Forum Index => The Library => Topic started by: Reggie on January 20, 2008, 21:47:24
Title: Engines: 318 Street Recipes
Post by: Reggie on January 20, 2008, 21:47:24
318 Street Recipes - From High Performance Chrysler Engines (Best of Hot Rod Series)
Below, excerpted from an article that originally appeared in Hot Rod Magazine, are the dynamometer (dyno) results from a baseline test of a stock 318 engine, and the horsepower gains recorded after various modifications. These results will give you an idea what to expect if you decide to upgrade the 318 engine in your M-body.
186 HP at 4000 RPM (Base Platform):
318 non-roller 8:1 compression cop car short block
Production 318 cam with 240* adv. dur. .390"/.400" lift
Heads were the 4323302 casting (302s) high swirl mileage/emissions heads with the heart shaped chamber (9.0:1 compression installed)
4BBL cast iron cop car intake manifold
Thermoquad carburetor
Stock exhaust manifolds
Factory stock (non lean burn) electronic ignition system
Added Mopar Performance P4286671cam (272* adv. dur. .455" lift)
Mopar P4120600 Gold Box competition ignition control unit
This combo added 39 HP
331 HP at 5750 RPM:
Swapped the 360 heads for ported and polished 302 heads modified with 1.88" intake/1.60" exhaust valves
Mopar Performance P4120249 valve springs
This combo produced a 41 HP increase over the previous combination, netting 1.12 HP per cubic inch!
This combo also produced more power than all of the other combinations from the lowest RPM on up
Notes:
All tests were conducted on an engine dyno stand with an unrestricted exhaust system.
4323302 casting heads (302s), 4343646 castings and similar castings are 1.78" intake/1.50" exhaust high swirl mileage/emissions heads that were used on all civilian duty M-bodies from late-1985 to 1989.
Actual cop car engine compression per the 1987 Factory Service Manual was 8.4:1 due to the open-chambered 360 heads. Compression for civilian model 318s with closed-chambered factory 302 heads was 9.0:1.
The base HP for civilian model 2BBL 318s was about 140, so expect HP numbers a bit less than the above baseline test if you add a 4BBL intake/carburetor and convert to electronic ignition.
Modifications usually work together to produce results. The 41 HP increase recorded in the last dyno test was achieved because the camshaft was much stouter than a production cam, and it was designed to take advantage of superior breathing heads. A similar increase should not be expected with the same heads and a stock cam.