Glowing M

Chad

The red glowing manifold, fire out the stack, etc. is pretty much normal for these engines when worked really hard. However excessive heat and fire can also be from late ignition timing (timing set wrong or centrifugal advance not working), or the carb power screw adjusted too lean.

Bad timing can also cause roughness and popping out the exhaust at idle. Timing should be 0 deg (top dead center) mark on the fan pulley at low idle, then advancing to the 2nd mark (32 deg BTDC?) at high idle.

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You might also replace the spark plugs with a set 1 or 2 heat ranges colder – though colder plugs will be much more likely to foul if the tractor also run under light load/low RPM conditions.

Don’t bother switching to higher octane gas – it won’t significantly lower exhaust temperatures. Higher octane is required only if the engine pings/knocks under heavy load. Otherwise running high octane simply empties your wallet a little faster!

We learned with these engines in stock trim switching from from 87 to 93 octane – also 100 octane av-gas) had no measurable effect on maximum power. In fact over long duration runs the highest octane fuels occasionally resulted in LESS power on account of lead fouling of the plugs and misfiring (this was still in the days when tetraethyl lead was the usual way to increase octane...)

However running by higher octane fuels it did let you make adjustments (like more advanced timing, running higher compression heads etc .) that would otherwise cause excessive knock/detonation in the engines. And these changes - in combination with the higher octane - gas DID result in significant increases in power.

Bottom line is we learned that simply switching to higher octane fuel and making no other changes accomplished nothing.

Incidentally we parked the last gas tractors in the mid-70's. We run 'em now only for parades, hayrides, pushing snow and the like. Their poor fuel economy relative to the diesel simply left 'em in the dust!

To get back on subject, my grandad told me about moonlit nights back in the 30's when he and his brother would trade off mowing hay all night with a Regular pulling two seven foot bars. He didn't mention anything glowing but he said there was always a flame out the exhaust.

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