Kaptain K
Member
I have a 68' 318 that is bored.040" over. My question is can I put a set of 340 J heads with 2.02" valves on this setup? I'm worried about cylinder wall clearance.
340 heads on a 318
- Thread starter Kaptain K
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Check it just in case but it shouldn't be an issue.
Kaptain K
Member
This may be a naive question, but how do I check that?
they'll go right on, but you're more than likely going to lose compression in the process.
they'll bolt right on. Many have put 2.02 heads on standard bore 318. You are .040 over, proceed.
MOPAROFFICIAL
Well-Known Member
While there still off... cc them and mill to 68cc.. then they will match the chamber volume of a typical 318 open chamber head and everything should still fit 'intake wise'
Total mill if they are bone stock should be around .024..
But if you use an aftermarket head gasket... typically around .046-.052.. you'll wanna figure that in too.. and add another .020 for a total of .046 ish.
Try and reuse the old ones with copper coat or just buy some mr.gasket thin gaskets to avoid the extra milling because at certain point you'll have to Mill the intake face of the heads as well to maintain proper alignment
Total mill if they are bone stock should be around .024..
But if you use an aftermarket head gasket... typically around .046-.052.. you'll wanna figure that in too.. and add another .020 for a total of .046 ish.
Try and reuse the old ones with copper coat or just buy some mr.gasket thin gaskets to avoid the extra milling because at certain point you'll have to Mill the intake face of the heads as well to maintain proper alignment
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Kaptain K
Member
They've been shaved .010" already
missing linc
Loose nut behind the wheel
Been there, done that, you'll be fine.
MOPAROFFICIAL
Well-Known Member
Means nothing if you don't measure them.
They're 72 cc stock.. 4 cc bigger.. so .010 ,from stock, would be 70cc. 2cc bigger than the 318 head.. then the gasket issue..
But hey, bolt them on and roll if ya want..
Yep, .010 is a nice clean up cut to straighten things out. Not meant to decrease the chambers. We did a skim cut then .030 on my 273 heads to get the chambers down to minimum. Then you add a composite head gasket (.028) over the stock steel shim and you loose about .020 of that. So I only ended up with a .010 over stock specs. The 340 heads have a large chamber for the 4.040 bore and an open chamber to boot. Ahhh, we could go on and on about compression loss but the larger valves and ports will make up for that, yadda, yadda, yadda!
MOPAROFFICIAL
Well-Known Member
There are other factors that contribute to increasing or decreasing chamber volume, like the valve job. If you max the seat.. AKA .040 smaller than the actual valve diameter.. then narrow it to .045...the valve sinks. More flow, but increases chamber volume...as does grinding the valves seat face.
Obviously the opposite occurs going the other direction.. wider seat, smaller the than valve size, new valve n so on.
As a machinist you can do a lot of things, and reuse stuff that would be considered worn out or need replacement. I see people with 2.02 valves that are actually 2 inch and smaller because they've already been faced so many times that because the margin became too thin, the valve was just turned down on the edge of a grinding wheel till the margin was right, the other seven would follow and the seat diameter got smaller. They just knurl the guides to make up for the stemware.
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mygasser
Well-Known Member
i bought kb399 domed pistons for my 318 build with 2.02 j heads. 
neil.
neil.
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