Setting points...retard or advance position...

Actually NO, so long as you have the points on the top of the lobe, you can set the gap in any timing position.
 
If you are talking about gap, as previously stated, the answer is no.

If you are talking about timing, you set timing in the full retarded position.

Chris W.
 
But,,,, When you change the gap without loosening the cam screw, the timing changes. That's the physical reality. But,,,, what happens is the timing is going back to where it was originally set --- also, rubbing block wear changes timing, that is really the reason the gap out if spec in the first place. Considering that we adjust timing manually as we drive, It's a mute point except for the gap, if it gets too far out of spec, the points deteriorate due to arcing.
 
Does anyone have a dwell spec for a Model A? I know we all THINK we can hit .020 exactly when setting points, but I'll bet if 10 of us set the point gap at .020, we'd have 10 different dwell values. It would be great if we could double check our work against the "official" dwell spec.
 
Thanks, Mitch. A post on a thread referenced in your post (did that make any sense :confused:) says...

"The B cam gives longer dwell time than the A cam. I compared them using a degree wheel. With a point gap of 20 mils (.020 inches), the A cam dwell was 32 degrees and the B cam was 43 degrees."

Sounds close enough to me. I'm running a B (dizzy) cam. I'll check how good my old eyes are with a feeler gauge tomorrow.
 
Spark happens when the points open. If the gap is too close, the points open later making the timing more retarded. If the points are open too far they open early and make the timing advanced. If you set the timing with the points set at .020, when you reset the points you know the timing is on.
 
Dick Steinkamp said:
Does anyone have a dwell spec for a Model A? I know we all THINK we can hit .020 exactly when setting points, but I'll bet if 10 of us set the point gap at .020, we'd have 10 different dwell values. It would be great if we could double check our work against the "official" dwell spec.
Click to expand...

You can check it with a dial indicator set at the back of the movable arm head. Its also a good way to make sure your cam runout is within spec
 
DougT said:
Spark happens when the points open. If the gap is too close, the points open later making the timing more retarded. If the points are open too far they open early and make the timing advanced. If you set the timing with the points set at .020, when you reset the points you know the timing is on.
Click to expand...

It's why you set the timing AFTER you set the point gap (and ALWAYS after you set point gap). I've found that one degree of dwell is equal to one degree of initial advance. Moving the point gap a tiny bit will affect timing.
 
BILL WILLIAMSON said:
Chief sed, "A worn Dime for the points & a worn Nickel for the plugs.:D Close enough for all practical purposes & Farm Equipment:D
Chiefs' Son
Click to expand...

I can remember using the end flap from the box the points came in to set them.

I have never seen a nickle worn enough to work for the plug gap, we just doubled the end flap.

Werked pretty goood in da old days :)
 
And it would still work today.

Ford engineers guessed the 40/60 front/ rear brake bias and were way out , as history has proven.

The A was ford engineers first guess at point gap too as the T had tremblers.

Modern cars before electronic ign point gap was usually .012 .

The .020 of the A would contribute to a higher rubbing block wear than it would be at .012 .

I wonder if one were to set their A gap at .012, would it make any difference than stock ?

Is the longest dwell that is possible better than one that is shorter or is to "spec".?
 
.012 seems awfully "tight" to me. I dug out my 1963 Motors Manual and took some random examples...

1962 Chevy II 4 cyl .019 31-34 dwell
1955 Chevy 6 cyl .019 28-35 dwell
1963 Chevy 300 HP V8 .019 28-32 dwell
1963 Falcon 144 CID 6 .025 35-38 dwell
1959 Dodge 361 V8 .017 27-32 dwell
1963 Dodge 6 cyl .020 40-45 dwell
1956 Ford 6 cyl .025 35-38 dwell
1960 Ford 292 V8 .015 26-28 dwell

.015 was the smallest point gap I could find (although I didn't look at all cars/years in the manual).

The Model A at .020 looks ballpark with newer points equipped cars.

I agree that it would be interesting to find out the pros and cons of the various dwell angels why some auto makers chose one dwell angle over another.
 
Notice in Dick's post#18 that dwell goes down as the cylinder count goes up. We want more dwell because at higher RPMs the actual time the coil and the condenser have to get charged up becomes less and less. As we go to 6&8 cylinder engines, there are 2 or 4 more dwell periods to fit in on the 360 deg. rotation. At the same time, the points need to get open wide enough to avoid arcing (burning). Too small of a gap gives more dwell that a 4 cyl. does not really need but the 6&8 could use it so they frequently are a little less. Dwell usually about 40deg. - 4 cyl. 35-38 deg. -6cyl. 20-25deg. - 8cyl. 12&16 cylinder engines have to do some other method because you can't open far enough and close long enough that many times in 360 deg. at highway speeds. Fun stuff.
 
100IH said:
12&16 cylinder engines have to do some other method because you can't open far enough and close long enough that many times in 360 deg. at highway speeds. Fun stuff.
Click to expand...

I've seen two distributors on some of those big old engines. Also, dual points can provide more dwell.
 
You must log in or register to reply here.
Back
Top