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Author Topic:   How loose ya run em?
posted October 28, 2004 10:12 PM
we have to run a 305 standard bore block in our class. I just took an engine apart....tanked it clean... honed it... & most holes are around 3.740 with one hole as big as 3.744.

The standard size bore for a 305 is 3.736.

I don't think the holes at 3.740 are anything to worry about for a low buck race motor... but how about the one at 3.744??

How much clearance can I get away with before its too loose???

[This message has been edited by ruggs66 (edited October 28, 2004).]

posted October 29, 2004 05:58 AM
that's too loose. most cast/hypereutectics need about .0015" clearance and some forged pistons need as much as .005".

rico 08
posted October 29, 2004 08:02 AM
My ohio cast pistons are at .005 right now,specs are minimum .003 to max of .006.Instructions say more than .006 will result in skirts breaking/collapsing.I've seen people knurl the skirts but i don't think i'd do it on a race motor.Another way to do this without trying to find a good standard bore block is to try to find a 262 block,bore it .065 over put in a 305 crank and pistons and you have a stock bore high nickel 305...only downside is these motors were only made a few years and are getting hard to find.