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kRaSh
Dodge Dakota
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8/11/2004
11:09:13
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 Subject: Crankshaft Swap
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Has anyone swapped a 360 crank into a 318 motor yet? I have a '99 begging for a little more power.
Right now its only 190RWHP & 330RWTQ.
I know I would need new connecting rods, but anything else?
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Not sure
Dodge Dakota
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8/11/2004
18:24:59
|  RE: Crankshaft Swap
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Don't think it'd be that easy. Different main journal size, I belive. That would be hard to over come as aligne boring to compensate would move the crank to cam centerline relationship.
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kRaSh
Dodge Dakota
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8/11/2004
18:46:47
| RE: Crankshaft Swap
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If I recall correctly the 318 and 360 are the same short block, just different bore and stroke. Thats why I thought I could just swap out the crank and the connecting rods.
I know on the old pre-mag 318 340 & 360, almost all of the parts were interchangable. Thats why they could use the same short block for all three engines.
But I didn't know for sure on these Magnum engines if they changed that much.
But you think the journal is different??? Hmmmm I'll have to look into that. Thanks for the heads up!
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pettie
Dodge Dakota
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8/11/2004
20:36:04
| RE: Crankshaft Swap
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How do you have 330rwtq?, what mods have you done?
A stock 360, will dyno in the area of 260-280 rwtq
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daddio
Dodge Dakota
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8/12/2004
09:58:06
| RE: Crankshaft Swap
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krash, check out this website: http://www.allpar.com/mopar/318.html
should be able to find the info you need.
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kRaSh
Dodge Dakota
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8/12/2004
10:59:08
| RE: Crankshaft Swap
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pettie- right now I have changed my 1.5ratio stock rockers with 1.7ratio HS alum rockers, and I have a cutout on before the muffler and after the cat. Thats it. I didn't believe the numbers either so I dynod it 3 times.
daddio- THANK YOU MUCH!!! That info was very helpfull! And it seems that I can swap the cranks afterall!
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daddio
Dodge Dakota
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8/12/2004
11:09:27
| RE: Crankshaft Swap
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first thin i'd check is the rod and main journal diameters. i didn't look at it but the 360's may be diff than the 318's. good luck
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pettie
Dodge Dakota
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8/12/2004
18:48:59
| RE: Crankshaft Swap
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Not bad gains at all.
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gen1dak
Dodge Dakota
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8/12/2004
18:55:21
| RE: Crankshaft Swap
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No, you can't just swap the cranks. The journals have to be ground down to 318 size. The 273/318/340 shared crank journal specs. The 360's are larger. You can get a quality stroker crank for under $400 that will drop right in. The rods are, however, the same length.
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gen1dak
Dodge Dakota
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8/12/2004
18:59:30
| RE: Crankshaft Swap
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Sorry. My goof. I was thinking about LA's, not Magnums.
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gen1dak
Dodge Dakota
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8/12/2004
19:05:32
| RE: Crankshaft Swap
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Take the opportunity to have the 5.9 crank balanced internally and you'll be able to use your 318 zero-balance torque converter without adding any external weight.
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kRaSh
Dodge Dakota
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8/13/2004
00:04:10
| RE: Crankshaft Swap
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gen1dak- so on the magnum motors, it'll swap right in but I need to have the crank internally balanced to work with my torque converter. I was planning on buying a brand new stock crank for a 360 from the dealership. Would it still need balancing?
What if I put a 360 torque converter on, or would that be dumb?
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gen1dak
Dodge Dakota
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8/13/2004
22:17:43
| RE: Crankshaft Swap
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A 360 converter is fine, or a 318 converter with balance weight added. Just make sure you order the right 360 crank...Magnum, not LA. At least Mopar took the time to standardize most of the parts on these Magnums, so the crank and rods are the same. Having a crank re-balanced (with Mallory metal)so the weight is internal has some advantages, (but tends to be more for serious racing) like not having to add external weights to a zero-balance converter, and it's the only way to run a Fluidampr harmonic engine damper. They don't work with externally balanced engines. Still, it does add cost, and you're more than sufficiently covered with a quality steel ring/elastomeric damper.
The problem is in the pistons. You're wanting to stroke a 318 with a 360 crank, right? So, you'll be using 318 pistons? There's the problem. To accomodate the increased stroke in the 360, the pistons of the 360 are 49.53mm top to bottom (excluding the skirts). The 318 pistons are 62.23mm. Mixing the 360 crank with the taller pistons....I'm thinking that's a disaster waiting to happen. The minimum piston-to-head clearance should be .055 inches, which works out to 1.397mm. No way are you gonna tuck in a 12.7mm difference. That's 0.5in! By the time you get some sort of piston solution, you'd see you're better bet would be to start with a 360. Even without the piston issue, a 3.58 stroke would net 344 inches with a 3.91 bore....or were you planning on something else?
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gen1dak
Dodge Dakota
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8/13/2004
22:26:02
| RE: Crankshaft Swap
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On new con rods. If you go with shorter ones, you'll be screwing up one of the best rod ratios in any engine ever made. The increase in displacement will net some power, but the shorter rods will alter the ratio, and this will make the engine a bit less willing to rev, at whatever level of performance, so you're really shooting yourself in the foot. Put a cam in that thing!
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GraphiteDak
GenIII
8/14/2004
00:59:54
| RE: Crankshaft Swap
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I remember back when I got a '86 Ram from my Dad. He gave it to me (this was 10 yrs ago) and the 318 had a thrown rod. (only because the owner before him NEVER changed the oil! SLUDGE!!!)
Anyway. I got my hands on a descent 360.
The oil pan from the 318 would NOT fit!!!!
I had to go get an oil pan for a 360. Of course this was the LA series engines.
When it was all said and done I had a good running 360. It was bored .030 over and ran a descent cam, intake, etc. The engine came like that from a wrecked car. I just threw it in real quick to get a truck at the time.
I didn't keep it long enough to switch out the really crappy 2.73 : 1 rear gears!
1st gear to 65-70 MPH. 2nd gear to 100 or so, etc!
And it STILL hauled a$$ somehow. Did burnouts like mad and revved to 6K easy. I'm surprised people say 360's fall flat so early. Maybe that's the diff from old school and the R/T engines?
Anyway, sorry so long. But there did seem to be some differences in those engines. Just the oil pans gave me a pain to get matched up.
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kRaSh
Dodge Dakota
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8/14/2004
02:19:31
| RE: Crankshaft Swap
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gen1dak- I thank you for the help and guidence. I totally forgot about the pistons being different heights. I thought they were just different diameters.
So yes I was "trying" for the 344ci but it sounds like a failed attempt at this point. I really dont have the money to go buy a 360, nor do I want 360ci. I wanted to make a "magnum" version of the 340. But I can plainly see that I have just been schooled and I need to go back to the drawing board.
And yes I could put a cam in there but the 1.7 ratio rockers seemd to be doing a pretty good job thus far. I get 19mpg on the hwy with a fully loaded and skid plated 4x4 ext cab with full grill/brush guard. It was just wishfull thinking.
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gen1dak
Dodge Dakota
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8/14/2004
20:58:47
| RE: Crankshaft Swap
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Now there's an idea...a 340 Magnum...Magnum. Hmm. I bet that'd be a real screamer. Sorry to dash your hopes, but at least you didn't get hip deep in the project before finding out.
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daddio
Dodge Dakota
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8/16/2004
10:21:02
| RE: Crankshaft Swap
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krash, that's was i was planning to do when my 3.9 dies. my ideal powertrain, a 340"magnum" w/ 5 speed manual in my '00 QC. there has got to be a way.
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Wal
Dodge Dakota
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8/16/2004
10:31:49
| RE: Crankshaft Swap
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the 340 was the same bore as the 318 but longer stroke. Why can't you build a "318 stroker" per say and bring her to 340? Wouldn't she be everything the 318 is but a torque monster on top of that? Or am I dreaming too :-)
Wal
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daddio
Dodge Dakota
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8/16/2004
10:41:43
| RE: Crankshaft Swap
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same stroke not bore.
318 = stroke - 3.31" bore = 3.91
340 = stroke - 3.31" bore - 4.04
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Wal
Dodge Dakota
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8/16/2004
10:52:42
| RE: Crankshaft Swap
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Sorry, you are right. Dunno where me head was. I must have been confusing it with the 349 stroker you can make from the 318 pistons and new crank.
Wal
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