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Old 11-24-2008, 01:41 PM
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Big Block Chevy Deck Height

Is there a minimum deck height that can reliably be run in a restoration type BBC, and if so what is it? I have a block that has been decked down around .045. Can I use this block with a .064 copper gasket and not have issues? I think Chevy used a 0.22 gasket, so the 0.64 would make up for the .045 deck job, plus around 0.020 of the 0.022 the factory gasket would have been. Or is this block better used as a piece of garden art or a boat anchor? It is a fairly rare casting and is correct for my car, so I hate to just junk it.

Again, this is for a restoration engine so I want to configure it close to stock, and the goal would be around an 11:1 compression ratio. I realize this would probably require some AVGAS added to the pump gas, but that is ok with me.

Thanks!

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Old 11-24-2008, 01:45 PM
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You may be fine, it depends on your quench distance and if/how far your piston protrudes from the bore. In fact running a .045" gasket may be the best thing you can do. As long as your piston doesn't protrude too much from the deck surface you just need to use a gasket to get you to .045"-ish for your quench distance.
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Old 11-24-2008, 01:56 PM
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By my calculation the .064 gasket would give about .04 quench

(-.025 deck clearance with 1.765 compression height, 3.76 stroke, 6.135 rod).
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Old 11-24-2008, 02:07 PM
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If your positive about that and the top of the top ring land is not near the top of the bore then you're fine.
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Old 11-24-2008, 02:45 PM
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Quote:
Originally Posted by crazy8s
By my calculation the .064 gasket would give about .04 quench

(-.025 deck clearance with 1.765 compression height, 3.76 stroke, 6.135 rod).
Sounds like to me that you're just playing with numbers without knowing the exact measurements of anything. You might know that the block was decked 0.045", but what was it before it was decked???

Put the motor together partially and measure the piston deck height. You won't know anything for sure until you do.
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Old 11-24-2008, 02:50 PM
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The deck height is 9.756 according to the machinist.
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Old 11-24-2008, 03:37 PM
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Quote:
Originally Posted by crazy8s
The deck height is 9.756 according to the machinist.
Would've saved both of us some time if you had posted that info in your first post. Why is it you guys want to hold back these little nuggets????

I don't think I'd use a solid copper gasket to get there. Too many problems with water control.

With the piston popped out of the bore 0.024", I'd be looking for a gasket around 0.070" to 0.075" to put the squish at 0.046" to 0.051". This is a big block, not a small block. The bore is bigger, so the piston can rock further on the pin and the crank, rods and pistons are heavier than small block items, so crank bend, rod stretch, etc. will be greater.

Cometic can make any thickness gasket you need. They have a custom gasket service.....
http://www.cometic.com/custom.aspx
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Old 11-24-2008, 11:45 PM
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The best fix would be to cut the pistons so you will have them about .005 in the hole, and use a standard available thickness Fel-pro head gasket. That way you wont have a morphadite combo. And if you ever sell it, the buyer might not be an engine guy, and would provide them with an easy fix should it need to be gone into again for some reason!
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Old 11-25-2008, 12:52 AM
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Quote:
Originally Posted by CNC-Dude
The best fix would be to cut the pistons so you will have them about .005 in the hole, and use a standard available thickness Fel-pro head gasket. That way you wont have a morphadite combo. And if you ever sell it, the buyer might not be an engine guy, and would provide them with an easy fix should it need to be gone into again for some reason!
See there, all it takes is a little common sense.
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Old 11-25-2008, 10:27 AM
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I think instead of playing with custom thick gaskets and possibly piston compression heights, a good used block can probably be had for $50-100.

I think what you have will work fine, but its probably cheaper to get a block.
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Old 11-25-2008, 06:58 PM
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I agree with CNC put the pistons in it and check how far out of the holes they and cut them to be 0 or -.005"

I have been machining my own and customers pistons for years now with no problems. I have gas ported about 10 sets for a local machine shop this year alone and they are all fine, someone has to do it and they pay me 100.00 a set for about 2 hours of work.

All the BBC's I have messed with start out about .025-.035 in the hole stock so you may be suprised just how little the pistons are out. Check them and cut them down you will be fine.
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