Stock 72 318 power gains

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smeef

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Hey everyone I am waist deep in a base 72 duster restoration/mod and was wondering just about how much power I may be adding with all of the motor upgrades I have sitting on my shelf. its a base 72 318 which was rated at 150 horse and 260 ftlbs of torque with stock manifolds and 2bbl carb and single exhaust.

I have a dual exhaust setup with flowmaster 50 series waiting. was going to port the factory exhaust manifolds. I have an aluminum air gap intake and an edelbrock 600 cfm carb. I also have a comp cam kit with cam at 260 duration and .440/.440 lift. was also planning on porting and polishing the original heads.

I am looking to get as close to 300 horse as possible does all this get me close? I know its difficult with the 8.6 to 1 compression
 
Should get you to at least 250 ish hp.

stock long block and xe262h cam 4bbl and headers dyno 282hp @ 5000 rpm

I wouldn’t worry about what it gets should give a decent increase in performance.
 
One of the big games of the 318 heads is when you have them reconditioned with seats see job guides in different order of course also ask for the valves to be back cut. Does valves have a tremendous ski-jump on them. At the moment I'm in the market for a new valve grinder, used but new to me, so in the 30 to head video I wanted to show a back cut along with the chamber and valve job work but I'm not able to at the moment. I feel that alone would add another 4-7cfm.
 
72 duster 318 here. The car had 75,000 miles, ran fine and didn't use any oil. I stripped it down to a shell, did the paint, suspension, blah, blah, blah. The eventual plan is to do a 360 or 408, but for now I decided to do an absolute bare minimum hop up on its stock 318. I already had an LD4B and 650 DP laying around. I got a Summit 272 454 cam and lifters on Black Friday for $99. Got a cheapo timing set. Pulled the valves out and did a quick pocket port and installed Comp 901 springs and new guide seals. Dougs headers. Summit 2.5 exhaust. HHR Electric fan. 904 with stock converter and TA RMVB. 3.23s. 275/60-15 Cooper Cobras. It's been to the track once and the best of four passes was 14.39 at 96. I just put a 9.5 PTC converter in a couple of weeks ago and am eager to get back to the track.
 
You're not tapping much airflow with that camshaft and those heads don't flow that much Peak anyways without opening the valve beyond the usable range of lift. The heads working better would in turn make the camshaft work better. It's not the cubic inch that limits you it's the heads. And giant heads would suck like Edelbrock or something, total Overkill. Those stock 675 heads can be made to flow 200 CFM by .400 lift easy. The 318 head porting for the Average Joe have flow numbers on the first page for the casting heads you have so whatever your cam lift is...you can look at the lift corresponding to the flow number and that's all you're getting multiplied x 2 for power.
Just putting it out there.
 
Copper head gaskets generally need o-rings, so I would use the Mr. Gasket thin gaskets instead. That said, you'll come a lot closer to your 300HP mark with headers. Manifolds will choke it more than you'll ever think.
 
My thoughts. Do a 318willrun port job on the heads with a 3 angle valve job and matching springs for the cam.
I did 360 manifolds into a jegs 2-1/2" duals, 340 cam, weiand stealth and HEI ignition. Nice sound and runs pretty strong.
 
I would use this camshaft and advance it 4 degrees COMP Cams 20-221-3 COMP Cams Xtreme Energy Camshafts | Summit Racing dont waste your time porting the exhaust manifolds, just port the heads, and run dakota 2 1/8 exhaust manifolds or if you have power steering run a 73 340 driver side manifold.

With compression it will be hard to get it to decent ratio with out changing pistons my 72 block was measured at 7:8:1 with stock heads and pistons. I milled 302 heads down to 58cc using 1008 felpro gaskets and barely got a 8:1 range. In your case i would put more effort in the heads and valve springs and advancing the camshaft
 
From the linked article:
Purchase a set of cast or -- preferably -- silicon-alloy hypereutectic pistons designed to deliver a 9.5-to-1 compression ratio with a 72 cc combustion chamber.
Click to expand...

That’s gonna be a tuff.......

Flat tops with no valve reliefs, at zero deck, with the Mr.G .028” head gasket, and 72cc heads....... you get 9.23:1.

I guess you’ll need some domes.........for 300hp.
 
Whattabunchahooey! There’s so much wrong information in that article the “writer” should remove it from the web.
 
toolmanmike said:
You want a laugh this morning? Take a few min. and read through this doofus' post. There's a lot of BS information on the internet! :mob::mob: How to Build a 300 Horsepower 318 Mopar
Click to expand...

The best thing about that article was the advertisement right smack in the middle of that explains exactly how to correctly wipe your ***.

I didn’t know there was a wrong way. Since I didn’t read the advertisement, I have to assume I’m doing it wrong.
 
Used 9.2:1 Flat top pistons with full floating rods came in the '89 to '91 318 truck engines. They also have the 302 Closed Chamber heads.

Pistons sit .040 ths in the hole.

Can use those pistons In your build.

20200608_134533.jpg
 
smeef said:
Hey everyone I am waist deep in a base 72 duster restoration/mod and was wondering just about how much power I may be adding with all of the motor upgrades I have sitting on my shelf. its a base 72 318 which was rated at 150 horse and 260 ftlbs of torque with stock manifolds and 2bbl carb and single exhaust.

I have a dual exhaust setup with flowmaster 50 series waiting. was going to port the factory exhaust manifolds. I have an aluminum air gap intake and an edelbrock 600 cfm carb. I also have a comp cam kit with cam at 260 duration and .440/.440 lift. was also planning on porting and polishing the original heads.

I am looking to get as close to 300 horse as possible does all this get me close? I know its difficult with the 8.6 to 1 compression
Click to expand...

Yur in trouble. Lower your expectations.
You didn't mention why you wanted 300hp; that's the first hiccup. And the second is Normally aspirated, lol.

Forget all that; Just install 3.91s and a 2800 stall TC and in the first two gears she will be a terror in the city. And keep the Dual exhaust and 600, but get you a small-port intake. Even a single-plain small-port.
But if a 4-speed, then make it 4.10s
 
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