1939 Model H

[thessler]

Hi first post here.
I have a 39 H that the previous owner couldn’t get started. I opened it up , all the push rods were bent.
Replaced the valves straightened the push rods , cleaned everything up. Cylinders look pretty nice, not perfect but nice enough. Reassembled and have no compression. Valve lash is set correctly. Checked valve timing and marks line up. I’m a pretty good mechanic, but am at a loss with this. I can crank it over and keep my thumb over the spark plug hole. I get no reading on a compression gauge.
is it possible that the crank timing gear was installed and indexed incorrect, or can it only go on one way ?
There is no evidence that the gear has been removed, but this thing sat for a long time and who knows what has been done to it.
Thank you, Tom

 

[Mike(NEOhio)]

You can see the crank to cam timing marks if you take off the crankcase cover. They're on the inside of the gears. Cam to governor marks are on the outside of the gears and you have to take the left bearing cover off to see them. If they are correct the slots in the magneto drive coupling will be horizontal with left cylinder at TDC. First check the flywheel to crankshaft marks. Could be out of position there.

 

[thessler]

Thanks, the timing marks inside are lined up. But I’m wondering if they are incorrectly indexed on the crank or cam. If they are correct I should have compression.

 

[teddy52food]

Hi first post here.
I have a 39 H that the previous owner couldn’t get started. I opened it up , all the push rods were bent.
Replaced the valves straightened the push rods , cleaned everything up. Cylinders look pretty nice, not perfect but nice enough. Reassembled and have no compression. Valve lash is set correctly. Checked valve timing and marks line up. I’m a pretty good mechanic, but am at a loss with this. I can crank it over and keep my thumb over the spark plug hole. I get no reading on a compression gauge.
is it possible that the crank timing gear was installed and indexed incorrect, or can it only go on one way ?
There is no evidence that the gear has been removed, but this thing sat for a long time and who knows what has been done to it.
Thank you, Tom

Did you grind the seats when you replaced the valves? If it sat for a while they are corroded to where they can't seal.

 

[thessler]

Yes ground the seats, took head back off and filled combustion area of head with water and the valves held the water.
this is bigger than that

 

[thessler]

Question: are the crank shaft timing gear marks on an H and a B in the same position?
I took the cover off my B and the gear dot is exactly opposite the crank journal. On the H it’s offset say at the two o,clock position if the B would be in the 12 o,clock position. If that makes sense.
Thanks,Tom

 

[rockcreek4630]

Hi first post here.
I have a 39 H that the previous owner couldn’t get started. I opened it up , all the push rods were bent.
Replaced the valves straightened the push rods , cleaned everything up. Cylinders look pretty nice, not perfect but nice enough. Reassembled and have no compression. Valve lash is set correctly. Checked valve timing and marks line up. I’m a pretty good mechanic, but am at a loss with this. I can crank it over and keep my thumb over the spark plug hole. I get no reading on a compression gauge.
is it possible that the crank timing gear was installed and indexed incorrect, or can it only go on one way ?
There is no evidence that the gear has been removed, but this thing sat for a long time and who knows what has been done to it.
Thank you, Tom

Use a blow gun and put air in spark plug hose and see where it goes.

 

[dan_41jdh]

The gear on the crankshaft has a projecting hub which, if installed backwards, will interfere with the LH main bearing housing, so it’s not likely that would be an issue. Besides, didn’t you already state the timing dots on the crank gear and the cam gear are timed correctly, which means you saw them inside the crankcase? It is possible that the cam gear wasn’t timed to the camshaft – the cam to gear mount is by tapered splines (6 splines, so the gear can be mounted to the camshaft in six different positions). The match marks on those parts are stamped “V’s”, one on the camshaft and the other on the face of the gear hub. (See the picture.) If the flywheel is timed correctly to the crankshaft ("V" stamp mark on the end of the flywheel aligned with the matching “V” on the flywheel), and if the flywheel is rotated so the “LH IMPULSE” letters are at the 3 o’clock position, the LH piston will be at TDC and you can see the timing dimple on the crank gear that should be timed to the dimple on the cam gear. The cam/cam gear marks will either be at the 9 o’clock position where you can see them looking into the crankcase, or they are at the 3 o’clock position and they will be out of sight. Rotate the flywheel one revolution to bring those cam/cam gear timing marks into the line of sight. If all those timing marks are properly aligned, your cam is timed properly. Then look for something else – drill a hole in a rubber cork jammed into the spark plug hole, blow some air into the hole, and see where that air might be leaking….

 

[thessler]

Thanks for your input.
The flywheel is correct on the crank. That’s the only thing I can say with certainty. The two dots one on cam gear and one on crank gear are lined up. But i question weather they are correct. The way I’m looking at this is the only way I can lose all the compression is valve timing.
I compared the crank gear orientation between the H and the B, and the dots are in different places. They both may be correct, but I’m guessing the H in question is off somehow.
Thanks, Tom

 

[rustred]

I thought the camshaft on an H turned opposite direction from the other models.

Yes ground the seats, took head back off and filled combustion area of head with water and the valves held the water.
this is bigger than that

Water? A person usually would use anything but water. Water makes rust for them freshly ground seats and valves.

 

[rustred]

Are the valves closed at TDC ?

 

[dan_41jdh]

Thanks for your input.
The flywheel is correct on the crank. That’s the only thing I can say with certainty. The two dots one on cam gear and one on crank gear are lined up. But i question weather they are correct. The way I’m looking at this is the only way I can lose all the compression is valve timing.
I compared the crank gear orientation between the H and the B, and the dots are in different places. They both may be correct, but I’m guessing the H in question is off somehow.
Thanks, Tom

If the flywheel is properly timed to the crankshaft, and if the flywheel is rotated so the “LH IMPULSE” letters are at the 3 o’clock position, the LH piston will be at TDC. And if the LH piston happens to be at the end of the exhaust stroke, all the other timing marks will align with each other simultaneously and will be in the position shown in the sketch. (If the LH piston is at TDC at the end of the compression stroke, the cam gear marks will be rotated 180 degrees from what is shown.)

So here’s an easy way to determine if your cam is properly timed to the engine –

Remove the tappet cover so you can watch the valve movement. Then, rotate the flywheel so the “LH IMPULSE” letters are at the 3 o’clock position. This will put the LH piston at TDC. But you won’t know if the piston is at the end of the exhaust stroke, or if its at the end of the compression stroke. Now roll the flywheel back and forth about 1/2 turn in both directions. If the cam is timed correctly, one of these two possibilities will happen:

1) If the LH piston is at TDC at the end of the compression stroke (when the LH spark plug fires), both the LH intake and exhaust valves will remain closed while you roll the flywheel back and forth – or

2) If the LH piston is at TDC at the end of the exhaust stroke and you roll the flywheel forward, the LH intake valve will open and the exhaust valve will close and remain closed. If you roll it backwards, the LH exhaust valve will open and the intake valve will remain closed.

If neither of those cases are true, then your camshaft is definitely out of time and you’ll have to chase down the reason.

 

[Mike(NEOhio)]

I thought the camshaft on an H turned opposite direction from the other models.

Water? A person usually would use anything but water. Water makes rust for them freshly ground seats and valves.

Any gear-driven camshaft turns opposite of the crank. The clutch on the H is on the camshaft so opposite.

 

[Mike(NEOhio)]

Thanks for your input.
The flywheel is correct on the crank. That’s the only thing I can say with certainty. The two dots one on cam gear and one on crank gear are lined up. But i question weather they are correct. The way I’m looking at this is the only way I can lose all the compression is valve timing.
I compared the crank gear orientation between the H and the B, and the dots are in different places. They both may be correct, but I’m guessing the H in question is off somehow.
Thanks, Tom

They would be in different locations because the H camshaft is behind the crankshaft. All the others it's forward of the crank.

 

[rustred]

Any gear-driven camshaft turns opposite of the crank. The clutch on the H is on the camshaft so opposite.

Ya that’s what I was meaning

 

[thessler]

Thanks for the replies.
I put the head back on and adjusted the valves. Cam timing is on the money, checked with dial indicator.
Blew air in at TDC and it all comes right out passed the piston. When I had it apart pistons and cylinders looked good. Can the rings just be stuck in the grooves ? I don’t think this thing is worth a total rebuild. Not sure what to do about this.
Any thoughts greatly appreciated.
Thanks,Tom

 

[dan_41jdh]

Thanks for the replies.
I put the head back on and adjusted the valves. Cam timing is on the money, checked with dial indicator.
Blew air in at TDC and it all comes right out passed the piston. When I had it apart pistons and cylinders looked good. Can the rings just be stuck in the grooves ? I don’t think this thing is worth a total rebuild. Not sure what to do about this.
Any thoughts greatly appreciated.
Thanks,Tom

You said the cylinder walls looked good, but was there much of a ring ridge on the walls? If there’s a significant ring ridge, even though the rings might be stuck, it might be time for a rebore, and then the $$$ start adding up. If there’s very little ring ridge, you might consider pulling the pistons and checking for stuck rings. If so, carefully remove them and scrape out the carbon from the grooves with a ring groove cleaner, replace the rings exactly as they were installed, give the cylinder bores a light honing, and try again. That won’t cost you any money, just time.

 

[thessler]

no ring ridge at all.
Thanks

 

[rustred]

If that’s the case , the rings might be stuck in the grooves from sitting. Fill up the cylinders with mystery oil or atf might be cheaper. Let it sit a few days. Then shoot it out the plug holes with a hose into a pail so it don’t make a big mess. Then either belt it up to another tractor and let it sit there and spin over for even an hr. Or pull it around. It will build compression and start if everything else is in order. I have had a few engines like that. With it spinning over u can even mist some atf into the intake to help lube everything. It should show a bit of compression on a compression check ??? Never had one at zero.

 

[rockcreek4630]

no ring ridge at all.
Thanks

Did the previous owner have it apart and forget to put rings in it.