How to Hot Rod a Small Block Mopar 318by Bobby R. Goldsmith
When most people think of hot rods and high performance, they think of big block engines cranking out high levels of horsepower and torque. However, small block engines offer plenty of hot rod performance potential as well. Here are a few tips and tricks to hot rodding the modest Mopar 318 small block engine.
Intake And Exhaust
Install a camshaft with a profile that provides adequate lift duration (.480 to .498) for both the intake and the exhaust. Any lift beyond .500 will require an upgrade of the stock valve springs, as OEM springs cannot accommodate that much lift. The camshaft should also feature a lobe separation that is practical for street driving but that allows for efficient intake and exhaust of air and fuel. A lobe separation between 109 degrees and 112 degrees is suitable.
Roller rockers or hydraulic rockers provide a good balance between performance and economy, though a true hot rod usually benefits from solid lifters and rocker arms. Make sure that the lifters are adequately matched to the camshaft's profile.
Replace the stock cast iron intake manifold with a dual-plane aluminum intake. The decreased weight, combined with increased flow of both air and fuel will provide significant horsepower and torque to the small combustion chambers of the 318.
Install full headers as a replacement for the stock exhaust manifolds. Efficient egress of exhaust gases is crucial to achieving the optimal performance from the Mopar 318.
Install aluminum heads with compact combustion chambers to achieve a higher rate of combustion per revolution of the engine. 64 CC combustion chambers provide on average a compression ratio of between 9:1 and 11:1. For a small block Mopar, that provides significant power.
Attach a medium flow AFB carburetor to the intake manifold to ensure the proper flow of air and fuel. Smaller engines like the Mopar 318 do not need high-flow carburetors that dominate the performance aftermarket catalogs. Too much fuel makes the engine choke, misfire and run inefficiently.
Ignition And Timing
Install a timing gear drive as a replacement for a timing chain system. The gear drive provides a more efficient transfer of power between the crankshaft and the camshaft.
Integrate an electronic ignition system that stabilizes the delivery of spark to each cylinder. This stabilization reduces the frequency of misfiring, and allows each cylinder to fully expel and explode the air and fuel in the combustion chambers.
Install an optical distributor as a high performance upgrade to the OEM distributor.
- check When it comes to the Mopar 318 or other small engines, there is little margin for error, so the engine upgrades must be planned in detail. Make sure that every high performance addition is compatible with the others, and realize that "more" is usually not "better" for most small block applications.
- close Always disconnect the battery prior to any work on any part of the automobile.
Items you will need
- photo_camera dodge challenger prototype image by Jorge Moro from Fotolia.com