70 john deere

[Anonymous-0]

Do I need to get my distributor built for the size motor I have? Denny's carb shop says I do. It is 7in bore with 9.25 stroke. The reason I ask is because it runs good for 30 min or so and then it starts popping and skiping.I changed the coil,plugs and going to change the wires.When it starts skipig and popping I shut it off and change the plugs and start it up again and it runs good again for 30min. Can you have too hot of a plug? I have even put smaller jets in the carb. I have no idea what is going on with it. Thanks for any help.

 

[Josh Blackburn]

You can try a new coil or is it possible valves are getting tight?

 

[Anonymous-0]

Josh I tried a new coil and it didnt help. I could try and check my valves and make sure there not too tight.

 

[FOX-G]

Sounds like the coil is getting hot, possibly to much gap in the plugs, or maybe restrictive plug wires, make sure they are solid core wires. I would also check the ballast resistor or make sure the coil has a internal resistor.

 

[504]

Not enough gas.

 

[PopinJohn]

Some of the pullers I know with engines that size have got away from conventional points and coils and have went to the capacitive discharge ignition systems and related spark plugs, etc., as found on hot rods, and late model cars, trucks, etc.

 

[supermpuller]

I'm sure Denny's will sell you a distributor and say it will give you 50 more hp.

 

[Kip-Utah]

My guess is that the valve lash is too close and the time it takes to change the plugs things cool down enough for it to run good again until it warms up. Kip

 

[wls9288]

I have found that the plugs tip get to hot and pre-ignit when the engine gets hot from running hard
change to a colder plug than try it

 

[Anonymous-0]

Thanks guys for all the information. Time to get to work and try these things.

 

[GoodtimePullingTeam]

what kind of gas are you running? With the compression your running and the heat from running it may be trying to diesel. We have had the same problem with our G we have to run at least 114 octane to keep from it.

 

[Anonymous-0]

Goodtime Im running 110.

 

[Josh Blackburn]

How are you running it? Idle or half throttle? Smaller jets on a bigger engine is not what you want. I have had engines lock up in dyno from running too lean and the fix was bigger jets and they popped and farted too. I would suggest putting bigger jets in

 

[Anonymous-0]

Josh I let it idle and wide open.I took the plugs out of it today and they have a grey look to them.

 

[ericsegaline]

Is your coil getting hot you my need a resistor i had this same problem with my G i had 55,000 coil and electronic ignition did the same
thing put 3 ohm resistor and it was fine. but as the others said it could be running lean.

 

[Diesel Dude]

Are you running anti freeze in the tractor? if so drain and run straight water and see if it will run longer. I had a JD G do this same thing and found it was a coolant leak into a cylider..... anti freeze kills spark plugs........ give it a shot i bet thats your problem!