Timing problem?

D

Diamond T guy

New member
Our '28 starts and runs fine with the spark all the way up. It evens runs fine on the road. However, when the spark is advanced it will slow down and run rough. After verifying the timing sequence and even checking that the TDC of #1 agrees with the timing gear detent, no problem has been found. We even ruled out a vacuum leak. The wire below the advance plate is good. We just can't figure it out. Any suggestions?"
 
Timing is off Just enough. Mine did that where I could go faster with the spark retarded. So, we retimed the car and closed the points to .018 and now she runs fine at 55 mph.

Check for dist. shaft play-rotationally-and take up the play. We did that by timing the engine with the spark lever down a notch or two.

Mike
 
When the timing pin drops into the cam gear detent, the rotor position should look like this, with any freeplay on the CCW direction. So, you may be able to turn the rotor a little counter clockwise, but should NOT be able to turn it clockwise when the points cam screw is tightened.

My rotor looks different because I balanced it.
 

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Your timing sounds too advanced. Tom of course has it right-that rotor needs to be pointing exactly as he has it shown. Your linkage and steering column position may not be exactly right either (this especially matters when using the Marco timing method), but if you follow Tom's (and Purdy's) timing advice your car will run with power you didnt know you had. It took me a while to learn but a stock Model A once set up properly (timing, gas, etc.) is quite a peppy vehicle.
 
Thanks Greg, Its also the easiest way. Of course , as you said the steering column tube on the two tooth steering needs to be set properly to get full advance and retard . I always set the points first. That way, it doesn't matter where the spark lever is at the time. Its where the rotor tip points with no clockwise backlash that matters. Most mess up by turning the points cam counter clockwise untill the points just begin to open and ignoring the clockwise backlash. This confusing method just cranks in backlash and retarded timing. I've tried to explain this here for years.
 
Tom, the picture you posted of the rotor position when the timing pin is seated, what position is the spark lever at, full retard, full advance or somewhere in between?

Joe
 
JOES31 said:
Tom, the picture you posted of the rotor position when the timing pin is seated, what position is the spark lever at, full retard, full advance or somewhere in between?

Joe
Click to expand...

All the way up.

distrib-2.jpg


The rotor position shown above is the proper position with the timing pin in the gear depression and piston #1 at TDC. The dashed line shows the position of the rotor when #1 fires with the spark lever fully advanced (down).
NOTE: This is for reference only and not a suitable method for final adjustment of the timing.

This is from Marco's site;

http://www.abarnyard.com/workshop/timing.htm
 
Thank you Mike. I'll be setting the timing using this method tomorrow.
You guys are the best.
Joe
 
JOES31 said:
Tom, the picture you posted of the rotor position when the timing pin is seated, what position is the spark lever at, full retard, full advance or somewhere in between?

Joe
Click to expand...

Actually it doesn't matter where the spark lever is set, because you are timing by the rotor position, not when the points open. However, with the spark lever all the way UP, the points should just be ready to open with the rotor in this position.
 
Tom Wesenberg said:
When the timing pin drops into the cam gear detent, the rotor position should look like this, with any freeplay on the CCW direction. So, you may be able to turn the rotor a little counter clockwise, but should NOT be able to turn it clockwise when the points cam screw is tightened.

My rotor looks different because I balanced it.
Click to expand...
It doesn't get any better than this. Thanks Tom,

Chet
 
I had the same problem, thanks to this forumn I changed a very bad upper and lower distributer shaft, now able to time correctly and runs better then ever.

Thanks
 
Yea dumb question. You don't turn the distributor to do the timing on the A. Forgot the lever just rotates the plate the points are on.
 
1930artdeco said:
Tom, I have to ask, how and why would you balance a rotor?

Mike
Click to expand...

Take an old distributor shaft and turn about an inch on the bottom to a 3/8" diameter, so you can stick it into a small electric drill, then install the cam and stock rotor. Now, turn the drill on and feel it shake your hand. The drill is probably 1000 RPM, which is what the distributor runs at about 40 MPH. These same shaking forces are working on the distributor bushings. Now, balance the rotor and try the drill test again. Smooth as a baby's bottom.:D

This is also why counterweights are used on crankshafts.
 
JOES31 said:
Yea dumb question. You don't turn the distributor to do the timing on the A. Forgot the lever just rotates the plate the points are on.
Click to expand...

Its just that most timing instructions are SO unnessarily complicated and confusing that the average person can't set the timing. Tom nailed it in the best way that I have seen. There is no need to worry about where the spark lever is when the timing is set. Set the points first, anywhere from .018 to .022 . If you have the two tooth steering column with the adjustable column tube, check the window in the back of the distributor cap and make sure that you have full movement both ways on the lever of the breaker plate or you won't get full advance or retard with the spark lever. If you don't have full movement, loosen the clamp at the bottom of the column tube and the two column clamp screws inside the car and rotate as needed . Remove all of the spark plugs so that you don't have to fight compression when trying to find the timing dimple. When the timing pin drops into the dimple , set the rotor exactly as Tom pictured and explained and your timing should be perfect.
 
Tom Wesenberg said:
Take an old distributor shaft and turn about an inch on the bottom to a 3/8" diameter, so you can stick it into a small electric drill, then install the cam and stock rotor. Now, turn the drill on and feel it shake your hand. The drill is probably 1000 RPM, which is what the distributor runs at about 40 MPH. These same shaking forces are working on the distributor bushings. Now, balance the rotor and try the drill test again. Smooth as a baby's bottom.:D

This is also why counterweights are used on crankshafts.
Click to expand...

One of the best things Tom did for me and that reminds me I have to send him 3 more....Great concept and great idea,....
 
Mike V. Florida said:
All the way up.

distrib-2.jpg


The rotor position shown above is the proper position with the timing pin in the gear depression and piston #1 at TDC. The dashed line shows the position of the rotor when #1 fires with the spark lever fully advanced (down).
NOTE: This is for reference only and not a suitable method for final adjustment of the timing.

This is from Marco's site;

http://www.abarnyard.com/workshop/timing.htm
Click to expand...

Unless something is wrong with the points cam, the timing will be absolutely correct when the rotor tip points as pictured with NO clockwise movement after the points cam is tightened. Ford specs for the points are .018 to .022. Ford considered it ideal for the points to be just ready to open at this point. Less points gap retards, more gap advances. Its only a matter of a few thousants. I prefer the maximum gap of .022 for quick throttle response and more time before the points will need to be reset. I still consider the timing to be correct with the points set anywhere within specs. Twenty two thousants is as far as a person should go with points gap without starter kick back when cranking. I often hand crank my model A's with no fear of kick back.
 
The mystery has been solved!
I do know something about timing a Model A so I was sure it was timed right but the reason for the roughness when the spark was advanced had us in a quandary.

While running rough with the spark advanced, I shorted the plugs. Both # 1 and 2 caused the engine to slow way down but # 3 or 4 would make no difference. What's up with that?

Here is what happened: The distributer cap had a hidden crack that allowed the spark to jump to the advance lever when the lever was moved below them. This probably has happened many times in the last 90 some years but has been forgotten.
 
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