After making sure the block was usable, we then focused on the heads. Now a 318-even during the "good" years-never came with a performance version of heads. By that we mean the valves are small. But how large a valve does a 318 actually need? The first thing we did to the heads was remove the valvesprings and do a basic check of the guides. From the factory, the valve-stem-to-guide clearance should measure between .002 and .004 inch. Let's just say that without even properly measuring, we had a lot more than that when checking the exhaust guides. So now we needed to replace the guides-there's one expense. Once you start figuring what certain machine work costs, you really need to sit down and decide if another alternative would be better. In our case, we planned to use the factory pistons and rotating assembly, so would our little 318 benefit from installing larger valves? Factory 318 heads came with a 1.780-inch intake valve and a 1.500-inch exhaust valve. We felt that increasing the intake valves to hi-performance 2.02 inches would be too much valve, and we would lose some velocity. But we did feel that installing a set of 1.88-inch intake valves and 1.60-inch exhaust valves would be beneficial. Again, figure what you'll pay for the required machine work and decide if you should just get aftermarket heads or rebuild what you have. Since looking up the cost of an aftermarket head is as easy as clicking your computer mouse, we decided to simply redo our cast heads to give you an idea of what rebuilding heads can cost. Replacing the valves cost us a total of $86.18. having the heads cleaned, eight new guides installed, and the seats opened up cost us $400. We did a little "home porting" of the runners, and installed the valves and spring ourselves, so that cost us nothing. If you want someone to do it for you, figure on a couple hundred bucks. if you have a shop do everything, you can figure on spending in the neighborhood of $700 or more for a set of "tweaked" cast-iron heads. What do aluminum heads cost where you shop?
Now that we knew what parts we needed to order, we needed to come up with a plan. We wanted a reliable engine that would move the Barracuda down the road, sound like a performance engine at a cruise night, and actually stay together. this is a budget engine and we're re-using the rotating assembly, which means we are dealing with the factory compression ratio of 8.8:1. We can practically run water through the carburetor and it'll run fine. Since we decided to open the valves a little and do some home porting, we felt that adding a little lift and duration to the camshaft would be a benefit. Keeping in mind we have no budget for a camshaft, we simply went with a hydraulic flat-tappet piece from Comp. We chose a Comp PN K20-223-3, which comes in with a .477/.480-inch lift and a .224/.230-degrees of duration at .050. To ensure we had everything we needed, we ordered the complete kit from Summit at a cost of $385.
Finally, we needed an intake and carburetor. We could have just put the two-barrel intake back on and got a carburetor, but who are we kidding? But what budget-minded intake and carburetor could we order that would be beneficial to our little 318? A single plane was out of the question because this engine wasn't designed to utilize an intake like that. So we looked around and found that Professional Products makes what they call a Crosswind (PN 55026). The Crosswind intake is designed to fit 318, 340, and 360 engines-both LA-style and the late Magnum V-8s. The manifold features an air space under the plenum chamber, which allows air to pass through to help keep the incoming fuel/air charge cooler than is possible with a conventional design manifold. The manifold is designed to accept the standard length bolts that came with your original engine. Special finishing plugs are provided to cap off the unused bolt holes. The intake set us back $150. Topping off the intake is a Speed Demon 650 carburetor (PN 1282010). you can buy this carburetor at Summit Racing for $350.
i have a 78'plymouth volare with a 318 in it what can i do or buy to make it faster