JD engine building

Going to be building my engine up on our JD 70, probably going to turn into a this fall/winter project. I've heard a lot of good things about Ray at Extreme, on here. Anyone have any work done with him? I'm curious what all is involved in a big cube motor. Can a regular guy (not an engine builder by any means) do all of the work or disassembly/reassembly/adjustment? And, how much maintenance is required on these engines once they are heavily built? (in other words, do they turn into a head ache, or do they pretty well take care of themselves). Any other thoughts/considerations would be appreciated. Ray told me to expect 10-15k for a seriously built motor....

I've got a chance to buy an already built 70, claims 120ish hp. Looks good too, and I'm not sure on the exact hp reading....but doesn't have any trouble winning or placing top 3 in most pulls....he's looking to get 15k out of it. I'm not sure which route is better. I know he's had things like the head welded then ground to increase compression, etc...I just don't know what happens when you buy a tractor like this and it breaks down, and you have no idea how its been put together once you tear into it.

Its cheaper to buy one built, but if you build it yourself you know what you got. If you have seen the 70 that is for sale pull and it does well and runs good, that might not be a bad route to go.

I agree about buying one already built you will save time and money. Most people you buy a tractor from can tell you what was used to put there engine together. That would help when you do have engine work that needs to be done.

I would not buy such an expensive tractor unless you
know the guy personally or can see it run on a dyno.
I know a number of people that got took on pulling
tractors including my dad.

How big are you wanting to go? You want a reliable crank with
big journals and a balanced assembly. The more of the little
things you pay attention to the less maintenance involved over
time. If your talking a big bore it takes a lot of time and
patience. You can do it yourself but might cuss a time or two!
Thats the nice part about buying one built but they have had
hooks and you really dont know what corners the person cut,
starting fresh is always a good idea. Besides ray and many
other engine builders I can also assemble and supply you with
a solid crank and any other parts needed

You sound like you are looking for a "Guarantee" that the tractor won-t Break...!!

Built-up and abused usually includes a few "Break-Downs"..maybe an entire engine, axle or broken gears..
60 Years of Use and they are still going..how much more you can get out of them is hard to say..
Why not start with something Lighter..??
There are plenty "Built" JD "A" and "G" tractors for sale..they can get into more weight classes and be built just as much as a 70..

Ron..

I haven't found any "close" for sale....that aren't all cobbled up and rough looking.

I'm not looking for any guarantees as far as breakages go, I understand thats part of it! I'm looking for an answer from someone who has a bored and stroked engine (through the crankcase) on how tough reassembly is and how tough it is to get it running correctly. And then also what it takes for maintenance as far as the engine goes.


Let me give you an example. I come from racing the new 4-stroke atv's. These engines have overhead cams/valves,etc....and once heavily built, require a ton of maintenance such as checking/adjusting valves (10-15hrs), new rings (20-30hrs), etc etc.


I guess I don't want to buy a package deal from an engine builder and get it shipped up here and find out I can't assemble it or get it running correctly. We've got some mechanical know-how, but like I said I'm not an engine builder by any means. We've sleeved old 4020's, new pistons in our old 4850, etc.

In my opinion if you take your time and make sure all grinding
grit is out of case and clean oil pump and lines maintenance is
simple. I've been running a 650 cube a for five years and just
change oil, checked the bearings twice and other than that no
issues. It's a ten minute job to check valve lash and they
usually don't move much if any. I wouldn't worry so much
about maintenance, you asked about making it run correctly.
That's the real thing to worry about. It does not take much to
lose 10 to 20 hp just in fine tuning on a big engine. Also when
doing a stroker for the first time there is a lot of little tips you
will need to know. So whoever you have supply parts will be
able to say you need pans so wide and cam width clearances
and top of rod clearances, rod bolts counter bored and even
After you think that you have enough clearance chances are
you don't.