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  #1  
Old 08-19-2010, 02:48 PM
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360 heads on a 304 block

From what I have read it would require notching the cylinder walls to clear the intak valves but I haven't found anything to confirm this.

I have a good friend whom built an engine like this using a 290 block 20 some years ago and can't quite remember how it was done but is sure they didn't notch anything. Anyone try this?
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Old 08-19-2010, 02:53 PM
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Since 401s are still easy to find, I don't know why anyone would want to do this. Just my $.02...
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Old 08-19-2010, 03:16 PM
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Looking for good gas milage in a CJ8. Not a FSJ. I'm hearing that you can pull 16 to 17 with the 360 heads on a 304 lower end. Breathes free I guess... The 401's I have seen around here are going for alot more coin then the 304 360 engines I'm triping over too...
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Old 08-19-2010, 04:08 PM
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the 304 head will give you the mileage, the 360 valves are badly shrouded by the cylinder,hence the clearancing needed. waste of time in my book.
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  #5  
Old 08-19-2010, 04:48 PM
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Quote:
Originally Posted by Ristow
the 304 head will give you the mileage, the 360 valves are badly shrouded by the cylinder,hence the clearancing needed. waste of time in my book.

X2

The shrouding will eliminate any benefits from going to bigger valves. Stick with 304 heads. Porting and polishing them will give you more bang for your buck than trying to make 360 heads work.
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  #6  
Old 08-19-2010, 04:57 PM
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OK, 401s cost more outside Colorado...

Put an Edelbrock SP2P intake and small 4 bbl on that 304 while yer at it.
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  #7  
Old 08-19-2010, 05:25 PM
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I have a 304 with 401 heads (which are the same as 360 heads as far as I know) on it in my '79 CJ-5. The guy I bought the project from had already done the engine work so I don't know what he did to it to make it work.

Bottom line though...I get 10mpg like all of my other AMC V8s...
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  #8  
Old 08-19-2010, 05:44 PM
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The reason 401's are less expensive in CO is that Flint has cornered the market

Got one in a yard here that is a supposed fairly fresh rebuild (your guess as good as mine) has iron mainifold and orange paint they wanted $750 for.
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  #9  
Old 08-19-2010, 06:06 PM
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Hijack/redirection alert...

What about going the other way? 304 heads on a 360?
I remember back in the day, a hot trick for SBC's was to use a 305 head on a 400 block. Great low end torque.
Low rpm torque generally equals better MPG.
The right AMC 304 heads would have a smaller combustion chamber for a boost in compression which generally helps power and torque too.
I know some of you will cry about high rpm breathing etc. but realistically an AMC V8 does not need to turn high rpm. Unless you are drag racing/mud bogging etc. On the street or on the trails low rpm torque will put a bigger smile on your face than high rpm horse power numbers.
Smaller intake runners (like an SP2P) and/or smaller valves increases intake charge speed. Increased intake charge speed equals more turbulance in the combustion chamber, more turbulance equals better air/fuel charge mixing equalling better combustion equalling more power/torque and efficiency.
So, other than high horsepower number pushers, is there any good reason not to try this?
So along with the small valved 304 heads, would you run a small runner intake too?

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  #10  
Old 08-26-2010, 11:07 AM
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Quote:
Originally Posted by derf
X2

The shrouding will eliminate any benefits from going to bigger valves. Stick with 304 heads. Porting and polishing them will give you more bang for your buck than trying to make 360 heads work.
My friends block was a bored over 290 block with 304 internals. Used at least 30 over 304 pistons but could have been more. Clames to get 16 mpg if he keeps his foot out of it. I imagine that over bore helped with the shrouding mentioned.
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  #11  
Old 08-26-2010, 11:41 AM
Ristow Ristow is offline
 
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Quote:
What about going the other way? 304 heads on a 360?


should give good crisp low end grunt. moreso than a 360 head? probably not really.

the dogleg 304 heads are also 58cc though.....????
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  #12  
Old 08-26-2010, 11:57 AM
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Quote:
Originally Posted by fulsizjeep
Since 401s are still easy to find, I don't know why anyone would want to do this. Just my $.02...


401's are only easy to find at your house...
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  #13  
Old 08-26-2010, 12:08 PM
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Quote:
Originally Posted by Lindel
401's are only easy to find at your house...
And we have all of them within 150 miles staked out too...
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Old 08-26-2010, 12:10 PM
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And we have all of them within 150 miles staked out too...

You better be careful!!! The Feds are gonna break up your monopoly.
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  #15  
Old 08-26-2010, 12:25 PM
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Quote:
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And we have all of them within 150 miles staked out too...
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  #16  
Old 08-26-2010, 09:53 PM
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If fuel efficiency is the goal, stick with the small-valve heads. The larger valves can add high RPM power to a 304 if done right (and I've also heard that it requires some grinding), but it slightly reduces cylinder pressure at low RPM (effectively sorta changes cam duration by exposing more area sooner). Flow velocity at those speeds suffers, which is why big cams go "lumpity-lump" and fill the air with the stink of unburnt fuel. Since fuel efficiency is largely about big throttle openings at low RPM, you want to keep cylinder pressure (and thus torque) high at low speed.

I can see a possible theoretical hook that larger valves reduce pumping losses, but the lion's share of those are at the throttle plate. I question the veracity of someone who claims that fuel efficiency can be enhanced by enlarging the already generous valve size of a 304, but I'm open to contrasting opinion.

If you want to change heads, go for smaller combustion chambers. If you want to maximize fuel efficiency, start with a manual transmission. My Wagoneer, with a hotrod 360 & 3.73 gears has seen over 20 MPG a few times, 22 once (all downhill to stinkin' Denver), and regularly gets 16-18.

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