John Deere A pistons

[Bill Marcusky]

I recently purchased a set of M&W style high compression .125 over pistons for my 1951 JD A. they were part number A7051 on oldjd4u.com. Can anyone tell me what these will raise my compression ratio to. Without decking the head or anything else like that? Also with this set up what carb work if any would be necessary to make a decent farmstock puller? Thanks for your help in advance

 

[Mike N Mo]

Those pistons should put the compression ratio around 6.25-6.5:1. As far as carb work, have the venturi bored from 1.125" out to 1.3125-1.375" and it'll gain you a few hp. You can also add a set of roller rockers from Murphy's. I've found the gain on a stock engine is about 4 hp

Mike

 

[BushogPapa]

A new Camshaft with improved valve timing would be a very good idea, while you have it apart..

Ron.

 

[Anonymous-0]

Bolt on a late #71 Carb. or a #51 (big nut) "G" Carb. You should have around 49 to 52 hp. Like the other fellows say change the cam, Jeff's Rockers and a good hot coil and a cold manifold it should give you a little more. Don't get crazy on the cam profile.
Find a dyno. A dyno will be your best friend to tune it in and gain that extra 2 to 5 more hp.

 

[Bill Marcusky]

my tractor has a DLTX 71 carb already and it has a magneto with band new points and condenser. and what is a cold manifold? Also with my compression up this high am I still able to run 93 octane pump gas ? please bear with me I'm still new to the performance JD arena. i've been pulling bone stock for a couple years and I'm tired of getting beat by just 20 or 30 feet by slightly modified tractors. I still want to be able to pass for farm with out getting my rear end kicked.

 

[Bill Marcusky]

is carb work a necessity? i'm trying to work on a budget here. Before my wife scalps me haha

 

[Bill Marcusky]

also any recommendations on what spark plugs to run ? this question might start an all out war lol

 

[Josh Blackburn]

1.3 on carb will only make top end power. If your going to run 1400 plus rpm than that would be fine. Cheapest hp Gains will be cam, head work, rockers and compression. Lengthen Rods out and have fun pulling. 56-58 @ 540 pto hp is achievable with that set up

 

[Bill Marcusky]

Not into lengthening the rods just want to maybe deck the head a little bit and stay at stock rpm and run on 93 octane. I'm thinking decking the head and putting in the bigger pistons will get me around 7.5 to 1 compression and keep me on pump gas

 

[Big Jugs]

Autolite 3116. Absolutely no Champions...just send me your money instead! LOL.

 

[Big Jugs]

If you're getting beat by 20-30 feet, don't expect what you're doing to get a whole lot closer....you will find that last 10 feet is $$$$$$$$.

 

[Bill Marcusky]

Good to hear autolites is all I run

 

[Bill Marcusky]

My biggest issue is not having enough power to run in 2nd and lugging it down too far and if I run 1st I don't have any momentum. I'm hoping this set up will give me the power to run in 2nd. That and I'm swapping cast rear wheels for pressed ones and taking off every extra part my rules allow. Rules say it must be field ready including pto and rock shaft but nobody knows if they're gutted or not lol

 

[buickanddeere]

Wish you would have posted here before purchasing those low compression pistons.
A set of LP pistons for a 60 would have been much better. The LP's are 7.3 to 1.
As for oversize. Those cylinder blocks are getting harder to find without cracks. It's barely possible to find the HP difference between .045 and .125 over with a dynometer. Save the block wall metal and only go .045 over from stock.

 

[Anonymous-0]

You have found the crossroads of tractor pulling. Should I leave it so I can farm with it or make it into a puller to bet the guys that have beaten me. It’s really hard to have both worlds unless you’re pulling against for real stock farm tractors. The set up you have now is fine for both. But if you want more comp., stroke and bigger pistons you now have just a pulling tractor.
I apologize on these numbers for manifolds it’s been awhile that I have messed with them. I’m sure someone will point you in the right direction on here.
An All-Fuel manifold would be an older style for cruder fuels so the manifold runs hotter like an A36R or A2383R manifold. A cold manifold works a lot better for better quality fuel as in gas. With the intake runner being more separate to the manifold. Later John Deere gas manifolds like A3386R-R0315 or A4039R-AA4543R Serial numbers after 488.000 and up. After market manifolds work well like Johnson or Heisler are names you might have come up in conversation.
Myself I’d bore the block out to 5 ¾ airplane or early JD GP, or JD R or 5 7/8 JD 70 gas and run some long rods. Try to find a Heisler head. But again your only limit in tractor pulling is your imagination, rules and the old mighty dollar.

 

[Mike N Mo]

You don't have to do carb work, but it'll make HP if you do. Josh says it won't lug if you open the carb up, probably so if you want the engine to have peak torque at 700 RPM. My approach is to give the engine the ability to hold higher RPM so it doesn't HAVE to lug down. To each their own.

Mike

 

[Bill Marcusky]

I'm not lugging because of rpm it's because I just flat run out of power starting at full throttle even with a governor string it just slowly dies out to the point that I have to pop the clutch out to keep from stalling. Just need the little bit more power to keep it running. Tired of running out of power before I slip a tire.

 

[Anonymous-0]

Why fart around trying to find old wore out org. pistons when they make shiney new ones every day. Im sure "back in the day" lp parts where a cheap up grade, but even if you found a good set (im sure there out there) rings are pricey. New alum pistons are lighter and come w/new rings any ways. Give Josh a call, talk to some one who builds John Deere's for a liveing.

 

[forty40]

6.625" dia piston, 6.75" stroke, 184 cc stock JD A comb chambers, flat top pistons, .75" piston-deck, 5.75" dia gasket w/.060 compressed hgt gives a 6.34:1 compression ratio. I was advised to keep the comp ratio at 7.45:1 or less in order to use 91 octane pump gas, however, "Mr Know-it-All" here put it together at 8:1 and it clearly knocks on 91 octane gas. VP Late Model Plus cured the detonation, but at $11/gal is a little pricey to mow a horse pasture.

 

[buickanddeere]

The A and 60 head slack a squish and quench to limit detonation.
There must be 94 octane pump gas in your area? Around here 100LL is $1.99 a liter.
Was the cam and followers reground to match the compression ratio? Cam duration and mechanical compression have to work hand in hand.
Is it running lean? Mag or distributer with a working mechanical advance ?

 

[forty40]

(quoted from post at 18:06:20 12/22/13) The A and 60 head slack a squish and quench to limit detonation.
There must be 94 octane pump gas in your area? Around here 100LL is $1.99 a liter.
Was the cam and followers reground to match the compression ratio? Cam duration and mechanical compression have to work hand in hand.
Is it running lean? Mag or distributer with a working mechanical advance ?

In my particular case, all the considerations for higher compression ratio were not adequately taken into account, specifically the fact that an open chamber JD A basically has no quench and the spark plug is located as poorly as it possibly could be for increased compression ratio. I wrote my error to prevent some other poor soul from making a similar mistake if they wanted to use the tractor for something other than pulling. The cam was reground, carburetor tuned, ignition timing checked at both idle 0 deg and max rpm for a 25 deg total advance. I haven't tried any other fuel than what we use in late model type racing engines and the old JD may well run on something less, but that's what was in the fuel storage shed.
My experience is with the Carrillo, CP assembly on the right, not the coffee can on the left. Bills 19 Mia 0, time for Bears & Eagles.

 

[BushogPapa]

I see, you have the Fast 1st gear..!!

The Late Styled has a "Creeper" 1st gear that will pull Stumps, Stock..

Maybe you can change the 1st reduction gearing..??

 

[Bill Marcusky]

Mike and Mo , I think I'm gonna have carb work done the way you suggested. With my new pistons and carb work running stock rpms how much power can I expect to make? Also do you know how much I can deck my head and still keep compression low enough to run 93 octane gas?

 

[Bill Marcusky]

do you mean 5.625 piston dia ?

 

[buickanddeere]

.

Sounds like you have the bases covered.
Some folk like to mill those intake eyebrows down flush with the top of the exhaust valve seats.

 

[forty40]

(quoted from post at 20:55:30 12/22/13) do you mean 5.625 piston dia ?

5.625 is correct and is the number I plugged into my comp ratio spreadsheet. 6.625 was a typo. This forum does not permit document attachment or I would attach it, then you could plug in any combination of numbers to check for a final result. The stock 1951 JDA head I checked (burret w/alcohol and plexiglass cover plate) was 185 cc cmb chmbr volume and after blending back the eyebrows and milling off .188 thickness, it checked 144. With a power block bored to 6.125 dia, 144 cc and the piston height at .600 it came out to 8:1. I usually go overboad and then have to back off, in this instance, didn't take the time to consider the big differences in comb chmr and piston configuration. Also, concur with Mike n Mo for HP in performance applications , figure out how to make the power and keep the rpms up.