JD a head cutting

[Ole Johnny]

Im trying to justify milling the original 1945 JD model A head by 200/000. Has anyone done just this without carb change? I want to know if it produces much more power by milling it...
Im weighing cost compared to hp gains.

 

[BushogPapa]

Not the best idea...

Much better to go ahead and install Higher Compression Pistons..
Go for no more than 7:1 Compression and you can still farm some with it..More and you will be forced to use premium Gas (or better)...
You have a Fast 1st gear..I think equal to 2nd gear in a 6 speed "A"..
With the compression increase, you just might be able to spin-out in 1st, instead of run out of power..
Many pullers are running 12:1 or higher..

.200" will get you in trouble with your push-rods being too long, too ( or possible will)..

Ron..

 

[Ole Johnny]

I am installing the M&W style pistons at 125 over also but wondered if cutting the head would give any more power. If it doesnt make but about 2 or 3 hp more to cut the head, it is borderline to spend the extra money to cut it. The machine shop told me that he could cut and weld the pushrods for me and this would add to the cost of the head machning.
How much would 150/000 raise compression and how much hp could i expect from the head planing.

 

[kendak]

I got a 47 "A" with HC pistons & late gas head cut down to the eyebrows [about .200] & raised the CR about .75 of a point...very not worth the trouble....pushrods can be shortened without cutting just turn off the same amount on the end they are solid for about 1" from each end

 

[cowboycorey]

weld the chambers. It's easy power. You can shape it the way you want.

 

[BushogPapa]

For the small amount you would gain, you'd be ahead to Clean up the Ports, Match them to the manifold AND get a TRUE High-Performance (Multi Angle Seat AND Valve angles, Polished)..

A New Cam with an improved Profile would be good move..

There is no real "Over-Lap" at TDC with the Original cam.
Even a JD "B" cam has better valve events than an "A"..!!

Ron.

 

[Anonymous-0]

(quoted from post at 16:05:42 05/26/12) I got a 47 "A" with HC pistons & late gas head cut down to the eyebrows [about .200] & raised the CR about .75 of a point...very not worth the trouble....pushrods can be shortened without cutting just turn off the same amount on the end they are solid for about 1" from each end

ello stranger. How you been?

 

[Anonymous-0]

Compresion isnt the answer to horse power. Your better off porting the head and puting a cam in it. Thats what we have had the best luck with, other than stroking it.

 

[jd b puller]

If you"re going to farm with it, leave it alone. If you want to pull it, get the compression up around 10-11:1.

Cutting the head won"t make a hill of beans difference if you"re starting at 6:1 compression and that"s all you"re doing. If you"re already at 9:1, 0.100" goes a long way.

 

[Ole Johnny]

where does one get a cam like you are speaking of? I regularly buy cams from Comp Cams and such but I dont know a source for a JD cam. Also, since I have the jugs off and rods oout, how much more woudl i need to disassemble to get the cam out?? Looks quite involved...

 

[Ole Johnny]

Thank you very much,,,,,,,, I listen to all you guys and I appreciate your help. I think I will take your advise and NOT cut the head and I am pretty good at porting and matching so that is the direction i will go. I may not replace the camshaft even though im sureit would help but i work on this thingin the drivewar in the rocks and im not a s young as i use to be. Going from about 27 hp to my (hopefully) 40 hp shoudl make me happy for a while. I do hope the pistons and port work and rocker ratio change should get me to 40 dont ya think??

 

[jd b puller]

If you don't want to pull the crank, you don't want to pull the cam either.

 

[Ole Johnny]

wouldt you think that i should be close to the 40hp mark with the m&w 125 over pistons, port matched manifold and head, machning of the eyebrow to unshroud the intake valves, changing the rocker arm ratio and port work in the manifold and head pockets to straighten the runners?????

 

[BushogPapa]

I would have you ask "Ray" at "Extreme"..

He would steer you right...and give you Event Numbers that would be good..

Ron..