Valves sticking on new rebuild

Sun Sep 09, 2012 12:41 pm

So I've been working on this Cub restoration for three years now. It's to the point where I'm trying to start it now but it ain't! I got the spark issue figured out and I have gas from the pony tank. I don't have a compression tester but a thumb over the spark plug hole is good enough when the compression is zero! I took off the valve inspection plate and tried turning over the engine. Only two of the valves are moving, all the others are sticking. I can rotate the sticking tappets slightly with a 1/2" wrench and they pop back down (assuming it's not their turn to be up). Then I turn the engine over again and all of them move up but only the two go back down.

The engine was gone through by a professional shop in the spring time. They put hardened exhaust seats and new guides in but I did the reassembly. The valves were not replaced as they were in decent enough condition and measured within spec. They slid freely in the new guides when intitially assembled. The tappets are also original and I made sure they went back in the location they came out of. I did reuse the valve springs and I did use an engine assembly lube that was pretty thick but not quite like grease. Several months have passed by (along with the seasonal temp changes) since the engine was reassembled.

Questions:
1. Did the time and temp changes cause something?
2. Will the valves free up as the engine assembly lube loosens up?
3. Should I have replaced the springs? It looked as if the engine had been gone through before so I don't believe they were original 1953 vintage.
4. Is there anything I can do before replacing the springs i.e. Kroil or Seafoam or something?
5. Is there a way to change the valve springs without taking the cam out?
6. Anything else I might be missing?

Thanks in advance for the help as I'm trying to get this running in time to tow the Homecoming parade float!

Re: Valves sticking on new rebuild

Sun Sep 09, 2012 1:03 pm

Valve tappet chamber, spray the tappets and valve stems with a good solvent. Rotate the engine a couple of revolutions and spray again.

Remove the spark plugs. When a valve sticks up, try to aim the solvent spray at the valve stem.

This may take a number of tries to get the valves to free up. Perhaps quite a number of tries. If this doesn't work you have two choices, remove the head to access the valve stems or the manifold.

Re: Valves sticking on new rebuild

Sun Sep 09, 2012 1:29 pm

geibes wrote:
Questions:
3. Should I have replaced the springs? It looked as if the engine had been gone through before so I don't believe they were original 1953 vintage.
5. Is there a way to change the valve springs without taking the cam out?


Eugene has some good info there. Try that first.

You can remove the valves, springs, etc. with out removing the camshaft, but you must remove the cylinder head first to allow the valve to be removed.

You need to use a valve compressor hand tool to remove the valve keys which allows the valve stem to move upward and out and then you can get the spring.

I would guess that if a professional machine shop went through your engine, the springs are probably ok as they should have looked at them during the disassembly phase.

Re: Valves sticking on new rebuild

Sun Sep 09, 2012 3:49 pm

I have had a lot of luck with penetrant, someone hand cranking and a wooden dowel or a screwdriver.

Take the plugs out, put the dowel on top of the valve that is sticking and as they rotate the engine with the crank, press down or tap the valve in question so it drops. Repeat till it drops on it's own and until all valves are moving freely.

Re: Valves sticking on new rebuild

Sun Sep 09, 2012 5:10 pm

Thanks for the comments everyone. I'll keep at it with the Kroil for now. Here's a picture of the tractor.

Image

Re: Valves sticking on new rebuild

Sun Sep 09, 2012 5:47 pm

you can from the spark plug hole see the valves. I would sprey some JB 80 or slick 50 into the valve guides. then take a screw drive with hammer tap the stuck valve down.

Re: Valves sticking on new rebuild

Sun Sep 09, 2012 6:00 pm

If it was rebuilt, there must not have been any lube used when installing the valves or they should have never stuck. I hope plenty of oil was used on the rings when the pistons were installed as well as the bearings. If not you may be looking at a larger problem when you start it. BE SURE TO PRIME THE OIL PUMP.
Boss

Re: Valves sticking on new rebuild

Sun Sep 09, 2012 6:49 pm

Went through the exact same thing last year on a new rebuild, I would use the tractor for maybe an hour then it would sit up for a week or two and when I went to start it a couple of valves would be struck. I loaded the gas tank with MMO and some in the base also and went out on a bare piece of ground and put the cultivators all the way down and made her scratch hard for about 15 or 20 minutes. The problem went away.

Re: Valves sticking on new rebuild

Sun Sep 09, 2012 6:51 pm

geibes wrote:I did reuse the valve springs and I did use an engine assembly lube that was pretty thick but not quite like grease.
My reading is that geibes used engine assembly lube to install the valves. Reading the advertisements for a number of engine assembly lubes; thick, stays in place, stringy, adhesive.

The service manual says to use engine oil when installing valves into valve guides. I use 3 in 1 oil.

Since the valve springs only require about 26 pounds to compress, my guess is the assembly lubricant is keeping the valves from rapidly closing. And, once the assembly lube is thinned down the valves will work properly.

Re: Valves sticking on new rebuild

Sat Sep 15, 2012 3:28 pm

It's been a week of spraying the valves and tappets and rotating the engine and pressing down on the valves with a screwdriver or rotating the tappets with a wrench. I tried brake cleaner, Kroil, WD40 and PB Blaster. Nothing seems to have changed. The two valves that were working still are but all the others are still sticking. Today I decided to take the head off (hint for next time: drain the air cleaner oil!). I pulled the #1 intake valve out and it did have quite a bit of the assembly lube still on it. I cleaned it off and put some 3-in-1 oil on and and put it back in. It slid very freely so I put the spring back on and tried rotating the engine. The valve still sticks. Crap! To me, that either means the spring is weak or the tappet is sticking or a little bit of both. I tried a valve spring from another engine I have access to and the same thing happened. My valve spring even had a slightly longer free length so it should have provided more force. Crap. I think that means the tappet is sticking. I think that means the cam has to come out so I can clean any assembly lube off the tappets. Crap. Does anyone else have any ideas? I'm wondering if heating up the tappet area might help dissolve the assembly lube. I have a heat gun or maybe a simple trouble light will work. Thoughts? I really don't want to pull this thing apart again. Oh side note, my daughter got elected to the Homecoming Court. Now it's imperative that the tractor is ready for the parade on Sept 28!!! Great news for her, bad news for me.

Re: Valves sticking on new rebuild

Sat Sep 15, 2012 5:12 pm

If you still have some of the assembly lube on hand, - see what will dissolve a lump of it. Might be gasoline, 3 in 1 oil or engine oil.
Crap. I think that means the tappet is sticking.
Did you check to see if the tappets are sticking?

Just me, I would spend a other hour or two unsticking the valves and tappets rather than disassemble the engine.

Re: Valves sticking on new rebuild

Sat Sep 15, 2012 5:51 pm

Should the tappets float freely and follow the cam even if there is no valve spring force pressing down on them? I just took out the rest of the valves and cleaned them up and rotated the engine while each valve was out. All the tappets were all sticking. I did manage to free one of them up using the heat gun so now I have 3 free. No luck with the others.

Good idea on finding out what dissolves the assembly lube. I will try that as well.

Re: Valves sticking on new rebuild

Sat Sep 15, 2012 6:33 pm

Engine lube is soluble in engine oil. Liberally spray the valve stems from the top and bottom with light weight oil. Same with the tappets. Roll the engine over and press the sticking valves and tappets down. Roll engine over, spray, press down.

Re: Valves sticking on new rebuild

Sat Sep 15, 2012 7:21 pm

Been doing that all week with various other solvents but will keep at it and try oil. It's easier now that the head is off to press the valve down as well. Thanks for the encouragement. I really, REALLY don't want to take the engine apart again! I did measure the free length of the springs again when I had them out and they were all shorter than the spec so perhaps I over compressed them when I put them in. I will probably end up getting new springs anyway.

Re: Valves sticking on new rebuild

Sun Sep 16, 2012 12:00 pm

Don't see that the valve springs were tested. To do so the measurement of the pounds pressure to compress them to a certain size is measured. We used to do that when we rebuilt old 36 Fords for stock car Racing.