How much horsepower will my built 318 make?

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Hosstyle

Hosstyle

Hoss Milton
Joined
Sep 6, 2016
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Vero Beach,Fl
I'm wondering how much horsepower my built 318 will make in my 1972 Plymouth Duster. It's getting painted right now & I'm itching to find out.

Engine specs:
Mopar 5.2L 318
Bored 30 over

Cam: Sum-1798
Duration - 285/285
Lift - .480

Edelbrock 318/360 intake
Edelbrock 650 series 4 barrel carb
Stock heads
Brand new headers

If anyone knows around how much horsepower it will be making I would love to know.

(The duster also has a 904 transmission & an 8 1/4 rear end with a 3.55 positraction gear. Anyone know what it will run in the 1/4 mile?)

Much appreciated,
Hoss Milton
 
Yup. Probably 250 or so at the flywheel.
 
My calc spits out about 270hp at the flywheel at 5200rpm and around 220 at the wheels. If the car weighs around 3400lb with you in it then a 14.5sec 1/4 is entirely achievable.

Those numbers are entirely dependant on how efficient your intake is, what your carb and ignition tune are like, and assumes around a 8.7:1 static compression ratio.

Edit: 10:1 will yeild around 310hp and 250 at the wheels with a 14 flat 1/4 if you hook up well.
 
Thanks everyone! Here's a picture of the engine.

image.jpeg
 
Good lookin engine. What pistons are you using?
 
Hosstyle said:
It's an original 1970 block 318. Got the engine already bored .030 over so I'm not 100% sure exactly what pistons. I think they are just flat top 9.6(ish)-1
Click to expand...

If they are stock replacement 318 pistons, there's no way in hell the compression is that high, unless the heads and or block have been very heavily milled.
 
I say that pretty paint is worth at least 3 tenths... I'm going with 14.20's because of the 3.55's and headers. If the heads were home ported, I bet high 13's would be reasonable :)
 
ir3333 said:
well...stock early 340's were 275 hp and you have less compression and smaller heads.
Rusty is probably close
Click to expand...
I truly believe the early 340's were more than the advertised 275. In the same years, the 318 2bbl was rated at 230. One ride around the block and you'd know there were more than 45 hp between and X-head 340 vs. a 318 2bbl. I'd say 310 - 320 hp would be more accurate. When they went to the net horsepower rating, the 318 fell to 150, while the 340 was still at 240. they all of a sudden had 90 hp more... lol.
 
For the stock heads, have the valves been upgraded to 1.88 intake and 1.60 exhaust? Have you tried any porting or gasket matching? 318willrun did an excellent thread on minor porting of the 318 heads.
 
One thing. If those spark plugs are painted, you need to clean them. Paint has metallic particles in it and will conduct electricity.
 
Stock 318 heads are on it right now, eventually we are going to beef it up, magnum head swap maybe and a bigger cam, heck maybe just a 360 swap. But right now, this is his first car and a driver.
 
I'd say 300 hp
Heads is the main thing holding that engine back, a set of EQ'S would probably give you at least another 50 hp.
 
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