i was told my 454 was bord .31 over do the shop so i can use a cast piston??
is it ok.. whats the bore so i can get a set of pistons

 

Welcome aboard thirdgen.org.

Are you sure you got that right? Stock 454 bore is 4.250". A .31" overbore would be 4.560". Not likely, I think, with a factory block.

Perhaps they said bored over to 4.310". That would make more sense. That's a 0.060" overbore, which is pretty common with Mark IV blocks.

You'd better get the cylinders measured so you know what you've got. I'd guess it's 4.310", but this isn't something to guess about.

Usually the pistons are purchased before the final honing of the cylinders to get the skirt-to-cylinder clearance correct. For a mild build, though, you'll probably be okay as long as the job to 4.310" was done correctly.

What type of piston to get isn't determined by the overbore. It's determined by the use the engine will have, cylinder heads, cam, etc. Cast are usually fine, hypereutectic a little better as long as you don't use a power adder (nitrous or supercharger), forged are the best but not really needed for a mild build.

 

i asked for .30 over ok..i was talking about going cast pistons i got it back and he said he bord .31 over so cast piston and expand??
i was going to go cast because its $300 for the set and im not draging it

 

when you say 30 over, you're really saying 0.030" over from stock which would make a 4.250" bore into a 4.280" bore.

As mentioned above, you should always have the pistons before getting the final honing done so they can size the bore to the pistons. Cast pistons expand very little and have a tight piston to bore clearance. Forged pistons expand the most and have a loose bore clearance. Forged pistons are noisy in a cold engine until all the parts warm up.

To properly build an engine, the block should be going back to the machine shop a few times as tolerances and clearances are checked during the built process.

 

Numbers are important. That decimal point needs to be in the right place.

"30 over" is 0.030 inch. Or 0.030". Not .30 inch.

Perhaps he meant he took it to 0.031" over. That would be 4.250" + 0.031" = 4.281". But, like I said earlier, the final hone should be done with the pistons in hand so you can set the skirt to cylinder clearance to the piston manufacturer's specs - that will vary with piston type.

Talk to the machine shop to be very clear about what he was saying - getting it in writing would be even better. Failing that, measure the cylinder bores. If you don't have the equipment to do that, take it somewhere that can do it for you. When you know what you have, order pistons. Cast are fine.

I haven't heard of anyone doing it for a long, long time, but they used to knurl piston skirts to restore the proper skirt to cylinder wall clearance. Hopefully you won't have to resort to that.