Performance 304

So my oil pump went out in my 304 and I have spun a crankshaft bearing--just my usual luck. Anybody have any suggestions on where to get a good complete rebuild kit or reman motor. Also if I decide to rebuild my 304, I would like to get the compression ratio up so I can make more horsepower. I would like to get in the 9.5:1 range so I can be approaching the 300 hp range. Has anybody built a similar motor. Where can I get pistons that are not dished? I have heard that using heads from my '75 CJ with 58 cc combustion chambers with flat-top pistons from a pre-70 motor will put me in that compression range. Can anybody confirm this? Also flat-top pistons seem to be difficult to find, does anybody know of a souce (cost minded)? Would I be money ahead to upgrade to a 360? Also I have read on AMC websites for Javelins, AMXs, etc that AMC motors are not as octane sensitive as GM or Ford motors with increasing compression ratios? Sorry for the large amount of questions, but nobody seems to have built performance amc engines when I search the web. I have never rebuilt an engine but it seems like a good time to learn. I see no sense in just rebuilding the motor to stock specs when just playing with the compression ratio can yield such an increase in horsepower. It may just be overkill but if I have to rebuild, I might as well make it better.

 

The performance AMC motors are the 390 and the 401. I wouldn't toss a lot of money into a 304 if your looking to make more power. Just step up to a stockish 360 for significantly cheaper. I have had tried them all except the 390. The only 390 I had any interaction with was in an AMX and it was just plain fast.

The 401 is a great HP motor. But they are getting spendy and a little hard to come by. The 360 in stock form makes great power. Almost too much for a CJ. The last 360 I bought I paid $300 for a 360/T-18/D-20 package.

 

Indeed. The best performance 304 is a 360. No reason to keep the 304 if you're planning to buy expensive pistons etc.

If you keep the stock compression (or slightly above), you can use pump gas.

Go to www.bulltear.com - the forum there focuses on AMC V8s specific to Jeeps.

 

I got a 390! yeeeee haww! R)

 

this 1979 304 runs on pump gas
and it has some ponies as well

 

i am interested in this thread also...

will be going to a V8 soon and have thought about going to a ford 289/302-T18-D300 combo. the reason considering the 289... might be getting one free plus its pretty light.

as far as the 304, i was gonna stay away from it. maybe a 360.

any input

 

IIRC the 304 and 360 are the same crank, but a different bore. The 304 necessarily uses smaller valved heads, because the 360 and 401 valves would not clear the 304 bore. You get more cid from the 360 plus better breathing. Nothing wrong with the 304, but you get more oats for your money starting with a 360, esp. if you need to rebuild.

I don't think changing to the 289 is worth it unless you have no engine currently. The 360 or 401 is a direct replacement for the 304 - exact same exterior dimensions. You'll need a 360 or 401 flywheel if you go to either of those, otherwise everything fits. The AMC V8s aren't particularly heavy, say 550 lbs, maybe a little lighter than a SBC. The Ford is lighter, but it's also a fairly short stroke engine IIRC - exciting in a classic Mustang, but not the torque monster you might want in a Jeep.

 

as far as the ford motor, i was also looking at the ability to run a D300 tcase and T18 (Ford) tranny. a perfect world would give me a D300 for my T18A. i dont have the donor engine yet but am keeping my eyes open for a 360 or 401.

thanks for the input, didnt mean to jack the thread... been thinking this one for a while. i dont wanna put anymore money into my .258

 

Anyone found a good intake manifold for the 304? Thinking of the Edelbrook but the catalog descriptions sound more or less the same amongst models. Beach cruiser with light trail is the goal and eventually the Howell fuel inj kit , which takes a "holley" bolt pattern.

 

carcraft magazine did an article on a 360 a yr or so ago. it may be worth checking them out.

edlebrock also released aluminum heads, and exact replacement headers (for the stock v8 manifolds) no exhaust mods. the parts are out their you just have to find them. you might also check with northern auto parts in souix city (?) they always have good buys!!

remember their is no replacement for displacement!!

just my 2 cents!R)

 

I have tried the route of adding all the performance goodies to a 304. I spent a lot of money on it and still ended up with a slug. I had it in front of a power robbing turbo 400 which made it even worse. As for what edelbrock manifold I think the performer is the one to look at. But I wouldn't bother with that on a 304. The 304 performed as well or better with the stock 2 barrel than it did with the performer and a small 4 barrel. It may have gained a couple HP but nothing noticeable. I have seem some articles on mega squirt that looked like it might be promising on a jeep.

 

My issue is an intake manifold with issues, and its going to be better in the long run to replace than to repair, and in a couple of years I might go to EFI. I've since found a couple of options, including a stock manifold for sale in my area for $20. This looks pretty much like an unbolt and rebolt kind of deal...did you run into any wish-I'd-known-beforehands when you did yours? I'm not changing out pistons, etc.

 

Doesn't the fuel injection bolt up to a two barrel manifold anyway? I would stick with the stock manifold/motocraft 2100 before I would do the performer and a 4 barrel. For the cost of the performer and a shiney new edelbrock 500cfm (not sure the exact spec, but around that) carb I would think you could adapt a chevy tbi with mega squirt electronics. http://www.megasquirt.info/

 

Well, on the edelbrock optons I'm looking at model 2131, but there is also a stock manifold for sale in my area. I haven't found a tremendous amount of info for this, lots on exhaust, not much on intake. I'll check out the megasquirt website, unfamaliar with that option.

 

Are you telling me that the 360 heads I have wont work on my 304

 

Yes, to the best of my knowledge.

 

When I first got my 304 I asked a machine shop about boring out to a 360 and they said the block can't hang with that. i think he said it would end up too thin in places.

 

You could always just put Chevy or Chrysler 1.88 valves in the motor to aid in breathing. A decently built 304 should easily make 300hp.

You can put 360 heads on a 304 but the block will need to be notched for the valves, this used to be commonly done on other makes of engines. The big draw back is that the valve then becomes shrouded a bit, limiting some of the benefit of the larger valves.

 

I think the 304 in stock form is plenty of power for me, I'm not a dragster, lol, but I bought an Edelbrock intake on Ebay for $170 so now I just gotta figure out how to install it and what all I'll need. Its a good project for me, something I've never done before.

 

Yeah, when the block is cast, the factory use a different core for each displacement so that there's just enough iron to form the cylinders. You can have the cylinders sleeved to support the thin wall, but it's sort of pointless considering the cost of a good 360 block.