72Pogo

Can anyone educate me on the exact difference between the base motor and hi-performance distributors? I am assuming it is the length due to a different intake manifold used on these engines. If so, just what is the difference?
The previous owner(s) of my base motor 72 installed a Holley Street Dominator intake and other mods to come up with an LT-1 clone. Am wanting to rebuild the distributor and am wondering which route to take.

Thanks in advance for any help in this matter.
Al

Paul L

The length does not differ. It's in the weights, springs and vacuum advance.

72Pogo

Paul67,
I can understand the different weights and springs for a different advance curve, but why two different mainshafts ? For example: Zip Products lists part number M-216 for the base motor mainshaft and M-2984 for the hi-perf motor. They also list two different distributors, two vacuum advances and two spring sets. They only list one item for the mainshaft bushings, so they must be the same. Just can't understand the two different shafts. I guess I must be having a senior moment. :D
Thanks for your reply.

Al

Jvette73

The difference in the mainshaft may be directly related to the advance curve. The shape of the advance cam on the top of the shaft has an effect in total mechanical advance. My guess is the hipo shaft has a cam that will allow more advance.

redvetracr

Pogo, If you look in an old Corvette parts book (P&A-30B) you will find there used to be a whole lot more than just two different mainshafts, they are all discontinued now so the best thing to do would (in my opinion) rebuild your distributor and take it and get it recurved. ...redvetracr

lars

There is a difference in the cam profile on the top of the mainshafts. This changes the characteristics of the advance curve. There are also different cam plates with different length advance slots.

This all becomes irrelevant, however, if you know how to set up a distributor. With a little creative tuning - playing with the slot length and spring tensions - you can custom tailor any distributor to provide a high performance curve. It doesn't matter what you start with - any distriubutor can be set up to provide a very responsive advance curve.

AV8RSVT

How come when I go into the auto parts stores I only see the Springs and wieghts for the HEI's would anybody have A part # for spring and weight kit for points distributor (stock dist). If I decided to retain my points setup it has been so long, Has anybody got A paper on the procedure for replacing points. Also I see on EBAY Alot of duel points for sale. would that be A better approach???

Gary

lars

Gary -
Don't replace your stock weights on a point-style system - none of the aftermarket weights will allow a correct advance curve. Use the stock weights and manipulate the curve with springs and slot length. Use Mr Gaslet part number 927 to get the springs and the stop bushing. Use NAPA part number VC1810 for the vacuum advance. Use my timing setup paper for setting up total advance.

Paul L

This is a rebuild with Lars' parts. The original band said #1111493: 1969 350/350. But those bands are basically just $0.10 worth of tin. As I said originally the components are the key. I will let Forum members know how things turn out when I get this in the car when the snow and cold goes away. My initial thought was to have it recurved but I have confidence in Lars' choice of parts, his instructions and my Sears advance timing light.