Two Push Rods Out

[KMacNH]

I got the NAA running. Went to start it last week and heard a sharp metal sound. Wouldn’t start. Compression test 1=95, 2 and 3 = zero, 4 = 125. Pulled side cover. Push rods for 2 and 3 are out. Not in position. Realize that I need to do a valve job and will will redo pistons while I’m there. Question: what causes the push rod to pop out of place? Was it too cold out? Don’t want to repeat it.

 

[Dieseltech]

Possibly those two valves sticking in the guides, and/or weak/broken valve springs. EXTREMELY loose rocker arm/valve clearance could cause it too.

 

[KMacNH]

thanks. I’ll def find out when I pull the head. Cheers.

 

[Duner Wi]

One reason could be sticking valve/valves. I had this happen on 4 cyl pushrod engine. I attributed to old oxygenated gas. I had flatheads with sticky valves more than once caused I think from same reason.

 

[Powered By IH]

thanks. I’ll def find out when I pull the head. Cheers.

Pull the valve cover first and take a look.

Check to make sure the pushrods aren't bent too.

 

[used red MN]

Was it too cold out? Don’t want to repeat it.

Hello KMac..,welcome to YT! Not sure how much you have ran the tractor, I see in your 1st thread on it that it had sat for some time in a humid area. If it was warmer when you last ran it, then if the valve stem were gummy or sticky in there guides in the head the lower temperature may have caused them to stick open. Do you want to open up the engine because you have a couple extra wheel barrows full of cash you want to dump into it? Then by all means proceed, especially if you want the experience. When you get the valve cover off there is a possibility that the valves can be freed up with carb cleaner and penetrating oil sprayed on the stems under the springs and working them up and down with light hammer taps and a pry bar. A cylinder that has a stuck open valve or a missing push rod will not have any compression. In my opinion this does not tell you that the cylinder head immediately needs removed.

 

[ErnieD]

old gas will cause intake valves to varnish and stick

 

[KMacNH]

Pull the valve cover first and take a look.

Check to make sure the pushrods aren't bent too.

They’re bent. Wibbly wobbly. Head is off. Going to do an in frame rebuild. It lived by the sea so it’s super crusty. Knocking off rust, replacing items. It has the ball governor. Will replace that as well. Just have to figure out how to remove the slotted pulley bolt that I read is a nightmare.

 

[KMacNH]

old gas will cause intake valves to varnish and stick

It had old gas. Smelled like varnish.

Hello KMac..,welcome to YT! Not sure how much you have ran the tractor, I see in your 1st thread on it that it had sat for some time in a humid area. If it was warmer when you last ran it, then if the valve stem were gummy or sticky in there guides in the head the lower temperature may have caused them to stick open. Do you want to open up the engine because you have a couple extra wheel barrows full of cash you want to dump into it? Then by all means proceed, especially if you want the experience. When you get the valve cover off there is a possibility that the valves can be freed up with carb cleaner and penetrating oil sprayed on the stems under the springs and working them up and down with light hammer taps and a pry bar. A cylinder that has a stuck open valve or a missing push rod will not have any compression. In my opinion this does not tell you that the cylinder head immediately needs removed.

Define “wheel barrow of cash”. I don’t mind tinkering with it. My 13 yo sold was helping me. “This is cool. Much better than video games”. I’ll call that a win. He can learn that thoughtful hard work pays off. This is engineering 101. I’m good with spending the money.

 

[Duner Wi]

Take a look at the pistons that has the bent valves. On mine the valves kissed the piston as push rod was escaping the rocker arm.

 

[Powered By IH]

So what happened was valves stuck from varnished gas.
Metallic sound was from pistons hitting valves.
Then the pushrods got bent because they are the designed weak link, popping them out.
You should be able to see on the pistons where they kissed the valves, like Duner Wi said.

 

[used red MN]

Define “wheel barrow of cash”.

Hopefully you know that was said jokingly. Mostly because all you had was the side cover off and you were convinced the head needed to come off. Not really a normal process in troubleshooting for a major engine repair. I understand it all now, having your 13 year old helping and learning is great. Depending on the intentions for the machine one can get upside down in one money wise pretty quick.

 

[KMacNH]

Last Question: Now with the head off, what should I do about the pistons? Cylendar #1 was 95psi. 2 and 3 Zero, no push rods. #4 was 125 psi. Would any of you folks change the rings, pistons, sleeves, or leave it alone? Deciding if I should buy the entire rebuild kit or just take care of the valves. Thank you.

 

[used red MN]

Would any of you folks change the rings, pistons, sleeves, or leave it alone?

Realize that I need to do a valve job and will will redo pistons while I’m there.

Now you have changed your tune! Unfortunately inexperience and jumping the gun has gotten you to where you are now. The zero PSI compression readings of cylinders 2 & 3 are of no value to indicate the condition of the pistons and rings because the valves or valve train is where the compression was exiting the cylinders. All you can do is turn the engine so the 1 & 4 pistons are down. Look at the cylinder walls of them noting there condition and amount of ring ridge at the top of the cylinders. Be sure the upper edge of the bore above the rings is not coated with carbon at the location you assess ring groove depth which should be on the side of the cylinder bore not the front or back. Look for vertical grooves or scratches. Next turn the center two pistons down and compare them to what you saw in the end cylinders. If they look about the same I wouldn’t have any concerns about putting it back together. I would also mention that you should look at the top of the pistons around there outer edges, if any places look very clean that is a possible indication that oil is coming up past the rings. That would be an indication that something needs done with the rings.
So now we’re back to the wheel barrow of cash. Do you dump it in and do it all or do you get the valves done and put the head back on an give it a try? Might also be helpful to know what the future intended use for the tractor will be.

 

[KMacNH]

Drag racing

 

[KMacNH]

Now you have changed your tune! Unfortunately inexperience and jumping the gun has gotten you to where you are now. The zero PSI compression readings of cylinders 2 & 3 are of no value to indicate the condition of the pistons and rings because the valves or valve train is where the compression was exiting the cylinders. All you can do is turn the engine so the 1 & 4 pistons are down. Look at the cylinder walls of them noting there condition and amount of ring ridge at the top of the cylinders. Be sure the upper edge of the bore above the rings is not coated with carbon at the location you assess ring groove depth which should be on the side of the cylinder bore not the front or back. Look for vertical grooves or scratches. Next turn the center two pistons down and compare them to what you saw in the end cylinders. If they look about the same I wouldn’t have any concerns about putting it back together. I would also mention that you should look at the top of the pistons around there outer edges, if any places look very clean that is a possible indication that oil is coming up past the rings. That would be an indication that something needs done with the rings.
So now we’re back to the wheel barrow of cash. Do you dump it in and do it all or do you get the valves done and put the head back on a give it a try? Might also be helpful to know what the future intended use for the tractor will be.

Thanks for the info. Appreciate it.

 

[Colin King]

It had old gas. Smelled like varnish.

Define “wheel barrow of cash”. I don’t mind tinkering with it. My 13 yo sold was helping me. “This is cool. Much better than video games”. I’ll call that a win. He can learn that thoughtful hard work pays off. This is engineering 101. I’m good with spending the money.

That's awesome that your 13 year old is interested! My 12 year old has loved this stuff for as long as I can remember and it's an absolute joy to have him as a tinkering partner. Enjoy the company and good luck!

Colin, MN

 

[Mad Farmer]

@KMacNH, glad to hear you are raising a young mechanic.

You can check the pushrods for bending, by rolling them on plate glass.

Try to keep each valve train part together, valve to lifter, until you determine if anything needs replacement.

My cousin's NAA had no compression on #2 and 3. Valves were moving OK. Adding oil before comp test only helped #1 and 4 a little; 5 psi.

Found this.



Cylinders looked good no ridge. Rockers/shaft looked good.

Poured some kero in the int/ex ports and found a couple valves leaking a bit. Ended up with a $600 bill at the machine shop but head got complete refurb with new guides/valves/springs, recut or new seats.

 

[Eman85]

Did you find why the pushrods bent?

 

[KMacNH]

Did you find why the pushrods bent?

Yes. Bad gas. The exhaust valves were stuck.