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JD70 Pistons

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ToddF

03-25-2002 15:00:54




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What should I expect to pay for a set of pistons for a JD70 that are .250" over as compared to a standard .125" over? How about if the over bored block is included? Thanks in advance --- ToddF




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70puller

03-30-2002 07:27:14




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 Re: JD70 Pistons in reply to ToddF, 03-25-2002 15:00:54  
bore your 70 to 6.125 and stroke it to 9-9.5in this advice comes from someone who wasted alot of money just boreing it also get a set of LP manifolds.



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G Taylor

03-30-2002 08:33:18




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 Re: Re: JD70 Pistons in reply to 70puller, 03-30-2002 07:27:14  
What is the cylinder casting wall thickness after boring the 70 gas out to 6-1/8th? Did Deere use the "G" molds & make the walls extra thick? What is the length from crankcase to the sparkplug on both the G & 70 gas? Thinking of trying to get as much rod length or room for the stroke as possible. I haven't set a G & 70 gas block beside each other but how far off are the bolt holes for bolting the G cylinder block into a 70 gas?

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G-MAN

03-27-2002 17:38:40




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 Re: JD70 Pistons in reply to ToddF, 03-25-2002 15:00:54  
Why not just sell the 70 and buy a G? Wouldn't that give you the displacement you want and be a lighter tractor to boot? I'm just asking here, I don't have my book with me to tell me the weight of a 70. I'm just assuming that a 70 would weigh more than a G, especially if it has power-steering, custom power-trol, etc.



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G Taylor

03-27-2002 19:54:35




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 Re: Re: JD70 Pistons in reply to G-MAN, 03-27-2002 17:38:40  
Depending on who zeroed the scales, our 70 gas rollo-matic row crop just makes it into the 6500 lb class. Has fenders but no power steering. I havn't held a "G" cylinder block up between the 70 gas crankcase & head but it shouldn't be impossible to tinker it all together. Longer push rods & some drilling & tapping. Another 1/4" or more bore & a modest stroker crank should make HP. There has to be lots more power to be gained in the restrictive intake/exhaust flow however.

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Ron

03-26-2002 12:43:12




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 Re: JD70 Pistons in reply to ToddF, 03-25-2002 15:00:54  
Would a Diesel block fit, and be set up for Gas..?? They are 6 1/8" Bore...



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Ron

03-26-2002 12:39:51




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 Re: JD70 Pistons in reply to ToddF, 03-25-2002 15:00:54  
JD made Gas and All-Fuel 70's, with the seriel #'s inter-spersed....I would (am) surprised to hear that the bolt paterns are different....???!! Doesent sound like something JD would have done.. I know that my Cousin's 70 had a 6 1/8" bore....That is a 5/8" overbore.....Don't think it was an "All-Fuel" to start with....AND...at 2,000 RPM+, it would really Pull..!!!!!



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BJ

03-26-2002 11:59:18




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 Re: JD70 Pistons in reply to ToddF, 03-25-2002 15:00:54  
Another thing you can do also is to get a set of first reduction gears for a 70 diesel they will give you some reduction in ground speed as the diesel runs at 1115 rpm (I think) compared to 975 rpm for the gas burner I done this to one a few years ago if you try this you will also have to leave the oil slinger gear in the cover off as the larger drive gear will not line up I compensated for not having the slinger by overfilling the trans. and did not have any problems

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ToddF

03-25-2002 21:36:37




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 Re: JD70 Pistons in reply to ToddF, 03-25-2002 15:00:54  
I should have been more specific. I have a 70 gas. I have a spare crank that I've been considering having stroked. Then I found this block and pistons and wonder about the combination. The pistons are for a stock stroke crank though, and I'm not sure if they will work with a stroked crank or not. I'm looking for advice if anybody has any. Around here we pull either paced or non-paced 6500 and 7500# classes. I've only pulled the paced classes and managed to get it hooked tight enough that she doesn't have the power to spin the tires (14.9 x 38). Maybe I don't need to bore and stroke, one or the other may provide enough power? If anybody has experience I'd love to here your opinion on what might be required. Thanks---ToddF

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Todd

03-26-2002 14:18:02




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 Re: Re: JD70 Pistons in reply to ToddF, 03-25-2002 21:36:37  
Like I said the Gas and all-fuel blocks have different patterns bolting for the crankcase, and the head. The all-fuel head will actually bolt on the G's, and the bore is the same (6 1/8") The bore on the gas model was downsized in order to produce a true gas burner from the factory for the 70 - G size. By downsizing the bore the tractor would use much less higher cost fuel compared to the bigger 6 1/8" which in the all-fuel state burned much more fuel, but the fuel was cheaper. The block could be punched out on the gas but still would not work due to the wrist pin location. The wrist pin location on the 70 gas piston was set up for the shorter gas block. The G - all fuel 70 piston would actually come out somewhere in the neighborhood of a 1/2" past the end of the block. If you had the two blocks side by side you would see the difference. if you use factory pistons with a stroker, depending on how much stroke you add, your piston may have to be milled off, or use a shorter aftermarket piston, or shorten the rods, or a little of all three. Been down this road with my 70, so I traded it for a G. The all fuel 70 is hard to come by in comparison with a G or 70 Gas.

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Ron

03-25-2002 16:34:13




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 Re: JD70 Pistons in reply to ToddF, 03-25-2002 15:00:54  
Why not just get an "All-Fuel" Block...it has Larger Bores to start with....6 1/8"...then put Gas pistons in it... it will have the same Cu. in. of a "G"..!!!



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Todd

03-25-2002 20:52:36




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 Re: Re: JD70 Pistons in reply to Ron, 03-25-2002 16:34:13  
If the tractor is a 70 Gas, the all-fuel block will not bolt up. As a matter of fact, I don't think the head will work either. The all-fuel 70 has many of the same patterns as a G (rods, pistons head pattern, but a 70 gas is a completely different animal



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Mike F.

03-25-2002 18:36:38




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 Re: Re: JD70 Pistons in reply to Ron, 03-25-2002 16:34:13  
That is true about an all fuel block. I don't suppose that is too cheap anymore as it used to be. Expect to pay alot for a big bore block and pistons, then rings too. I would say ballpark is 800 to 1000 bucks. all ready to use. If not more.



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