std on piston crown

I would say no. All it is telling you is the piston/bore are standard (STD) size - not been bored over size.
Even if it said .30 still could have been from the factory if they found at STD size it was too big for that piston.

You sometimes see this with crank main & rods same deal turn it under size and use it.
Dave ----

I'd tend to think that it has been rebuilt and those are replacement pistons. I haven't seen a stock piston marked with STD on top. AMC did, however, use more than one source for pistons, and it could be a factory installed piston. I haven't seen everything!

Have that head magnafluxed while at the shop. 196 OHVs are notorious for cracks after running hot. This is due to not keeping the head bolts torqued and having been overheated multiple times over the last 50+ years. Call it a design flaw if you want to, but the 196 has to have the head bolts retorqued every 10-12K miles/2-3 years. The massive head expands/contracts enough to eventually loosen the bolts over time. The design of the head is the reason, partially due to the fact that the engine was converted from an L-head design, so some compromises had to be made to keep as much of the L-head tooling and parts as possible (to reduce cost). Not much point in spending a lot of money on a cracked head, though good ones are hard to find now. These never came with removable valve seats, so yours has had work before.

If the piston says STD, more than likely was replacement pistons. Factory wont say STD, They say nothing.

Farna. While I wasn't there during 196 OHV and Flathead production I can personally gaurantee that all AMC pistons were machined inhouse. The pistons came in rough turned from the die caster (TRW iirc). The needed to beroughturned to be loaded into the coil feeders. 1st operation was turning operation on Six Spindle Baird Automatic Lathes to finish turn head diameter, semi finish skirts and cut the ring and oil control grooves. Theythen went to machining lines to rough, semi-finish and diamond bore the pin bore. Also done were smoke holes or slots. Last operation was to machine the skirt drop off. This was done with spindles mounted at an angle to the motion of the vertical slide they were on. The cutters were o the inside of heir carriers and opened and clised hydraulically. The piston was held stationary the slide lowered. The cutter brought in and the slide fed up. Drop off around .005 per side. Later the 4.0 pistons were done with the smoe holes and pinbore done on two Tri-Way transfer lines with the piston head, grooves and skirts being machined in Giddings and Lewis Vertical Lathes at about 3500 rpm. The skirt profile was actually controlled by an amplifier the moved the tool in and out in relationship to the spindle at full speed. KEP maintence personell were not allowed to touch these beyond installation and alignment. When I started some of the older piston equipment was still around including the eccentric grinders that had beenused for theskirts on cast iron pistons. The first machining line I mentioned were LaSalle's and ExCellos. If you want to know more about production processes and/or humerous screw ups that happened (like the guy that ordered a Spirit AMX and got a 360 slipped into the production que. Hand built with an exactly weight matched set of rods, pistons to exact weight. The cam I think was an aftermarket one. Along with aftermarket lifters. Plus the heads had work done on them. When the engine hit the line tobeinstalled the line stopped as the exhaust system did not line up due to differences in the 304 and 360 exhaust manifolds. The only reson he didn't getcanned was hehad an uncle in management over in Detroit.

Kanter's in New Jersey has them and those pistons are not forged. The are cast aluminum. Joe