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Tractor Talk Discussion Forum

Valve seat recession and unleaded gas

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05-11-2012 14:18:40

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I've been hearing the many stories for years about the results due to a lack of unleaded gas in older machines. 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 up 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 could 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 had 0 PSI, #2 had 75 PSI, #3 had 60 PSI, and #4 had 0 PSI. If hadnít 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.

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05-12-2012 06:00:40

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 Re: Factory in-place induction hardening in reply to d beatty, 05-11-2012 14:18:40  
Quoting Removed, click Modern View to see

If I got 130 (if that is a normal spec) by adjusting the valves I think I would run it unless rescission was a known issue with your engine... It sounds like you know were you are at no doubt its not like you are putting your reputation on the line with a customer....

I have a 60 140 Farmall that I brought 5 years ago,, its always been a tad under-powered, smokes some... I use it maybe 4 hr. a year,,, It was not running when I got it I cleaned the fuel system got it going and its useable.. I got caught up a mo are so ago so got all the little thinks fixed up and went after the leaking valve cover gasket... While their checked the valves and all the exhaust were to tight no clearance,,, adjusted them the smoke is gone and power is back... I don't plan to do anything else to it unless I run out of something to do... Now am I wrong to think this way... If smoke and power become a issue I will go into it....

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05-11-2012 21:48:23

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
I used to run an engine machine shop and my experience was that soft seats would run under light duty conditions.

Work them hard and the exhaust valves would sink. Cut them out and put in inserts. If the seats are hardened in the head itself I don't think you would have any problem.

It was seats cut into plain cast iron that caused the problems.

RT (My 2 cents)

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05-12-2012 05:25:56

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 Factory in-place induction hardening in reply to RWT, 05-11-2012 21:48:23  
OEM seats ground directly into the head were 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.

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05-11-2012 20:28:46

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
Why not just pull the head off and have hardened valves and seats installed and solve the problem?
They've been ground at least once already. They've recessed from there... You can estimate the odd of it dropping a valve better than just about anyone here...
Is a valve job really more money than a valve job and a set of cylinder kits?
I like to gamble with such things too, but....


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Hal/Eastern WA

05-11-2012 18:42:13

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
So what are you going to do with it now? I think that if it was mine, I would readjust the exhaust valves, with a couple of thousandths extra clearance, and then see what a compression test would show. If you are a little lucky, the engine will run fine, and you can put it on your list to check the valve clearance more often in the future. If you are less lucky, you might have burned exhaust valves, which might be salvagable after you tear it down, or which might need to be replaced. If you end up having to remachine the head, I bet there is a shop somewhere that can install hardened seats. I would also look into the possibility of getting stainless steel exhaust valves.

I have read about exhaust valve seat erosion and recession for years, but in my personal experience, it never has seemed to be a problem. Especially on old tractors, which seemed to have been built to stand almost anything, and which were seldom worked that hard. But apparently your JD is having a problem that is losing your valve clearance and that has to either be erosion at the valve and seat area, or the other possibility is that the valve stems are stretching. I have seen valve stem stretch in very hot running, air cooled small engines, but never in a liquid cooled engine. As a matter of habit, I always add a thousandth or two of clearance from the specs for valve clearance on solid lifter engines. I would much rather have a little bit of valve noise than too little clearance that results in burned valves. But that is just my way of doing things...and maybe I am wrong.

I sure think tinkering with it a little would be worth a try, and doing so would not cost almost anything except some time. Good luck!

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George Marsh

05-11-2012 18:08:48

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
I've run into a few briggs lawn mower engines with valve seat recession. They were flat heads and some times it was the intake valve.

I remember the old VW air cooled engines. They had no oil filters and you were to change the oil every 1500 miles and while you were at it, pop the valve covers off and adjust the valves. The VW was bad for burning valves and valve seat recession. BTW, we had lead in the gas too.

However, today's briggs and kohlers with overhead valves, it seems to be the opposite problem. The valve clearance increases, causes the compression to go up and it acts like you have a bad starter or a dead battery. I had to readjust the valves on 3 briggs this spring. I'm no rocket scientist, but I would think if one had valve seat recession on OHV engine, the valves would tighten up, not do the opposite.

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36 coupe

05-13-2012 04:43:33

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 Re: Valve seat recession and unleaded gas in reply to George Marsh, 05-11-2012 18:08:48  
The 12 hp Briggs was a stinker for loosing valve clearance and valve seats coming loose from the block.I wonder if valves were getting longer.Back when I worked on Chevy sixes there were a lot of badly burnt valves.I always set valves wider to avoid burnt valves.

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Bob Bancroft

05-11-2012 16:13:04

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
Also- that would have already had inserts for exhaust seats wouldn't it?

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05-11-2012 17:10:26

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 Re: Valve seat recession and unleaded gas in reply to Bob Bancroft, 05-11-2012 16:13:04  
No, the 1010 didn't have valve-seat inserts. Valve seats were ground into the head casting. The 1010 DOES have exhaust valve rotators.

The new engine that followed in the 350 also did not have any seat-inserts. That was the Dubuque/Manheim 300 series engine. 3 banger in the 350 and 1020, 4 banger in the 2510, 2020, 450, etc. 6 banger in a 540 skidder, 4030 tractor, etc. I don't recall seeing factory seat inserts in any of them until turbos came out - or French built (Saran) engines were used.

As I recall, it was the Deere Waterloo engines that first appeared with seat-inserts but maybe somebody will correct me.

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Bob Bancroft

05-11-2012 16:10:22

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
Thank you for filling us in on the resolution. If I recall correctly, there was overwhelming agreement on ignition as the issue.

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05-11-2012 17:34:50

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 Re: Valve seat recession and unleaded gas in reply to Bob Bancroft, 05-11-2012 16:10:22  
I didn't mention the ignition thing in an effort to less-confuse things.

Call it bad timing or call it co-incidence. I changed my breaker-point ignition just before I started the pond project. It ran and started well before the change-over to Pertonix. After it still started and ran fine for a few days - and then started getting worse and worse. I had assumed the problem had something to do with the ignition work. That's when I posted my low 8 volt reading for cranking-voltage. It still cranks at 8 volts and I'm sure the starter is drawing excessive current. But it is NOT a problem with the ignition. Pertronix claims their breakerless module runs with 8 to 16 volts. I tested mine down to 6 volts and it still worked fine.

Seems as I ran this crawler hard, all day, almost every day for a few weeks the valves got deeper and deeper. Probably didn't matter much until it got to zero clearance.

When I put the engine together 10 years ago, the exhaust valves were set at .018". So now if less then 0 clearance - I assume I've got at least .020" wear. But it IS possible that two gaskets settling a bit caused some of the problem. Keep in mind that unlike other engines - the 1010 has two gaskets under the head - not just one. A deck gasket and a head gasket. If, in 10 years with bolts torqued 150 lbs. - those gaskets even got .005" thinner from compression - that would take .005" away from the valve clearance (assume a 1 to 1 rocker-arm ratio. I don't know what the ratio actually is.

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05-11-2012 15:20:40

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
One of the things that always throws me on this topic is that lead wasn't introduced til the 1930s and even then many if not most tractors were "dual" fuel; start on gas then work on distillate/tractor fuel which had no lead. LJD can you borrow a bore scope and inspect the valves without tearing the head off, I think it is curious that in maybe 100 hours of work you could have caused that much damage. I have been wrong before,too many times but still doubtful.

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05-11-2012 17:25:12

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 Re: Valve seat recession and unleaded gas in reply to gtski, 05-11-2012 15:20:40  
I rebuilt the engine 10 years ago but have no way of knowing how many hours are on it. It's been a part-time user these past 10 years until recently.

These past few weeks, I ran 200 gallons of gasoline through it. It's something I really notice because it's the only gas engine machine I've been using. All the others are diesel and I have bulk diesel here. With gas - I'm constantly running down to the gas station with 5 gallon jugs.

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05-11-2012 15:04:49

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
Actually 25-30% 100LL should give you enough lead for valves, but that is only a temporary solution as 100LL is being phased out or getting increasingly difficult to get. The FAA has approved STC's to allow most general aviation aircraft to run on Autogas. I question some of the valve seat recession wisdom. John Deere offered propane 1010s did they have hardened valve seats 'cause propane has squat for lead, what about all the old distillate engines-did tractor fuel or distillate or TVO have lead? Last month there was a big discussion about modern fuels causing problems with red tractors with six cylinder engines, work 'em hard on autogas and they melt pistons. I've seen air-cooled engines (VWs and some Kohlers) having fuel related issues that caused exhaust valve failure, the seats were fine but got some stretch on the exhaust valves. This was when leaded gas was still available, a root cause was the engine running a little to lean. Back in the air-cooled VW's heyday a common cause of death was breaking #3 exhaust valve, the valve would stretch a bit, where the stem got thin it would break and the the valve head would bounce around in the cylinder spreading hate and discontent. It was always #3 because it was tucked in behind the oil cooler and ran a little hotter than the other cylinders so when you pushed it out to the edge #3 gave up first. If you were "lucky" some times you'd loose a small enough section on the valve face to not screw up to much before you got it shut down.

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05-11-2012 15:41:25

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 Re: Valve seat recession and unleaded gas in reply to wisbaker, 05-11-2012 15:04:49  
All-fuel and diesel usually left enough soot and carbon on the valve seat to protect the seats. Melted pistons are the result of detonation. Detonation is in turned caused by too much advance, too lean a mixture, too much compression, too high intake air temps, or glowing soot on the combustion chamber.For the octane of the gasoline being burned.

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05-11-2012 14:48:10

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
From what it sounds like the lead is avgas is already half of what it used to be as it's being phased out. In reading down in the section titled, "In Aviation Fuel".

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05-11-2012 14:41:18

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
100LL should leave a protective layer of lead on the seats. Without leaving a lot of lead deposits to damage the rest of the engine. Some claim that mixing 100LL 50-50 with regular unleaded still provides enough protective lead. Too bad the days are gone when we could just go to the hardware store and blast our own ponds, stumps and stones.

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05-11-2012 14:34:40

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  

Another thing I've learned today that I had no idea about.

I just had my valves ground and head work done. I just read the definition of valve recession and have a question.

The article I read after yours was about how pre 1975 engines need a lead substitute to help lubricate the metal of the valve seats. My question is, does the octane rating of the gas have anything to do with valve recession? ....or is it just the lubrication properties of the fuel that help keep from this happening?

By the way, what product will you use to add to your fuel?


Ha, Mark, looks like I should of waited on your reply first.
This post was edited by 641Dave at 14:38:00 05/11/12.

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05-11-2012 18:21:03

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 Re: Valve seat recession and unleaded gas in reply to 641Dave, 05-11-2012 14:34:40  
Octane has nothing to do with valve seat recession in older gasoline engines, nor does the "lubrication" property of the lead. Rather, the lead provides a cushioning effect between the valves and seats.


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05-11-2012 14:33:57

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 Re: Valve seat recession and unleaded gas in reply to LJD, 05-11-2012 14:18:40  
Good info, thanks for sharing it.

The reason you don't hear a lot about older engines having problems with unleaded gas is that most of them have had a lifetime treatment of lead. But once you grind the valve seats, you're back to bare iron.

Supposedly, if you run an engine on leaded fuel for ten hours or so, it will have all the lead it needs until overhaul. Of course the only leaded fuel available is 100LL avgas, and it will probably go away in a few years. But you might try running a couple of tanks of avgas through your engine after you re-do the valves. I'd say that's more likely to work than any snake oil "lead replacement" additive.

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05-11-2012 14:55:58

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 Re: Valve seat recession and unleaded gas in reply to MarkB_MI, 05-11-2012 14:33:57  
I thought most tractors already had harden seats from the factory from the 1940s onward. It was mainly automobile engines that did not have harden seats un the early 1970s.

Even with "soft seats" the erosion would not be that bad on a low compression engine.

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05-11-2012 17:01:36

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 Re: Valve seat recession and unleaded gas in reply to dhermesc, 05-11-2012 14:55:58  
None of the Deere engines that I can recall had valve-seat inserts - gas or diesel until they started using turbo-chargers. I did all the cylinder-head work at our Deere dealership. 1020, 1030, 2020, 2520, 350 crawlers, 450 crawlers - some built early 80s had no valve-seat inserts.

I just did a valve job on a 1992 GM 6.2 diesel in a Chevy Suburban and that does not have valve-seat inserts either.

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