340 deck clearance
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1970Duster
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Depending on the model year, the 340 did have pop up pistons but they were changed to flat top pistons in later model motors. Personally I don't really like that so I go flat top pistons with closed chamber heads.
Now to answer your question about the Tdc with pop up, I don't know.
If your motor has pop up pistons you'll need an open chamber head (closed chamber would have the piston hitting the head). With a flat top piston you can use either the open or close chamber head.
Now to answer your question about the Tdc with pop up, I don't know.
If your motor has pop up pistons you'll need an open chamber head (closed chamber would have the piston hitting the head). With a flat top piston you can use either the open or close chamber head.
Yup. From 68 to mid year 72. Any standard open chamber small block head will work.
If your Pistons are pop ups, your limited to an open chambered head. There is an Edelbrock head just for the positive deck height slugged 340. It has a relief in the heads chamber just for that series piston in the 340.
If your slugs are in the hole, then any head will do. Though is stay away from the early 273 heads. Weird bolt angles.
If your slugs are in the hole, then any head will do. Though is stay away from the early 273 heads. Weird bolt angles.
2 Darts
A-body Addicted
There are two factory pistons for the 340. The 68-71 sits 0.045 above the block deck, the 72-73 piston sits 0.054 below the block deck.
X2 Any small block open chamber head will do.
X2 Any small block open chamber head will do.
.........the 70 340 i'm doing now sit .045 above deck............kim............
So the Edelbrock "340" head has a .060 clearance IIRC. That leave.015 plus what ever gasket you use. The thin .028 gasket would provide enough clearance with excellent quench. .043 worth.
Nice!
Nice!
The pistons on my '68 340 ended up .018" above the deck (KB243's). I used a set of open chamber "308" heads that had a 65cc chamber and run them with a .035" head gasket to keep the compression under 10:1.
It also depends on what cam you're planning on running, as you need to watch the valve-piston clearance as well.
It also depends on what cam you're planning on running, as you need to watch the valve-piston clearance as well.
Even the flat tops will be above the deck on an early 340. My KB243's are flat top pistons, they're still .018" above the deck.
Closed chamber heads would have to be checked for clearance. Edelbrock's aluminum heads are closed chambered, and they make a special version just for the 340 that's basically an open chambered head to clear, so Edelbrock doesn't think a closed chamber head will work. I've heard it's possible, but you would have to determine exactly where your pistons are in relation to the deck on your engine. And then you'd have to check the piston to head and piston to valve clearance.
The other thing to consider is the compression ratio. If your flat tops end up .018" proud of the deck like mine, you won't want a close chambered head if you want to run pump gas anyway. With 65cc chambers I'm at 9.8:1, and it only runs on 91 octane with the total timing pulled back to 35*. Granted, that's on California grade 91 octane and fairly close to sea level, so your results may vary.
fishy68
Tyr Fryr's Inc.
The style of piston (flat top or dome) doesn't matter. What matters is where it sits in the block and that is determined by the pistons compression height and the actual deck height which varies from block to block. Aftermarket pistons can be found in different compression heights. If you want to run closed chambered heads you need to find a piston that doesn't stick out of the block or you'll have to run thicker head gaskets to get the piston to head clearance you need. Generally speaking .040" is enough piston to head clearance. Also keep in mind that when swapping to a different piston that the rotating assembly will most likely need rebalanced.
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