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AR timing problem

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MikeH-Tx

11-26-2002 15:26:23




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My AR restoration is almost complete. However, when I crank the starter to see if everything looks right, I get some air blowing OUT of the intake manifold (carb is off, still). Not good. I was very careful to allign the marks on the crank gear with the cam gear. Double checked by looking at the pushrods and making sure neither of the LH pushrods were engaged when the flywheel pointed at the LH impulse mark. I put the head back on, rechecked, then did a compression check. It was 60 lbs in both cylinders +/- 2 or 3. I think I am one gear off on the governor shaft, because the distributor wants to be a little off horizontal to time the spark at TDC, but that shouldn't matter, right?

What might cause the air to rush out of the intake? Sticky intake valve is my guess. I didn't do any work on the head, thinking I would try it for awhile and see what happened. It looked pretty good: no obviously burned valves, but I didn't remove the valves to see how they moved in the seats.

So, what is my next step?

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Clooney

11-26-2002 15:58:03




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 Re: AR timing problem in reply to MikeH-Tx, 11-26-2002 15:26:23  
Mike, it sure sounds like a leaky valve or valve timing problem. The 60 PSI cranking is slightly low but within reason.
~Probably the place to start is push on both intake valves to see if they promptly return to seated, if that is ok then adjust the L/H exhaust valve to .020" & slowly turn the flywheel in the running direction & feel the L/H exhaust push rod to see when it just gets tight [0 lash], at that time the [L/H ex open] on the flywheel should be within 1" or so of the case mark [at 3 o'clock behind the flywheel].
~If that checks out good then turn the flywheel until the L/H piston is at TDC on compression, then take an old spark plug, gut it & weld a fitting to it that will fit your air compressor fitting. Then install that in the L/H side & put about 50 lbs of air pressure in that cylinder to see if & where the air comes out. If you have a leaking valve that will show it. Then do the same for the R/H side.
~If it's all all fuel & you are making 60 PSI compression you can't have too much air coming out the intake manifold, maybe you just have a little rust on the valves & seats. If it's a gas burner you definitely have a problem...

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MikeH-Tx

11-27-2002 15:02:47




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 Re: Re: AR timing problem in reply to Clooney, 11-26-2002 15:58:03  
Good grief. I followed your advice and figured out I have both problems. Two valves are leaking, one exhaust and one intake. Also, the cam is not timed correctly with the crank.

I don't know what I did wrong, but I sure did it wrong. It will be curious to see what happened. I was very sure that I alligned the two marks on the gears. No harm done, except that I have to undo a bunch of the reassembly that has been done.

What's the easiest way to reallign the crank and cam? I had EVERYTHING apart when I put them together. Can I open up the LH main bearing without touching the RH reduction gear cover and RH main? Sure would be a PITA to have to undo the clutch, pwr troll lines and all to get at the RH bearing. Or is it easier to free up the cam and move it?

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Clooney

11-27-2002 15:36:16




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 Re: Re: Re: AR timing problem in reply to MikeH-Tx, 11-27-2002 15:02:47  
Mike, you used the 'L/H exhaust open' & not the L/H impulse, correct? Is the flywheel on correctly? With that air coming back out of the intake it is probably timed wrong but you don't want to re-time it if you think it's wrong because of a side issue.
~On the cam re-time, what year AR are you working with? Not sure it will make a difference but lets make sure we are talking about the same tractor..

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MikeH-Tx

11-27-2002 16:09:15




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 Re: Re: Re: Re: AR timing problem in reply to Clooney, 11-27-2002 15:36:16  
It is a 51 styled AR.

I moved the flywheel to LH impulse and made sure the push rods were free, then did the compressed air test. Repeated with the RH valves closed. Two were leaking, one intake, one exhaust.

I didn't have to move the flywheel very much after LH impulse to have the intake valve open, where as it should stay shut until the piston is fully down.

I also put the flywheel on LH exhaust and checked the LH exhaust valve. It was nowhere near ready to open. It is definitely timed wrong. I have the tractor disassembled back to where I can get the head off, but wonder how best to change the cam-crank connection.

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Clooney

11-27-2002 16:34:14




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 Re: Re: Re: Re: Re: AR timing problem in reply to MikeH-Tx, 11-27-2002 16:09:15  
Mike, I don't know about the best way as I can't remember re-timing the cam on a late "A" while assembled. Actually I usually pull the cam when the block is off as it will come out the front that way with the gear still on it.
~I think if I were going to try to re-time while assembled with as little disassembly as possible I would pull the flywheel side cam bearing cover & see if I could push the cam in against the R/H pressure spring & see if there is enough cam displacement to move the gear timing. If that didn't give me enough I would pull the L/H cam bearing from the cam [it will probably get ruined but they are cheap] & see if that gives me enough cam displacement. If still not enough then I would pull the L/H main bearing housing & if the R/H main bearing isn't too tight that will probably be enough.
~You might try to E-Mail Mike Aylward as he has probably re-timed a late "A" cam while assembled and can probably add more than I can..... .

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