super c c123 step head pistons

I have new overhaul kit in hand for my super c, Crank as been machined etc. I have know been informed by the machine shop that the milled .50 off of the head. Is there still enough room to accomidate my step head pistons now ?

.50 or .050?

I would assume he meant .05, because he'll need all the help he can get if they shaved a half-inch off the head. I don't think the step-head pistons would be the largest concern at that point.

To the OP, did you ask them to take that much off? I wouldn't think it would need to be taken down that far to get rid of any damage...5 or 10 thou would seem enough in my mind, but then, I haven't been around this old iron that long.

AR

No Problem! It should get ya around 29 hp

You may want to hand crank the engine over a few times after installing the head and rocker arms to make sure everything has enough clearance. Hal

Please forgive my worrisome nature, but a half-inch sounds like an awful lot to take off to true up a head.

.005 is a shave, .050 is a haircut, .50 is pretty close to a beheading. Did they mill the top of the crankcase, too? If so you need to add the two numbers together to figure how much clearance you've lost between the tops of the pistons and the head and valves.

Double check your numbers with the shop.

.005 you needn't worry about the step heads
.050 it couldn't hurt to check the fit cranking by hand as Hal suggested.

.50, you REALLY need to check. If the pistons you have in hand don't clear, a Fire Crater (more of a high spot or bump on one side than a step) or just a flat-top piston will probably do the trick. If that's the route you wind up having to take, you'll still get a decent step up in compression, just by having so much volume taken off the head.

I remember seeing threads in the past about a way to check that clearance using a dry fit with someting soft on the top of the piston. I'll give a look in the archives and see if I can find it -- if so I'll post back with a link to it.

You can also do some hand measuring in advance. The accuracy of your results will vary according to what you have for tools to measure with. You can measure the height that the step rises above the edge of the piston, and reduce that by 2/3 of the depth of your new head gasket (to allow for the gasket being crushed down by a generous 1/3 from its original thickness). That's how far your piston will protrude into the cavity in the head. Compare that result with the depth from the underside of the head to the surface of the valves. Maybe someone can chime in with what the minimum clearance there should be, to give you an idea of whether to go ahead and try to use the pistons you have, or to return them for something not as tall.

If it is .050 there shouldn't be any problem. If there is ever a doubt, just set the head on the assembled enging without a head gasket and turn engine over by hand. You will be able to feel the head "lift" if the piston hits, the head gasket will insure extra clearance.

Thanks for all your posts, I left out a zero in the first post , 5 thousandths was removed from the cylinder head.