new ap 46 piston made

Do those need 170 cut off the tops still

Im interested in a set of these if they are available. And will come back to see if they do need milling or not for a d17

yes sir steve  i still thank you i am keeping it on file in case you need it agian

When I used SP-46 pistons I had to remove .170" from the outer top lip because the piston would hit the cylinder head !!!   I had 240 psi of cranking compression and always felt it was around 11 to 1 ratio.    110 octane fuel was easily good enough along with retarded ignition timing of 20 to 22 degrees BTDC at full throttle.

Edited by DrAllis - 10 Jul 2024 at 8:48am

Sure. They have to be told exactly what you want and they will make it like that.

I would have preferred the top ring height match the old pistons location to keep the compression exactly the same. I know it will be a very slight difference.

I've never used flat tops because I always felt Power Crater was better. When I had Ross make me custom pistons I was able to spec the bowl diameters (top and bottom) and bowl depth (cc's) and compression distance (pin to piston top) to exactly what I wanted. So, why not go with the Power Crater design ?? I also have never had the time or money (maybe the other way around) to build an engine with 8.25 to 1 compression flat tops and then tear it apart and install 8.25 to 1 Power Craters from a 175 tractor. I would assume all things being equal (4 inch bore and same compression, same cam, head and carburetor) the Power Craters would show some slight advantage. I would also be willing to bet if the flat tops were at 9.0 to 1 instead of 8.25 to 1, that might be the winner in making the most HP. We will never know.   My pulling engine is 4 5/8" plus bore and cranking compression tests at 300 psi with Ross custom made Power Crater pistons.

Edited by DrAllis - 12 Jul 2024 at 2:57pm

I've always said that using an SP-46 M&W piston that .170" had to be removed from the top of the piston. This was not a way to get the compression where I wanted it. It was necessary to keep the piston from smacking the head !!! The cranking compression will be approximately 240 psi when doing this. Remember, the connecting rods have their limits !! My pulling engine uses stronger rods than the ones you will use, so I can tolerate 300 psi of cranking compression.

The sample piston was used in a WC/WD with a 4 inch stroke crank. Not a 4 1/2" stroke crank.

I have an original WD 45 Crank Shaft in good shape I would sell. $300 plus shipping.

They are, basically, a clone of the M&W pistons that have been used for years.

It's been 40 years ago, but i thought mine ran 240 psi cranking compression, maybe 250 psi. I used D-17 conn rods. D-17 and newer rods are a little more stout than an old WC/WD rod. Always used 110 octane fuel or better. Timing was around that 18 to 20 degree BTDC.  Did you install new valves?? that were bigger diameter than stock valves ?? That could raise the compression a little. I wouldn't know how much to tell you to remove. It's only the outer edge, not the whole piston top.

i welded up my carb flange and milled new holes in for my d19 carb  still waiting on my crank and head