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Tractor Pulling Discussion Forum

520 rebuild

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JEN

11-04-2004 08:22:52




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I am building a JD 520 this winter and hope to have fun at the county fair pulls next summer. (We don't have classes around here. It's just for fun.)
I don't want to do anything fancy, but while I am at it, I just wanted a little extra grunt.
I have added electronic ignition.
I am going to bore it .125 to smooth the cylinders out. Is there a piston that would be better than stock?
And what can be done to the heads? I am familiar with porting and polishing on cars, but with the original carb. and only running at ~1500 rpm, does that do any good? Is there anything to be done to the valves and springs? Clutch work??

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BushogPapa

11-04-2004 18:37:14




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 Re: 520 rebuild in reply to JEN, 11-04-2004 08:22:52  
You could look for "LP" pistons...they are 8.0 to 1 compression.. Spending time reshapeing the valves for a smooth contour, with the seating cut being the only flat part on the valve, and a Multi-angle cut above and below the seat will be well worth your time..!!! There is a lot of power to be found in that area. be SURE to Match the intake ports to the head..many are way off.. Clean the airfilter, and intake air tube out real good... That should get you into the mid-40 horse range.. You may still be a little "short" for pulling in 2nd gear..maybe, maybe not...depends on the track.. Ron..

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buickanddeere

11-05-2004 15:35:55




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 Re: 520 rebuild in reply to BushogPapa, 11-04-2004 18:37:14  
Dry airfilter conversion, cam from Robert's carburator, nail head back cut the intake valve. And that "eye brow" that shrouds half of the intake valve. Get the local machine shop to open it up with a valve seat cutter another 3/8 to 1/2" in dia. Have to watch out not taking sealing surface off from between the cylinders, or hitting water under the deck. LP manifold adds a wee bit more power. Blend the rough edges out of the ports and valve seats. Don't try to get fancy and hog the ports out larger at the manifold past port matching unless you are a pro with a flow bench. The flow increases are around the valve, as previously stated. All this is academic as all the HP in the world won't pull unless the tractor's weight is balanced and the tires are biting in. Max legal weight and drawbar height too. On hard tracks. Spend your coin on a old hard set of Firestone 23 degree tires and spin them in reverse on concrete. This shortens and sharpens the bars. On loose chewed up tracks a set of tires with tall 45 degree bars will cut through the loose stuff and toss it aside so the bars can dig in.

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