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Discussion in 'Intermediate CJ-5/6/7/8' started by ReLoaded, Dec 23, 2008.

  1. Dec 23, 2008
    ReLoaded

    ReLoaded Professional Drunkard

    Santa Ynez, CA
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    May 24, 2008
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    Of a 360 conversion on a 304 jeep? I have a 72, which stock pushes 150 hp and 245 tq. I don't really get what the big deal about the 360 is, I mean unless it's a four barrel it's like 15 hp more...Unless your talking about the 71 but then again the 71 304 was rated at just 35 hp less. Every time I even hint about rebuilding my 304 on a forum people just tell me to trash it and get a 360, it makes getting advice for the rebuild pretty tough.

    If a freggin ford 302 can be a good engine why can't an amc 304? I understand that for the money the 360 will have a higher output but it can't be terribly different seeing how close they are stock when near the same compression. Any input?
     
  2. Dec 23, 2008
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    This forum? Opinions are like elbows ...

    There's nothing wrong with the 304, but a 360 provides an easy power boost and has easier logistics.

    The 360 is much more available than the 304. The Wagoneer used the 360 up until 1991 (?) and there are quite a few of them around. Wagoneers are cheap donor vehicles. The 360 has better heads and bigger valves, so the power increase is more than the 360/304 = +18% displacement increase would suggest. The 360/401 heads won't fit on the 304 - the larger valves interfere with the bores. Lots of people want the 401, but they can't find a cheap one and can't afford or won't pay for an expensive one, so the 360 is the next best option. A built 360 can make a lot of horsepower.

    If you are happy with the 304 and you aren't looking for a cheap replacement, then you're right - keep the 304.
     
    Last edited: Dec 23, 2008
  3. Dec 23, 2008
    ReLoaded

    ReLoaded Professional Drunkard

    Santa Ynez, CA
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    I got the heads off now, I could just get em machined with some larger valves and call it a day. The shortblock is in great condition so that'll do with a ring and bearing job but at this point I'm not really seeing the benefit of a 360. Most people sell the 165 hp smog version around here anyway...I think to get it up to standard would cost just as much and be 3 times the work.

    Timgr what do you think about getting some larger valves, like maybe some chevy 1.94'' 1.55'' on there? Would that help any?
     
  4. Dec 23, 2008
    ReLoaded

    ReLoaded Professional Drunkard

    Santa Ynez, CA
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    Woops meant the 130 hp version*
     
    Last edited: Dec 23, 2008
  5. Dec 23, 2008
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Compare the intake valve diameter of the 304 (1.787" diam) to the intake valve diameter of the 360 (2.026" diam). You cannot go as large as the 360/401 valves... they will collide with the smaller bore diameter on the 304 block.

    I would guess that the 304 valves are already as large as they can be without interference. The difference in diameters between the 360 and 304 bore is 0.330", and the difference in intake valve diameter is 0.239", so if there are no other geometric constraints (ie position of the valves in the combustion chamber), you could maybe go as much as 0.091" larger on the intake, or 1.878". The 1.94" valves will be too large, I predict.

    You could relieve the block, but it's almost certainly easier to swap in a 360 block and heads (sorry) - the 304 and 360 crank are the same, but the 360 bores are larger. I would just grind, port and polish the 304 heads and call it good - the AMC heads flow well already. Trans-Am Javelins ran the 304 just like the Mustangs ran the 302, so there's plenty of potential there.

    How about an old-fashioned overhaul - rings, valves, rod bearings? That'll freshen up your engine and make it much stronger without a big investment. What's your oil pressure?
     
  6. Dec 23, 2008
    ReLoaded

    ReLoaded Professional Drunkard

    Santa Ynez, CA
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    Oil pressure is about 15 lbs at warm idle, I'm looking to do a couple oil mods while I have it apart as well but I figured I might ask on here before I get to the machine shop to see if anyone has some thoughts on a bit of a performance increase. Your probably right about the valves, I really don't know anything about the procedure I had just heard of a couple people doing it.

    Port and polish is probably a good idea
     
  7. Dec 23, 2008
    High5

    High5 Member

    Urbandale, IA
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    Bulltear.com has a lot of great AMC V8 parts. I would check out what they have to offer. A big culprit of low oil pressure is the aluminium timing cover. They offer upgrades.

    Good luck,

    High5
     
  8. Dec 23, 2008
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    If you want a performance upgrade, a bigger carb helped the 304 in my '73 a lot. Back then, I used a 500 CFM Holley 2300 2V. Great on the street, but terrible off the pavement. Today I'd probably go with the Holley 470 CFM Truck Avenger... or fuel injection. Edelbrock makes some excellent 4V manifolds for AMC. That, and a cam, and higher compression will make a big difference. Ignition upgrade would be good too.
     
  9. Dec 23, 2008
    ReLoaded

    ReLoaded Professional Drunkard

    Santa Ynez, CA
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    Do you have any suggestions for raising the compression a bit? Like I said my pistons are fine so I'll probably keep em, so that leaves me with using a thinner head gasket or maybe decking the block? Off hand is there a cam you recommend?
     
  10. Dec 23, 2008
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    You can shave the heads. Talk to a good machinist. I have not shaved V8 heads - I recall that you also need to remove material from the intake mating surface to compensate. Regardless, I think the only way you can increase the compression drastically is to install new pistons ($$). The guys at the BullTear forum could probably advise you better about this.
     
  11. Dec 23, 2008
    CJ-X

    CJ-X Member

    Ohio
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    I have seen people really wake up a 304 with just a better carb and headers. Nothing wrong with that in my elboes..................I mean opinion. :)
     
  12. Dec 23, 2008
    ReLoaded

    ReLoaded Professional Drunkard

    Santa Ynez, CA
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    Would it be totally pointless to attempt a 3 angle valve job on such a mild motor? At this point it's looking like a 4 bbl intake+ carb (which I have) rings and bearings (which I'll get) Porting the heads (which I can do) and a cam.

    Hei and a decent set of headers were on there previously, so I got about $300 left to spend after the heads get re-worked and I buy what I need. Suggestions?
     
  13. Dec 23, 2008
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Also, the early 360 4V manifold is square pattern (Holley pattern) and will bolt on to the 304. Cheaper than the Edelbrock manifold, but you'll have to seek one out. The later manifolds use a goofy spread bore pattern (Motorcraft 4350) - don't get one of those unless you can machine an adapter to a more common carb pattern (Holley, Quadrajet). BTW the Rochester Quadrajet is an excellent off-road carb, and an equally good performance carb. You can get an adapter from the square pattern to Quadrajet, and I suppose you could make an adapter from the Quadrajet spread bore pattern to the (different!) 4350 spread bore pattern. Kind of complicated to tune, but an excellent choice if you can do your homework and understand what it needs.

    <edit> AFAIK all quality valve jobs are 3-angle. Common thing. You can get a 5-angle if you want more performance IIRC.
     
    Last edited: Dec 23, 2008
  14. Dec 23, 2008
    khamill

    khamill Member

    Kansas
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    The reason I went with a 360 instead of rebuilding the 304 was $$$. It was going to cost me over $1000 to do a simple rebuild with a new front cover and oiling upgrades. Any issues I found were going to add to that. I was able to find a recently rebuilt, used 360 for $300. That allowed me to spend the rest of the budget on other things that go along with the rebuild (clutch, heater hoses, radiator hoses, water pump, etc.).
     
  15. Dec 23, 2008
    ReLoaded

    ReLoaded Professional Drunkard

    Santa Ynez, CA
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    Hmm, thanks for all the input guys! I'll get these over to a machine shop and hopefully I can find my digital camera to get some before and after shots.
     
  16. Dec 23, 2008
    80cj

    80cj Member

    Hawaii
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    The name of the game is torque and the 360 has an abundance of it.
     
  17. Dec 24, 2008
    seventythree

    seventythree New Member

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    the previous owner of my 304ci powered 73 raised the compression to 10:1, installed a cam (i dunno which), MSD distributor/ignition box, edelbrock manifold/600cfm carb. and headers. monkeys This thing hauls ***! I have a 98 mustang cobra and a 03' silverado SS so I know what kinda fast is...and if I could keep the jeep pointed in a straight line I'm sure it would keep up with the others.
     
  18. Dec 24, 2008
    drexotic

    drexotic Happy now?!?!?

    San Diego
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    I got one if you (anyone) is interested . . .

    It's heavy !!! Shipping might be a few $$$

    monkeys monkeys monkeys
     
  19. Dec 24, 2008
    evanjm

    evanjm Yeah, it's got an F-head.

    Leesburg, VA
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    You can always bore out your 304 to a 360--hell or even a 401 if you wished. If its bored out, then there goes your valve-to-bore clearance issues. Then again, slap on a nice pair of aluminium heads, 4bbl intake, and carb and you'll get a good bit of kick out of your old 304.

    As far as milling goes, you could take 20 off the block and 20 off the heads to boost compression. Remember though, boosting compression will mean higher octane gas is required---more $$ on a daily basis.
     
  20. Dec 25, 2008
    80cj

    80cj Member

    Hawaii
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    Though the AMC v-8 block are externally the same, I've read that you will likely come very close to hitting water if you try to bore an 304 to 360 or 401. Bore sizes are 3.75, 4.08 and 4.165 respectively. A lot of boring for a 304 block.
     
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