AMC 304, 360, 401 ????

Hey everyone !

I just picked up for a song a complete '78 CJ-5 with a 360 V8 hooked up to a ford truck 4-speed.

It runs great, but the original owner warned me that although the heads have a recent valve job, the engine has 130,000 miles on it.

My question is this, Which engine would be the most desired power plant to drop in this thing when that time comes?

I know 304's were a stock option in this year, and the 360 is readily available in most Wagy's, but what about this 401 I've been hearing about?

I plan on haveing a friend of mine Build me a motor in the coming months, What should I start with?

Also, I've got a Ford 351 Cleveland 4V sitting on an engine stand I was going to put into a 'Stang, but have recently sold it. What would you think of this motor in my CJ ??

Thanks guys, Rob
__________

'48 CJ-2a
'58 CJ-5
'67 CJ-5 Tux
'78 CJ-5

 

No help here Rob. Just a welcome back

 

Hi Rob - re the 351C, Novak recommends against that motor specifically, but I don't know why. They lump it in with the Ford big blocks. They say the 351W is ok, although long. The oil pan sump is in the wrong place on all these Fords unless you use a Bronco pan.

Re the AMC engines, the 401 is a great engine. All the modern AMC engines (290, 304, 343, 360, 390, 401) should be as close to a bolt-in as is possible. The earlier series (290, 343, 390) has a different deck height than the later 304, 360, 401 series. The 304 and 360 are very similar except for displacement and the valve sizes. If you use 360 heads on a 304 you must notch the cylinders. The 401 is a different animal - special high-nickel block and a forged steel crank, unlike the cast crank of the 304 and 360. The 401 cylinder walls are quite thin, and can't typically be safely overbored more than 40 thou (or such ... IIRC). Because of the hi-po cache', the 401s are very much in demand. Good cores are hard to find because of the wall thickness problem (they can be sleeved, but that's an added expense).

In 1973 when I bought my new CJ5, the dealership (Brian Chuchua) had a demonstrator with a crate 401 in place of the original 304. They would sell these Jeeps off the lot, with a full factory warranty. The changeover couldn't be simpler - pull the 304, move the accessories, drop in the 401.

 

Yes, cooling ... in addition to any problems you might have keeping axles under the Jeep.

 

the 401 will drop right in cause it is the same block as the 304.that is why they have the thin walls,AMC just put in bigger pistons.I might be wrong but I am pretty sure.I talked to some guys with the 401 and they where scared to drive there cj5,way to much power for a short wheel base on the street.I aways look on ebay for a 401,that is my plan for my 73!

 

I drove one on the street - pretty exciting. I didn't have the chance to power into any curves and such, but in a straight line it really jumped.

BTW I twisted (but didn't break) the rear axles and broke spider gears on my '73 - exactly the same Jeep I drove with the 401, except the stock 304. The Trac-loc from that period is known to be weak, but the one piece Dana 44 axles are a pretty good upgrade for V6 era Jeeps.

Re the cylinder wall thickness, The ultimate bore size is certainly set by the cylinder-to-cylinder spacing in the casting, However, each of these displacements uses a different casting, and the displacement is cast prominently into the driver's side of the block. When the block is cast, the "core" determines where the unmachined cylinders are and where the water passages are. The shape and position of the water passages is different for each of these three blocks, such that you can't necessarily bore out a 304 to 360, etc. The core was also designed to minimize the amount of machining that the rough block would need, sp. cleaning up the bores.

There were some 360 service blocks that had thick walls and could be bored to 401 (some kind of dodge around the racing rules) but you're not going to find one of those. You can also sleeve a 360 block to 401, but it's probably cheaper to find a 401, and then you'll have a steel crank too.

cj-dano, if you really want a 401, watch the FSJ boards. Late 70s wagons and trucks came with them as an option...

PS the 360 (and 304) respond very well to induction changes and a new cam - nothing to sniff at. They're roughly equivalent to engines of similar displacement from the same era. Has some oiling problems though, especially on high-mileage engines.

 

I really didnt mean they just put bigger pistons in the 401,there might be some inturnal changes,but the timing chain cover,intake,headers engine mounts,ect., are all the same.

 

Hey, Thanks you-all for your input. Sounds to me that my choices here are going to be driven by oportunity. My original 360 has never been re-built, so it may get a once -over, paying attention to upgrades in intake manifold and carburation along with internals such as cam shaft selection.

One of you mentioned crate motors, is there AMC motors available this way?? I've had great success with a GM change out in my Chevy truck a few years ago.

Would any of you know roughly the price diff. between haveing a motor 'built' or getting one in the mail?? I'd probably like HP in the range of 300 +

Thanks, Rob

 

The crate motors came new from the AMC factory. No more AMC => no more motors.

I'd be biased to having it built locally, since then you'd be able to hold the builder accountable.

 

There are now aftermarket aluminum AMC engines: "Indy" I think. Loads of improvements, but you will spend some coin. An LS1 family Cheby engine would probably be more practical in the long run and give you twice the gas mileage of a 401. I'm saving my 401 for an AMX/Javelin.

 

The 351C is a great engine in a street car but in a jeep the powerband is all wrong especially with the 4V heads.. they like to make all there power up top.. I would say the best way to go in my opinion would be the 360.. they are easier to find than the 401...


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