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trev1
Dodge Dakota
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2/05/2007
20:32:48
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 Subject: Compression
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Hey yesterday there was a series of posts on a engine the someone had built. They said thier compression was 10 to 1 i believe..?? What does that convert to in psi?? I couldnt find the posts and was interested in the parts list/machine work had been done on this engine to get 240 horses. I got a 3.9 that I need to rebuild and would like to see if it is economiclly fesible for a poor working stiff like me to do this build. Any help is greatly appreciated. Great info here thats for sure....
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works2long
Dodge Dakota
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2/05/2007
22:25:48
|  RE: Compression
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thats real close to 210 ps, kinda scary if you have stock rods.......
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hemichuck
Dodge Dakota
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2/06/2007
16:13:45
| RE: Compression
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What year v-6 are you building? 10 to 1 one comp wont hurt your rods but it might hurt your gas budget.If you are rebuilding to drive everyday keep it below 9.5 to one.Magnums can get away with a little more compression if you get the right piston to head clearance(quinch) Let me know what your building and maybe I can make a suggestion
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trev1
Dodge Dakota
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2/06/2007
16:43:43
| RE: Compression
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Message:
92 dak 3.9 magnum 4wd. mtr is original with 248,000 on it. Trans rebuilt about 2 yrs ago is tight. front end rebuilt about 1 yr ago. Compression im mtr is bet 80 and 105 right know... any help appreciated...THANKS
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Fasstdak
Dodge Dakota
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2/06/2007
20:18:21
| RE: Compression
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Be careful with the compression being too high on these engines. I'm running 10.5:1 on my '97 V6 (along with quite a few other "enhancements") and we had to custom program the PCM. At the rear wheels: 219RWHP (260HP at the crank if you do the math).
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hemichuck
Dodge Dakota
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2/07/2007
08:54:01
| RE: Compression
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Kieth black and silvolite both make a 318 piston the same thing as v-6.Their web site is http://kb-silvolite.com/index2.php and it has all of the info on comp height and ratios. I have a brand new set of factory .005 pistons for a V-6 but I dont have any rings.I dont know if the rings are still available from the dealers or where you could buy them.I would sell the pistons cheap because I have no future plans to build a V6.Good luck
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J and J Auto
GenII
2/07/2007
22:31:45
| RE: Compression
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Message:
hughesengines.com has a good choice of pistons
from stock 9.2 to 12 to 1
around 269 for the 9.8 to 1 with the stock 58cc
heads mill them .020 and your just about 10 to 1
the 318 and 3.9 mag same pistons and with a little
machine work you can use the 318 rods
Larry
J&J Auto
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Fasstdak
Dodge Dakota
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2/07/2007
22:52:59
| RE: Compression
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Yup, i'm using Carillo rods in my '97 V6 along with 10.5:1 KB Silvolites. The machining on the crank is simple enough for any machine shop - widening the journals.
On the heads, be careful though - the pop-up pistons that some manufacturers use cause problems with the chamber design. We had to open mine up to 65cc's for clearance (makes for a really nice quench area though - good flame travel as well).
Stock compression is 9.1:1 and chamber size is 60cc's.
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trev1
Dodge Dakota
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2/08/2007
04:36:54
| RE: Compression
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Heads have been milled and rebuilt about 1 1/2 yr ago when the head gasket blew. But when i tested the compression 4 were at @90 1 at 105 and 1 at 80. Dont think the heads are bad. It is burning a little oil but not a whole bunch. Im not real familar with the dodge engine and there is really no one around the SW Mo area that is. So when I go to rebuild the Mtr I've got to know exactly what to to so it doesnt get all screwed up and become a trot line weight. There is a good machine shop just down the rd hes reasonable and does good work but is a Chevy man. To tell the truth I'll probally stay with new stok Pistons but would lke to know who makes a good set of rings. Dont want to go too extravagent with it. Its my work trk. I drive it 80 miles a day and want to keep the gas mileage somewhat reasonable. But I remember reading some where that a good HP to Weight ratio will actually help in the mileage area. I want to bee able to put my foot into it and go if necessary, But most of the time it will be driven at 70 to 75 on the interstate.
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