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Randy
Dodge Dakota
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10/29/2003
16:49:53
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 Subject: is 3.9 truly a cutoff 5.2?
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It's been said the 3.9 is exactly the same as a 5.2 minus the two slugs. This is the case with the chevy 4.3 vs. 5.7 as well. These two chevy motors use the same of everything except for the cam and crank. My question is will a 2001 3.9 use the same aftermarket mods such as rockers, double roller timing chainset, underdrive pulleys, and valve springs as the 5.2? To take this one step further is the front of the block the same, allowing interchangeability of water pump and front cover?
This should probably be a seperate post but for someone VERY familier with the small block chevy, is a cam swap for a 3.9 the same or are there going to be things in different locations? I don't have the truck yet but I want to know what I'm getting into. Thanks alot
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b1llyw
GenII
10/29/2003
17:46:08
| RE: is 3.9 truly a cutoff 5.2?
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Yes to everything. It's going to be a different cam on a 3.9 (shorter obviously) but the swap would be exactly the same as a 5.2
Bill White
'95 CC 4x2, SLT - under construction
'03 Ram 1500 QC 4x4 Hemi Off-Road
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Randy
Dodge Dakota
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10/29/2003
19:24:14
| RE: is 3.9 truly a cutoff 5.2?
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and is the install the same as a smallblock chevy (in my case a 4.3 chevy)? The fact that it's the same geometry as the 5.2 saves me some homework on finding parts, thanks.
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b1llyw
GenII
10/29/2003
19:27:14
| RE: is 3.9 truly a cutoff 5.2?
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Having had a small block Chevy in a race car for the last two years - yes.
Bill White
'95 CC 4x2, SLT - under construction
'03 Ram 1500 QC 4x4 Hemi Off-Road
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Randy
Dodge Dakota
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10/29/2003
19:40:48
| RE: is 3.9 truly a cutoff 5.2?
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awesome. I was thinking of just doing 1.7 rockers but if it's something that I'm familier with I'd rather do a cam and get some better duration. Do you know what lift the stock springs are good for?
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Joe
Dodge Dakota
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10/30/2003
06:15:56
| RE: is 3.9 truly a cutoff 5.2?
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I did the math on the size and the power output and the 3.9 and 5.2 are exactly the same hp/liter and size per cylinder. I tried to compare the 4.3 to my old LT1 but no similarities, I also think the 350 has alot more torque for its size compared to the 4.3. Probably already knew this but hear it again.
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Randy
Dodge Dakota
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10/30/2003
07:30:50
| RE: is 3.9 truly a cutoff 5.2?
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I'm not surprised the dodge v6 is more efficient than the chevy, when I was building my fathers dak on their website I chose the v6 for him because the power was similar to the 350ci chevy truck he was currently driving. He also got the manual trans so he's losing less power than the 350ci automatic. But I was just using the two chevy motors for comparison because the geometry is the same. I'm kicking myself for not pushing the 4.7 on him because now I'm going to end up with his truck when he gets a new durango. My goal when I get his truck is to bump up the power close to what the 5.2/5.9 has while keeping it naturally aspirated. Losing bottom end power isn't much of a concern because it's manual so I'll get used to it. Then after it's all said and done I might top it off with a blower, but part of me says thats cheating.
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titus3.9
Dodge Dakota
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10/30/2003
15:21:07
|  RE: is 3.9 truly a cutoff 5.2?
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Maybe so, but blowers sure are fun!
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b1llyw
GenII
10/30/2003
15:29:00
| RE: is 3.9 truly a cutoff 5.2?
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Stock springs are good for .500
Even if the cam you get is under that, I'd still put in a new set with the cam, lifters too.
Bill White
'95 CC 4x2, SLT - under construction
'03 Ram 1500 QC 4x4 Hemi Off-Road
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Randy
Dodge Dakota
JOIN HERE
10/30/2003
15:32:54
| RE: is 3.9 truly a cutoff 5.2?
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Don't the magnum 3.9's have roller lifters? There's no need to replace lifters when doing roller cam swaps. Please correct me if I'm wrong.
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b1llyw
GenII
10/30/2003
15:37:19
| RE: is 3.9 truly a cutoff 5.2?
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It's cheap insurance in the grand scheme of things. Lifters wear just like anything else whether it's in the lifter bore, or where it presses against the cam. It wears a pattern either way. You can get a set of new lifters for your 3.9 for under $50.
Bill White
'95 CC 4x2, SLT - under construction
'03 Ram 1500 QC 4x4 Hemi Off-Road
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