Pre-Magnum 318 Power - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 07-30-2006, 01:34 AM
CC Rider
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Pre-Magnum 318 Power

New here and thanks for the great forum.

I just read the article from this site on performance tips (and there were plenty, many conflicting) about how to boost 318 power. Being a long-time Mopar fanatic, and having modified several 318's, I would like to contribute.

The W2 head comment was of course un-realistic - expensive and race only stuff is overkill for 4x4 use. 360 heads on a 318 will result in a net drop in horsepower because the chambers are larger, effectively lowering the compression ratio to about 7.2:1. If you're in California, your mid-eighties 2BBL 318 (like mine) is legally restricted to be nearly stock as there is almost nothing out there that is CARB approved. But there are a few things which are effective.

1) A MP 340 cam is unseen by the smog gods, and will easily boost performance without resorting to solid lifters or exotic valvetrain mods.

2) True dual exhaust is out in California except on pre-77 vehicles, but low restriction catalytic converters are legal and out there. I'm running a low-restirction 2-1/2" in/out cat and it made a noticeable difference in power.

3) Low restriction muffler - goes without saying.

4) Electric fan - freeing up about 3-5 extra accessory horsepower you don't need at speed.

5) Valve job using older 1973-74 heads with larger valves, porting.

6) If legal in your state, I've had excellent results using the Edelbrock SP2P manifold and 600CFM Carter 4BBL. Great torque and driveability. Make sure the float levels aren't too low or stalling could result at steep angles.

7) Timing is everything. As any Mopar guy knows, SB LA engines need at least 8 degrees of static advance, with 10 degrees being even better. If you ever let a Chevy mechanic "tune" your engine, you'll probably notice that it runs like crap afterwards. That's because they retard the timing too much.

8) If you're into the engine, Hi Comp pistons (9.5:1) are free horsepower, but be prepared to run premium.

9) Minor things: Cutting half the water-pump impeller blades off, windage tray, headers, true duals (if legal).

10) A clean air filter. K&N will give you measurably more power, but for off-road work, it doesn't filter as well as paper or foam. If you're racing, it won't matter.

Without getting radical or illegal in some states, that's about it. Of course for serious power, the 360 swap is the best way to go - especially if it's an older E58 engine. Look for them in old Diplomat Police Cars.

The great thing about sticking with the 318 is the excellent reliability, durability, steel crank, simplicity, relatively good fuel economy and inexpensive/common parts/repairs. They're hard to break.

I don't know if that helps anyone out there with a pre-magnum, post smog vehicle like mine... Again thanks for letting me vent after reading the article.

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