alternative CCK Timing Process
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  1. #1
    Senior Member sdunt's Avatar
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    alternative CCK Timing Process

    Trying to set the ignition timing on an Onan CCK when it is installed in a Case 646 tractor is next to impossible. The design of the 646 has the oil reserve tank above and in front of the engine, along with the oil cooler in front. There is no way to look into the front of the engine to see the timing marks.

    Also with the oil tank above an engine that is sucking in a ton of air means ANY spills or leaks from the reserve tank right above, are going to get sucked right into the engine and COVER the gear cover where the timing marks are. Here is what an engine from a 1973 Case 646 looks like, good luck finding the timing marks:



    (The other fun part is that the Onan service manual says to time the engine with a timing light by shining it down through the hole in the top of the shroud onto the timing marks on the gear cover.. Again I ask; "WHAT marks?"

    Setting the engine timing based on the movement of the pistons is a documented process. The service manuals I have for my 1958 JI Case G-148 engine talks about measuring piston movement to determine timing. Since removing the heads is part of the regular maintenance of the engine, why not take the opportunity to time the engine?

    The exact amount of piston movement vs degrees of rotation of the crank, is dependent on the stroke of the engine and the connecting rod length. The Onan CCK has a 3” stroke and the connecting rod I measured was 6 inches from center to center. The amount of movement is NOT a simple 3 inches divided by 180 degrees figure. Because the rod moves in an arch there is a formula to calculate the movement: http://dansmc.com/mc_software2.htm Sorry that's in metric, but it works.

    The process I would like to suggest should remove any deviation from engine to engine. I have tested this process on that 1973 engine pictured above, that is well worn. Also on a new short block that is going into this tractor. The process is accurate regardless of engine wear. I cannot set the engine timing any more accurately by hand and eyeball with the engines out of the tractor, than by using this process.

    Once you have removed the engine heads, it's not necessary to remove the gasket from the block, or clean up the face of the block. It is necessary to de-carbon the piston before hand. It does not matter what rotation of the engine you are on nor which piston you use. Because the CCK is a wasted spark engine, it fires the spark plugs EVERY TIME the pistons come to 20 Degrees before TDC. The spark plugs both fire at the same time, when one piston is on the compression stroke and ready to fire, the other piston is on the exhaust stroke.

    You will want 2 of the short head bolts, a metal or wooden bar or angle that will fit across the piston opening that can rest of the two bolts and be clamped in place.. A picture is worth a thousand words:

    IMG_20210101_115048370.jpg


    In my shop I found a scrap of aluminum angle iron. The goal is to give us something solid that does not move to rest the base of a digital caliper on. This should also help to prevent rocking the calipers from side to side. I first tried this process by resting the caliper on the edge of the block. But I could not maintain a consistent position and the results were not accurate enough. Ideally clamping the caliper down would be best, so there is ZERO movement of the caliper base.

    The difference between 20 Degrees BTDC and 19 Degrees is only .011”. Which if you are holding the calipers solidly it's not a problem. If you are trying to hold the caliper with one hand and turn the flywheel with the other, its not that easy.

    The process, once you have the piston head clean and the block, bar, angle clamped in place is to extend the caliper some distance, place the base of the caliper against your block, with the depth rod sticking down towards the piston. Turn the engine over so that the piston comes to Top Dead center and a little past it. ZERO OUT THE CALIPER, reset the caliper by pressing the Zero button WITH OUT changing the measurement.. This is how we are factoring out the deviations from engine to engine and piston to piston.

    Caliper Position.jpg

    What we need to measure is the OFFSET from TDC and zeroing the caliper removes the variables so all we have to concentrate on is getting the correct reading which is .117” or if you go with the Onan manuals, and 19 degrees BTDC it's .1056”.

    Once you have set your caliper to zero, extend the caliper again, past .125 or so at least. Hold it in exactly the same position if possible and turn the engine over. As the piston nears Top Dead Center again, you need to stop turning when the caliper reads .117”. Which is NOT that easy to hit. You can back the engine up and try again, or advance it and try again.

    Having a helper that could turn the engine over from the starter side one tooth at a time would help you get a more accurate reading.

    For point ignition and also if you use a Kirk engine Trandensor, the process is to:

    1. Set the point opening BEFORE setting the timing.. By rotating the flywheel until points are at maximum open, and adjust to .020 with thickness gauge.

    2. ONCE the .020" point opening is set, Proceed to set the engine to 20 degrees BTDC. Once the engine is at 20 degrees BTDC, loosen the points box and move it left or right so that the points are JUST beginning to open.. Kirk Engines Trandenser has an LED that makes the process very easy.

    A complete list of the piston offsets and degrees before TDC for an Onan CCK are:

    Degrees Offset
    18 .095
    19 .1056
    20 .117
    21 .1286
    22 .141

    P.s. if you can NOT get the points to open to .020 the push rod may be worn down: https://casecoltingersoll.com/showth...-Timing-Issues the phonelic push rod in a CCK should be 1.355 inches long. Check it with calipers..
    Last edited by sdunt; 01-11-2021 at 08:02 AM.

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  4. #2
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    I've never had a CCK, but I'm wondering, is this motor still apart? If so, can you loosely attach the flywheel on it, and set it to TDC? Do the bolts on the flywheel, line up with the same area, as in TDC? (this would be the bolt holes where the flywheel screen is attached to,)

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    Senior Member dcdonah's Avatar
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    I don't have this kind of engine, but I was interested in your procedure. I read it a couple of times because I found it somewhat confusing, but if I had the engine in front of me, it might help. Some things I didn't see, but maybe I missed them, was, which direction do I turn the engine, and did you add in the thickness of the aluminum rest for your caliper measurement?

    EDIT; In one paragraph you stated the the aluminum angle is to rest the caliper base on, and in another paragraph, you say to rest the caliper base on the block.
    Last edited by dcdonah; 01-11-2021 at 12:08 PM.

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    Senior Member sdunt's Avatar
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    Welll, old buddy, here is that same engine out of the tractor, I currently have 3 CCK blocks rolling around in the shop. This one that was orginal to the tractor, the new short block and a junk CCK that I paid $50 for to get a flywheel and oil pan.
    That same engine, cleaned up and with the CCK flywheel at TDC:


    CCK's don't have flywheel screens, at least not the version used in Case 646's. The only holes in them are for the gear puller and they look to be off of any kind of alignment. I tried the same TDC alignment on the new short block and the puller holes are in the same spot.

    Quote Originally Posted by Lionel View Post
    I've never had a CCK, but I'm wondering, is this motor still apart? If so, can you loosely attach the flywheel on it, and set it to TDC? Do the bolts on the flywheel, line up with the same area, as in TDC? (this would be the bolt holes where the flywheel screen is attached to,)

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  9. #5
    Senior Member sdunt's Avatar
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    Thanks for the feedback. I had to re-read it a couple times to find the "rest the caliper base on the block." comment you referred to.

    I think your referring to this: "The process, once you have the piston head clean and the block, bar, angle clamped in place is to extend the caliper some distance, place the base of the caliper against your block, "

    What I am trying to say is to hold the base of the caliper against whatever it is (YOUR block) that you have clamped across the head - piston opening. In my case its that aluminum angle iron, but you could use key stock or flat stock.

    From the front of the engine normal rotation is clockwise. If you are on the right side of 646 where there is an opening you can reach into access the flywheel, you would be pulling toward you on the bottom to rotate clockwise. There is a direction stamped - molded into the flywheel, but it usually covered in dirt and hard to see in the tractor.

    The process of turning the piston to Top Dead Center and then ZEROING the caliper subtracts the thickness of your angle iron or key stock or whatever you used to bridge across the cylinder.. That's part of the beauty of using that process. On my old engine, I measured variances in dimensions when I tried to make the measurement at the top, bottom left or right of the piston. I also measured differences in the TDC dimension of the right vs the left piston.

    So the process of zeroing out the caliper factors out, or subtracts all of those differences from the measurement. Therefore, all you are measuring is piston movement.

    Quote Originally Posted by dcdonah View Post
    I don't have this kind of engine, but I was interested in your procedure. I read it a couple of times because I found it somewhat confusing, but if I had the engine in front of me, it might help. Some things I didn't see, but maybe I missed them, was, which direction do I turn the engine, and did you add in the thickness of the aluminum rest for your caliper measurement?

    EDIT; In one paragraph you stated the the aluminum angle is to rest the caliper base on, and in another paragraph, you say to rest the caliper base on the block.

  10. #6
    Senior Member dcdonah's Avatar
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    To be clear, I'm only trying to understand your system. If you know the distance to TDC that you need (BTDC), why keep measuring it? Wouldn't a piston stop work? When I was building engines, I needed to calibrate the timing marks. The maximum travel is not the same as TDC. As the connecting rod passes over the top of the stroke, there is a few degrees of travel that isn't transferred to the piston. The only way to find TDC is to stop the piston short, in both directions, and the midpoint of those stops is the true TDC. It seems that if that was done, the timing marks could be transferred to a visible location. Maybe I'm making too much of this. My engine says it's set at the factory and can't be adjusted. I still like to know how things work. As far as calling your support bar a "block", I caused the Air Force to re-edit an approved tech manual due to the writer referencing different things by the same name. It was so bad, that I couldn't understand the section describing my own design area.

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