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Should I be burning 93 octane fuel?

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Butch WI

09-23-2007 03:56:14




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In a previuos post I made about spark plugs, a question was asked of me why I burn 93 octane fuel? The previous owner recommended that I do that for the valves. What is your opinion on the rating of fuel to use in a 460 Utility?

Butch




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Doc Larry

09-24-2007 05:35:45




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 Re: Should I be burning 93 octane fuel? in reply to Butch WI, 09-23-2007 03:56:14  
The recommendation for 93 octane fuel in the old IHC tractor manuals is based on the "old" way of measuring octane. Regular 87 octane as octane currently calculated ((R+M)/2)) is more than sufficient for your tractor. Low compression engines don't need high octane, never did and never will.
Larry



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MN Scott

09-23-2007 19:45:29




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 Re: Should I be burning 93 octane fuel? in reply to Butch WI, 09-23-2007 03:56:14  
Sure wish the Tractor Vet would get his computer fixed, he's the expert on the IH six bang gassers. Keep in mind the 6 cylinder gas engine IH used in its tractors is the for the most part the same one used in its pickup trucks so they are stressed to the max and every thing has to be near perfect for them to last. If you run less than 93 octane in a IH six bang and work it hard you will score cylinder walls. I know, been there done that. The problem is low octane fuel burns quicker causing more heat in the combustion chamber. The cast aluminum pistons will swell from the extra heat and score the sleeves or melt holes in the tops of the pistons. If you look in the owners manual for a IH gas 6 cyl tractor it states that at least 93 octane is required. Don't beleive me? put in a tank of low octane fuel and go plow or other hard work. Won't take to many hours and you'll be back with a missing popping severelly sick engine. Now if you do light work you might get by with low octane but with the cost of parts why risk it?

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Pat-CT

09-23-2007 11:23:14




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 Re: Should I be burning 93 octane fuel? in reply to Butch WI, 09-23-2007 03:56:14  
someone mentioned carbon build up so i will chime in with saying that sea foam cleans almost all the carbon out of your engine and cleans the crap out of the carb at the same time just a random chime in but tis a great product



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Owen Aaland

09-23-2007 06:47:56




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 Re: Should I be burning 93 octane fuel? in reply to Butch WI, 09-23-2007 03:56:14  
What you need to watch to avoid burning valves in those IH gas engines is the ash content of the oil. You need to be using an oil with an ash content of 1/2 percent or less.

The problem with the exhaust valves comes from the valve stems getting a layer of carbon buildup on them. This is not a problem as long as the load is kept constant on the engine but when you go to pull it hard the valves will get hotter and the stems expand. The carbon buildup then causing the valve to stick as little. When the valve sticks open under heavy load the combustion gasses leaking past the seat will cut them almost like a cutting torch. The low ash oil will not entirely eliminate the problem but it does greatly reduce it.

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John T

09-23-2007 05:53:03




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 Re: Should I be burning 93 octane fuel? in reply to Butch WI, 09-23-2007 03:56:14  
I wouldnt burn any higher octane gas then absoulutely necessary to prevent pre ignition spark knock, so unless your tractor has been modified for higher compression that would likely be 87. Higher octane gas is designed purposely harder to ignite (avoid pre ignition) so why use it and perhaps have a less efficient burn and left over products??? If there were more lead in it would be one thing which may help reduce valve wear but if its still unleaded I see no reason for its use unless you raise the compression.

John T

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Jim Allen

09-23-2007 05:28:21




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 Re: Should I be burning 93 octane fuel? in reply to Butch WI, 09-23-2007 03:56:14  
Butch, there's no more protection for your valves in 93 octane than there is with 87... and an engine with a compression ratio as low as that 221 certainly doesn't need the octane. If your valves have no hard seats, then you can use a lead substitute additive (available at any auto parts store) to prevent valve seat recession. If you aren't really working the tractor hard, the damage would be so little as to be negligable. A study was done years ago when cars were weaned off leaded fuel and it was found that only high performance cars that were run hard and trucks that were worked hard was valve seat recession a major issue. As I recall, on the more easily worked rigs, it dropped about 10-15 percent off normal life off the valves. When worked hard, it could be from 40-60 percent. If yours is a parade tractor or an occasion field toy, it could take a long time for you to have any problems. Maybe beyond your lifetime. In any case, the protection-in-a-bottle is easily available and inexpensive.

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Bob Kerr

09-23-2007 19:51:34




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 Re: Should I be burning 93 octane fuel? in reply to Jim Allen, 09-23-2007 05:28:21  
I can add to what Jim Allen said. The high performance cars and truck engines that had valve failure was usually engines that had valve rotators. When lead was added to gas it would build up on the valve faces and they added rotators to keep the excess lead skimmed off but the lead residue also acted as a lube for the valve face and seat. When the lead was removed there was no more "Lube" and the valve face would wear into the seat and recess the valve into the head. The rotators will spin the valve stem and it sometimes keeps spinning as the valve closes causing it to scuff on the seat. Engines without rotators usually don't have ressesion problems but would get build up of lead when it was used and the lead would flake off causeing the gasses to burn the face. With no lead gas, the seat closes tight and has no build up to worry about as much. As far as octane goes, use the cheapest gas you can that doesn't cause "ping" and you will be fine.

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