Trouble under head...

I believe I already know the answer to my question/problem, but wanted to throw it out in the ring in case I missed something, and to point out the error of my ways.

First, we're talking about an 8-N, had it for 15 years, used mostly for grading and landscape work.

It's been a very good tractor, but has steadily lost power over the years.
This last fall, we had to resort to pulling it to get it started...and so decided to open it up this winter to figure out what was wrong.

Most of the "advice" from well meaning "old guy's" was "it's your rings".

Well...okay, we'll see...I knew the rings were worn cause it burned a little oil, but not much, only a quart a year, and I've owned some real smokers over the years, but they always started pretty easy.

Once the hood and misc. obstructions came off, a compression test showed, starting at #1, 80-35-30-35, not so good!

Removed the head to find VERY burnt exhaust valves on 2, 3, and 4.
Number one was okay.

Cleaned everything up, ground the seats, and installed new valves (all).
With the new valves ground, and lapped in, clearances set, and lots of other work like new wiring, carb rebuild, etc. completed, we decided to put it together with the old head gasket "just to see what would happen".

Compression was now (starting with # 1) 90-100-110-95.
Not perfect, but not bad...after pondering a bit, and knowing we really should pull the engine to rebuild the bottom end, we chose to put it back together (with new head gasket) and see how it ran.

We did, and it fired right up, smooth as silk it ran, for about 5 minutes, at which time it stumbled a bit, and then recovered.

A little later in the day, satisfied that it was in useable condition again, we bolted the radiator on, filled it up, and ran it for a half hour to get it warm so we could retorque the head.
While it was warming up, we noticed oil dripping from the oil filler tube, darn, takes a lot of blow by to make oil drip out (the filter was present)...so, we pulled the plugs for another compression test.
Good news! We had 110-120 across the board...except for #1, it had 0, as in none?

Valves appear to be seating, at least as seen through the spark plug hole, so, if they are okay, the other option is broken rings, a big hole in the piston, or a broken rod?

There is a slight amount of air coming out of #1 on the upstroke, but not enough to move your thumb or get a reading with the gauge.
If the rod was broken, there would be at least a little noise, no?
If the rings were broken (really broken) the blow by from the other cylinders could, in theory, come past the rings on #1 and up through the spark plug hole...no, that doesn't work, as all the plugs are out.

Anyone care to take a guess at this one?
Remember, no noises, nothing out of the ordinary, and it started right up with just a quick pull of the choke...and ran smoother than it has for years.
Really weak rings done in by the new valves...but #1 was the cylinder with good compression before we replaced the valves?

We're gonna tear it down tomorrow.

Rob

I'm with Dan, check yer valves..... ...Dell

Good luck and keep us posted,
Dan

Thank you for the quick responses.

While the head was off, and during the valve seat grinding and other operations, the cylinder bores were covered/protected.

The bores were also cleaned as well as can be without removing the pistons...if anything got in there, it was very small/very little.

Lest anyone misunderstood, my reference to "old guy's" was a way of saying perhaps I should listen to them more closely...as they've taught me well over the years!

Anyway, since tomorrow is WAY too long to wait, I pulled the side cover and found the keepers had slipped, and or been incorrectly installed on #1 exhaust valve, (YAHOO!!!)

My compression readings are now 110-115-105-110, still not perfect, but seems good enough to put the old girl back to work?

Gee, I'm rather glad I decided to post this problem here, and didn't go the usual route of assuming...

Hobo, You're right, a leak down test would have revealed the cause before we ever pulled the head.

We did do a leakdown test AFTER installing the new valves (with the old head gasket)but duh...the keepers weren't installed at the time.
Guess I thought the springs would hold 'em down.
My readings with 90# on the gauge showed only 10-15 pounds holding...figured the rings must be mighty worn out...darn assumptions!
A mechanic I am not, though since my 18 year old son is going to the local college learning to do so, we decided to let him take this project on as a learning experience, he has certainly learned a lot so far!
He installed the keepers while I watched, and kept a screwdriver under the spring, just in case.
Guess dad wasn't doing such a good job of supervising...but all's well now, and he'll be a good mechanic some day.

Soon as my son gets home, I'll give him the good news, and we'll fire it up again, hopefully with much reduced blow by!

He's already itchin to button it back up and start on our next project, a 30 year old V-6 air compressor, 1/2 runs, the other half pumps air.

Thanks again! Rob

My guess is that, with the valves in seats in good condition, the pressure in the cylinder from the leakdown checker would have simply held the valve seated, and it probably wouldn't have leaked!