the parts used are the real deal and not parts that resemble the original.
Service replacement aka NOS distributors typicall do not have the same cam, shaft, etc as a distributor that you car came with when new.
We run into the same thing with the FI distributors. All those NOS FI distributors on Ebay, etc resemble the original but the guts are not the same. DR used about every cam they had on the shelf on those distributors. Whatever fit got used. Have proof. John
John

[Gerard F.]

Re: Couple of distributor questions.

Although the advance cam is now installed correctly in the version that LICS sells, be advised that it is NOT the same as your original. The main concern is that the ramped side that the heels of the advance weights ride on is oriented properly. Many of the parts houses (at least Paragon, that I have verified via photo that they sent me) is still selling shafts with the football installed upside down, with the pins installed upside down as well, which means that it will be "functional" and only close examination reveals the problem. In any event, the advance program with the generic SHP cam will be slightly different from original, but not enough to significantly affect engine operation.

Your shaft failed because the tach drive gear stripped. Be sure to install either a thrust button of a set screw for the driven gear, and keep end play to no more than .008".

Heat the old wire mount on the breaker plate and pry open the wire tabs once the solder has softened. Place the new wire in the open tabs, close them, and then reheat, keeping the heat away from the solder on the plate end. Use a soldering iron to heat the closed tabs and the wire, just enough to allow a small amount of new solder to flow into the joint. Orientation of that wire is CRITICAL, so if removing the old mount clip, remember to place the new one EXACTLY as the old one was. Keep the wire length exactly the same as the old wire as well. Unnecessary to replace the upper bushing, but pack the cavity with fresh grease and install a new nylon cover and new felt washer. Set shaft end play to no more than 0.010", with about 0.005" being ideal.

Properly oriented main shaft cam ("football") is the one shown above the distributor. The installed "football" is upside down:

Joe,

Are you sure which football is upside down in your photo?

The one on the distributor looks a lot like my original (#165 on the right) and an NOS #54W (on the left) in the picture below. The original is from my 67 327/300 - 194 distributor:



They sure look a lot difference on a SHP engine

[Joe C.]

Re: Couple of distributor questions.

Joe,

Are you sure which football is upside down in your photo?

The one on the distributor looks a lot like my original (#165 on the right) and an NOS #54W (on the left) in the picture below. The original is from my 67 327/300 - 194 distributor:



They sure look a lot difference on a SHP engine

There were a LOT of different cams that GM used on original shafts, and they all had VERY slight nuances/differences which had small effects on the centrifugal advance program. Many of those require close scrutiny to differentiate between them. For the life of me, I don't understand why GM was so fastidious with these advance cams in production, while they were so careless in other ways, especially with critical parameters for designed-in SCR (static compression ratio). In any event, that is why the repop houses only sell TWO different shafts with two different advance cams.................."SHP" shafts and "non-SHP" shafts. The "SHP" shaft sold in reproduction actually uses what looks like an advance cam used in a 1972 454 engine!

The difference in engine performance when using different advance cams is so slight, that most people don't notice it, and that's the reason that they were all consolidated in reproduction as only 2 different versions. In fact, the SHP shaft (I don't know about the non-SHP shaft) was being incorrectly assembled for some-time and sold that way before I discovered the problem and notified them all last summer. Whoever installed them as-is never noticed a difference and their cars all started and ran well enough not to set off any alarm bells with their unsuspecting owners.

All original advance cams were brazed onto the main shaft, unlike at least one of the reproduction suppliers who use a press fit; at least one other brazes the joint. Please note that THEY ARE ALL PROPERLY CLOCKED WITH RESPECT TO THE DISTRIBUTOR GEAR ROLL PIN HOLE, AND THAT INCLUDES THOSE "FOOTBALLS" THAT ARE INSTALLED UPSIDE DOWN AS IN MY PHOTO IN POST #5). This is important, as it affects the orientation of the distributor housing and interference of the advance diaphragm housing in the same way as the driven gear dimple orientation.

Here's another photo (courtesy of Wayne Midkiff) showing what looks like your cam ("54") on the left, and the "247" on the right. Note that the "247" bears a striking resemblance, except for the absence of any stampings, to that being sold in reproduction as the "SHP" cam (ref: my photo in post #5):

[Wayne M.]

Re: Couple of distributor questions.

I don't think we can say that differing slopes on the football define improper installation, indicating reproduction.

I have 7 distrib's in my basement (or 9 counting those on my cars) and there's considerable variation -- and I'll swear that none of these has repro parts, nor has been in the hands of a restorer, although some are GM service (1975 era).

Examples below: on the right is from a 1111267 (tach drive K66 for race Camaros, sold OTC). The one on the left is off a service 1111157 [350hp K66], dated 4K9, and the football on a 1112038 ('71 LT1), tag 0_J_3, has the sharp notches on the same position as the latter, although the football is stamped 170W on the underside of the cam (which might lead someone to think that it was installed upside down).



c

[John D.]

Re: Couple of distributor questions.

A NOS 54W has a different aka SR football on the shaft.
I have a NOS 1961249 FI distributor shaft with a 54W cam. Old parts book list it as being correct for 62 to 64 FI. The football is not the same as the real deal.

[Domenic T.]

Re: Couple of distributor questions.

I didn't read thru all the distributor threads but other than the shaft bushings, is the up & down play that is in the shaft.
The first time I rebuilt one I checked the specs and shimmed the up & down to .010. I have never seen one shimmed correctly for up & down play. You can measure the play in a stock one with a yard stick. when I do initial timing with the engine on the stand I have to remove the play to assure that the shaft cam is at the proper running position. As the shaft moves up & down it moves the points cam about 5 degrees. I will look in the old manuals and see if I can find the specs some day and post them.


DOM
DOM

[Duke W.]

Re: Couple of distributor questions.

The 1963 Corvette Shop Manual, page 6Y-29 specifies .002-.007" shaft end play. It's even in bold face type. Shims were available from GM back in the day in .005" and .030" thicknesses. They are currently only available in the aftermarket.

It's my understanding that, maybe, FI distributors were shimmed to this spec in production, but most non-FI distributors were in excess of .060" end play.

The note in the '63 Shop Manual does not refer to only FI distributors. As it is written, it applies to all distributors.

Shimming up the end play to this spec is critical to obtaining proper ignition system performance, especially on high revving SHP engines.

Sloppy end play causes spark scatter and can lead to premature point bounce and ignition breakup. A snug fitting breaker plate is also essential to proper ignition system performance.

Distributor rebuilding and "blueprinting" procedures have been discussed numerous times on the TDB including a thread last December where I reported the results of going through a local chapter members L-79 distributor. Of note was that the ground wire on the breaker plate broke off as we removed the plate. We jury-rigged a replacement from some generic terminals and wire I had laying around, and the owner later bought the NAPA repair wire and was able to install it without removing the distributor.

Fortunately the bushings and tach drive gears were okay on this 90K mile car that had been in storage for about 20 years before being purchased by the local chapter member. There was still some functional grease on the tach drive gears, but the upper bushing grease well was essentially dry other than some residue.

Be warned - there are probably many distributors out there with breaker plate ground wires about to fail at any time. Removing/installing and conducting a "blueprint overhaul" on the distributor is not a complicated task. I'm sure many have never been disassembled, cleaned, inspected, and regreased. It's an easy DIY project that can save you from being DOA on the side of the road, stripping the tach drive gears, or having to deal with replacing the shaft bushings.

The distributor is probably the most overlooked component on the engine. Proper function is required to obtain maximum performance and fuel economy, but most guys just run them until they fail. If you get to the task before the tach drive gears fail or bushings are excessively worn, you will save yourself a lot of money and grief in the long run.

Duke

[Anthony P.]

Re: Couple of distributor questions.

I just looked in my 1966 Chassis Service Manual and it states as Duke said for the 63 .002-.007 end play! I have my original dist out to grease the tach drive gears and after 44k miles and 47 years the end play is .013. Tells me the factory had it closer to the service manual specs. FWIW.

[Timothy B.]

Re: Couple of distributor questions.

Anthony,

You may want to look inside the distributor where the tach gear rides for wear and install the brass button. This will keep the main shaft and tach gear from being damaged over the long run.

[Joe L.]

Re: Couple of distributor questions.

What happened to my post regarding factory end play specifications?