Can someone tell me if all distributor shafts are the same for 1969 distributors? I purchased new bushings, shaft and springs for my transistorized distributor but it does not say specifically it is for this type. Couldn't find anything on the parts websites that say there is a difference even for small or big block. Mine is a 390hp.

 

They are the same.
Be careful of repop shafts. They are NOT all indexed correctly. Compare the tops with the roll pin hole. The Paragon shafts are made correctly.

 

thanks Big Bird
appreciate the help

 

Most of the reproduction shafts are made for the standard distributor and not correct for the TI distributor.

Over the production run of the tach drive distributor GM made a horde of different shafts and the main difference was the top of the shaft that control's the weight position. This controls the timing curve of the distributor and will ultimately change yours.

Compare the new shaft to your old one and you'll probably see the difference.

Will it run in your distributor... yes.

 

Thanks, appreciate the response

 

Thanks Appreciate the help

 

If you know a good welder you can remove the top lobe from the old original shaft and braze it on the new shaft.. I should have told you that in my last post but most won't try that.

When we are building a distributor in our shop dialed in to factory specs and the lobe is different, that is exactly what we do. Food for thought

Willcox

 

Paragon has both standard and high performance shafts the difference is the top cam. I have measured the curves the two top cams give. The HP one basically gives you the same curve as in the Chevy power book, very linear. The standard cam has very retarded timing for the first part of the curve and would hurt power. It would work fine in you 427 390 and probably be very close to oem if you do not want to go welding.

 

Leigh, did you have that chart of footballs and weights?

 

There is a guy named Dave Fiedler (SP?) and he specializes in the Factory T.I. Systems. I have one that came on my 1968 C3 and I had him overhaul my distributor and update the control board. He does amazing work and is a very knowledgeable person when it comes to Corvettes and T.I ignition systems.

I met him at Corvettes@Carlisle I believe so they might know how to find him.

After rebuilding my system I packaged it in vacuum sealed bags and stashed it away with other original parts from my Corvette. Today I have a MSD Billet Distributor with mechanical tachometer drive working through an MSD 6AL. This system works and the original is there in case someone wants to make it "original" again. Now I am getting ready to have my new Holley Sniper Stealth take over the ignition as well as the fueling of my Corvette. Having a mechanical tachometer can be a drawback when converting as everyone wants you to use a different distributor that don't have tachometer drives built in.

 

Big Bird you must mean these:
Below are the two available cam shapes:


Below is a chart from TI specialties showing the full range of Chevy's 28 advance cam curves: This shows a 10 degree variation at mid-rpm.


Below are the results of my own testing on the two currently available aftermarket advance cam curves. (I may have a little measuring error on the last couple points they don't look smooth enough)

The Hi Perf curve is virtually dead linear, and at mid-range advances the timing about 4 degrees more than the std one.
The 1964 327-365 was the last real chevy to get a 100% performance ignition curve from the factory with a lot of initial and total all-in by 3000. Every thing after that was a compromise between emissions and performance, with greatly retarded timing at many rpms, total not arriving until 5000 etc, vs the optimum advance curve as listed in the chevy power curve which is virtually identical to the '64 365 BTW..

A linear advance curve is what you want, and that is exactly what the Paragon High Perf part gives you. I confirmed it.

Then change your springs til you get all-in by 3000, and set your total to 34-36. It'll run a lot better and you will feel the difference.

If you are all about 100% stock just use the High Perf cam. It will be within a couple degrees or so of your factory one and you'll never feel the difference.
It'll work with your TI distributor.

If you really think your cam shape is different than above, and want to try to weld your old on onto the new shaft, then you must index it onto the shaft at the same angle as the OEM one vs the distributor "Tang" & roll-pin. At least "eyeball" close would be close enough, it not only shifts the oil pump shaft, but the "dimple" on the distributor gear that you use to index the distributor properly.. It would be way more of a challenge to stab the distributor in correctly if that was not close to correct.

 

Oh and here is that chart from TI Specialties that gives all the original OEM distributor advance curves for the TI distributors:
You just have to figure out your distributor number. Notice the first two has total all-in at 1250, that's 2500 engine rpm, that's the "hot" one.
Everything else is retarded so all-in does not occur til 4000-5000 engine rpm.

 

Thank you. All the variations boggle my mind. There is a story there, I just do not know what it is.

 

Yes, but you can bet it's a really good story too..