Commutator adjustment - Spark Advance

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Model T Ford Forum: Forum 2012: Commutator adjustment - Spark Advance
Top of pagePrevious messageNext messageBottom of page Link to this message  By Rowland Smith on Tuesday, October 16, 2012 - 07:18 pm:

Hey All:
My "new" 25 coupe (21 motor) now has new plugs, radiator, hoses, fluids, etc....
Seems like I've had to advance the spark lever far more than what most posts on the forum suggest...not to mention I can't hand crank it, but it will start on battery and run on magneto.
So I went thru a couple of processes here on the forum of finding TDC and checking to make sure commutator is set to spark at 15 after.

Here's my issue: I've bent the rod to get the commutator where I need it to start sparking #1 at about 4-5 notches, but now, when I advance the lever down several notches, like I would when cruising, the pin/cotter pin are hitting the fan belt.

Is there something else out of whack or could I have TDC wrong? The crank pulley pin is horizontal and I check piston pressure with my thumb while turning engine to find compression.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Tuesday, October 16, 2012 - 07:51 pm:

Rowland,
With the spark lever fully retarded, (all the way up), you should be able to slowly turn the motor over and when #1 starts sparking/buzzing the crank pin should be about the 9:30/3:30 postilion for 15 degrees ATDC. Some people set the timing closer to TDC but never before TDC. The closer to TDC, then the further the pin will be from hitting the belt when advanced.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Bamford, Edmonton AB on Tuesday, October 16, 2012 - 08:00 pm:

I'll piggyback on your question with my own very similar...

I've shadetree-set the timing on my touring and speedster (both have roller timers, Z-heads and healthy magnetos) such that when the engine is hand-cranked on battery, the coils start to buzz just after the crank goes past TDC (judging from the crank pulley pin position).

My thinking on this was that the closer the buzz starts relative to TDC, the more I could advance the timing once running — advance from an initial setting of, say 4° or 5°ATDC, instead of the recommended 15°ATDC, would allow up to 10° more advance BTDC. That additional 10° might not be necessary or desirable but having it available couldn't hurt.

Thing is, I need to use maximum or almost maximum advance for either engine to run strong and smooth. My understanding is that Z-heads require less advance but that has not been my experience.

So now my question: if I set the timing for greater ATDC initial timing, ie 15°, will I counterintuitively end up with greater BTDC advance running on magneto (something to do with the 22.5° magneto pulses perhaps?).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rowland Smith on Tuesday, October 16, 2012 - 09:09 pm:

thank Jim...I'll relook at the pin position to be 9:30/3:30, not 9 and 3. First thing I did, before messing with the spark advance rod was to remove the #1 plug and see where the spark started.

I turned battery on and started advancing the spark...i got to the 10th notch before it started firing, leading me to believe I needed to move the commutator counterclockwise to engage spark sooner (4th/5th notch)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rowland Smith on Tuesday, October 16, 2012 - 10:02 pm:

sorry...clockwise


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Tuesday, October 16, 2012 - 10:06 pm:

I think there' an accepted method of doing this, but I adjust mine so that with the lever fully retarded the spark starts when #1 is past TDC 1/16" on the downstroke.

Seems to start well and never a kickback.

schuh


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Tuesday, October 16, 2012 - 10:13 pm:

BTW setting it this way (with a new day timer) yields the exact 2 1/2" measurement as is described in the Ford manual. Maybe a coincidence but thats the way it worked out on my car.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Tuesday, October 16, 2012 - 11:15 pm:

Schuh,
Your 1/16" down calculates out to 12.7 Degrees ATDC. That's close to the 15.

Rowland,
Actually using the crank pin as a indicator works on all four cylinders. Cylinders 1, 2, 3, and 4 all should fire with the pin just after horizontal. One of the coils should buzz at the same location each 1/2 rotation.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rowland Smith on Tuesday, October 16, 2012 - 11:18 pm:

Good info...thanks! I think I'll put the commutator rod back to original shape and use the "pin just after horizontal"...seems that gets to the right range of ATDC degrees. I'll report back tomorrow.

thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Wednesday, October 17, 2012 - 12:42 pm:

Rowland,

It's very common for the timer rod & cotter pin to hit the fan belt. It means your fan belt is too long, and not necessarily that your timer has rotated too far.

A long fan belt allows the fan mount arm to swing too far to the right and therefore brings the fan belt too close to the timer.

Not saying you haven't got timing issues, just don't use the fan belt as your gauge of timer position.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Wednesday, October 17, 2012 - 12:44 pm:

Rowland,

You never mentioned how the car actually runs and drives. Comparing spark lever position from one T to another is pointless due to decades of timer replacement and timer rod bending, let alone the multiple choices of timers available.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Wednesday, October 17, 2012 - 03:35 pm:

Set your timing the correct way and save yourself a broken arm and a starter. The procedure has been posted time and time again here.

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Barker, Somerset, England on Wednesday, October 17, 2012 - 05:18 pm:

If you think for a moment, the adjustment of the timer rod has no effect on whether the timer boss hits the fan belt when at the best running position. It only affects where your hand lever will be. If the boss is already close to the belt with the spark just ATDC, there is a problem with the cam timing or the timer casing or roller geometry.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rowland Smith on Wednesday, October 17, 2012 - 07:44 pm:

Thanks all....the car runs pretty well but doesn't seem to have the power in high, especially on very low grade hills. But I was noticing that even after running (after starting on battery), I couldn't hand start it on magneto with the lever at 4-5 notches....didn't even cough...just acted like key was in off position. It does run the same (a bit faster) on magneto after started.

so I pulled the #1 plug and found TDC, turned on the key and moved the spark lever until I found spark....it was 12 notches down. This led me to believe my commutator rod was adjusted wrong. The problem was when I bent the rod to reposition the lever, the end/cotter pin would rub the fan belt.

today, I ran it for a few minutes to warm up and then set the spark lever at 11....it hand cranked for the first time.

so I guess I'm wondering if I shouldn't try to reposition the lever somehow to be closer to 4-5 notches at 15 ATDC.

Jerry may have the answer, with needing a new fan belt.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Wednesday, October 17, 2012 - 08:06 pm:

If there is any slop in the linkage, you will have to take that up before the timer even moves. I have to advance both of ours more than the 4-5 notches recommended for MAG starting due to slop in the linkage. The important thing is that it is AFTER top dead center when the lever is fully retarded. Some will disagree, but I tend to think like Chris Bamford. As long as it fires AFTER top dead center on BAT with the lever all the way up, I don't get real concerned about exactly how many degrees ATDC it is (Within reason. You don't want it at 20:-)). Mine are probably closer to 5 than 15. With the slop in the linkage, the extra advance comes in handy on the other end.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug Money - Braidwood, IL on Wednesday, October 17, 2012 - 11:11 pm:

Rowland, the lever should be all the way up and adjusted to 15 ATDC. The more notches you are down at 15 ATDC the less timing you will have overall. The purpose of the 15 ATDC is a safety when cranking so it won't kickback. No more is necessary.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, October 18, 2012 - 06:38 am:

Adjust it (as many have said) so that the starting position is with the lever all the way up. Otherwise you can't achieve full advance, and the car will be down on power.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rowland Smith on Thursday, October 18, 2012 - 07:54 am:

that's my point Royce....seems I'm running out of timing because the lever would bottom out when running the car out full, if I don't have the lever totally retarded for battery start, or slightly advanced to hand crank.

it seems to work fine as long as I'm rotating the commutator enough to get to spark...but that is 10-12 notches down.

If I adjust the rod to rotate the commutator a bit more and bring my lever up in notches, the pin/cotter pin hits the fan belt when you start advancing alot.

Keep in mind, the car runs great as long as the commutator is rotated enough....guess I'll take it off and make sure nothing is screwed up inside with the roller or something.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Thursday, October 18, 2012 - 01:32 pm:

ANY lost motion from the lever to the timer will have a huge effect on timer rotation.
Eliminate lost motion first.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, October 18, 2012 - 02:20 pm:

You can achieve the correct timing without the rod touching the fan belt. Just keep trying until you figure it out. It worked on the other 14,999,999 Model T's. Yours should too.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rowland Smith on Thursday, October 18, 2012 - 04:23 pm:

Good point Royce!:-)


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