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Has anyone rebuilt a 3.7? Can you put 6.0 rods in it without replacing the crank?
3.7 rebuild question
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What are 6.0 rods?
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6 inch rods vs the factory 5.7 inch
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Highly doubt it, but I can't say for certain because i've never tried it.
First question that comes to mind is where is the piston going to go at TDC? Your pistons and heads will be having an intimate encounter thats not very favorable to continued engine opperation. In an area of the engine where tolerances are tight, adding a few inches wont work very well.
First question that comes to mind is where is the piston going to go at TDC? Your pistons and heads will be having an intimate encounter thats not very favorable to continued engine opperation. In an area of the engine where tolerances are tight, adding a few inches wont work very well.
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Very true, a few inches would be a problem, but .3 inches should be ok, I would think? It's my first rebuild so I am not sure. I'll ask the machine shop when they bore it and do the heads.
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I'm just curious as to why you would even want to try this. I can't imagine any scenerio where a 3.7 would need longer rods to reduce cylinder wall loading. Come to think of it, where did you even find the rod length specs? Chrysler doesn't publish that in the factory service info.
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My engine blew 2 nights ago and I need to rebuild. I love dodge, but honestly, the 3.7 in the ram is a joke, works great for the Liberty though. I am looking to gain horsepower while I am having the machine shop polish clean up the block and heads. A few friends of mine build race engines and have suggested longer rods.
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14,200 Posts
If your friend builds race engines, he should know that increasing the rod length won't do a thing for horsepower. You may be able to squeeze a few more ponies from your engine but the bottom line is that there just aren't many good performance parts available for this engine.
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3,850 Posts
If you are looking for more hp but don't want to get rid of the truck or buy another, swap a 4.7 in. They are the same family. But it's your engine.
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This is what I would do! :smileup:
Talk to your friends a little more, they should know that there is a lot more to stroking a motor than adding longer rods.
You are pushing the piston further up into the quench area and you will need pistons that have valve reliefs so you don't have piston/valve contact. There are a lot of measurments to be taken before throwing in longer rods.
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Longer rods won't change the stroke, it will just change the location of the piston within the bore.
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You are absolutely correct!:smileup:
Thank you for pointing that out.
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1,017 Posts
I have the Liberty with the 3.7 and it has been a rock solid engine. Lots of torque for what it is. This engine responds very well to intake and exhaust mods. a decent CAI and better flowing exhaust give it another 30 ponies or so. It's very noticeable. Rebuild it stout and boost it, or find you a low mileage v-8 from a salvage yard to throw in it, Get creative.If you have engine guru's to help you, bump up the compression and go with some larger valves and stiffer valve springs for some more fun factor. I also had a 98 model Ram 1500 with what I believe was the 3,7... It was no speed demon, but like the Liberty it had bookoo torq. They like 5w-30 full syn. oil too. I picked up a few more mpg's running Mobil one syn in her at 5k intervals. The Liberty has 95K on the O.D. and still does not use a drop of oil. Wifey drives it, except for now she has fell in love with my Express and steals it quite often. Not cool, might have to kick her to the curb! Anyways good luck with whatever you decide. Just throwing some ideas at ya'.
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Your 98 had a 3.9, different animal altogether (although it was derived the same way, they took 2 cylinders out of a 318).
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The Jeep guys swear by the Magnaflow cat back system. I have listened to a lot of sounds clips and it actually sounds darn good for a V-6!! I would love to put one on my jeep but its pricey.. Adding a CAI makes for nice gains. I did an EBay cheap CAI on mine and noticed an easy 10h.p. on the butt dyno
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That explains why it was such a good engine. I pulled a car that was buried to the frame in sand out easily with no throttle..Just eased the clutch out in 1st and out she went. I miss that truck but it was embarassing having to wave off people wanting to race me. It was a red 2wd & had the chrome wheels and trim plus a mopar sport fiberglass hood. Looked mean anyways. Cops watched it like buzzards on road kill.
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