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Unread 02-04-2008, 05:41 PM   #1
Bobz007
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Join Date: Dec 2006
Location: Massachusetts
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Buying 304, questions

OK, well I've finished the aesthetic part of my 82 CJ7 build now I'd like to work on the drive train. Right now it has a 4.2, t-4, d300. I found a good deal on a complete running 304 locally and think I am going to pick it up. The t-4 wont last long behind the v8, usually I see people going to the t-176. However I also know someone who has an ax-15 out of a YJ that I could get for a good price. I'm pretty sure it will still bolt up to the 304 but is it a good choice, I hear they are fairly stout and stand up well behind 4.0 which puts out decent power in the newer tj's. I like the idea of having the 5th gear to drive on the highway. I do not plan to take the jeep offroad. Also the d300 will bolt up to the ax-15 with an adapter if I am correct. Let me know how this sounds? thanks in advance!! -Bob

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Unread 02-04-2008, 06:47 PM   #2
only in a jeep cj
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I responded because I have several CJs. I did a 304 swap in my 75 CJ-6 (from a 4.2). Others may agree, but IMO, I would go the 360 or 401 V8 if I were to swap another V8 in. I did because I had no engine, short time, and a donor CJ with everthing for 400 bucks. Yes, it does have more power, but mainly in the midrange and with more weight, gas comsumption, and NOISE. I have the T-15 3 speed and 3.73 gears in the receiver CJ. In my experience, a good running (read strong) 258/4.2 is about the same as an worn 304. I believe that the main difference in the drivability of a CJ with respect to its power and preformance is due more so to the gearing in the axles and transmission. My DD is a 86 CJ-7 with 3.31 gears...when I swapped in a temperary T-4 in place of a T-5 during a rebuild, I found my RPMs were so high, my top speed dropped by 25MPH (85 down to 60) and my MPG was almost cut in half. All due to 5th gear. In the same fashion, my buddies 258 lacked power, so he actually took my advice and switched from 2.72 gears to 3.54s for is 31" tires.....he loved it and got all his power back. I tell you all of this because I would keep the 258, make sure my tires match my gearing, my transmission match my driving and engine and run with it for a lot less trouble. Weigh the pros and cons of motor mounts, wiring, fuel lines, transmission adaptors, driveshaft mods, etc, etc. Just my opinion.
__________________
Ed

1975 CJ-6 304 T15 Dana20 30/44 3.73
1983 CJ-8 258 T5 300 30/44 3.31 Looking for full or half hardtop buy or trade
1986 CJ-7 Laredo 4.6 stroker T5 300 30/44 3.31
1986 TJ-7 Trail Jeep project in the works
2003 Inca Gold TJ Rubicon
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Unread 02-04-2008, 08:27 PM   #3
jeepdaddy2000
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1971 CJ5 
 
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Quote:
Originally Posted by only in a jeep cj View Post
I responded because I have several CJs. I did a 304 swap in my 75 CJ-6 (from a 4.2). Others may agree, but IMO, I would go the 360 or 401 V8 if I were to swap another V8 in. I did because I had no engine, short time, and a donor CJ with everthing for 400 bucks. Yes, it does have more power, but mainly in the midrange and with more weight, gas comsumption, and NOISE. I have the T-15 3 speed and 3.73 gears in the receiver CJ. In my experience, a good running (read strong) 258/4.2 is about the same as an worn 304. I believe that the main difference in the drivability of a CJ with respect to its power and preformance is due more so to the gearing in the axles and transmission. My DD is a 86 CJ-7 with 3.31 gears...when I swapped in a temperary T-4 in place of a T-5 during a rebuild, I found my RPMs were so high, my top speed dropped by 25MPH (85 down to 60) and my MPG was almost cut in half. All due to 5th gear. In the same fashion, my buddies 258 lacked power, so he actually took my advice and switched from 2.72 gears to 3.54s for is 31" tires.....he loved it and got all his power back. I tell you all of this because I would keep the 258, make sure my tires match my gearing, my transmission match my driving and engine and run with it for a lot less trouble. Weigh the pros and cons of motor mounts, wiring, fuel lines, transmission adaptors, driveshaft mods, etc, etc. Just my opinion.
Gotta agree......
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Unread 02-04-2008, 09:31 PM   #4
Bobz007
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Join Date: Dec 2006
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I know the 4.2 is a great engine I never said it wasn't, but I really want a v8, if for no other reason then just to say my jeep has one. Plus my 4.2 has seen better days, it burns a little oil, and hates the cold. I said 304 only because i found a good deal on one, if it was a 360 this thread would have a different title but is the 304 really worse of an option then the larger displacement versions? Im 19 years old and will have 4 months off from college this summer and I need something to take up my time. My time and motivation are almost endless I just want to know if this is a good combination to be thinking about.
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Unread 02-05-2008, 06:25 AM   #5
jeepdaddy2000
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Bob, you asked for opinions and you got 'em. IMHO swapping a 258 for a 304 isn't worth the trouble. The swap to the 360 will deliver better power for the cost, time, and sacrifice in fuel economy. Realistically, "I found one cheap" isn't usually a good long term reason to install anything, especially used engines which have a habit of costing in hidden repairs over time. On that note, the quote "but I really want a v8" and "I do not plan to take the jeep offroad" tells me your gonna probably be a bit hard on the skinny pedal. Again, I would opt for the long term durability of a cast iron transmission, preferably a 176. As Ed stated above, gearing plays a huge role in both power and economy. Many five speeds won't pull high gear with larger tires because the gearing is poor. Money spent in this area can eliminate much misery in the long term. My best advise it to decide exactly what you want your Jeep to do and plan your build around that. Whichever route you choose, I bid you the best of luck.

Scott
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