As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

[Bob S.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Now THAT'S a strange one..... Padding, huh? Cheap fix!

[Todd L.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

What does it mean to "blueprint the distributor curve" and how do you do it?

[Joe R.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Todd,

It means to set the advance in degrees versus RPMs curve, by playing with the centrifugal advance springs. It is best done on distributor machine, but can be done with a dial back timing light.

Joe

[Patrick H.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

What does it mean to "blueprint the distributor curve" and how do you do it?

1. Remove distributor.
2. Ship to Bill Clupper.
3. Send money to Bill Clupper.
4. Receive recurved and rebuilt distributor at your doorstep in a UPS box.

So far this is my favorite method for several distributors.

[Duke W.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

What does it mean to "blueprint the distributor curve" and how do you do it?

Go the the "sticky" near the top of the page on convention seminars and download the pdf of my presentation.

Duke

[Bob S.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

1. Remove distributor.
2. Ship to Bill Clupper.
3. Send money to Bill Clupper.
4. Receive recurved and rebuilt distributor at your doorstep in a UPS box.

So far this is my favorite method for several distributors.

Now, that sounds like fun!!!! OK, Bill, here's the story. I never mentioned who my mechanic was during this whole sorted story. Since he was dead right (As usual) it's Jeff Reade. Now, he is excellent at what he does, and at times, can be difficult. Like, "No..I will NOT lower your final drive. You dont need to do that!" So, I'm wondering if he knows about "Mapping" Do you know if he does? If not, I'll put on a helmet and some pads, and ask the man

How difficult is it? How much do you charge?

Thank you,

Bob
(9944)

[Duke W.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

See post #20.

Duke

[Patrick H.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Now, that sounds like fun!!!!

Works for me. I've looked into getting a Sun distributor machine but like with many larger sized tools it's easier to "rent" them than to own them. I "rent" one at Bill's workshop and let him do the work too.
For the half dozen or so he's done it's not worth the space in my garage or barn for a distributor machine.

Patrick

[Bob S.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

What exactly IS curve mapping?

[Timothy B.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Bob,

Distributor mapping is simply a term used to describe the actual advance curve that's in your distributor. The best advance curve gets the centrifugal advance in as fast as the engine will allow with detonation being the limiting factor.
The factory advance curves are conservative so the curve can be quickened which will provide better low rpm throttle response in the motor.

Does your 68 use a manifold or ported vacuum source for the vacuum advance as the timing curves you use in the distributor can be different depending on how you bring in the vacuum advance. If it's ported, the initial advance can be set higher to 14-18* and centrifugal set to 20-22* all in by 3000rpm. As long as the motor does not have hot start issues with the higher initial timing it's fine.

With manifold vacuum for the V/A, a lower initial timing (6-8*) is used combined with the advance provided by the vacuum advance at idle. This yields idle timing in the low 20's which helps with idle cooling issues etc. The centrifugal advance is different in that it needs to provide approx. 30* additional advance usually all in by 3000rpm.

This is a long debated topic (manifold or ported vacuum) on which is better but it depends on the motor/camshaft combo and the factory curves for each have much to be desired. Many people here recommend using a manifold vacuum source for the V/A but I think either curve has it's own advantages IF the distributor curve is set correctly.

[Clem Z.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

a quick and dirty way to try speeding up the advance curve is to remove one of the springs and give it a try.

[William C.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

OK, distributors at one time were designed for optimal performance/mileage back in the 50's-early 60's. As the government became more involved via emissions regulations, which became more severe with passing years, automakers learned "workarounds" that allowed then to tune the distributor curve to meet the benchmarks on the gov't mandated emission tests, although generally at the cost of reduced economy and performance. Also over time, distributor performance can change due to corrosion and or lubrication issue causing a deterioration in performance. With a distributor machine a points-style distributor can be returned to an original state, or modified to represent a different era, with disassembly, a thorough cleaning, some modifications and or repairs. The original curves are readily available and you can compare them over the years if you look at a curve from a 1965 327 High-performance Corvette distributor, you will find it to be quite different from a 1974 version of the high-performance 350. Back in the day, I got beer money making early 70's distributors work like earlier versions. Catylitic converters freed up the engineers to gain back some of the performance in the distributor works, and Computers with feedback loops driven by knock sensors and distributorless igniton systems controlled by the computer feedback to maintain the knock threshold when cruising are some of the major contributors to today's fuel economy.

[Bob S.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

a quick and dirty way to try speeding up the advance curve is to remove one of the springs and give it a try.

Yikes! Really???

[Bob S.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

Bob,

Distributor mapping is simply a term used to describe the actual advance curve that's in your distributor. The best advance curve gets the centrifugal advance in as fast as the engine will allow with detonation being the limiting factor.
The factory advance curves are conservative so the curve can be quickened which will provide better low rpm throttle response in the motor.

Does your 68 use a manifold or ported vacuum source for the vacuum advance as the timing curves you use in the distributor can be different depending on how you bring in the vacuum advance. If it's ported, the initial advance can be set higher to 14-18* and centrifugal set to 20-22* all in by 3000rpm. As long as the motor does not have hot start issues with the higher initial timing it's fine.

With manifold vacuum for the V/A, a lower initial timing (6-8*) is used combined with the advance provided by the vacuum advance at idle. This yields idle timing in the low 20's which helps with idle cooling issues etc. The centrifugal advance is different in that it needs to provide approx. 30* additional advance usually all in by 3000rpm.

This is a long debated topic (manifold or ported vacuum) on which is better but it depends on the motor/camshaft combo and the factory curves for each have much to be desired. Many people here recommend using a manifold vacuum source for the V/A but I think either curve has it's own advantages IF the distributor curve is set correctly.

Thanks ...making more sense now. I'm guessing this would be part of what is called by racers...."Super Tuning" Yes?

[John H.]

Re: As I Live & Breath (427/390 Auto w/ 3.08 final Drive) Yeah...Me!

I'm guessing this would be part of what is called by racers...."Super Tuning" Yes?

Bob -

I'd just call it "good tuning practice" - the distributor is the key to good performance, but it usually just sits back there in the dark, buried under the shielding for 30-40 years, and gets no maintenance at all other than an occasional set of points and a condenser. It's a wonder many of them work at all, given how little attention they get.