1979 CJ7 engine choice - 258 or 304? - JeepForum.com
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post #1 of 24 Old 04-01-2020, 09:44 AM Thread Starter
Allegan11
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1979 CJ7 engine choice - 258 or 304?

Greetings. If there is a thread for this, please let me know.

I am in the midst of a complete frame up restoration for a 1979 CJ7 Golden Eagle. My project CJ7 currently has a 258 mated to a T150, dana 20, with stock axles. My parts Jeep has the 304 V8, t4, dana 300, and stock axles. From what I've read, the 79 Golden Eagle edition with the 304 and T150 is a much rarer version than the 258. What I would like to hear from all the knowledgeable people out there, is if you had the options that I do, what would you go with?

My ultimate goal is an all stock OEM CJ7, all the way down to the fabric seats material and buttons that go with them.

Any guidance will help.


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post #2 of 24 Old 04-01-2020, 11:36 AM
Axhammer
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Well, I am far from being an expert or knowledgeable with CJ’s, but I would definitely go for the 304 option.

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post #3 of 24 Old 04-01-2020, 11:40 AM
Hurricane4
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I have owned CJs with both the 258 six and the 304 V8. My current Jeep - '79 CJ5 has the 304 with the T150 3-Speed - 3.54 gearing & 31 X 10.50 Tires on 15X8 steel white spoke wheels.
I think either engine is a good choice.

Also very important is your differential gearing and tire size.

This is from Novak on the T4/T5 transmissions:

http://www.novak-adapt.com/knowledge...s/manual/t4-t5

Borg-Warner T4 & T5 Transmissions

The Borg Warner T4 & T5 transmissions were standard shift, four-speed & five-speed transmissions (respectively)
found in 1982 to 1986 Jeep CJ models. They are light-duty transmissions found behind the AMC 150 (2.5L) I4 and the AMC 258 I6 (4.2L).

These transmissions are popularly replaced with the SM420 and SM465 transmissions, since they share a similar bellhousing bolt pattern and compact installations.


Transfer Case Compatibility
The Jeep T4 & T5 was factory-married to the Jeep Dana Spicer Model 300 transfer case.
Because of the weaknesses of this transmission, we do not make adapter assemblies to join it to other transfer cases.

Engine Compatibility

AMC Jeep
As the T4 / T5 was married to the Jeep engines mentioned above, it is OEM compatible with them.

GM
Because of the transmission's weak service record behind stock Jeep powerplants, we do not offer any conversion to V6 or V8 power.
This is essentially a small car transmission in a truck. The customer's time and efforts are best spent converting to a stronger transmission.

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post #4 of 24 Old 04-01-2020, 11:43 AM
Kruzin
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If your goal is an "all stock OEM" restoration, then you should rebuild it with the stock OEM engine that Jeep was built with per it's VIN#. Otherwise, it's not "all stock".

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post #5 of 24 Old 04-01-2020, 02:07 PM
EricRThompson
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I agree, if you are going for all stock/original, then go 258. I have had a '79 with a 258 and my current '79 had a 304. The 304 stock is not much better than the 258. I went from a T150 to a T176 and that was a great improvement. I felt I was stuck on normal roads between 2nd and 3rd a lot with the T150. I think any of the V8s are good base motors if you plan on increasing hp. I had my 258 in the mid 90's and it struggled to get around tractor trailers. I'm in PA and speed limits have gone up in the past 20 years and feel I need a little better engine to try to stay with traffic today. The ave. mini van can do 90-100mph today.
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post #6 of 24 Old 04-01-2020, 02:08 PM
caseypotts
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Quote:
Originally Posted by Kruzin View Post
If your goal is an "all stock OEM" restoration, then you should rebuild it with the stock OEM engine that Jeep was built with per it's VIN#. Otherwise, it's not "all stock".
I was confused as well on that comment.
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post #7 of 24 Old 04-01-2020, 02:34 PM
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As for me I'm 'all in' for more power and, as it happens I was reading one of my old bike mags from the '70's last night and there was a guy with a '30s side valve Harley and wanted to make a chopper out of it. His bike was 99 percent original and complete and the editor's response was save that ride as is and if he wanted to build a chopper, get another bike as this one was going to be a collector bike in years to come, was the gist. I know I get plenty of thumbs up on my '78 and to me, that's not yet a classic.
So as you have a basket case CJ maybe one course is to save it for a custom build down the road, and restore your runner. Just sayin'

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post #8 of 24 Old 04-01-2020, 05:39 PM
BrutusBlue
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Your Jeep would only be rarer if a 304 matched the VIN. I would keep it all original if your doing a full on restoration. I have had CJ’s with 258 and 304 motors. I had a Cherokee Chief with a 401. I liked them all for what they offered. I would stay original if that’s your focus.
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post #9 of 24 Old 04-01-2020, 10:54 PM
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I see you have another CJ7, a 1984 258 with a T5? If you restored a 1979 with a 258 and T4 why would you want both, are they not similar (I have two similar, so not criticising)?

I suggest you make your Jeep how you want it, unless you are really talented at restoration it is not going to be worth a lot more for being exactly what is on the VIN. A 304 replacing a 258 is not a backward step if you keep it roughly model correct.

The 304 mated to a better transmission would be a good choice, a V8 over your I6. I would suggest finding a T176 and Dana 300 to put in there or go to a T18 or something. The T150 is a good 3 speed but there are also several good 4 speeds

i have one period correct all original Willys but when I say original I mean all the main parts came from CJ3as. Some bits are MB or M38, of the period and could have been fitted (no idea when they were). So where do you draw the line and say you have something which is "all stock"? suggest building it to the VIN is not practicable.

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post #10 of 24 Old 04-02-2020, 08:35 AM
John Strenk
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Was the T-4 or Dana 300 available in '79? I thought that was an 80 thing....
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post #11 of 24 Old 04-02-2020, 10:41 AM
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No, they were not available in 1979.
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post #12 of 24 Old 04-02-2020, 04:07 PM
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Quote:
Originally Posted by John Strenk View Post
Was the T-4 or Dana 300 available in '79? I thought that was an 80 thing....
That's his parts car.

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post #13 of 24 Old 04-03-2020, 03:46 PM Thread Starter
Allegan11
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I guess this is more of a discussion around the engine choice. I'm staying with the T150 and Dana 20. Both are correct to the vehicle and are original to the CJ7. I have VIN plates that go with both engines and will have to get a new/OEM 79 tub. The only concern is the VIN that is stamped on the frame. I'm not sure if that will even be viewable once I strip it all down to the base.

Also, is the bellhousing for the 304 and the 258 the same?

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post #14 of 24 Old 04-03-2020, 04:12 PM
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The next CJ I own will have an inline 6.

I've never owned an I6, and it's about time. My Cherokee was a 2.5L, my CJ5 was a 304, and my WJ is a 4.7L.

The 304 was pretty awesome. Mallory ignition, Crane Cam, Edelbrock intake, exhaust headers, Holley 4bbl carb -- and I spun a hub pulling a Ford Ranger out of the mud sideways. Lesson learned: An AMC 20 won't handle a heckuva lot of power with two-piece hubs. Later, I managed to blow the ring and pinion. Twice.

I was young and dumb and enjoyed standing the Jeep up on its rear tires, but young and poor enough that I couldn't keep fixing it.

Next CJ will also have a Dana 44.

Be aware that, if you have the original axles and it was a 304 from the factory, you likely have 2.72 gearing in it.

Just some random thoughts that might or might not help.

Josh
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post #15 of 24 Old 04-03-2020, 06:11 PM
REDnBLUES
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I would rebuild the 304 and run that with the 3 speed. Just my .02
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