MikeM

I'll let you be the judge which is easier but there was full agreement on how to advance the timing and how to retard it and I avoided any indecision about what changing the point dwell would do.

426 Hemi

OK, ventured out to the sub-freezing shop and fired up the Sun machine.

Set dwell at 28º--then set the strobe pointer to 0º

Slowly adjusted the dwell to 32º. Pointer indicated 2º advance (EDIT wrong, retard is correct)---which I believe you double to get crankshaft degrees.

Critter1

Thank you !! So, I/we were right from the beginning. One degree of dwell change is ONE degree of timing change at the crankshaft.

Not 2° like the original poster stated.

But didn't the timing retard by 2°, not advance?

DansYellow66

Well that kind of refutes the idea of why so many tuneups resulted in the car running so much better because the timing was retarded from point block wear and narrowing gap. And it seemed logical too.

Thanks for checking it. Love those old distributor machines. I asked down at our local speed shop the other day, if they still had theirs that I once had my TI checked on. They said they got rid of it a few years back. Too bad.

survivor66

I don't know these machines but is it possible an accidental reverse polarity connection would change a correct retard reading to advance? Rotating the opposite direction would do the same but I doubt the machine has that capability.

426 Hemi

Hey guys, my screw up.

When going from 28º to 32º the strobe pointer moved to the left of the zero---which is retard.

(When spun up and the centrifugal kicks in the pointer moves to the right---advance.)

Again my bad. I'll take the D- on the report.

MikeM

Increasing dwell let's the points close earlier and open later.

Critter1

Yup, absolutely right.

Is everyone on board with us now?

Where's Duke? He started all this.

He posted the exact same thing over at the NCRS board too but no one corrected him yet.

MikeM

Quick, check the Cosworth Vega site! Oh wait, they don't have points, do they.

Powershift

Glad we got this straight and agreed to in print. Many of us have KNOWN this fact for over 1/2 a century. Years ago many (like myself) played with dwell, points replacements/changeouts, and timing (incl power timing) just about every weekend. Some things you just don't forget, no matter how old you are.

Larry

SW Vette

Since it was my car Duke and I were playing with in the first place, I guess I'd better go recheck my timing now - it may be retarded a degree or 2.

DansYellow66

No problem - we are back to where things make sense again.

MikeM

It is Paul Harvey time!

MikeM

Well?

Critter1

Still no reply from Duke?

SW Vette

Did it the lazy way - a seat of the pants check - car runs great!

SWCDuke

Sometimes we make mistakes. The owner was working the Allen wrench and reading the dwell meter while I was working the timing light. It appears that one or both of us either didn't follow the test plan correctly or misread the equipment.

It would help if someone else would run the test on a car. This thread, as of this writing has nearly 2500 views and 76 replies, and you are the only one to lend a hand. Thanks for taking the time.

Duke

Critter1

It wasn't necessary for me to do a test. I knew what I was talking about from the beginning of this thread.

I hope you go over to that other place and straighten that out too. Most of those guys believed you.

PAmotorman

if you want to adjust your timing without a timing light and know where you are just convert the vacuum advance to a threaded rod and knowing the number of threads per inch you can calculate the number of turns gives you what degree change. I did this on some short track and drag race engines.

PAmotorman

any time you increase the dwell the points stay closed longer and open later and that is when the ignition fires. the ignition fires when the points open