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Unread 10-01-2012, 07:13 PM   #1
ahar9
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Best cj5 engine swaps?

What are some of the best engines to swap into a cj5? I have a Amc 304 it runs good but with my Chevy axles and 37s and old motor I've calculated 7.4 mpg. I've been holding off and daily driving but realizing I cant afford that. I've always wanted to do an engine swap with a badass super strong drive train so what are some good swaps?

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Unread 10-01-2012, 08:29 PM   #2
roadhog304
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I would consider a fuel injected chevy engine. With big axles and tires I think it will be hard to get great fuel mileage with anything. I get a bit but not much better than you with my 360 but i am only rolling on 34" rubber.
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Unread 10-01-2012, 09:11 PM   #3
ahar9
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Quote:
Originally Posted by roadhog304
I would consider a fuel injected chevy engine. With big axles and tires I think it will be hard to get great fuel mileage with anything. I get a bit but not much better than you with my 360 but i am only rolling on 34" rubber.
I see a lot of 5.3 swaps and I'm considering that. I think a small diesel would be awesome to but I don't know much about diesels. Part of me wants to put a monster 401 in but that wouldn't help my cause haha
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Unread 10-01-2012, 09:30 PM   #4
brownbagg
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basically what you have or maybe 340/360 but no matter what motor you go to, ford, chevy amc its still only going get 8 mpg
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Unread 10-02-2012, 04:31 AM   #5
ahar9
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Originally Posted by brownbagg
basically what you have or maybe 340/360 but no matter what motor you go to, ford, chevy amc its still only going get 8 mpg
That's what all my friends have been saying. Maybe I'll go fuel injection and clean up my 304. I know I don't have full compression in every cylinder and shes smoking the blue stuff so It could use a rebuild
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Unread 10-02-2012, 05:25 AM   #6
Matt1981CJ7
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In theory, a more powerful engine would increase your gas mileage slightly, if you could keep off the skinny pedal. But what fun would that be?

More reasonably sized tires, in the 32-33" range, would also improve your mileage considerably.

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Unread 10-02-2012, 07:43 AM   #7
CSP
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Unless you've swapped out your speedometer gear you're probably getting better mileage than your calculations show too. Bigger tires mean you're traveling further than the odometer shows.

One rotation of a 37" tire covers almost 2' more distance than one rotation of a 30" tire.
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Unread 10-02-2012, 01:19 PM   #8
ahar9
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Originally Posted by CSP
Unless you've swapped out your speedometer gear you're probably getting better mileage than your calculations show too. Bigger tires mean you're traveling further than the odometer shows.

One rotation of a 37" tire covers almost 2' more distance than one rotation of a 30" tire.
Wow never thought about that. I was completely full of gas one day and I drove 21 miles until
The next fill up. Next fill up was 3 gallons on the dot. So I calculated 7mpg. So if it's actually 2 miles more for each mile that would be 43/3? That can't be right because I know my mileage isn't that good
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Unread 10-02-2012, 01:20 PM   #9
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Originally Posted by ahar9

Wow never thought about that. I was completely full of gas one day and I drove 21 miles until
The next fill up. Next fill up was 3 gallons on the dot. So I calculated 7mpg. So if it's actually 2 miles more for each mile that would be 43/3? That can't be right because I know my mileage isn't that good
Sorry read that wrong never mind. I was thinking 2 miles but you meant 2 feet.
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Unread 10-02-2012, 01:22 PM   #10
ahar9
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Quote:
Originally Posted by Matt1981CJ7
In theory, a more powerful engine would increase your gas mileage slightly, if you could keep off the skinny pedal. But what fun would that be?

More reasonably sized tires, in the 32-33" range, would also improve your mileage considerably.

Matt
That's what I was thinking. And I'm pretty hard on the skinny pedal. My 304 does sound pretty good and it's always fun to romp on it right out of the school parking lot when all the girls are looking
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Unread 10-02-2012, 04:29 PM   #11
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Living in California, I've been daydreaming of putting a 5.3 E-rod in mine. All smog legal, all aluminum, fuel injection, 320 hp
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Unread 10-02-2012, 04:43 PM   #12
ahar9
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Originally Posted by Mr_Ranger
Living in California, I've been daydreaming of putting a 5.3 E-rod in mine. All smog legal, all aluminum, fuel injection, 320 hp
Haha that would be nice. I'm not worried about smog because I have historic tags. No inspections of any kind
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Unread 10-06-2012, 10:30 AM   #13
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Quote:
Originally Posted by ahar9 View Post
What are some of the best engines to swap into a cj5? I have a Amc 304 it runs good but with my Chevy axles and 37s and old motor I've calculated 7.4 mpg. I've been holding off and daily driving but realizing I cant afford that. I've always wanted to do an engine swap with a badass super strong drive train so what are some good swaps?
Just checked your profile. 31's or 37's?
If you're running 37's, No engine will garner you any substantial mileage without a gear swap. That size tire will require a minimum 4.56 gearing to get the engine even close to the power band.
Gearing aside, I have always felt an upgrade to a 360 was a cheap, simple increase in both power and torque.
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Unread 10-06-2012, 10:39 AM   #14
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My CJ-7 with 35" tires and a warmed over 304 and an automatic transmission does manage to break into the double digits. I think the best swap would be some type of Chevy V8 (Either a TBI 350 or a newer V8) or a larger AMC V8, depending on your budget. You can probably pick up a AMC 360 for a lot less than the cost of a Chevy V8 conversion.
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Unread 10-06-2012, 10:10 PM   #15
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Quote:
Originally Posted by jumbojeepman
My CJ-7 with 35" tires and a warmed over 304 and an automatic transmission does manage to break into the double digits. I think the best swap would be some type of Chevy V8 (Either a TBI 350 or a newer V8) or a larger AMC V8, depending on your budget. You can probably pick up a AMC 360 for a lot less than the cost of a Chevy V8 conversion.
An AMC V8 won't need any adapters or conversion radiator either just motor mounts, (might only be the drivers side motor mount to?) flywheel for whichever AMC motor you are putting in, they don't interchange. Exhaust headers of manifolds and fix you up a nice sounding dual exhaust!

My 81 speedo was off by 20% on the actual mileage with half bald 33's, so 16 MPG's was actually 20.
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