Hey all I have a BBC 427 that is standard bore and I'm looking for pistons that are .005 over standard bore so that would be 4.255 pistons. Does anyone know who can or does make some? These would be for closed chambers and 10:1 or just under. Thanks for the help.
Kb Pistons size there std bore stuff .005 over normally measured std. Most Pistons today from cnc finishing are very good on sizing,they have the clearance machined into the piston so you would fit it to the advertised bore size. A piston for a 4.0300 bore will measure 4.0270. To allow for the .0030 Clarence needed. All kb stuff and most follow suit except the kb std stuff where they know the machinist will have enough to straighten the cylinder out and fall within the needed size. I use their forged line quite often,the hypereutectic stuff I stay away from. A lot of machinists have good things to say about them,I do not. In general a forged piston is very forgiving,hyper,not so much.
mostly we just punch a worn block to .030" and don't worry about it. It's kind of challenging to hone .005" of taper out of a bore, and end up with a straight bore
When I went to buy the pistons for my 427 I was told by the piston maker to bore it out 30 over because could sell pistons much cheaper than standard bore pistons and if you hurt one piston he could sell you one piston. If you hurt a standard bore piston you have to buy a whole set.
In my experience, most Sixties era std bore bbc's with typical mileage on them will have too much taper to go .005, even if God himself is running the hone. .005-.008 taper would be considered between average and better than average.
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