Point gap affect on timing

retep

retep

Member
What affect on timing does having gap to large or small have on advance setting?
I am trying to set 40B (1936) distributor without much success. By this I mean I have back firing through the exhaust when going downhill.

The point setting is .013
Will setting wider impact this?

When I set up advance on distributor it was at middle mark. Rough running and vacuum reading 15. Moved to full advance reading now at 17.

Will changing gap make any change for the better?
 
Each degree of dwell setting ( on the drivers side set ) will change timing two degrees.
Ex: A distributor that should run a 27 degree dwell setting using 22 degrees would change timing 10 engine degrees....advanced ....
Only the drivers side effects the timing the pass side effects coil build up.

As the distributor is case timed to the engine cover its important to be correct for sure....
 
MGG said:
Should the gap on both points be set the same or are they different?
Click to expand...


Most manuals show them as being the same . On a machine the dwell setting is different per side .....The drivers side is set at 22 1/2 degrees for small points ( with pass side blocked off) and 27 degrees for strap points. Then the pass side is set running both sets at 35-36 degrees..........
 
As you increase the gap, the dwell angle will decrease because the points will open earlier. The spark occurs when the points open, hence increased spark timing.
 
I am pretty lazy guys so I am going to take off distributor (3 time) and reset points to .015 and see what happens.

As a matter of interest the last time I set advance using Henry Fords method as described in his patent application for his distributor from 1933.
 
I'm back.
Here is my update.
I tried the lazy way (setting points at .015) and no improvement.
I used Willit Stop procedure and no change.

Before I go the route of buying a rebuild and possible electronic upgrade I would appreciate any other suggestion for my problem ie. Carburetor, vacuum leaks etc.

Symptoms once again:
Backfire in exhaust, running rough, low vacuum readings 17-18 and I believe overheating.
I did pull out choke and it did not improve road test.

Thank you for what ever you have to offer.
 
Back snapping/rapping/cackle on deceleration indicates a lean condition at idle. Check for vacuum leaks and possibly enrich the idle mixtures.
 
Still playing around with solving this problem.
I once again tightened down manifold and carb (vac leak)
Cleaned and gaped plugs. Would appear to be running rich (black carbon)
Checked to make sure coil polarity correct using voltmeter
Replaced fuel pump

Could condenser be an issue? I have Dennis Carpenter coil adapter with condenser supplied.

Carb is my next consideration.
Again thanks for any input.
 
Condensers are definitely on the list of possibilities. If they don't charge up completely or leak the charge out as fast as it is drawn then the breaker points and the ignition function will suffer greatly.

Black coated plugs indicate either poor ignition function, excessive oil in the combustion area, or a rich fuel mix from something like an internal carb leak. Those old carbs can leak from bad gaskets or power valves depending on the make of carburetor. A compression check will tell you if the rings or valves are suspect.
 

[/B ]I will replace condenser. Do you have NAPA number for 1936 (40B) condenser?
I will have to borrow a compression gauge so it might be a few days before I report back.
 
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Just a thought. Have you cleaned or replaced the fouled plugs? If you have made adjustments/changes and the plugs are still fouled it will continue to run badly.
 
I pulled plugs. They were as described then cleaned and gapped.
I haven't run car other then test. No improvement.
 
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