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Subject: Setting timing

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Dave Smith    Posted 10-18-2018 at 17:56:23 [URL] [DELETE]        [Reply] [Email]  
  • Setting timing
  • When you static set the timing on a front mount distributer, you are actually setting
    it at 4 degrees before top dead center. (TDC) The same as for the side mount
    distributer. WHY? Because gasoline does not actually explode, It burns very fast
    especially under compression. (The same for gun powder) That is why you set the points before TDC at 400 RPM. When the engine turns over faster the mechanical advance
    moves the timing faster to compensate for the piston moving faster. Too much spark
    advance can cause knock and if ignored can burn a hole in the top of the piston.
    (I know that from experience on a 1950 Chevy PU). Too slow of timing can cause over heating because too much fuel is burning on the exhaust stroke. Ask a old Ford model T man when
    they had the spark advance on the steering Colum. If you forgot to advance spark after it is running it would over heat. Retarding spark while starting helped in starting and may save a broken wrist if hand cranking

    Farmer Dan    Posted 10-21-2018 at 17:26:47 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • The distributor is timed at TDC, at 0 rpm. spin the engine to idle speed of 400 rpm and the spark advance mechanism changes the timing to 4 degrees BTDC. I learned all this while working with the Sherman High Performance head and by reading my FO4 manual.

    Dave Smith    Posted 10-21-2018 at 17:45:54 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • Dan, Like I said. When I installed the static timed distributer and ran the engine at
    400 rpm It showed 4 dg. BTDC. You are right.
    Dave <*)))><

    Tim Daley(MI)    Posted 10-21-2018 at 09:58:12 [URL] [DELETE]        [Reply] [No Email]  
  • Here's Dave's How-To's on adding timing marks...

    JMOR    Posted 10-19-2018 at 18:26:36 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • Can you demonstrate this claim? "When you static set the timing on a front mount distributer, you are actually setting
    it at 4 degrees before top dead center. (TDC) The same as for the side mount

    Dave Smith    Posted 10-19-2018 at 19:27:55 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • You must have missed it. But a couple of years ago I added timing marks to a 41 9N
    engine. (Look in the how too under engine) After getting the engine back together

    I checked 2 front mount distributers that I have. Both static timed showed to be right
    on 4 degrees before top dead center.
    Dave <*)))><

    K.LaRue-VA    Posted 10-19-2018 at 20:41:01 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • Darn! Now I'm going to have to move the pile this weekend, get the 1940 9N engine on a stand, and do my own test. I have at least two front distributors rebuilt, timed, and ready to go. It's hard to believe all the operator and service manuals for the front distributor engines that say "Top Dead Center" are wrong.

    Dave Smith    Posted 10-20-2018 at 07:07:49 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • K L, Do you have a front mount engine with timing marks
    That you can check them on? If so do the test and
    Tell us what you found.
    Dave <*)))><

    Tim Daley(MI)    Posted 10-20-2018 at 04:29:50 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • We learn something new about these old FORD's all the time.

    Tim Daley(MI)

    Tony C    Posted 10-20-2018 at 16:34:21 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • Should be easy to verify using an ohm meter and an accurate dial indicator. Set the timing accurately as described in the manual. Zero the indicator on the piston at TDC, making sure all the backlash is out and at the exact point of reaching it. Rotate the engine until the points break at the piston you are indicating. Convert the difference in movement in thousandths of an inch until the points break to degrees of rotation.

    What has to be considered is there has to be approximately 4-8 degrees of crankshaft rotation to allow the piston rod combination to break over and begin downward travel. Engineers have to allow for that lead into every engine or any timed machine converting linear motion to rotary motion.

    Dave Smith    Posted 10-20-2018 at 07:12:51 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • Tim, If you think about it, the spark is still
    going on as the piston hits TDC.
    Dave <*)))><

    Farmer Dan    Posted 10-20-2018 at 13:30:58 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • when I was running the sherman head I had to advance the timing 4 degrees.

    K.LaRue-VA    Posted 10-21-2018 at 12:34:13 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • This was bugging me enough that I had to go check it out. I decided to check the timing on my 2N. No idea why this was bugging me. Setting timing at the distributor has always worked fine so I never had any need to know actual degrees of advance. I wouldn't trust the accuracy of my measuring and math to drill an access hole and add timing marks to the flywheel.

    Remove No.1 Spark plug.
    Remove distributor cap.
    Crank engine till rotor is near where No.1 cap terminal would be.
    Stick something in spark plug hole to feel/see position of piston.
    Turn engine to find point where piston begins to drop before and after TDC.
    Mark those spots on the engine pulley and timing cover.
    You should have two marks on pulley and one mark on timing cover.
    Move engine so timing cover mark is centered between two marks on engine pulley.
    Accuracy: Since I'm working alone I moved the crankshaft till I could see a mark on my probe had dropped to the same point either side of TDC. Moved engine back and forth to check the marks. My pulley marks were about 1" apart. That is roughly equivalent to 2 degrees on a pulley that is 5.5" outside diameter. Somewhere close to midway between those two points is TDC. Being very pessimistic, let's say my accuracy is plus or minus 1 degree.
    Now the hard part. Get a look at the position of points and the distributor cam.
    Rather than play that game, I took a sharpie, marked the rotor location on the distributor and removed the distributor.
    Install timing jig made by TOH.
    My rotor was pointing right at the mark I just made on the distributor housing.

    Reinstall distributor, distributor cap, spark plug and fire engine to make sure I haven't messed anything up. Shouldn't since I didn't touch the points or timing adjustments.

    Near as I can tell without resorting to micrometers, setting the points and distributor timing on this 2N as described in the manuals appears to result in the initial retarded timing being set to open the points at TDC.

    K.LaRue-VA    Posted 10-22-2018 at 17:59:21 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • When writing up the procedure above, it got too long. I meant to edit out the part where I found TDC for the wrong cylinder. After installing the timing jig, I discovered the distributor bench timing is actually done with the rotor pointing at the No.3 terminal. Grrr. Go back out, reinstall distributor and find TDC on No.3.

    Another edit I thought got too long-winded was my piston probe made from a bent piece of wire so I could put a mark and match up the same piston movement going both ways with the crank. It was an offset measurement, but seemed reasonably accurate at the time.

    After all that, as TOH correctly points out below, my calculation slipped a decimal point somewhere, so rather than 2 degrees apart, my pulley marks were more like 20 degrees apart! That certainly lowers the accuracy to the point nothing was actually proved by this effort. Good thing I enjoy fiddling with these tractors, so this complete waste of time was at least somewhat fun.

    TheOldHokie    Posted 10-22-2018 at 18:25:14 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • I do think one useful thing came from this - the idea of adding timing marks to the rim of the crankshaft pulley and a TDC pointer on the front of block. With the head off that is a really easy thing to do. Once you have those marked there is no need to muck with the flywheel or rear of the block.


    TheOldHokie    Posted 10-21-2018 at 15:40:12 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • Just to be clear I do not disagree with your conclusion - just question the acuracy and reliability of the measurement procedure. The same goes for Dave Smith's modifications. It is hard to discriminate the small values neede to accurately gauge the result. What I do know is the Ford documentation is quite clear on this and can be found in a number of different publications:

    The spark advance for the engine is also given numerous places as:

    4 BTDC @ 400-500 RPM

    This is 100% consistent - at 400 RPM the centrifugal mechanism in the 9N-12100 distributor advances the spark 4 from it's static (0 RPM) setting of 0.

    If the static setting is 4 AND the 400 RPM setting is also 4 then we have to assume the centrifugal advance mechanism in the 9N12100 distributor is inoperable between 0 and 400 RPM. Conceivable but given the documentation it seems more likely the manual is correct and the advance is linear throughout the RPM range.


    Ozlander    Posted 10-21-2018 at 16:06:12 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • Me thinks that Henry, knowing that these tractors could possibly be hand cranked,
    set the very low rpm spark advance to zero.

    Tony C    Posted 10-21-2018 at 19:40:26 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • and.... a simple reliable fool proof mechanical advance mechanism.

    TheOldHokie    Posted 10-21-2018 at 17:17:04 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • I tend to agree - hangover from the Model T days ;-)


    JMOR    Posted 10-21-2018 at 15:37:26 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • How did you probe the piston top with this configutation?

    Dave Smith    Posted 10-21-2018 at 17:35:20 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • For DOO DOO and giggles, I used a piece of insulated no 12 copper wire
    striped short on each end. I inserted one end through the spark plug
    hole with a slight hook down on the inner end. Connected the other end to the ohm meter. I rotated the crank very slowly until I got continuity.
    Naturally on the compression stroke. I stopped and put a chalk mark on the pulley and engine block. Then
    continued to turn the crank slowly until I lost continuity. Again I chalk marked the pulley. I did this several times to be sure nothing shifted.
    Midway between the two marks was TDC. That I believe is a fairly
    accurate for this purpose.
    Dave <*)))><

    JMOR    Posted 10-21-2018 at 18:09:29 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • Must have been an awfully recently rebuilt engine to be clean enough to get continuity to the piston top! I'm amazed. Even more so that valves didn't move your wire.

    Dave Smith    Posted 10-21-2018 at 19:30:14 [URL] [DELETE]        [Reply] [Email]  
  • Re: Setting timing
  • It was a rebuilt engine. Don't forget the valves are closed.
    Dave <*)))><

    JMOR    Posted 10-21-2018 at 23:01:12 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • closed all the time you were rotating toward TDC? And furthermore, you actually think the wire did not move the first time the piston touched it? Wow!

    TheOldHokie    Posted 10-21-2018 at 15:42:43 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • How did you probe the piston top with this configutation?

    Indirectly and inaccurately ;-)


    TheOldHokie    Posted 10-21-2018 at 14:09:53 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Setting timing
  • I think you have a math problem here.

    My math says the circumference of a 5.5" pulley is 3.1416 x 5.5" = 17.28".
    So 1" of arc length subtends 360 / 17.28 = 20.8 degrees.
    Four degrees of arc length would subtend 17.28 / 90 = .192" or just under 3/16"

    That may or may not change your conclusion but it does suggest issues with the expected error and reliability of the final measured result.


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