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Len Rahilly
10-02-2007 08:21:16
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Re: Farmall H manifold switch,,,,,,,,,,,,,,, in reply to Bernsy MN, 09-24-2007 05:46:19
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Many of the tractors made from the twenties through the forties (at least ones I'm familiar with from my so-called youth) had provisions for "changing over" the manifold for use either on kerosene/distillate or on gas. Some had a sort of baffle that had to be reversed, to keep some of the hot exhaust gases away from the intake manifold when using gasoline (gas doesn't need as much heat to vaporize as the other fuels do). Some had a lever which could be controlled from the driver's seat (F-20 and F-12 were like this). The H manifold had a lever, too, but I think it had to be moved at the manifold itself.
When you now, very occasionally, see one of these manifolds on a tractor at a show, the
levers are often broken, frozen in one position, twisted off, etc. I used a number of such tractors when I was growing up in the 40s, but by that time, nobody where I lived wanted to be bothered with kerosene, so they switched permanently to gas and let the change-over device on the manifold rust fast.
You will notice that the gasoline manifolds that were available from after-market suppliers had very little heating surface for the intake manifold. This is also true of the gas manifolds that came on the later tractors of the H and M era. Unfortunately, the kerosene/distillate manifolds eventually burned through and were replaced by gasoline manifolds. It is rare to see an F-20 in a show today with anything but an aftermarket replacement.
I don't know if a kerosene/distillate manifold will give as much power as a true gas manifold (one thing is pretty sure: there won't be as much power if the baffle or lever has been put in the K/D position--the gas would be overheated and expand too much, I think). If your tractor is more for show than work, you probably would have a more interesting and possibly slightly more valuable tractor with this now-rare manifold. If you aren't going to work the tractor hard, you probably aren't going to notice a difference, anyhow. I worked several IHC K/D tractors ("Regular," F-20, 10-20) on gas for over 10 years in the forties, and they produced good power, BUT...kerosene/distillate
have to be used with a fairly-low compression ratio (4 to 1 comes to mind as typical) or they will knock like crazy. Many of the tractors from the 20s and 30s had a "spark control" to allow the operator to retard the spark if knocking occurred (so did most cars until around 1930, because the gasolines were of low octane ratings, and many of the early cars did not have automatic spark advance). Some tractors also had water tanks which would let a little water into the manifold to stop the knocking when the tractor was working hard.
So, blah, blah, blah, but long story short, if the tractor still has a low-compression head, it won't produce quite as much power as a tractor with a "gasoline head," which might give a compression ratio in the area of 6 to 1.Incidentally, I tried kerosene once, and once was enough. If the tractor has been stopped on kerosene and allowed to cool, you have to drain the carb, then turn the tap on the little tank to put gas in the carb. Crank. Pull up the radiator blind (or close the shutter if that is what the tractor has) to get the engine hot.
Turn off gas, turn on kerosene. Get right to work to keep the engine hot. Pay attention to knocking and retard spark if necessary. Adjust the shutter or blind as needed. If the tractor had no heat gauge, you had to guess at the right place for the blind or shutter (steam coming from the radiator, but no boiling over; engine pulling without spitting and sputtering). If you stopped for a few minutes, you didn't want to go through the starting process again, so you let 'er idle. The engine would cool down a bit, and then you might get some spitting and sputtering when you tried to get back to work. Enough already!
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