Super A head

Trying to make sure the machinest gets the correct valves, etc for the Super A head. Part number, cast into the top of the head is not listed in the parts manual. The number is 251172R1, cast in Dec 1953 shortly before the introduction of the Super A-1. That doesn't seem to matter as most of the head numbers for the late Super A and the SA-1 are the same. It appears that the part number should be 355046R1 (R number could be higher). It also appears that the valves, springs, guides, and seats are the same for all heads. So--why isn't my head number listed??

CNKS, I don't know the correct answer to that, but I do know that CIH drops many of the old , unused part #s from the parts website.As you know, sometimes the dealers computer parts lists will show old #s not on the CIH website. Did you look for it on the CIH website or go to the dealer?
On my '48 SA, the PO replaced head is 251172R1 and will accomodate the 3 1/8 " stepped up piston.

Lots I don't know about SA tractors but I think the number on your head is for a bare casting and the other number you posted is the same head with parts added.

Yes, but I thought the subheading was for a bare head, although looking at other numbers there is some conflict there too -- thanks.

I looked in my parts manual and the website -- parts manual is much easier to read, and is, I believe the latest version. The block in the late SA and SA-1 and the Super C was a C123/3.125, block number 354898 but the kits that most places sell are 3.25 overbore (without boring the block)-- I assume that the 3.25 piston will work with the 251172 head -- but I am not sure. I would also like to know if the stepped head 3.25 piston will work with that head.

Looked at a IH parts merchandiser catalog for 1956 and it looks like your head used intake valve 57797 D, exhaust 57798 D, guide 356583 R1 and valve spring 24544 DA with plain valve spring retainers and 356842 R1 spring used with valve rotocaps. What is the serial # of your block?

Your numbers agree with my parts book, there is only one listing for all gas heads including the Super A1. Chassis serial is 350942, engine serial 352899, block part # 354898R2, head part # 251172R2. I think eveything will work. I just don't have complete conformation of the bare head #, but I think mine is correct.

CNKS,
yes IH"s head numbering system does lead to a lot of head scratchin To simplify for GAS heads at least from the C/Super A up through the numbered series there are two basic units as far as valve sizes. Your 251172 is the original head which uses smaller diameter and shorter valves (57797D/57798D) than the second head 366299 introduced with the 130/230 series of tractors (which uses valves 366302/366303). The latter head has larger valves as well as a shallower combustion chamber, so it requires valves with a longer stem as well as the larger head.

As I"ve posted before, I still haven"t seen a 355046 head but I believe it also uses the same valves as the 366299 head. IH seemed to drop old part numbers and only list the current replacement part available at the time of that parts book, so they only list the newer head with larger valves as the generic replacement for all the motors even back to the Super A (same with the engine block where they list 366204 (130/230 block) for the earlier tractors as opposed to the 251069/354898 that they came with).

The 3-1/4" pistons will fit fine with either head, it"s actually less of an issue than with the 3-1/8 pistons as the 3-1/4" (at least all that I"ve ever seen) have about 1/10" lower compression height and the stepped head is nothing to write home about compared to the typical domes we see on the 3-1/8" after market pistons. The extra 10 cubic inches is nice, but expect a little lower overall compression. I guess the lower compression height must have been standardized for compatibility with the C135 with longer stroke?
Stan(VA).

Thank you. You answered my question, except are you saying that the 3 1/8 piston may give more HP than the 3.25 because of higher compression or ?. Seems that the kits I have looked at all have the 3.25 overbore for the 354898 block. Also do you mean the stepped head 3.25 pistons are ok for the 251172 head, or am I safer with the flat head piston?

Good question, my "dyno" arrangement is not detailed enough to make that call. I use a PTO generator and load bank to vary the loading to help tune a motor, but I wouldn't try to pick a qualitative number based on it.

I don't know if the compression decrease would nullify a 10 cubic inch increase in displacement? My gut feeling is you are still ahead with the extra displacement, just not as much as could be if they sold a higher compression 3-1/4" piston.

Basic point was if you're accustomed to seeing the dome on the aftermarket 3-1/8" pistons, don't be surprised/disapointed by the 3-1/4" step head pistons.

The aftermarket only seems to have two options (in stepped head designs) for the two blocks, 3-1/8 for 251069/366204 or 3-1/4 for 354898, so I would go with the stepped head 3-1/4 pistons, (vs flat) you want all the compression you can get. I've used those pistons with both heads and no clearance issues (even with an experimental stroker where the piston protruded above the deck, the area of the step was not an issue).
Stan(VA).

Ok, thanks, I will go with the 3.25 stepped pistons. Engine is at the machinest at the moment, have not ordered anything as yet.