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Unread 02-16-2013, 07:54 AM   #1
Jr76
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Cj BS'ing about engine swaps

So I have a 76 CJ-7 with the AMC 304 thats got about a half billion miles on it. Its all stock down to the two barrel and smog pump.
I have been thinking of a swap, but wanted to see what others thought.
I am looking for dead on reliablity (yes I know its a jeep). and about 250-300 hp. For the $ spent would I be better off swaping out to a Chev 350 or staying with and rebuilding the 304 or should I look for a 360/401 instead?
I have it hooked to a SM4?? 4 speed and a 300 twin stick. Everything works well for me, just time to refresh the power. Its a mall jeep with a lot of use in the logging roads/snow runs and some sand dunes. No mudding and no rocks

I can weld, and the mounts and swap would be no problem. But 250hp is not really that much these days. And I know the AMC parts are a bit more than the Chev, but I would not need to swap radiators/mounts/exhaust/wiring.

I would self perform all work, including the rebuild of what ever I end up using.

What are your thoughts?

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Unread 02-16-2013, 05:27 PM   #2
Repete
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I'm guessing it's hooked to an SM465, which means you must have an adapter. Or else the 304 is hooked to a T18. I'm assuming you have a granny gear.

If it is SM465, then it's already got a chev transmission, which means removing the adapter would allow for direct bolt up to a Chev motor. My thoughts are you'd be easier off building a chev motor if you want to stay in a tighter budget - building an AMC motor will cost more, and it will take some effort to get that horsepower out of a 304, which means more expensive parts. It can easily be done, but comes down to money. If you are interested in modern electronics, you could likely put a newer 5.3 in there.

My 2 cents, but since my reply is from Canada and we just phased out the penny, my opinion is now worth nothing LOL.
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Unread 02-16-2013, 05:52 PM   #3
ki4cye
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My 2 cents worth, I'm a big fan of the chevy tbi 350. Simple and reliable.
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Unread 02-17-2013, 11:01 AM   #4
ramjett
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I prefer the injected 302 , but I have to go with the tuned port Chevy as well. Simpler and less expense . Go to a wrecking yard and get the harness and a low mile engine and it will run for a long time.
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Unread 02-17-2013, 08:46 PM   #5
Jr76
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Im not a huge fan of electrical work, something about letting the smoke out of the wires...
But it might be time to man up and learn a little something.

SM420 , Granny first gear, reverse down and to the left.
I got it for a ok deal, would not pass Cali smog with its current set up. I tagged it in WA. so no more smog problems for me !

I need to hunt around and figgure a few more things out. I think the Chev is the way to go. I dont care for the AMC oil pump/system.

Last edited by Jr76; 02-18-2013 at 09:16 AM..
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Unread 02-18-2013, 08:25 AM   #6
Jr76
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Well I was wrong, its a SM420
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Unread 02-19-2013, 07:57 PM   #7
kw89425
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Quote:
Originally Posted by Jr76 View Post
Im not a huge fan of electrical work, something about letting the smoke out of the wires...
But it might be time to man up and learn a little something.

SM420 , Granny first gear, reverse down and to the left.
I got it for a ok deal, would not pass Cali smog with its current set up. I tagged it in WA. so no more smog problems for me !

I need to hunt around and figgure a few more things out. I think the Chev is the way to go. I dont care for the AMC oil pump/system.
Down and to left?
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Unread 02-20-2013, 11:09 AM   #8
TIPPEDITOVER
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I've been where you are now. My concerns were the same. Now there is a 1990 chevy 350 TBI under the hood of my jeep. It's a 1000 times better than the 304 that was there. You NEED fuel injection if you want to enjoy your jeep off road. OEM chevy TBI is the easiest, most reliable and least expensive way to get fuel injection. You will be in love with it once you've had it.

Couple the TBI 350 to an sm420 or sm465 and a dana 300 t-case and you will have a smile permanently stuck on your face.
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Unread 03-13-2013, 09:50 PM   #9
Jr76
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Well Im ont 100% sure its a sm420 reverse is down and to the left next to 2nd. Very low first gear, I see no adap from the bell to the trans so I dont know.
Just going off what the PO stated, But I bet its something jeep installed.

Its more of a Mall/snow/sand jeep. Hard core rock trails and all that are not my game. I like to drive it to work, hit the dunes in the summer snow runs in the winter type stuff. Im not into beathing the poo out of my junk to see what brakes first.
Might just play with the 304 for a few years and think about the swap
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Unread 03-14-2013, 01:50 AM   #10
TIPPEDITOVER
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Yeah it's down and left, I just popped out and checked mine to be sure. Be aware it's nearly impossible to get input shafts for these things anymore. You will almost have to buy another SM420 to get one. Same goes for some of the gears. Absolutely an awesome gearbox, but parts are getting hard to find now. Not that you ever need those parts, just sayin..
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Unread 03-22-2013, 10:56 PM   #11
Jr76
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If I see one laying in the dirt or at a swap meet I will pick it up!

Kind of wish I had overdrive, but Mr. Hankey really don't like going 60 anyhow.
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Unread 03-25-2013, 08:06 PM   #12
JeeperDon
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You could just rebuild the 304 and add a Howell or Holly injection system (if they make them?) You would skip all the adapting to something else work and expense, and still end up with a decent V8.
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Unread 03-29-2013, 08:57 AM   #13
Jr76
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I think that will be the plan, might shop around for a 360.
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Unread 03-30-2013, 10:59 PM   #14
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Mainly because of money, if I had it to do all over again I would have kept the original AMC 304, put a Howell TBI kit on it (so I could have fuel injection), rebuilt the original T150 3 speed (smoked input shaft bearing), put a 3.15 gear reduction kit in the Dana 20 t-case. Those mods would have covered everything I felt I needed regarding engine, trans and t-case. Yeah, now that you mention it, I suppose a 360 would have been cool.

Instead I went with a Chevy TBI 350, SM420 trans, Dana 300 (4.1 reduction gears). It's absolutely awesome with those mods, but the time and money invested doesn't equate. I sure did learn alot through the process. One thing was for sure. The way my CJ was when I got it was unusable on the trails here where I am. The gearing was all wrong. Low range was not even close to being low enough. It's all good now though, more than good.
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Unread 03-31-2013, 06:58 AM   #15
JeeperDon
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My general thoughts are based upon basic power. To me, even though I do like power (born and raised in Detroit a looong time ago), in a Jeep for normal on-road and off-road driving, a couple hundred HP is enough. The only time I would swap to bigger/different is what I did, from a 4 cyl. Any other motor that originally had 200HP or more should just be rebuilt. Gears make a huge difference in perceived power too. I've got maybe 200-210 HP in my V6 (was 4 cyl) and 4.88 gears, manual trans, 4:1 in the t-case, and I can go from crawling to 75 mph on the freeway (rarely do, but it can) with confidence and stability.
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