Re: Zero deck or not to zero deck on 340 build
[Re: topside]
#560095
12/22/09 05:13 PM
12/22/09 05:13 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
Need more of that pesky "technical info", but overall:
For 91 octane with iron heads and ANY advance curve, you're limited to about 9.0:1 unless you run a cam with a fair amount of overlap to bleed off cylinder pressure; downside to that is soggy throttle response.
Don't machine anything until you have pistons and some plan for the motor. You should have the heads measured to see what you have for chamber size.
You may well end up zero-decking your block, but that's not where a build, or a plan, starts.
huh...my 9:1 (actual measured) 318 with a 33 degree overlap roller cam (259/259, 208/208@.050 on a 112 LSA, installed at 108) runs fine with a quick advance curve (all in by 2000 RPM, no appreciable quench (.055" in the hole with .028" head gaskets and magnum heads), and 87 octane.
I'd build the short block at 0 deck with flat tops, that makes setting up future head options much easier if you're looking for tight quench. with typical open chambered heads, that'll net you 9.5:1 compression with a thin .028" head gasket, which coupled with a cam like a comp XE268 should run fine on 89 octane and get you in the 350-375 HP range depending on the quality of the head work.
then if you ever want to upgrade the heads, with a .039" head gasket and typical 63cc closed chamber (magnum heads, or eddie heads) and .039" gaskets, you're looking at 10.1 compression with tight quench, which should allow the engine to run on similar, if not lower octane than it did previously.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: Zero deck or not to zero deck on 340 build
[Re: patrick]
#560096
12/22/09 05:43 PM
12/22/09 05:43 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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John, you really do need a plan going in before you do any milling. Your open chamber J heads ( not a bad head by the way ) are typically 68 - 72 CC's. You can use 70CC's when computing your CR. You will probably end up with zero ( or close to it - I always like to leave myself a little room - .005 to .010" down in the hole )deck height. Much of the info out there is based on zero deck height. 9 - 9.5:1 are good numbers to shoot for.
Fastest 300
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Re: Zero deck or not to zero deck on 340 build
[Re: patrick]
#560097
12/22/09 05:48 PM
12/22/09 05:48 PM
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Joined: Jan 2003
Posts: 9,826
las vegas
70AARcuda
master
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master
Joined: Jan 2003
Posts: 9,826
las vegas
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off the shelf pistons only come in two compression heights for 340s...
1.84 for the 68-71 high compression 340s
1.74 for the 72-73 low compression 340s
the high compression piston will be out of the hole about .008 depending on the actual deck height of the block....
the low compression will be down in the hole about .090 depending on the actual deck height of the block.
so unless you are going to special order pistons you will need to accompdate the compression heights of the pistons available...
either out of the deck or milling around .090
I would use the KB 243 pistons and adjust the head gasket to get your quench...plus the KB piston is ALOT lighter then the old trw/seal power piston...
Tony
70 AARCuda Vitamin C
71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield)
71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas)
71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)
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Re: Zero deck or not to zero deck on 340 build
[Re: tee-john]
#560098
12/22/09 06:22 PM
12/22/09 06:22 PM
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Joined: Feb 2009
Posts: 1,274
Ontario.Canada
can.al
pro stock
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pro stock
Joined: Feb 2009
Posts: 1,274
Ontario.Canada
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..my 340 has L2316 pistons(old style TRW forged)which stick about .022 above the deck.
my deck was squared and my X heads(70 -72 cc) had a clean up cut.
i did the math and i think it was less than 9.5:1
Last edited by can.al; 12/22/09 06:27 PM.
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Re: Zero deck or not to zero deck on 340 build
[Re: can.al]
#560099
12/22/09 07:22 PM
12/22/09 07:22 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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what octane are you going to run and what cam (or how mild/wild of cam) do you have in mind. Here is a very user friendly CR calculator. http://kb-silvolite.com/calc.php?. As said .040" quench will let you run a much higher CR (& CR is squeeze and squeeze is power) but will take (alot)more machine shop labor to machine/equalize the open chamber recesses on your current heads then if you switched later to a closed chamber head it'd require a custom Cometic gasket but I am a firm believer in getting it right for your CURRENT combo as opposed to what you might do in the future. Stay close to us (& away from the chebby boys) 
live every 24 hour block of time like it's your last day on earth
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Re: Zero deck or not to zero deck on 340 build
[Re: can.al]
#560102
12/23/09 12:14 AM
12/23/09 12:14 AM
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Joined: Nov 2004
Posts: 2,495
Oregon City, OR
Baxter61
top fuel
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top fuel
Joined: Nov 2004
Posts: 2,495
Oregon City, OR
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Quote:
..my 340 has L2316 pistons(old style TRW forged)which stick about .022 above the deck.
my deck was squared and my X heads(70 -72 cc) had a clean up cut.
i did the math and i think it was less than 9.5:1
 on a 340 unless you cut those j heads down a bunch, if you dont have the pistons sticking .010 to .020 out of the hole your not gonna have 9:1 comp. Even at 10:1 and a decent cam your motor should be fine on pump gas and make plenty of power.
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Re: Zero deck or not to zero deck on 340 build
[Re: tee-john]
#560105
12/23/09 08:37 AM
12/23/09 08:37 AM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 12,675
Columbia, CT
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tee - What are you planning to do with this car? What trans and gearing do you have planned?
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: Zero deck or not to zero deck on 340 build
[Re: moper]
#560106
12/23/09 09:17 AM
12/23/09 09:17 AM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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I'd use the KB hypers, and a comp XE268 with comp 906 springs.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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