318 300-350 hp goal : now 323 cu.in

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ValerianMagnum

ValerianMagnum

the little car that could
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Picked up a rebuild shortblock , stock build nothing fancy , not even 10 000 miles , needs a cam and intake , since im not keeping the stock heads , i have a set of 340 j heads , or was thinking to maybe. Buy 360 heads and mill them ? And a lil 600 cfm 4 barrel and headers , want good compression for street and will run headers , 340 stock cam grind ? Let me know what you guys think! Going in a 70 duster

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build it like its a 340.
340 cam is a decent choice, but before you pick cam what gears and stall you willing to run?
 
Rule of thumb for a mopar street engine to get you 1 horsepower per cubic inch
  • Decent street cam (.450-.500 lift/216-230 @ 050)
  • Decent exhaust (duals, good manifolds or headers)
  • Decent compression (8.5 - 9.5)
  • Decent heads (good factory/or mildly ported poor factory)
  • topped with a 4 bbl
 
Here we see my 70 340 with j heads beside the 318 , to built it like a 340 is a very good plan , i have already a double timing chain , hv oil pump , m1 la intake dual plane , but dont know what heads to choose. , the 2 last engine i buit was 2x 380 hp mopar crates but never played with a 318 ( surely not to make it a pocket rocket !! ) *** want a street driver so in a light 70 duster , 3.23 or 3.91 gears , and already have a 4 speed for it.
 
318willrun i hear ya !!! Ahahah but how do you make the compression go up ? I have to go to a machine shop but dont even know were to start . Since the pistons are plain jane 30 over , the only way is to mill the heads right ?
 
ValerianMagnum said:
318willrun i hear ya !!! Ahahah but how do you make the compression go up ? I have to go to a machine shop but dont even know were to start . Since the pistons are plain jane 30 over , the only way is to mill the heads right ?
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Well, 318's are "advertised around 8.5 to 1", don't mean your there, though. How far the pistons are down the hole, and the CC's of the heads will determine that.
  • Means your .030 over, that will gain you compression, but what pistons did they use??? If they used a flat top piston, and they are no further down the hole than the factory, that may be enough to get you a true 8.5 to one.
  • Yes, you can cut the heads .040 and gain close to a half point..... IF you use the same thickness of head gasket as the factory used.
  • only true way to know the compression is to measure heads and short block, don't forget the head gasket thickness.
  • A true 8.5 to 1 compression is plenty to perform on the street with pump gas.
 
ValerianMagnum said:
Here we see my 70 340 with j heads beside the 318 , to built it like a 340 is a very good plan , i have already a double timing chain , hv oil pump , m1 la intake dual plane , but dont know what heads to choose. , the 2 last engine i buit was 2x 380 hp mopar crates but never played with a 318 ( surely not to make it a pocket rocket !! ) *** want a street driver so in a light 70 duster , 3.23 or 3.91 gears , and already have a 4 speed for it.
Click to expand...

With those gears i wouldn't go bigger than comps xe262h with headers or 265deh if running manifolds. Stock 340 cam is similar to xe250h. 318 with 3.91 is similar to 340/3.73 and 360/3.55
 
you might be happier with 250 - 275 hp. A 350 hp 318 will need to rev and
that is not too good for lo rpm power.The old 204/214 429 /444 cam will shine here.
Should pull hard from 800 - 4800 rpm.
 
Id go something like that cam if he goes 3.23, but if goes with 3.91 especially with 4 gear Id go bigger, with 3.91 and 4 gear don't need a lot of bottom end. Yes 318 needs more rpm to make the same power as a 360. But were probably talking a peak of around 5500 rpm for 350hp for a 318 and with a xe262h cam probably make 325 hp at 5200-5300. Not exactly a high rpm screamer for either.
 
ir3333 said:
a stock hi comp. 340 only made 275 hp
a lo comp 318 .... 325hp ?
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stock 340 is really about 9.5:1, I assume he's going for around 9:1 not much difference.
engine size really has nothing to do with hp. just where the powerband is and torque.

If you build a 318 to 340 specs, should make about the same hp at about 300 rpm higher.
Valve shrouding might steal a few ponies but at 275-325 hp probably not.
Idk 318 with 9:1 340 heads 4 bbl headers and possibly more cam depends who he listen to.
sounds like a 325 hp engine to me.
 
340s made 299 hp ; what all the infos says and 314 hp with the 71 thermoquad and intake , so with this combination and j heads with big 2.02 x 1.60 with a decent cam or even the 340 cam. And headers, pretty sure i can break the 300 hp mark and torque too. Dont want to spend a fortune right now , thats why i bought a fresh 323 cubic inch engine . dont think that 17 cubes will really make a difference.
 
I would do magnum style heads. Remember that those with the crummy barrel ram and an extremely wimpy stock cam makes 230hp and 300lb-ft NET with all the accessories and the stock manifolds.

My friend and I built a 94 318 magnum for his demon, where everything on the short block other than the cam and valve springs is stock and we used a small hydraulic roller from Lunati. I wouldn't be surprised if this made right around 300hp and its very torquey and also daily driveable. The car has a stock 904 with a stock converter and 3.23's.
 
are these 325 hp 318's measured on a dyno?
...no water pump,no alternator,no fan,no air cleaner,no mechanical fuel pump,no exhaust through open headers ?
 
OMG! Everyone’s treating the 318 like a 2 cylinder down 273 with a million miles! Goooood freaking Lord!

Mill the heads some and stab it with a 268XE or similar cam. You’ll get what your looking for.
 
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ValerianMagnum said:
How much is needed for the heads ( milling ) !!!
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Prices vari hugely! Way back when....
25 years ago....
I had 3 quotes. $100 per head up to .060.
$50-$150 depending on the amount milled.
$35 for the pair.

All within 20 miles of each other.

I just paid $80 per head, aluminum.
 
rumblefish360 said:
OMG! Everyone’s treating the 318 like a 2 cylinder down 273 with a million miles! Goooood freaking Lord!

Mill the heads some and stab it with a 268XE or similar cam. You’ll get what your looking for.
Click to expand...
The Rodney Dangerfield of engines. ....no respect.

Jeff
 
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