70 or 720 engine mods for pulling

jeddy15 · Feb 14, 2009

we have built several pulling engine for pulling and we now have obtained a 70 john deere diesel and would like to know what mods can done to these engines to make them run strong than they already do. fuel pump, stroking, or what ever cause we do this our selves please let us know. thanks. or e mail @ [email protected]

buickanddeere · Feb 17, 2009

Go to the JD web site and study the difference between the 720/730 and the 70 engine.
The later engines had larger intake valves, 13mm pumps and if memory serves, 5 hole narrow spray injector tips with 10 thou holes. The later pistons had a narrower/deeper "dish" and keystone rings.
To make power they need oversize intakes, port matched manifolds, blended valve bowls and a dry aircleaner conversion. A cam with more lift. And after the airflow is improved, 830 injector tips.
Check for a loose flywheel before going any farther. If installed and maintained properly they are fine. However many were worked on by hillbillys who wouldn't know what a torque wrench was if they seen one.
If the flywheel bolts were under torqued and too loose. Or if they were over torqued and stretched loose. The flywheel will come move and ruin the splines.

Mpuller · Feb 17, 2009

buickdeere, good advice on the flywheel. Bought a 70 diesel years ago, flywheel was loose, wouldn't tighten. Tried to spot weld flywheel to crank. Bad idea. Crank sheared neatly behind flywheel next to crankcase. Kept on running tho, but no low end torque. Got a 720 diesel later, made sure flywheel was tight & checked to make sure it stayed tight.

jeddy15 · Feb 17, 2009

thanks for this information if you have any other like cam specs and how high rpms can be set this would be help full, also this engine is .125 over can the bowl be be changed on the piston for improvment or not thanks again Les....

buickanddeere · Feb 18, 2009

There are some cam grinders listed on this site that specialize in pullers.
The new pistons will likely be the new 140 degree narrow bowl type. The original 70 injectors will be the 160 degree wide spray type.
Extra fuel without extra air is just extra smoke, not more HP.
The airflow of the engine really doesn't support rpms over 1100-1300 at peak HP.

gpuller · Feb 18, 2009

thanks for this information if you have any other like cam specs and how high rpms can be set this would be help full, also this engine is .125 over can the bowl be be changed on the piston for improvment or not thanks again Les....

You can send the cam to Berry Cams in Lester Prairie, MN. They reground the cam in my 720. They send a cam card with the specs but have yet to see the specs on the factory cam, so couldn't tell you what changed. If you call them ask for Scott, tell them what have done to the engine and what you plan on using the tractor for. Mine was ground for stock RPM pulling. I run mine 10% over stock RPM.
Convert the oil bath to a dry filter, the stock oil bath can be gutted, a dry filter from a 3020 Deere will fit into the can.
70's have 10mm pumps, larger 13mm fuel pumps from a 720 or 730 can be installed. If more fuel is needed you can get custom injector tips and pumps from Garry Power in Texas. Adding fuel will make more power, yes it will make smoke too. If you have anymore questions I can send you an email.

jeddy15 · Feb 19, 2009

Thanks for the replies I know Scott and Orvale that run the crank shop in Lester Praire well have had them do work for me in the past. If you would drop an email so I can get other information When i get into the engine more thanks Les....

70 or 720 engine mods for pulling

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Mpuller

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