Unstyled John Deere A Stroke

I am looking at getting a 7.5 stroke and cam grind for my A. I was wondering what other modifications, if any, will be needed to make it work?

Thanks,

don't cost much more for 9 . you have to change your carb ,valves and everything else anyway so do it once . call Ray at Extreme he'll give free advice .

I have 7.5 x 5 3/4 in unstyled block with flat head , if I could do it again I would go larger stroke and use styled block and head , u will want to do some head ,manifold porting work and of course do some carb work , will need to degree in the cam , 7.5 is an easy install but your better off going a little bigger now , little more $ now will save a lot more later

(quoted from post at 17:54:02 05/02/17) I have 7.5 x 5 3/4 in unstyled block with flat head , if I could do it again I would go larger stroke and use styled block and head , u will want to do some head ,manifold porting work and of course do some carb work , will need to degree in the cam , 7.5 is an easy install but your better off going a little bigger now , little more $ now will save a lot more later

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If I go bigger, what is recommended? If I go any bigger then 7.5 will there be any clearance issues? I planned on buying a styled A head and getting it ported and a valve job. Also, planned on putting a G carb on it. I was also told I may need to modify my pistons, is that true? I have .090 over aluminum pistons.

Saw a late A pull last winter. 175 hp.
Murphy's built the motor. Think would be
cool to put 630 sheet metal on it. Oh it
won the 6mph class at Richmond ky. Sorry
but can't remember what weight. Think was
around 4500

Saw a late A pull last winter. 175 hp.
Murphy's built the motor. Think would be
cool to put 630 sheet metal on it. Oh it
won the 6mph class at Richmond ky. Sorry
but can't remember what weight. Think was
around 4500

If you want big go with what we put in this one. 7" straight bore, 720 cubes with no give up in it. The block and head were designed, cast and machined by Brian and Tim. That was it's first pull at Waterloo this winter. Front end barely touched down the whole length of the track.

Many have "Dummy sparkplugs" in the side and have the actual plugs in front, along the frame rails..

Then you have no need for a huge slot milled into the pistons..

Carb from a late A has the same sized throttle and choke plates as the G carb.

(quoted from post at 05:41:35 05/03/17)

(quoted from post at 17:54:02 05/02/17) I have 7.5 x 5 3/4 in unstyled block with flat head , if I could do it again I would go larger stroke and use styled block and head , u will want to do some head ,manifold porting work and of course do some carb work , will need to degree in the cam , 7.5 is an easy install but your better off going a little bigger now , little more $ now will save a lot more later

Click to expand...

If I go bigger, what is recommended? If I go any bigger then 7.5 will there be any clearance issues? I planned on buying a styled A head and getting it ported and a valve job. Also, planned on putting a G carb on it. I was also told I may need to modify my pistons, is that true? I have .090 over aluminum pistons.

Click to expand...

I was steered away from the 7+" stroke improvement because it is only a moderate improvement in performance. If your plan is to pull 3-1/2 mph from 5000 - 7000, its still probably going to be a 2nd gear tractor, maybe a marginal 3rd gear. I found its hard to compete in 2nd gear because there's no real speed left at the end and the motor dies in 3rd. If the compression is increased with a flat head, then the tractor can pull in 3rd gear. I went with 9" stroke and aftermarket parts, it is quite a bit of work. Windows in the transmission wall, grinding thin under the governor, also on the RH side, and over the starter bump. The oil pressure regulator and canister also need to drop down.

Preliminary measurements looked like an 8" stroke could be used with minimal clearancing, but the std rods would have to be c-bored another 1/4" and the rod bolts shortened a little. May have to clearance the cam as well, you will need another 5/8" to the existing clearance. The positive point is the compression ratio is raised quite a bit since the original piston is down in the bore about 3/4", with an 8" stroke. Its 5/8" closer to the head, but the compression ratio gets too high without machining 1/8" off the top of the piston to get it down around 11:1. Higher than 11:1 and the stock type head gasket starts causing trouble. Compression relief valves are needed with that ratio, it just won't crank over without bleeding off pressure. A stock cyclone head is 180 cc combustion chamber, with 3/16" milled off, it becomes 140.

The tractors I've seen with just the aftermarket flat head and std stroke have enough HP to pull 3 to 3-1/2 mph in 3rd gear and looked to me like the easiest way to gain HP.

By definition those parts are not NATPA legal. The problem is no one enforces the rules. I guess if you can make any parts you want without director approval the other colors can to. Now you just need to design a governor for an A and a G that keeps the rpm's under the limit as they have been over every time I have seen them pull.

So it is ok for a brand new engine that was not ever in an agricultural application to pull with NATPA as long as it is a John Deere?

A Hercules engine was was deemed unfit in a cockshutt this past pulling season but the guy pulling it made the mistake of a actually winning I guess.