To mill, or not to mill?
Thread Starter
Member
Joined: Nov 2002
Posts: 88
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From: Lowell
Aj, once again, thanks. But, this tensil strenght on forged piston heads, I dont understand it. Tensil strenghth is the strength it takes to pull something apart. Wouldn't compression strength be a more effective validation. What am I missing?
Anyway...I am debating wether or not to remove my car from the road and make it strictly auto-cross. I would like to crack the block and uprade the guts as well as compression. Why can't perfect timing be re-acquired after milling, isn't TDC TDC, does this mean to acheive perfect timing you would have to machine custom cam gears to make up for the gap distance between p/head and valve. Would the same apply to a thinner HG.
Forged pistons sound good, would you recomend a set? Pistons and connecting rods....should they be bought together?
Finnaly.....I live in Massachusetts, we are not known for our women, weather or race tracks. Anyone who reads this that is in the New England area, w/i 100 miles of Lowell MA, please recomend a decent race shop, we have a bunch of hacks in Lowell.
thanks DEV
Anyway...I am debating wether or not to remove my car from the road and make it strictly auto-cross. I would like to crack the block and uprade the guts as well as compression. Why can't perfect timing be re-acquired after milling, isn't TDC TDC, does this mean to acheive perfect timing you would have to machine custom cam gears to make up for the gap distance between p/head and valve. Would the same apply to a thinner HG.
Forged pistons sound good, would you recomend a set? Pistons and connecting rods....should they be bought together?
Finnaly.....I live in Massachusetts, we are not known for our women, weather or race tracks. Anyone who reads this that is in the New England area, w/i 100 miles of Lowell MA, please recomend a decent race shop, we have a bunch of hacks in Lowell.
thanks DEV
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Joined: Sep 2002
Posts: 794
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Tensile strength has a lot to do with piston skerts cracking, and rods bending, the point I was trying to make, is that any forged either piston or rod will take a substancial amount more abuse then stock.
TDC is TDC, but, I'm not reffering to cam timing, I was reffering to ignition timing, ussualy the timing needs to be retarted up to 2.5 degrees, depending on how much you mill it, which is partly the case with higher compression pistons, in the case of milling though, you really have no good estimate as to how much your compression went up, so it's hard to gauge the thin line between a lot of timing, and detonation, funny that you mention cam timing, because you really need to be careful of that too, because with milling, unlike higher domed pistons, you move the whole combustion chamber closer, rather then just a small section of the pistons, which ordinarily have valve reliefs cut any way.
With pistons, most manufacturers have gone through the trouble of already figuring out what you're compression should be, all else constant, in addition have taken into account proper valve clearance amongst many other variables, that you probably would even think about. If you read head gasket labels such as Spoon and Mugen, they say: "about", or "as much as". In otherwords it's more of a vague estimate and although probably very close, not perfectly accurate.
Forged pistons and rods are really nice, and I would recomend a set if you have the money to blow, although, they really aren't necesary for a daily driver, or even for most all motor street cars that are really pushing it. A set of factory CTR pistons ussualy would do the trick for less than half the price of a nice set of after market forged pistons.
Later,
Aj
TDC is TDC, but, I'm not reffering to cam timing, I was reffering to ignition timing, ussualy the timing needs to be retarted up to 2.5 degrees, depending on how much you mill it, which is partly the case with higher compression pistons, in the case of milling though, you really have no good estimate as to how much your compression went up, so it's hard to gauge the thin line between a lot of timing, and detonation, funny that you mention cam timing, because you really need to be careful of that too, because with milling, unlike higher domed pistons, you move the whole combustion chamber closer, rather then just a small section of the pistons, which ordinarily have valve reliefs cut any way.
With pistons, most manufacturers have gone through the trouble of already figuring out what you're compression should be, all else constant, in addition have taken into account proper valve clearance amongst many other variables, that you probably would even think about. If you read head gasket labels such as Spoon and Mugen, they say: "about", or "as much as". In otherwords it's more of a vague estimate and although probably very close, not perfectly accurate.
Forged pistons and rods are really nice, and I would recomend a set if you have the money to blow, although, they really aren't necesary for a daily driver, or even for most all motor street cars that are really pushing it. A set of factory CTR pistons ussualy would do the trick for less than half the price of a nice set of after market forged pistons.
Later,
Aj
