340?
- Thread starter JBC
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Brian Hafliger
Well-Known Member
I would change pistons, but for every .0065 of deck removal is 1 cc and I would take .007 off the intake flange. That'll be close. You can't remove too much off the intake face because you'll remove most of the valve cover flange.
I'd only go .040 then .038 on intake side, that will give you about 64 to 65 cc chambers. The formula is for every .010 block side cut .0095 on the intake side. Chrysler Racing Manual.
superbee79
Well-Known Member
why are there two different sets of edelbrock heads 1 reg set for small blocks and one set for early high compression 340's. i would check piston to valve clearance before i started milling heads for a 340.
Just some friendly advice, so please take it in that manner. Milling heads is not a very efficient way to raise compression. By the time you're done paying a machine shop to mill the heads and intake, buy new pushrods because you WILL need them, you probably could have gotten different pistons....which is a much better way....and a more correct one to raise compression. Just my 2 cents....and probably worth less.
superbee79
Well-Known Member
are they j heads with 1.88int/1.60exh
One set is to clear the pop up 10.5:1 pistons of the early 340's, the chamber is opened up to clear. The other is for the later low compression piston 340's. The pistons do not protrude past the deck.
Paul
Paul
superbee79
Well-Known Member
they were the same pistons flat top just different deck height giving you a different compression ratio like in 72 or 73 when they got de tuned they went from x heads to j heads where the only difference in the two was intake valve size 2.02
dgc333
Well-Known Member
Before you worry about milling the heads you need to know where the pistons sit in relation to the block deck and what the actual cc's of the heads are. The blocks typically were machined with a deck height on the tall side of the spec which lowers the compression and the heads could be anywhere from the 68 or so to over 70 cc's. Time to start measuring your parts, then you can make a plan on what machining to do.
Also, if the heads are no good why are you spending money on them. If no good means they aren't a good design that is not true. A 75 360 head is for all practical purposes the same as the head that would have been on the 69 340 with the exception of the valve size. All the open chamber factory 340/360 heads have the same basic port size and shape and the same chamber until the 308 casting that came out in the late 80's which has an improved exhaust port shape.
superbee79
Well-Known Member
nothing wrong with them heads i say do a good valve job and use them
bones427
Well-Known Member
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also run the thinist gasket you can get. i am going from a .040 to a .027 and comp goes up from 11.1 to 11.6 on my 340
.............if ur doing ur engine now, just have ur machinest offset grind the crank..........kim........
The heads have no cracks and seem to be ingood working order. I cleaned up the inside of the ports. I going to upgrade to lunati valvesprings, and replace the rocker arms with stock replacements. Should I have the intakes cut to 2.02
superbee79
Well-Known Member
3769974 360 1975-76 1.88 1.60 looks like a regular open chamber head with same valve size as the j heads, bigger intake valves really wouldn't hurt them.
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