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#1
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j-heads and 318
a time ago there was some discussion about the 360 heads on a 318, and someone mentioned that it's not so clever to mill them too much because of the piston clerance, and someone say mill 0.35... and someone to 58cc....
I want the comp. ratio to be around 10:1, how much do I have to mill then? any suggestion? (stock block and bottom end) it's 98octane on the gaspump in norway! |
#2
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Are you using the stock pistons? I think they end up about .080" down in the hole. That means with a .025" thick gasket, your heads will need to be about 52 cc. I think you would need to mill about 0.100" from the heads. I think that is possible.
If you were to use some aftermarket pistons that would be flush with the deck, and used a .025" gasket your heads would need to be about 63 cc. A KB167 might be a good piston to consider. With the open chamber heads piston to head clearence should be fine. Valve to piston clearence should be checked. |
#3
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yeah! stock pistons! you think milling 0.100 is possible? hmmm...
i'm not sure... 0.100" is a great piece! maybe it's better to buy new pistons then? what about the stock flat-top pistons...is it thick enough to take my dremel and make a groove to the valves?? dartswinger said: This(360 heads on a 318) has been a really common swap. We always had them milled .050 first.Worked great. Only in the last few years has it been claimed that you shouldnt do this. why?? |
#4
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.100" mill?
.100" is right out! I wouldn't go over .060". I don't think the 340/360 chambers are that much bigger than the 318 chambers. .030" usually got my heads down to 62-63cc. Make sure they mill the intake surface as well. A set of 302 heads would be a good alternative to the 360 heads.
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#5
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Mr. Kruger,
Not all 318 Mopars have the same deck heigth. Early LA 318's came with higher pistons with four valve reliefs in each piston. Later 318's changed the heigth from year to year, appearently to satisfy the emissions police. Also, I have found as much as .017" difference in deck from left front to right rear or across the other way. You don't Know until you measure. I have a pair of "J" heads, 915 casting number, that have been milled .060". A portion of the eyebrow around the intake valve was removed at this cut. Another .040" would have distroyed the valve seats. These heads with stock 1.88" valves measured 57 cc. I would not try to cut valve reliefs in stock cast pistons. they are not that thick. The cam lift, duration, and center line are what determines how much head milling you can get by with when using any piston. Measure before you cut !!! |
#6
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Look at your J's intake valve seat....see how it rises out of the combustion chamber....lay a straight edge across the head and measure how much room you have before the mill hits the boss. You can't cut into that boss you'll never get a valve job on them.
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#7
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right! hmmm..maybe the best thing to do is to get some new pistons, or a 360
thanks for the help! |
#8
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Biggest lie in the world
"Bolts Right On" |
#9
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I want the comp. ratio to be around 10:1!!!
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