Unleaded gas did a number on my valves

[jdemaris]

I've been hearing the many stories for years about the lack of unleaded gas. Many say it's all nonsense and some (like me) believe test results.

I've read test after test that an engine that lacks hardened valve seats suffers valve-seat recession if used long and hard.

Well it just happened to me.

I've got a 1010 gas crawler with an engine I rebuilt maybe 10 years ago. I personally did the valve job so I know exactly what condition the valves and seats were in. Wasn't too bad when I got it, but I recut/reground the valve faces and seats - all to specs. I did NOT install any seat-inserts that would require machining the heads to accept them.

Up to last month, I've never really used my 1010 long and hard. It's gotten plenty of use, but intermittent.

This Spring, I've been building a pond. Much of the work was done with my Allis HD6 and huge Pettibone backhoe/loader. But - I wound using the 1010 crawler -loader much more then planned since it can get around on mud and has a bucket to transfer fill around. I used it heavy, all day, every day (more or less) for three weeks. I finally literally ran the tracks off it. I was almost done when the tracks were so bad I no longer could keep them on. So, I pulled the crawler in my shop and started tearing down the undercarriage. It's been in my shop now for two weeks. Note that when I pulled it in the engine ran perfect. Purred like a kitten, no smoke, great power, etc. But on that last day of use it started getting hard to start. Once running, it was fine. After getting in the shop and needing to start it once in awhile to move sprockets, lift in the air, etc. it got even harder to start. Finally yesterday - I could not start it no matter what I did. I was kind of stumped. I usually try to be smart and diagnose problems. This time - in desperation - I changed the spark plugs, played with the timing, pulled the carb apart, etc. After nothing worked - I reluctantly did a compression test, which seemed absurd to me. An engine I knew ran perfect and rebuilt not very many hours ago? Well guess what? At cranking speed, #1 has 0 PSI, #2 has 75 PSI, #3 had 60 PSI, and #4 had 0 PSI. If hadn’t seen it, I would not of believed it. So I took off the hood, gas tank and valve cover and checked valve lash clearance. The intakes were fine and still at .012" like I put them at 10 years ago. The exhaust valves? None were closing. Less then 0 clearance. Since the intakes were still correct, I cannot blame this on the head-gasket or sleeve-deck-gasket shrinking. It has to be exhaust valve seat recession. So, I loosened the valves and now have 130 PSI on each cylinder. I assume when I get it all back together it will start fine. Now I'm thinking of using a valve-recession additive since I'm not eager to pull the head, machine for valve seat inserts, pay a fortune for gaskets, etc. I DO wish I had done that years back. I have the equipment to reface valves, grind or cut seats,, knurl valve guides, etc. I do NOT have the equipment to bore the heads for seat inserts. There is also no local machine shop around anymore to do it.

The seemingly odd thing is it ran great once running. I'm assuming it got to the point that when at running speed, there wasn't ample time for the compression to leak past the valves fast enough to affect anything. But at cranking speed - it lost compression as fast as it could make it - and ergo - no start.

A friend of mine recently had a similar problem with his Ford diesel tractor. But in his case - it was a month after installing a new head gasket. It "settled", i.e. became thinner under pressure. This caused the engine to loose all the valve clearance since the pushrods were pushing further into the head. When I checked it for him, he had no clearance on the intakes or the exhaust.

[Lavoy]

From what my machine shop guys have told me, it should take a substantial amount of hours, much more than what you ran to cause valve recession. That being said, none of the engines I rebuild ever goes together without hard seats. If this is what happened to yours, it just reinforces my reasons for doing so.
Lavoy

[DukeofDeere]

From what I have seen over the last 15 years of playing with old iron it is quite important to check valve clearance as a regular maintenance item.
My '56 phase I JD 420 T has seen several hours of hard work.
I have adjusted the exhaust valves 4 times in the last 10 years and gained back compression.
When it is time for a major overhaul,
hardened seats for sure.

My gas 440C has been getting quite a workout.....
I haven't checked the valves yet.
Hoping it has hardened seats.

Duke

[jdemaris]

From what I have seen over the last 15 years of playing with old iron it is quite important to check valve clearance as a regular maintenance item.

I did the valves in my flathead Hercules engine 20 years ago (in an Oliver Cletrac dozer). I've never had to touch it since and I really had to grind those valve seats deep into the block when I got it. They were rusted something awful. So, who knows?

OEM seats ground directly into the head are induction hardened. It's a spot high-frequency heat process. Deere, Ford, GM, et. all used the induction-hardening process. Problem is when doing a valve job with a seat cutter or grinder - that hardness is often lost. It's not very deep and you feel it when you grind through it.

Supposedly - an engine previously run on leaded gas and then switched to unleaded does not have a big problem. That because of a chemical-metalurgical process that occurred with the leaded gas. It causes a "self-hardening" of the cast iron seats. The big problem - as I understand it - is when that hardness gets ground away during a reseat job and then only unleaded gas is used.

A few posters have asked why engines run on fuels other then gas don't suffer? I'm not sure but I do know that burning gasoline creates iron-oxides that act like sandpaper on the valve seat. I suppose other fuels don't create the oxides to that extent?

Now with my 1010? Hey . . . I got 10 years out of it before trouble. Chances are I'll never use it this hard all-at-once again. I'm not even sure I'll be "running" in another 10 years.

I'm just going to loosen the valves and put back together. I'm also hoping the seats might "work harden" a bit.

But yes - I certainly agree that installing hardened valve seat inserts is the best way go if you've got a local shop that can do it. We don't have any auto-machine shops in my area anymore. The last time I used one - before he went out of business - he ruined four of my diesel connecting rods. That because he hadn't been calibrating his inside mike.