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R. Middleton
Dodge Dakota
9/24/2001
22:40:02
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 Subject: Engine Displacement theory ?'s
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What are the pro's and cons of gaining displacement using Bore vs. using Stroke? Does one produce more peak HP? Is one method easier on components?
What does Rod Ratio have to do with it?
TIA
Middy.
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Hersbird
Dodge Dakota
9/24/2001
23:22:48
| RE: Engine Displacement theory ?'s
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http://www.iskycams.com/techtips.html
check out this page, the part about rod ratios. Chrysler's small block does have a taller deck allowing for better factory Rod ratios then the chevy but as this article points out there really isn't much to be gained. Increasing displacement is another story, I think increasing stroke will do more for the low to mid range power and a bigger bore will help more in the top end but makes it tougher to get good cumbustion burn hurting feul economy and emissions. Smokey Yunick wrote a whole book about this stuff, if only I knew how to read...
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R. Middleton
Dodge Dakota
9/25/2001
00:22:14
|  RE: Engine Displacement theory ?'s
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Not long after I posted that ? I found this site. It's got some great theory stuff on it!
Thanks for the input I'm off to Isky cams.
http://www.victorylibrary.com/mopar/mopar-tech.htm
Middy.
(Middy's thought for the day. If I put a 5.2l crank in a 5.9l block That's bored .40 over, I could have a MPI 340 Magnum. I find that extremely cool!)
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Hersbird
Dodge Dakota
9/25/2001
00:50:03
| RE: Engine Displacement theory ?'s
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of course the 5.9 crank has different journal diameters. Just put a 340 crank in a bored 318 and you'll get a 340 magnum. I think in the changeover to Magnum small blocks in 92 they didn't mess with the crank, rods, and such. A crank from 1968 should drop right in the current motor.
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Brad
Dodge Dakota
9/25/2001
12:09:33
| RE: Engine Displacement theory ?'s
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The 318 and 340 have the same stroke 3.31". The journals are bigger on the 5.9 2.58" if memory serves. Also don't know if you could get away with boring the 360 out that much. I've been told .3 is the most these blocks will allow.
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R. Middleton
Dodge Dakota
9/25/2001
18:29:43
| RE: Engine Displacement theory ?'s
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The bore for the 318 is 3.91, the bore for the 340 is 4.04 making an overbore of .130. The fault is mine on two accounts in my original post I sad bore it .40 over when I should have put .040 over, but there is no getting around the shorter crank having a smaller journal size.
so I guess if I want a 340 MPI, I'll have to build up a bare MP 340 block from the Catalogue and build my own intake.
Ah nevermind I'll just get a 380 hp 5.9 crate motor! Yeah thats the ticket!
Middy.
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Rich
Dodge Dakota
JOIN HERE
3/28/2010
13:59:47
| RE: Engine Displacement theory ?'s
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Can a 5.2 (318) Magnum be bored to 4.04?
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Todd93/96Dak
Dodge Dakota
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3/29/2010
21:43:18
| RE: Engine Displacement theory ?'s
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I don't recommend it. Not on the magnum block. If you got the LA block, i think you can bore it that big. My 360 Magnum is bored .060 over. Machine shop wouldn't recommend any larger on that.
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daddio
Dodge Dakota
JOIN HERE
3/30/2010
08:44:41
| RE: Engine Displacement theory ?'s
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Rich, NO. There is no way you can bore that block 0.130" over. Especially if maximum recommended is only .060.
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