rebuilding a jd 520

[greenfeverms]

about 2 rebuild a 520 and i have a 520lp im using 4 parts. i want a really strong puller but want 2 still b able 2 work it 10 hours in the field if need b.any suggestions?

 

[buickanddeere]

While I believe in "blue printing" and tuning an engine. I'm not much for souping an engine into a short lived tempermental race engine.
There isn't a whole lot to gain as Deere souped that B engine a long way.
LP pistons,LP manifolds,Berry cam,five angle valve job,port match the manifolds to the head and carb. Blend the rough edges and ridges out of the ports and valve bowls. Make certain the aircleaner mesh and inside of the intake pipework is 100% clean.
After assembly put the tractor on a dyno with 91-94 octane pump gas or 100LL. Tweak the timing advance and total advance along with the air/fuel mixture.
You might be able to obtain the HP levels close to a stock 70 gasser or a stock 620 gas.

 

[Machinery-Man]

If you put the flat top lp pistons in the 520 gas you will be in for a suprize...more compression than you can write home about but erratic performance...carburation problem and less burn time on timing...I would advise no...I did this on a 520 and later changed back to standard pistons....the lp are flat top and way to much compression to calibrate with timing, valves and carb. Had about 170-175 lbs compression.....but compression alone doesn't do much as burn time is more important on these lugging engines....you loose that with the Hi compression....

 

[BushogPapa]

Can a 520 be Bored +.250..????

I have a LS "B" that is +.180 and it gained one full gear on the other matching "B" we have..

JDBPuller says no HP parts he has will work on the 520..but..
I am leaning more toward a longer stroke for my 520.
I have a freshly overhauled (Standard Bore) 630 here and it pulls 4-16" in 2nd and 3rd..
NO WAY will that 520 EVER equal that...!!

I know, JDB's "B" would "Stroll" with it, but that is a Horse of another color..!!
HOW Many Cu In...??? Maybe pushing the 5 Century Mark..!!!

Ron..

 

[buickanddeere]

(quoted from post at 11:22:00 03/18/10) If you put the flat top lp pistons in the 520 gas you will be in for a suprize...more compression than you can write home about but erratic performance...carburation problem and less burn time on timing...I would advise no...I did this on a 520 and later changed back to standard pistons....the lp are flat top and way to much compression to calibrate with timing, valves and carb. Had about 170-175 lbs compression.....but compression alone doesn't do much as burn time is more important on these lugging engines....you loose that with the Hi compression....

If you try to run cheap on 87 octane then yes the tractor will only detonate and knock.
If you can't afford the extra 5 to 50 bucks a year for premium fuel. Don't spend several thousand on an overhaul.
Carburation is independent of compression ratio.
Burn time is related to valve timing and piston speed, not rpm. With the low rpms and short duration cam. There is oportunity 5 times over for combustion to take place.
Are you the guy who wrote here one time how you thought a 1/2 speed distributer was needed for high compression applications? You were under the impression that spark on the exhaust stroke casued detonation.

 

[Mike M]

Just rebuild it correctly with the correct parts and it will pull better then ever ( or at least 40+ years )all day long for many,many years.

There were high altitude gas pistons made for them by Deere and M&W.

I'd rather see the LP fixed up as it is rarer. LP is 100 or 105 octane I think ? Wouldn't know why an LP engine couldn't run on 100 octane gas.

 

[gtx1967jewison]

i am sorry & mean NO offense but i cant believe what u write. u have no clue how an engine works or generally what your telling these people. 175# is not even that much more than stock & MANY gassers are running lp pistons, even in the field. just because you couldnt get yours to run right does not mean it wont work. you just need to understand an engine a little better.