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Discussion Starter #1 (Edited)
I bought my '83 446 back in '99 and have never decarbonized the heads.

The past few years it didn't see much duty as I was using the '86 448 mostly, and also my '76 444/448 repower I bought from a neighbor, so none of the tractors saw much duty as I used all three, but mostly the 448.

Well the 444/448's engine was traded for the Ferguson's engine and then got parted out.

The '86 448 I bought from a cousin 2 years ago and other than change out the fluids I haven't done any other maintenance on it - so I decided its time to go through these machines and do a full maintenance on them.

The 446 and 448 had all the fluids changed out, the 446 also had installed a newer tcv with the holding valve, and when I finish this the only thing it will need is a charging diagnosis as it won't hold a charge.

I stopped at the local dealer I use for misc. parts and he told me not to worry about decarbonizing the heads, with todays fuels it wasn't necessary, however, he did say if the engine burned some oil then it should be done.

Well I have no idea how many hrs are on the 446, the 448 has near a 1000hrs and these are mine and I would rather replace a head gasket than an engine so I ordered gaskets on line, besides I was really curious as to how bad it would be.







They weren't that bad at all, however I noticed a lot of dirt in the fins of the heads and both spark plugs were loose.







These next two pics show a yellow mark on the heat shields were I will be drilling a big (enough) hole in them to gain access to the bolt that holds the head shield in place - what a pita.




 

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Great pics. No bad at all carbon wise. Prolly nothing a little Seafoam couldn't clear up. Right on about getting a good look at the cooling fins though. I know on my little 10hp, just by pulling the spark plug I found a little self tapping screw buried on top of the head [hidden by the sparkplug] that had been laying there so long it vibrated most of it's threads smooth and left a small worn spot on the surface of the head. I also had a chunk of what looked like tape that got sucked in, trapping a bunch of dirt that couldn't get blown out. Stuck my finger over the plug hole, blew'er all out with compressed air and replaced the plug.

Joel
 

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If they look that good and have never been de-carbonized, something is working well. I am going to do my B48M this fall and it will be interesting to see how they look after 900 hrs. I use 89 octane fuel and 1 oz. of SEAFOAM every tank fill ...
 

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Camaniac
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I agree, seafoam. Not to disagree using 89 octane but I wouldn't use a higher octane unless required. I've read if you don't have the compression required it results in incomplete burning of the fuel. Looks like you are on your way and good luck!
 

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... I've read if you don't have the compression required it results in incomplete burning of the fuel. Looks like you are on your way and good luck!
I heard that too. Supposedly the 'slower burning' properties of higher octane rating fuels can carbon things up.

Joel
 

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Treefarm
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Just thought I would post a method which has worked well for me and many other mechanics in the past on auto engines.

Any GM dealer will sell you top end cleaner or automatic transmission fluid works as well and is usually close at hand.

While the engine is running pour transmission fluid in the carb but not so much as to stall or stumble the engine. You will see a huge amount of white smoke but transmission fluid is an excellent cleaner and the drop lets bouncing off the pistons and valves does an excellent job of removing the carbon. It is best to do this outdoors as the smoke is unbelievable but it works wonders.

When you are done it is best to change the oil and filter.

I have little experience with smaller tractor engines but have used this method with great success on chevy small blocks.
 

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Landscaping Nut
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I tried seafoam at 700 hrs in an onan 18. Did the pour in carb throat and the balance of container in the tank. Drove it for about five minutes. I manually cleaned one head and took pictures of it before and after.

On the seafoam only head it was considerably cleaner apparantly just from seafoam. Since I didn't pull that head before to take picture, can't be absolutely sure. But since neither side smoked before or after and motor runs smooth for a two cylinder I had to say seafoam is effective at partial decarbonizing.

I still manual removed the rest with a wood scraper and used a vacuum to try and prevent those abrasive little carbons from going where they shouldn't.
 
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