304 swap???'s

[poppatello]

Something I realized today. There is one question that none of the forums on this topic is asked so here it is.

What fuel does the AMC 258 i6 / 4.2l , AMC 304 , 360 and 401 use?

That is another million dollar question.

I've done a bit of research on it myself and what I've found is this;

If the AMC 258 i6 / 4.2l is bone stock that regular 87 octane is fine. If you have an aftermarket intake, ignition, or internal work done on the AMC 258 i6 / 4.2l you should run 89 or 91 octane depending on what you have in your area.

AMC 304 is min. 91 octane. Go up one if you don't have it.

360 and the 401 should run on the highest octane fuel you can get.

That may be a curve ball for some folk and also would explain the difference in mpg many are getting.

Now the notation of the fact that we all are running jeeps so mpg doesn't matter is just plan foolish. Everyone no matter how much money they have has a limit and budget. No reason to ride foolishly if it can be helped. Besides, it also means you have that much less time on the trails.

So yes mpg is very important no matter what your running, jeep or not. AMC 150 , AMC 258 i6 / 4.2l , AMC 304 , 360, 401 or SBC. MPG matters to everyone even those that don't addmit it...

 

[CJ]

~~~ AMC 304 is min. 91 octane. ~~~

~~~ 360 and the 401 should run on the highest octane fuel you can get. ~~~

Huh? My 72 factory window sticker calls out 87 octane from the factory and I ran 87 octane for 20 + years with no problems. The Wagoneer we had before with the 401 ran fine on 87 as did the 390 I ran in my CJ. All of these engines had factory compression less than 10;1.

 

[jasonmark1993]

You want to run the LOWEST octane you can without detonating.

Running higher octane when you don't need is a waste of money.

My old AMC 304 was like 8:1 or something; def. did not need anything over 87. Pretty sure all the AMC V8s came from the factory with pretty low compression.

Not sure where in AZ you are but I have a AMC 304 in the corner of my garage. Burns some oil but runs other than that. Id do a cheap rebuild before I put it back in anything. I'm a little west of Yuma.

With Jeeps being so light the 6 cylinder can do pretty good. In stock form its not going to have the same feel as a stock AMC 304 though.

 

[vintagetrks]

You want to run the LOWEST octane you can without detonating.

Running higher octane when you don't need is a waste of money.

My old AMC 304 was like 8:1 or something; def. did not need anything over 87. Pretty sure all the AMC V8s came from the factory with pretty low compression.

Not sure where in AZ you are but I have a AMC 304 in the corner of my garage. Burns some oil but runs other than that. Id do a cheap rebuild before I put it back in anything. I'm a little west of Yuma.

With Jeeps being so light the 6 cylinder can do pretty good. In stock form its not going to have the same feel as a stock AMC 304 though.

I'm in Paulden,Az just north of Prescott. How much are ya asking for the AMC 304 ?

 

[vintagetrks]

I'm hoping a AMC 304 bolts right up to my T-176 tranny. My AMC 258 i6 / 4.2l runs good and gets decent mileage but I'm mostly looking for the power of a V8 and I've always wanted to have a jeep with a V8. So it's really not about mpg. It's not my daily driver more of a weekend warrior. I like tinkering on jeeps. I plan on getting a JK next spring to handle the majority of my trail duties as well. But I dig these old CJ's and I'm having fun tinkering on this one. Here in Az if ya don't have AC in your rig it's gonna be hot out on the trail and my CJ has no AC so she's probably gonna see the majority of her wheeling in the spring and fall when temps are cooler.
So the AMC 304 is more of a fun thing than a practical thing. I just wish they would have done more in the way of stock V8 applications to the jeep from the word go. I like the straight six but honestly theres no replacement for displacement when it comes to making power. I looked into the 4.0 head swap and I can buy a running AMC 304 cheaper than I could even get the head work done on the 4.0 head not to mention all the other headaches that come with that install. I prefer to keep things simple. In my past experience simple seems to work better and be more reliable. So thats why I'm leaning towards the AMC 304 .

 

[poppatello]

I'm hoping a AMC 304 bolts right up to my T-176 tranny. My AMC 258 i6 / 4.2l runs good and gets decent mileage but I'm mostly looking for the power of a V8 and I've always wanted to have a jeep with a V8. So it's really not about mpg. It's not my daily driver more of a weekend warrior. I like tinkering on jeeps. I plan on getting a JK next spring to handle the majority of my trail duties as well. But I dig these old CJ's and I'm having fun tinkering on this one. Here in Az if ya don't have AC in your rig it's gonna be hot out on the trail and my CJ has no AC so she's probably gonna see the majority of her wheeling in the spring and fall when temps are cooler.
So the AMC 304 is more of a fun thing than a practical thing. I just wish they would have done more in the way of stock V8 applications to the jeep from the word go. I like the straight six but honestly theres no replacement for displacement when it comes to making power. I looked into the 4.0 head swap and I can buy a running AMC 304 cheaper than I could even get the head work done on the 4.0 head not to mention all the other headaches that come with that install. I prefer to keep things simple. In my past experience simple seems to work better and be more reliable. So thats why I'm leaning towards the AMC 304 .

Good for you and keep us posted as I'll be working on this behind you...

 

[Saddle Tramp]

I'm hoping a AMC 304 bolts right up to my T-176 tranny. My AMC 258 i6 / 4.2l runs good and gets decent mileage but I'm mostly looking for the power of a V8 and I've always wanted to have a jeep with a V8. So it's really not about mpg. It's not my daily driver more of a weekend warrior. I like tinkering on jeeps. I plan on getting a JK next spring to handle the majority of my trail duties as well. But I dig these old CJ's and I'm having fun tinkering on this one. Here in Az if ya don't have AC in your rig it's gonna be hot out on the trail and my CJ has no AC so she's probably gonna see the majority of her wheeling in the spring and fall when temps are cooler.
So the AMC 304 is more of a fun thing than a practical thing. I just wish they would have done more in the way of stock V8 applications to the jeep from the word go. I like the straight six but honestly theres no replacement for displacement when it comes to making power. I looked into the 4.0 head swap and I can buy a running AMC 304 cheaper than I could even get the head work done on the 4.0 head not to mention all the other headaches that come with that install. I prefer to keep things simple. In my past experience simple seems to work better and be more reliable. So thats why I'm leaning towards the AMC 304 .

All 1972 & up AMC I6 & AMC V8s all have the same bell housing bolt pattern. The flywheels are not the same and are engine size specific as the V8s are externally balanced. The early V8s, 290, 343, & 390 (predecessors to the AMC 304 , 360, & 401), were a high 10+ compression ratio and required Ethel (leaded high octane) where the AMC 304 , 360, & 401 were all 8+ compression and run fine on Regular (87 octane) gas assuming all engines are stock. All the AMC V8 engine blocks have a high nickel content.

 

[jasonmark1993]

I'm in Paulden,Az just north of Prescott. How much are ya asking for the AMC 304 ?

Not sure what they go for. I saw some other guy get one for 400 so hows that sound? I just googled and looked on Ebay and could only find remanufactured ones. I can probably swing something where I meet you in Yuma if that makes a difference. The PO had new exhaust put on it right before I got it so you can have that too. Comes off the manifolds into a single muff and a tail out the back.

Let me know I can send you some pictures of it.

 

[Saddle Tramp]

Not sure what they go for. I saw some other guy get one for 400 so hows that sound? I just googled and looked on Ebay and could only find remanufactured ones. I can probably swing something where I meet you in Yuma if that makes a difference. The PO had new exhaust put on it right before I got it so you can have that too. Comes off the manifolds into a single muff and a tail out the back.

Let me know I can send you some pictures of it.

Up here in the Pacific NW rebuildable cores in AMC 304 or 360 that haven’t been stripped down go for $300-$400 depending upon the goodies that come on it.

 

[jasonmark1993]

You guys have it GOOD up there.

I'm originally from Bellingham but had to move down to CA for work.

My best friend up there can find 401s, jeeps, whatever all day long at a reasonable price.

Down here its 1000 bucks for a torn down 401 missing two pistons, one cylinder sleeved, and a mismatched turned crank.

Sounds like Im in the ballpark then and this one comes with everything. I unbolted the carb for some reason so its just on there loose.

Pretty sure I still have the motor mounts for it too.

 

[Saddle Tramp]

You guys have it GOOD up there.

I'm originally from Bellingham but had to move down to CA for work.

My best friend up there can find 401s, jeeps, whatever all day long at a reasonable price.

Down here its 1000 bucks for a torn down 401 missing two pistons, one cylinder sleeved, and a mismatched turned crank.

Sounds like Im in the ballpark then and this one comes with everything. I unbolted the carb for some reason so its just on there loose.

Pretty sure I still have the motor mounts for it too.

Some parts may be priced a little better up here but it seems like the boys at JP magazine are able to find whole Jeeps of various flavors for prices so low that we can only dream (or maybe fish stories and jeep stories bear a similarity to one another.) If the carb is the original Motorcraft your good to go, just rebuild it.

 

[agood1]

Ok, just want to clarify, if you have a CJ with the stock AMC 258 i6 / 4.2l , a AMC 304 will drop in with no mods, or do the motor mounts have to be changed?

 

[CJ]

Ok, just want to clarify, if you have a CJ with the stock AMC 258 i6 / 4.2l , a AMC 304 will drop in with no mods, or do the motor mounts have to be changed?

You will need to change one frame mount, both rubber engine mounts and engine brackets, various wiring may need to be altered, rad. hoses, heater hoses, maybe the throttle cable, exhaust, clutch linkage, may need a larger rad., and a few other small items.

 

[agood1]

Thanks for the reply.

I've decided to go with a 360 since I found one pretty cheap....but I need to rebuild it....where is the best place to get parts and find out what to use for a camshaft and such?

 

[CJ]

Summit has some of the best prices on the net.