Super A Pistons

[Sterff89]

Im working on my Grandfather's 51 Super A, and was wondering if these are factory original pistons, or would they have been changed at some point? I've never seen any like this with the step, and the part numbers don't seem to lead me anywhere. I know its been apart before, it has 115 + psi of compression, just took it apart for a headgasket leak, and to go through the head. My Grandfather sold this in 2000 and I recently bought it back. Trying to figure out what the last guy did. I believe he just did rings and hone the cylinders, not sure. There is a nice crosshatch on the cylinder walls.

 

[Janicholson]

The originals were flat head, no raised area, unless high altitude pistons were ordered new, then they were not simple raised surface "dome" If you measure the bore you are likely to find it is 123Cid size. Jim

 

[Sterff89]

I went out and measured and its right on 3.000. The pistons all have IH 351524R1 on them and the sleeves say 6075D. The other odd thing is cylinders 1,2,3 all have a "C" stamped on the piston/sleeve, and #4 has a "B".

 

[Jim Becker]

Those are 5,000 foot high altitude gasoline pistons. They were commonly used as replacements to up the compression ratio and get a little more power.

The stamped letters are size markings from when the sleeves/pistons were matched up at the factory. Nothing odd about it unless you find something like an "A" piston in a "D" sleeve.

 

[Sterff89]

Interesting. I thought the pistons looked unusual.

 

[Sterff89]

Alright maybe you guys can help me with my next question. The other problem I was having other than the headgasket leak was with fouling plugs. Ever since I changed carburetors this thing eats spark plugs and I know it is running rich (black smoke). I usually run Autolite 3116, this time tried D21s (I had one 3116 in last time to try and get it home after the one fouled). The original Carter UT 0-653 was too damaged to go again so I bought a new Zenith two years ago or so. I took it apart yesterday and found that it has a #21 jet in it. In my service manual it says that it should be a #18. Is that part of my problem?

 

[Janicholson]

Yes that would make it very rich Does the original carb jet fit? Jim

 

[Sterff89]

I feel kind of dumb about never checking the jet but, thats the way you learn. I looked in both of my spare parts Zeniths and they both have #21 jets. I did find my old Zenith catalog and it says I need a C52-6 18 jet. I found one at McDonald carb for $12 so I guess I'll order one. I dropped off the head at the machine shop today so it's no hurry at this point.

 

[Janicholson]

If you use Ethanol added fuels you might need a 20 or 21 jet. Also check the float level a high float will allow rich mixtures. Jim

 

[Sterff89]

I use non ethanol 90 octane in all my Farmalls which probably doesn’t help on the running rich either. I just don’t like to let them sit with ethanol fuel in the ones I don’t run a lot. I’ll check the float once i remove the carb. I might just order two different jets to have options. Thanks!