Modified 318 horsepower guesses?

[drobertson]

So what I have is a 1973 318 motor that's original to my 1973 charger. It is bored .040 over, so thats about 325 cid. It has the stock 8.7:1 compression ratio, .454 lift summit street strip camshaft, stock heads, a 4 barrel intake from a 79 360, edelbrock 600 cfm 4 barrel performer carburetor, moly rings, dual 2.5 inch exhaust, 2 turbo mufflers, and summit racing full length headers.


I just have a few questions. I'm almost done building the engine, and I was wondering whether the .454 lift camshaft would be safe on factory spec valve springs. Secondly, what kind of power should I be making? The engine was rated at 150 hp from the factory with the low-flow manifolds and tiny carburetor along with single exhaust and small cam.

I hope the 318 will be making about 240-300 horsepower. Does that sound about right?

 

[Cranky]

You'll probably be closer to 240 than 300. A stock early 340 was rated at 275 and they would usually run high 13's in an 'A' body. If you run an ET calculator and type in 13.50 for a 3000 lb car, it'll spit out around 250 hp....

 

[rumblefish360]

I'd change the valve springs

 

[Seventy]

I wouldn't run stock valve springs... I think you are going to be around 200-220hp with an electronic ignition, port matched heads and intake, free flowing exhaust, and air cleaner...

 

[drobertson]

I wouldn't run stock valve springs... I think you are going to be around 200-220hp with an electronic ignition, port matched heads and intake, free flowing exhaust, and air cleaner...

Do you think that stock 340 valve springs would be okay??? I can get some for like 2 dollars a piece from rock auto.

 

[drobertson]

Ok so some more mods: I changed the 79' 360 intake to a weiand aluminum 4bbl intake from summit. I also went ahead and bought an MSD blaster 2 coil to help the ignition out a little. I will put in thin head gaskets to up the comp. just a little bit.

So the combustion chamber volume is 63cc, the engine is bored .040 thousands over, .454 lift, 260' duration camshaft, 340 valve springs, thin head gaskets, weiand 4bbl intake, MSD coil, edelbrock 600 cfm carb, and full length headers with true dual exhaust. All I want is for the car to be a little quicker than stock. Sometime down the road I'll just build up a 440 for the car.

 

[QQBlue1]

I have a similar set up. It is a 1968 318 with the original heads, although we put in stiffer springs and did a pocket port. I put on a duel plane Eddy intake and 600cfm carb with a similar cam and headers. It makes 192 hp to the rear wheels and 225 lbs of torque.