Point gap and timing

[Ian in Mississauga]

Anybody know just how much a change in the point gap affects the timing? I recently opened up my gap to .020"and the first time I drove over 45m.p.h. the engine stumbled until I retarded it a few clicks. Sorry, I didn't measure the point gap to begin with but the engine ran fine.

[Tom Wesenberg]

Always set the points first to .020", then set the timing. From then on you shouldn't have to even thing about checking the timing, just reset the points to the correct .020" clearance. Only if the distributor cam is loosened do you have to reset timing.

[40 Deluxe]

Originally Posted by Tom Wesenberg

Always set the points first to .020", then set the timing. From then on you shouldn't have to even thing about checking the timing, just reset the points to the correct .020" clearance. Only if the distributor cam is loosened do you have to reset timing.

But, "setting the timing" is an age-old ritual that many go through because it makes them feel that they are accomplishing something. You know: Buy the gadgets, hold one's tongue just right, then fiddle and refiddle! "Ah, perfect!" Then start the engine, pull the lever down and thus change everything!

[Jacksonlll]

I find a lot of engines like the point gap a little less than .020.

[40 Deluxe]

Originally Posted by Jacksonlll

I find a lot of engines like the point gap a little less than .020.

That's possibly because the coil is weak and needs the extra dwell time to build up voltage.

[Richard Lorenz]

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One thousandth point gap change affects the dwell by 2 percent with a "B" distributor cam.

[Jim/GA]

Originally Posted by Richard Lorenz

One thousandth point gap change affects the dwell by 2 percent with a "B" distributor cam.

2 percent or 2 degrees?

[Patrick L.]

I'm thinking that if the engine stumbles with much advance and runs better when its retarded a bit, there is a problem that is not connected with the point gap.
I would think there is a primary wiring issue or it could be a weal coil issue. But I would still at other things before the coil.

[Dick Steinkamp]

One degree of dwell is equal to 1 degree of initial advance.

For each degree of dwell increase, the spark is retarded by one degree at the crank.

[Mike V. Florida]

A narrower gap gives more dwell and a wider gap gives less. Taking it to extremes, excessive dwell means that the points close too soon after opening, cutting off the magnetic field collapse before it delivers all its energy. Too little dwell gives the magnetic flux insufficient time to build up to the maximum.

Both conditions give a weak spark which gets even weaker as the engine RPM rises and produces misfiring at normal operating speeds.

[katy]

Speaking of dwell, does anyone know what the dwell would be, with an A cam? With a B cam?

[Mike V. Florida]

Originally Posted by katy

Speaking of dwell, does anyone know what the dwell would be, with an A cam? With a B cam?

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