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cylinder and valve plunger assembly

1672 Views 10 Replies 6 Participants Last post by  gmcarlmrnet1
I replaced my cylinder head gasket on my 1965 L8 and am having problems. It went together but my valves were quite off so I wonder if I switched sides on some things. One had no gap and the other was over 0.03. And then as I tried to fix the gap the bolts were very hard to move so I took it apart again. I have three questions on reassembly

1) the "rocker" that sits on the cam shaft that drives the valve up has "wear" from the middle to one side. I conjectured that the plunger should face so that the wear is internal. Is that correct.

2) the plunger assembly that holds that plunger. There are obviously two of them but mine are not the same. One of them the barrel of the plunger (that which the plunger slides into), has a milled groove and the other doesn't. does it make a difference which one is for the exhaust side and which one for the intake side. I wonder if the groove allows more oil flow? I may have mixed them up

3) my bolts that are used to set the gap of the plungers are very tight though I get move them with a fair amount of torque. Should I try to use kroil oil to loosen them some or are they supposed to be that tight?


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I should mention that the exhaust valve was ground down some so I expected to have to adjust the clearance a little but there was no gap at all and it was probably up another 0.01+ inch

1) The rocker (valve lifter) can be turned around 180 degrees so it wears on the other side for 50 years.

2) When Gravely went to the single piece valve plunger/cover assy, the first ones did not have a groove and would fill with oil and leak around the upper cover gasket. Then they put the groove in to allow the oil to drain. The third design didn't have a groove, but a camfer at the top of the plunger travel. I would put the one with the groove on the exhaust side and take a hack saw blade and cut a shallow groove on the one you use on the intake side.

3)The adjusting bolt on the valve lifter/plunger is meant to be tight but maybe not as tight as you describe. Screw the adjusting bolt in and out a few times - not all the way, just in the adjusting zone. The original design had a lock nut which was a real pain to adjust.

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Thanks Gravely_n_fla.

I think what threw me was the valve adjustment bolt wouldn't move on either side so thought I had done something wrong as I didn't completely understand how they worked.

None of the service manuals mention anything about differences on the sides though I did find a 12/1967 IPL ( of my engine which shows the intake lifter/plunger with a "keyed" groove and the exhaust side without. I suspect you can use them either side interchangeably.

It is together now and after putting the adjustment bolt in a vice and working slowly with some kroil oil got everything loosened a little so now was able to get the proper 0.15 inch valve clearance.

I was afraid I would mess things up trying to cut a groove so didn't do that but it makes sense.

Tomorrow will put the motor back on the chassis and hope I get the rest of it together correctly. I appreciate the expertise of the forum when I get stuck.
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Today was working on the timing of my '65 L8. Have looked at a lot of threads regarding this, not always agreement.

I have the Wico with the slash and two dots.

First I timed it the "technical" way. I have the head off so very easy to find TDC. My piston head travels up just 3/32 short of the head. So I dropped the piston down 2" to take out slack then up to 15/32 from the head (3/8 plus 3/32) and then centered the slash marks on each other. When this was tightened I hand turned the shaft and it fired ~1-2/32 before TDC.

I then read about Roger Beno's method and simply timed the impulse just at TDC. This was kind of trial and error but eventually got it and the nice thing about this was that you did not have to do it when the impulse spring was wound. With this method, if I measured my piston head at that point when the slash marks are lined up is about 8/32. So Roger Beno's method has my timing retarded with the head having traveled up about 7/32 further then when I used 3/8 (and 5/32 if I were to use 5/16 as my spec as some sources suggest).

Roger had discussed magneto "starting" vs "running" impulse as apparently when the impulse is wound up for starting this is different then when running. And also that the "specs" are meant for full throttle max hp and maybe that isn't real world. I don't know if I completely follow what that is about.

I got that sense though that some argue that if the magneto fired right at TDC when starting then running the timing would be retarded a little and maybe that is why the specs have it set to fire a little before TDC when starting so when it runs it actually fires at TDC. Though I worry that puts you at risk when starting of the dreaded reverse piston.

I don't know if my explanation above is clear. Maybe there is enough tolerance that any of the above two methods work but I would appreciate any comments. Intuitively I am drawn to Roger's method/thinking so have my L8 presently set to his recommendations.

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Use the marks as a guide when installing the mag. But use the snap/spark at piston TDC. Turning the engine by hand for timing. The measurement method is way too anal, and does not take into account for wear. The retard built into the mag makes for easier starting. You can advance the timing, but you won't make any real HP. Just make it harder to start.
Yes you are correct the timing is set for greatest effect at WOT, great for machines like mine that are only used for mowing. I've heard how some will time an L for lower RPM use. I've actually advanced the timing just a tad over spec as I need to milk every bit of power from my L for mowing duty.

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The beauty of the T head gravely engine is the torque produced at low RPMS. I think the rated HP was at something like 2600-3000 RPMS. Compare that to the rating of a briggs 5HP or other type engine, which were rated at a much higher RPM. Most of the Gravely L's I have now have a governor. But the ones I had before without one, Did not need to be run at more than half throttle.
... The rocker (valve lifter) can be turned around 180 degrees so it wears on the other side for 50 years...
I love pieces of advice like this! Upon removing my valve plungers, I noticed the same issue as the OP (the "rocker" that sits on the cam shaft that drives the valve up has "wear" from the middle to one side). I would have just reassembled it in the same fashion that it was removed had gravely_n_fla not shared this tidbit of information. Thanks gravely_n_fla!!!
Here is a link to detailed instructions on how to correctly "marry" your magneto to your tractor, which sets the timing properly:
Today got everything together, timed, gas and it started right up. Thanks for everyone's help.

Working on attaching a 6 foot snow v plow made of heavy poly that I used to push snow with my car. I'll send pictures once I have it done. Have to do a little engineering to attach it.

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