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Unread 12-17-2014, 08:49 AM   #1
Thunder_Chick3n
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Straight 6 or V8

So the 258 in my CJ is giving me some issues. It leaks oil, there is a massive exhaust leak, and it leaks antifreeze. Its also a bit under powered. I called tho local engine shop (Carroll's Engine Rebuilders) and they quoted me 2500 to rebuild the motor, port and polish the head, bore it over, and put a more aggressive cam in it. Should I go with that or should i invest the 2500 in a small V8 like a Dodge 318 or a Chevy 350? I have the Borg Warner 5T running to a Dana 300. I have the stock running gear under it, but I have twin GM10 bolts to put under it when I get the time and money

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Unread 12-17-2014, 09:44 AM   #2
Matt1981CJ7
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Oil, exhaust, and antifreeze leaks aren't necessarily signs that the engine needs to be rebuilt. Those can be fixed relatively cheaply, depending on where the leaks are.

Lack of power could simply be a tuning issue. Things like vacuum leaks, improper timing and carb adjustments, and worn out ignition parts will cause power problems. Again, all those things can be addressed for much cheaper than rebuilding the engine. Besides, you'll have to do all of that, anyway, if you rebuild.

The best thing you could do is a compression or leak-down test. That will tell you the general condition of the engine. From there, it's a matter of systematically tearing into the engine to see what it needs. Often times a full rebuild isn't necessary, and a general overhaul will suffice.

Now, if you've got money to burn, and just want a fancy new engine with more power, then a AMC V8 will be the easiest/cheapest swap. You could also look at swapping in a 4.0 head, or an entire 4.0 engine, but the small performance gains may not make you giddy like a V8 would.

Swapping in a Chebby or Dodge engine will likely require expensive adapters, different drive lines, motor mounts, etc.... to make them work, but it's certainly doable. It just depends on what your goals are, and what your finances will allow.

Good luck,

Matt
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Unread 12-17-2014, 10:24 AM   #3
dirtdudeaz
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If you aren't happy with the power from your 6 now, I would be willing to bet a new cam, even a 4.0 head and EFI, would not be enough.... Like Matt said though, you can do things to maximize the power out of these engines.

I agree, before rebuilding, you want to make sure you diagnose what's going on.

I am assuming the $2500 was out the door with parts and labor included? It seems a tad high for a rebuild on an inline 6... And porting and polishing the 258's isn't worth the time/money for return you get. Check around for other builders and machine shops. I would think around $1000 would be reasonable for this engine for labor, and maybe $600-700 on parts. Hell, even Collin's Brothers are $1500 after the $400 or whatever for the core fee. With parts and labor to rebuild my 258, it was about $1700. That included the new comp cams kit, engine labor, engine parts

By the way, your T5 probably won't like any v8, so you would want to switch that too if you go to a bigger engine. If you stick with an amc v8 engine and transmission that came in a CJ, I bet you could do it for 2500 or less. If you go to a different engine brand, you probably will spend more.

http://www.novak-adapt.com/index.htm
Go down to the "Knowledge" section on the left side of the screen. A lot of good reading there about the possible conversions.
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Unread 12-17-2014, 11:10 AM   #4
Renegade82
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What they said^^. Fix the 258, it's going to be cheaper and quicker when all said and done.
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Unread 12-17-2014, 11:20 AM   #5
Hbryant123
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I agree with matt, most of the problems are just stuff that breaks and needs fixed like exhaust and radiator leaks, around where i live they fix radiators cheap. I also agree tunning can make a world of difference. I would try and fix what you have before spending 2500 or anything. Swapping a chevvy or dodge IMO would be a waste when a 304 or 360 bolts right in. I bet you can fix alot of the engines probles for way way less than 2500 and find a amc 360 or 304 for way less also.

If i were to want to spend a crap load of money ide swap in a 350. I have found them to be great long life engines.
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Unread 12-17-2014, 01:35 PM   #6
my1986cj7
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Quote:
Originally Posted by Matt1981CJ7 View Post
Oil, exhaust, and antifreeze leaks aren't necessarily signs that the engine needs to be rebuilt. Those can be fixed relatively cheaply, depending on where the leaks are.

Lack of power could simply be a tuning issue. Things like vacuum leaks, improper timing and carb adjustments, and worn out ignition parts will cause power problems. Again, all those things can be addressed for much cheaper than rebuilding the engine. Besides, you'll have to do all of that, anyway, if you rebuild.

The best thing you could do is a compression or leak-down test. That will tell you the general condition of the engine. From there, it's a matter of systematically tearing into the engine to see what it needs. Often times a full rebuild isn't necessary, and a general overhaul will suffice.

Now, if you've got money to burn, and just want a fancy new engine with more power, then a AMC V8 will be the easiest/cheapest swap. You could also look at swapping in a 4.0 head, or an entire 4.0 engine, but the small performance gains may not make you giddy like a V8 would.

Swapping in a Chebby or Dodge engine will likely require expensive adapters, different drive lines, motor mounts, etc.... to make them work, but it's certainly doable. It just depends on what your goals are, and what your finances will allow.

Good luck,

Matt
I could have put a sbc in my cj7 for what I'm going to have in my 258 but then I would just have another cj with a sbc in it.
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Unread 12-17-2014, 03:35 PM   #7
row684
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Quote:
Originally Posted by my1986cj7
I could have put a sbc in my cj7 for what I'm going to have in my 258 but then I would just have another cj with a sbc in it.
I'm not disagreeing, I just think that argument is a little weak. You could flip that and say "it's just another jeep with a 258, yawn. Dime a dozen."
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Unread 12-17-2014, 06:25 PM   #8
82JeepCJ7
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The T5 will take a dump, not if, its when. I twisted one with a 258.. Have a T-18 in there now, very happy with it.

Lower gears will also get the RPMs back up into the power band. Adding more HP is not always the answer.

Either fix the 258 or swap in an AMC V8... its a bolt in.
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Unread 12-17-2014, 06:36 PM   #9
Manhattan
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I agree with Matt and the others - if you can patch up the 258, that's the best route.

If you have to swap the motor, another 258 would be, by FAR the cheapest route - everything will swap over, e.g. mounts, bell housing, intake, exhaust, brackets, wire harness, fuel lines... on and on.

If you go to a "different" motor, the SBC is going to be the cheapest - AMC stuff is just enough more expensive (not as competitive) that, when you finally close the hood, you'll have spent more $$$ on a 360 than a 350.
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Unread 12-17-2014, 08:29 PM   #10
dg6772
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These guys all seem to be right on. I have a sbc in my CJ 7. But I started with nothing and built practically everything to accept the swap. I salvaged most parts so I have very little in the change over.

Ex.... Engine/trans combo $200.00, motor mounts (bought from friend) $50, adapter $50 from a guy who parts old jeeps out, input for 700R4 to D300 $187 from 4wd; had to get most everything else replaced anyway.....

Point is... What do you want? How are you willing to get there?

Dave in Muskegon using JeepForum app
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Unread 12-17-2014, 09:51 PM   #11
jeepdaddy2000
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Quote:
Originally Posted by 82JeepCJ7 View Post
The T5 will take a dump, not if, its when. I twisted one with a 258.. Have a T-18 in there now, very happy with it.

Lower gears will also get the RPMs back up into the power band. Adding more HP is not always the answer.

Either fix the 258 or swap in an AMC V8... its a bolt in.
Most of the "my Jeep is gutless" issues stem from too tall gearing coupled with oversized tires.
I would spend some time with a tach and get a feel for what you're turning before dumping a bunch of money into a "tired" motor or engine replacement. You may find a drop in gear ratio's will not only wake your existing power plant up, but even give you a usable fifth gear and bump fuel economy to boot.
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Unread 12-17-2014, 09:58 PM   #12
Tollster
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I would also stick with the 6 think about where ya wheel, and if you could use the power of the 8 without tearing things up. Sometimes that usable low end torque and finesse is much easier on everything and everyone than raw horsepower.
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Unread 12-17-2014, 10:22 PM   #13
jeepdaddy2000
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Quote:
Originally Posted by 82JeepCJ7 View Post
The T5 will take a dump, not if, its when. I twisted one with a 258.. Have a T-18 in there now, very happy with it.

Lower gears will also get the RPMs back up into the power band. Adding more HP is not always the answer.

Either fix the 258 or swap in an AMC V8... its a bolt in.
Most of the "my Jeep is gutless" issues stem from too tall gearing coupled with oversized tires.
I would spend some time with a tach and get a feel for what you're turning before dumping a bunch of money into a "tired" motor or engine replacement. You may find a drop in gear ratio's will not only wake your existing power plant up, but even give you a usable fifth gear and bump fuel economy to boot.
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Unread 12-18-2014, 08:24 AM   #14
2001WJv8
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i bought mine with the sbc in it so can't speak to the 6, but for the fun factor when I put my foot in it .... well ... it's an American V8 ... big grin everytime

so if smiles > cost, my vote is the sbc ... but again, that's got nothing to do with which is "smarter" (I have to be an adult all day at work and make smart/responsible decisions, sucks to that after 5 pm - fire up the gas guzzler and listen to the duals rumble )
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Unread 12-18-2014, 12:19 PM   #15
Manhattan
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Quote:
Originally Posted by 2001WJv8 View Post
i bought mine with the sbc in it so can't speak to the 6, but for the fun factor when I put my foot in it .... well ... it's an American V8 ... big grin everytime

so if smiles > cost, my vote is the sbc ... but again, that's got nothing to do with which is "smarter" (I have to be an adult all day at work and make smart/responsible decisions, sucks to that after 5 pm - fire up the gas guzzler and listen to the duals rumble )
I agree with most of that... 'cause I have and have had CJs with lots of power. My current CJ8 is well north of 300hp. With R.E. 4.5 springs, a 1" BL, 35s... That power can be a handful. When I lift off from a hard pull, the Jeep "settles" and it's a trip. If you understand what happens to leaf springs under a ton of torque, it makes sense. The rear axle actually turns to the right - the REAR axle. As one side squats more than the other, that shackle kicks back, that moves the spring center point back... which moves that end of the axle back... You get the picture.

If I were to build the Jeep again, I'd shoot for 200hp and lots of torque... so a fresh 4.0 would be ideal... or a diesel ;-)
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