390 Pistons?
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390 Pistons?
I have heard alot of talk about using 390 or 360 pistons. I just sent my block to the machine shop, the motor was rebuilt before I got it and it is already bored .040 over. I want to have around 9.1-9.5 comp ratio, I am zero decking the block and milling the head also. I am just curious if I should just stay with the .040 and get half dish pistons or just go .050 and use the 390 pistons, also what else has to be done to use these pistons. sorry to ramble on there
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I have heard over on fordsix.com that using 352 pistons is the best dollar for dollar upgrade for bumping compression. Same stock bore, same wrist pin, they are flat top, and the compression height is only like 70 thousands or so taller so you can just mill the piston crowns to zero deck. You should have the shop measure bore taper and thrust surface wear to be sure you can keep the 40 thousandths overbore already there. Though maybe just a small bore cleanup (bump it up to 50 thousandths) and having 352 pistons machined for a zero deck would be the most economy-for-results way to go.
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The Clifford build is what you are doing by taking that much off the block and head. Clifford uses a dish pistons and gets close to 10:1. Others get to the same place by using the 390 piston. It seems you would be getting more by using both, but I would speak to a hp shop, and either go online to calculate the c.r., or have the machinist/shop calculate it for you. You need to eliminate the guess work.
GUYS WHO ARE READING THIS: can you post a link to a site where he can calculate c.r.?
GUYS WHO ARE READING THIS: can you post a link to a site where he can calculate c.r.?
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From: Spokane, WA
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I don't have a problem useing the stock dished pistons if that will get me to around 9.5cr. The pistons are like new and the bores are good probably doesn't event have to be honed. I just don't want to leave those pistons ,deck the block etc, and still have low cr?
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Cranky Old Guy
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From: Raphine, Virginia
United Engine & Machine Co. Incorporated This is the Keith Black site and you can check on pistons at the same time.
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