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Thread: 304, 360 and the 401 Are they............

  1. #1

    Default 304, 360 and the 401 Are they............

    I'm brand new here and to Jeeps, so I have a newb question for you Jeep Sages/teachers. I'm into Dodge Ramchargers currently, but a bit different than most, I have a 2x4 modle going for the ProStock look. I believe I'm about to trade my boat for a 78 CJ7 with the 304 motor, and I was wondering if it's worth rebuilding back to stock or better doing a bowtie swap? I'm an old guy, 60, and my ricky racing days are somewhat past me, so I really expect to give this CJ mild abuse, say in the form of dirt roads or across a hill or two, but nothing heroic. How would a fresh 304 stand up to that? The next question comes of ignorance of AMC products. I'm sure you heard about something a 'first time', well this is mine so be kind. Is the three motors 304, 360 & 401 the same basic block/heads thing , something like Dodge has with the 273, 318, 340 and then the 360 with swappable things between the Mopar family of small blocks. The only AMC I ever knew of was a 401 in a Javelin, like a 68 or 69 or so, just after highschool days. It was Fast, the guy raced it at the Orange County Raceway back when it existed in So Cal. So if you could, tell me briefly about the AMC motors...............Thanks ...Rich

  2. #2
    Moderately Senior lunghd's Avatar
    Join Date
    Aug 2000
    In "The Comfy Chair".


    Fellow old guy here - it's been years so check around with those still running these.

    I've had a 304 CJ, 1 304 Javelin and 2 401 Javelin AMX's.

    Sadly AMC Corp. was running on fumes (crack fumes...) in the management department & was well into cutting corners in the early 70's. What their engineers were smoking is beyond comprehension... still, anyone who's ridden in a 401AMX and didn't risk pissing their pants was likely a speed junkie. Those motors could flat put a Javelin down the road. They had a bad habit of tearing out the rear shock mounts on one side off the line - just ripped them clean thru the trunk floor. (Crappy design combined with wheel hop.)

    I once saw a 401 GREMLIN X at a local cruising strip. Yep - a FACTORY 401 Gremlin! Kid tore the driveshaft out doing holeshots - don't think dad let him drive it twice. I damn sure wouldn't... I'm just trying to visualize what I would have done with a Gremlin stuffed with 401cu ! (Likely 5-10 years after the cops caught me! )

    The motors are good - just have the issue of maintaining an older design that doesn't have as many 'bowtie' parts available. You can mix and match cranks & other goodies if you are into strokers - intake issues though. Weak point of the motors is the crappy cast pot-metal timing cover with the integral oil pump housing. AFAIK you can still get those aftermarket. If you could find a 401 to swap in there you could have a LOT of fun with that CJ and no one looking at the engine would be the wiser that it's not a 304.

    If your CJ has an automatic tranny beware the rear transmission mount on the transmission itself! Mine snapped off and basically made useless an otherwise good transmission.
    "...the advice given above is somewhat arrogant and in some cases wrong..." . (I'm not an expert... I just play one on the internet.)

    Another Freakin' Jeep Cherokee Website. _____________ Sure you're smart... but do you have what it takes to make "The List"?

    Here's a place to LEGALLY get .pdf Factory Service Manuals on CD or in print form.

    1990 XJ

  3. #3
    Join Date
    Jul 2009
    Brownsville, Tx


    My buddy had a 304 in his yj on 1 ton axles and 5.38 gears and could not spin the tires offroad from lack of torque. The 304 are usually not the perfered engine. As for the 360 I had one in my cj and it was a great engine that I never had problems with. The 401 is better but harder to find. Most of them (if Im not mistaken) came from the factory with steel cranks as apposed to the cast in most other engines. But as far as a chevy swap...... you can build the engines cheaper with more torque and power as apposed to any other engine out there. I use to race nothing but chevys but got bit by the jeep bug and never looked back. Im more of a 4cyl guy that relys on driving skills instead of power and money. If your a die hard jeep guy go with a 360 or a 401 if you can find one. Because once you figure in all of the modifications to swap a chevy in and labor cost (if you dont do it yourself) it would be cheaper to stay AMC.
    97 tj 2.5 HP dana 30 with RCVs ,ARB, and 4.88 dana 44 with 33 splined chromos , ARB, and 4.88, teralow 4to1 and 2lo 3.5" rubicon express short arm lift sitting on 35" MTR with rock-a-thon 32 bolt beadlocks

  4. #4
    Registered Chris142's Avatar
    Join Date
    Sep 2002
    Apple Valley,Ca AKA:Methville


    A 304 should be fine for a cruiser. Play with the timing and put a decient exhaust on it to improve power some. A 360 would be more fun as would a 401.

    Heres a secret: If 401 shopping forget about the AMC section at PicAPart since everybody else has already been there looking for a 401.

    In 1974 and 1975 International used the AMC401 in Pickups and Travelalls. They called it a 400. I believe the 401 was only used in 1/2 ton trucks and Travelalls and 3/4 ton and better got the real IHC engines.

  5. #5


    I once saw a 401 GREMLIN X at a local cruising strip. Yep - a FACTORY 401 Gremlin! Kid tore the driveshaft out doing holeshots - don't think dad let him drive it twice. I damn sure wouldn't... I'm just trying to visualize what I would have done with a Gremlin stuffed with 401cu ! (Likely 5-10 years after the cops caught me! )

    There were more than a few 390 and 401 Hornets, Gremlins, Concords and Spirits roaming the streets back in the day, thanks to AMC's brilliant decision to offer the 304's in Gremlins, Concords and Spirits, and 360's in Hornets. And, even though only ~800 '71 Hornet SC/360's were built, the 360 was available as an option in regular Hornet models. With all AMC V8's sharing common block dimensions, 390's and 401's were a 100% bolt-in swap. I would laugh so hard I'd almost wet my pants every time I saw all the trouble the bow-tie boys went through to shoe horn SBC's into their Vegas!

    I had a friend who bought a brand-new Spirit with a 304 for his wife, then swapped in a 390 as soon as he got it home. Warranty? We don't need no stinkin' warranty! But, if you really wanted to cover your ass, you could order a 401-powered Gremlin X through your AMC dealer at one time. A performance-minded AMC dealer located in Mesa, Arizona, had a contract with AMC to swap 401's into 5-litre Gremlin X's. AMC would ship the new cars to Randall AMC, they would do the swap, add a "Randall 401-XR decal, and ship it to your local dealer WITH A FULL FACTORY WARRANTY. Base price was $2,995. Performance right off the showroom floor was 12.25 seconds at 115 MPH. Sadly, only two dozen were built because nobody knew about them. Randall went on to build some 401 Pacers, but without factory support.

    The guys in the suits at AMC kept a pretty tight lid on the ones who got grease under their fingernails on the weekends. For the most part, the attitude was, "We'll let you build 'em, but we won't sell 'em." Many AMC dealers treated AMC performance like underground porn. They would sell it if you knew what was available and asked for it, but they would never tell you what they had "under the counter". In 1970, my dad went into an AMC dealership to buy a Rebel MACHINE. The dealer REFUSED TO ORDER IT!!! He had some nice-looking Javelins on the lot, every one equipped with a 232. Dad eventually got his MACHINE from a more enlightened dealer. The performance was way out of line for the stated horsepower in such a heavy car. My dad was quizzing a factory rep about the HP figures one day, and the guy leaned in close and said, "You do realize this engine COST more than you paid for the whole car, right?" Another secret was a $500 "Service Package" for the MACHINE that boosted engine output to over 400 HP and included 5-point-something rear-end gears. The MACHINE was a loss-leader, intended to get the word out about the level of performance available from AMC products, but the effort was sabotaged from within the company.

    Back in the early sixties a dealer in southern California was boring Rambler 287 and 327 V8's to accept Chevy 409 pistons. Those "Gen 1" Rambler V8's were big block motors that the factory chose not to exploit to their full potential, so there was plenty of meat there to work with. These monsters displaced 418 cubic inches. Other than boring the cylinders, the small end of the rods had to be modified, and the heads were re-worked to accept larger valves. The dealer, Bill Kraft, drove one to Kenosha for a meeting with AMC brass in an effort to convince them to design their own pistons and heads to put the beast into production. You know how that went. Might the ungainly Marlin be remembered differently if it had 418 inches of shark teeth under it's hood? How about the 2-door and convertible models in the Classic and Ambassador lines? (The Rambler American couldn't swallow the Gen 1 Rambler V8's, so had to wait until AMC debuted the narrower "Gen 2" mid-block design in 1966).

    Even AMC fans are unaware of the performance potential of the the old Rambler 287 and 327 engines, so they junk them in droves to drop in the lighter Gen 2 blocks. I don't blame them for following an easier and cheaper route to performance, but I can't forgive them for scrapping the old motors instead of saving them, just as I can't forgive the guys who junk their 304 AMC blocks. Sure, there are plenty of 360's laying around now, but they won't last forever. Some day those lowly 304's will be worth their weight in gold when 360's and 401's can't be found. Same goes for 258's. It may make more sense from a cost/benefit standpoint to just drop in a 4L motor today, but DON'T SELL YOUR OLD 258 BLOCKS FOR SCRAP. In 1981, AMC and PPG Industries collaborated to build a 450 HP turbocharged and fuel injected 258 CID pace car for the CART/PPG Indy Car series. Not an inexpensive backyard project by any means, but thirty-some years later, with factory FI and turbocharging having become commonplace, eBay is a treasure trove of bits and pieces to build such a monster on a reasonable budget.

    What saddens me about the state of the car hobby today, is that nobody wants to actually "build" anything anymore. Nobody wants to experiment. Everybody wants to buy parts, bolt them on, and say, "I is a kustomizer." Read the threads in all of the performance forums, and all you see is "cheap and easy".


    1972 Gremlin 401-XR .jpg


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