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Thread: Unleadead fuel in your Classic

  1. #1
    Super Moderator bmorgil's Avatar
    Join Date
    Dec 2018
    Northwestern Ohio

    Unleadead fuel in your Classic

    Another great discussion that comes up from time to time.

    Ethanol and the rubber components in vintage vehicles are not compatible. It will ruin the hoses and quite possibly the internal rubber components in the fuel system. Search for "Recreational Fuel" in your area, and use that in your classic. On another note the discussion ventures into the valve seats and valve material. If you don't have lead or a lead additive, you consider the seats and the valves. Here is one explanation on why.

    It has long been established that hardened seats are needed on the exhaust seat to prevent the seat from receding into the port. The hot exhaust and the pounding from the valve causes the seat to slowly sink. To prevent this manufacturers harden the exhaust seat. I bet most 134's are already hardened. It was common on all hard working engines even "back in the day". Not all older engines need it but it is there on all modern unleaded motors. Most re builders like to be sure and put in hardened seats on engines without them as a precaution, because unleaded fuel can accelerate this wear on the exhaust seat.There are a lot of people going either way on this. I am old school, I would not assemble a motor without hardened exhaust seats. It certainly will not hurt. Stainless valves are a nice high quality addition to the valve train. Modern stainless valves are lighter and stronger.

    The Willys engine (Basically a Continental Industrial Engine) may have had harden seats from the start. The reason being the exhaust valve gets hot and pounds on the hot exhaust seat. Hardening and/or lubricating the valve and seat, and in some cases the use of valve rotaters, makes it last much longer. The lead in leaded fuels provided great lubrication. When unleaded appeared, many auto engines without hardened seats, had valve seat recession. The exhaust valve would pound its way right down into the seat. I would not put a motor together without hardened exhaust seats. There is no draw back only positive, contrary to popular belief they do not fall out when installed correctly. All aluminum heads have inserted seats.

    There are many who don't do it, and may or may not use an additive. They are not wrong for three reasons. If you don't put the motor under loads for extended periods it probably makes no difference. If the motor is loaded hard for extended periods it will make a difference. There may not be enough material to install them. And it is quite possible the seat area has been "hardened" already. If you clean up the exhaust seat area, you may see an insert or a "Hardening Ring" where the metal looks a little different, where the seat may already have been induction hardened.
    Last edited by bmorgil; 08-03-2021 at 08:47 PM.

  2. #2
    Senior Member 5JeepsAz's Avatar
    Join Date
    Aug 2019
    Huge help with my build! Thank you. The donor to replace my cracked head presents all of the above challenges you've addressed. Once they clean it up and give it a thumbs up, it'll get the hardened seats if not already there.

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