Spark plugs for two cylinders

mdross1 · Dec 3, 2015

Could not find any topics using search. Spent the summer breaking in and using 70 at pulls and plow days using a set of Autolite 3116's. Thinking next season might try a set of Autolite 388's one step hotter, anyone here use these?

buickanddeere · Dec 3, 2015

Run the coolant at 195 and lean the air fuel mixture back to where it's supposed to be .

RickB · Dec 3, 2015

388's are a pretty hot plug. Not sure they are needed or appropriate for a fresh engine.

mdross1 · Dec 5, 2015

Thanks for the input this spring will hook up to a dyno and play. Want to see what the difference is between muffler and straight pipe. When plowing the muffler has to be on the tractor at the pulls some say why not a straight pipe then we can hear you. We will see same goes for plugs and fuel mix. Already have the 195 stat. This tractor also has K&N air filter,propane exhaust manifold and 2.0 roller rockers.

buickanddeere · Dec 6, 2015

The straight pipe may or may not lean the mixture to some degree.

mdross1 · Dec 7, 2015

How do you check the fuel mix. I have been tuning carbs for a lot of years on muscle cars and Harleys these duplexes do not have a lot to play with and I'm new to them.
Mike

buickanddeere · Dec 7, 2015

There is a vast selection of nozzles and jets for the duplex carb's . The all fuel 70 main's flow more than the gas 70. The all fuel metering for the 720/730 are a size larger yet again.

mdross1 · Dec 8, 2015

Now you have peeked my interest I would very much like to know all there is to know about these carbs. First off how do you judge the mix other than being hooked to a dyno? These engines being low compression and all reading the plugs is next to impossible. My first instinct is too lean the mix out a little where the plugs are so dark.

Mike

buickanddeere · Dec 8, 2015

Weld a bung or drill and tap into the exhaust manifold just prior to the flange where the pipe to the stack bolts on. Thread in a wide range O2 sensor and read the voltage .
Summit racing has them on the shelf. Needs a 12V neg electrical system .