I noticed the wire from the pck-up coil on my TI distributor is badly frayed just past the grommet. I don't want to put this back on the car as is. I have had no problem with the ignition or timing so I would like to disassemble and inspect before deciding if I can simply replace the the pick-up coil coil and do some basic clean-up, or if more work is required. But I can't seem to locate any disassembly for a TI distributor, not in service manual, chassis manual, or through the forum search engine. Any help would be much appreciated.
Thanks

 

Try here: https://www.tispecialty.com/articles.htm

Larry

 

Thanks Larry,
I actually did find that site through other threads regarding distributors on the forum. But it does not describe the disassembly procedure, more of a description of the work he will do after disassembly.

 

Disassembly is exactly the same as a regular distributor, except that there is no breaker plate. Instead of the breaker plate, you have the pickup coil and a thick brass washer under the coil. The thin "C" clip that retains the breaker plate in a regular distributor retains the pickup coil instead. The distributor housings are the same.

RON

P.S. DO NOT remove the screws that hold the pickup coil together. The top plate with the 8 points, coil and bottom plate come out as 1 piece.

 

The distributor shaft has to come out first. Unscrew the tach gear adapter, pull off the centrifugal advance weights/springs, then knock out the roll pin in the drive gear. Once the shift is out, you should be able to take the pickup off the breaker plate. If you need access to under the plate to knock out the wore grommet, there's a very thin snap ring that holds the breaker plate onto the upper shift bushing. You should be able to push the grommet out and then pull the wires and connector through the distributor housing.

 

I have an article I wrote on reconditioning a tach drive distributor in detail with plenty of pictures.
PM me with your email address if you would like a copy.
Joe

 

Ok, thanks very much for your help. I have it almost apart. Will remove the connector tomorrow so I can pull the wires through the housing and then start cleaning everything up and inspecting.
Joe, I will PM you, thanks.

 

You will have to take the plastic connector off of the pickup coil lead in order to completely remove the coil from the housing. Take note which wire has the stripe on it, as you can reinstall the wires in either position in the plastic connector. I don't see the brass washer---Is it stuck to the bottom of the pickup coil ???

RON

 

While it's apart very carefully remove the plastic grease seal (to reuse) below the pickup coil and fill the well with Mobil 1 grease. Likely all you will find are a few solid specs... what remains of the old grease. Shimming up the end play to the 2-7 thou spec as I do for single point distributors will reduce spark scatter for smoother engine performance.

Check the shaft side play in the housing. If it's more than barely perceptible you might as well have new housing bushings installed now while it's apart.

Duke

 

Thanks Joe for your write-up, very nicely done. It has already served me well.
Ron, I have removed the plastic connector and pulled the wires through the housing. The stripe was barely noticeable because of age I guess, thanks for pointing that out. The brass washer was indeed nicely stuck to the underside of the pick-up coil.
Duke, the felt under the pick-up is in remarkably good shape compared to everything else, but that seal was very dry and fell apart easily revealing a nice supply of dried up old grease. The end play is excessive, almost .050 and thats including a .030 washer/shim that was already there. I assume the end play can be corrected with additional shims and or is there a maximum to amount of shims?

The biggest issue I found is side play on the shaft, it is very perceptible and I measure .006 on a dial indicator placed about 1 inch from the bottom of the shaft. As per the pic, you can also see that it is scored, very similar to the picture of the shaft on Joe's paper. I measure .4875 at the area where it is scored vs .489 where the shaft is clean. So I assume in addition to the pick-up coil (because of the frayed wire), my needs will also include the mainshaft and a bushing set. At this point, I might as well also order a set of weights and springs and vacuum advance for a full rebuild.

Obviously I do not have a distributor machine in my garage. So the key question is, given that the parts available are more generic and meant to cover many different applications, are there any parts such as weights and springs, or mainshaft (because of cam profile) that I should try to salvage and reuse in order to eliminate the need to need to inspect on a distributor machine? Or is inspection on a machine a must regardless? And if the advance curve is not exactly as per spec for my engine, are there any adjustments that can be made to the distributor?
I guess I need to educate myself a little more on the subject!
Thanks for all your help.
Luke

 

How does the tach gear on the mainsheet look?? This may determine if you can re-use the shaft..........although it looks scored. Side clearance of 0.001-0.002 inches is the preferred number, so new bushings are likely needed. They need to be precision reamed to fit after installing.

The plastic seal for the oil well is still available using the GM part number. About $4-5. I personally used cotton pads cut to the correct OD and ID and saturated with 20w oil. Pads were women's makeup removal square cotton pads, which worked nicely. Needed about 3-4 stacked in the well.

Larry

 

The spiral gears actually look pretty good, no detectable wear to the eye. Are the bushings normally sold undersize on the ID to allow for machining?
Luke

 

Maybe I missed it, but you need to state which engine you have. TI was an available option on all and required with L-71/88.

Duke

 

Apologies for that, It's an L68, OEM cam, no mods, street driver.
Luke

 

That's a really good street high performance cam. In fact for how most of this drive these cars today I think the 390/400 HP big blocks are a better choice than the SHP mechanical lifter versions

I recently did some tuning on a '66 L-36, which is basically the same engine with a four barrel instead of the trips. The distributor was really buggered up. The OE VAC was sticky and the centrifugal was limited to only 20 degrees. We did a complete blueprint/overhaul and basically took it back to stock for California's 91 PON premium, and it worked out well after a LONG day including a run out to David Sokolowski's place for parts.

About the only thing you can do to improve it is bring in the centrifugal a little earlier. The OE centrifugal is 32 @ 5000 which is pretty lazy. Depending on what the CR and centrifugal curve are today and your available fuel octane you may be able to make it more aggressive without detonation by using the black-silver-gold springs in that order from the Mr. Gasket 928G spring kit. It's something you can do once it's back in the engine.

What's the number stamped on the rotating pole piece assembly.

You can get a head start on the tuning by searching for threads started by me and downloading and reading the tuning seminar... also the L-79 distributor blueprint/overhaul thread. The TI and single point are basically the same... just some parts swaps. The base for both is identical to you can easily convert one to another either way.

Duke

 

Duke, I have downloaded both the threads you mentioned. I will be reading them again carefully, thanks.
In answer to your questions, the number stamped on the pole piece is 734 . However, the number on the distributor tag is 1111093 which I believe is original to 66 425HP, not L68. Not sure how that will impact the centrifugal curve. I usually run Shell V-Power 91 premium with no detonation issues. I also have access to 94 Octane but it contains ethanol, so I limit its use to long drives when I know I will use up the whole tank.
Luke

 

I've not run across a 734 rotating pole piece and the "34" would indicate 34 degrees crank (17 distributor) centrifugal advance, but that could be limited by a bushing on the pin under the top cam on the mainshaft. You can used a small protractor to measure then verify when it's back on the car.

Yes, and ...093 distributor would be for the '66 L-72. The max centrifugal spec is 30 @ 5000 and the OE VAC is stamped 360 12, start @ 6", 12 deg. (crank) @ 12". What's the ID on your VAC and start and stop points in Hg"

Duke

 

The VAC is stamped 355 I5 (not sure if that is the letter I or the number 1). The only source I have for start stop specs is a very good Lars Grimsrud paper 'Specs and facts for GM Point-Style Distributors', that I also read in a quest to better educate myself on the topic of Distributor advance. But this VAC is not listed. A new VAC unit is included on my shopping list for this restoration as this VAC has been on the car since for minimum 35 years!

Based on the input and what I've read so far, my plan is to salvage the (what I assume to be) original mainshaft and cam for the distributor I have, and replace everything else including the lower bushing (upper bushing seems ok, virtually no side play). I will order new weights (I will keep the old weights as back-up just in case), and the Mr Gasket 928G Spring set in order to improve on the OE centrifugal. I'm assuming I should order the 360 VAC unit.
Let me know I'm heading in the right direction or missing something. Thanks
Luke

 

Keep and use the original weights.

Use a Mighty-Vac to see when the vacuum can begins to pull in and when it is all in. Easy to do and will also verify that it still works..........but you may still want to replace it with something better for your car.

Larry

 

Thanks, makes sense. Will get on that tomorrow.
Luke