Last month, we tore down our small-block for a garage overhaul. This month, we'll check all our parts and re-assemble our engine with new goodies from Summit Racing Equipment.
As we discussed in part one of our small-block overhaul, rebuilding an engine can have many meanings depending on how the word "rebuild" is defined. While engines that are excessively worn or have had some catastrophic failure should certainly be rebuilt by a professional machine shop, engines with normal wear can usually be freshened up in the home garage using basic hand tools and a few specialty items.
The condition of our '72 model 318 was unknown when we began this project, so nothing would have surprised us when we pulled it apart and looked inside. As it turned out, our engine was in pretty good shape. Our crankshaft wouldn't need to be reground, and our rods were in good shape as well. Unfortunately, the same couldn't be said for our block-apparently water had invaded a couple of cylinders requiring the block to be bored oversize for new pistons.
After ordering our new parts from Summit Racing and sending the factory parts to the machine shop, we cleaned all the hardware and small parts ourselves. This will make assembly go quicker when the machine work is finished and our parts show up.
While the required overbore and new pistons did add some cost to our budget rebuild, all was not lost. By just having the machine shop bore and hone the cylinders, and by purchasing an economical set of Speed Pro pistons, pins, and rings, we only added a few hundred dollars to the cost of our overhaul. Fortunately, our small-block Mopar engine came with full-floating wrist pins, so we changed the pistons ourselves without paying the machine shop for that service. While we did pay the machine shop to clean our components in their hot tank, we'll save additional money by installing the cam bearings and freeze plugs ourselves. We'll also install new rod and main bearings, and reseal our 318 with new gaskets and seals.
Although this rebuild is on a tight budget, we decided to upgrade a few things about our 318. Since the camshaft had to be replaced anyway, we ordered a performance hydraulic flat-tappet cam kit from Summit. Also, by purchasing a Summit brand timing set, we got a true, double-roller timing chain and gears for about the cost of a stock replacement timing set. While our engine came with a cast-iron, two-barrel intake manifold, we'll be upgrading by installing an Edelbrock Performer aluminum unit and topping it with a Holley four-barrel. Another item that our engine needed was a new harmonic balancer. The rubber insulator of our factory balancer had deteriorated significantly so we decided to replace it. Rather than purchasing a new, factory replacement unit, we again looked at the Summit brand balancer for the 318. For barely more money than a factory replacement, the Summit brand dampener is SFI-certified and NHRA-legal just in case our small-block sees any time at the track.
Any part you get back from the machine shop should be thoroughly cleaned with soap and water, and then dried with compressed air before assembly starts. Remember that dirt is the biggest enemy a new engine can have, so the cleaner the parts, the better the engine.
When it came to the cylinder heads for our 318, we had issues. Our original intention was to lap the valves in our stock heads, install new valve seals, and reuse them. When we tore the heads down, however, we found that the valve stems were corroded, the guides were severely worn, and several seats would need to be replaced. While we could have salvaged these heads by sinking considerable money into new valves, guides, and seats, the bottom line is, these stock 318 heads just aren't worth the expense. Because we wouldn't be reusing our heads we had to make a decision. we could simply exchange them for a set of overhauled stock units, but we wouldn't see much of a performance gain. Since we know the newer "swirl-port" 302 casting cylinder heads will bolt right on and offer additional performance due to a better combustion-chamber design, we decided to look for a pair of those instead. As luck would have it, our friend Tod Struck at Inline Performance Specialist had just what we needed-a set of slightly used swirl port heads with decent valvesprings. So for around a hundred bucks we made the choice to ditch the factory '72 heads and run the used swirl ports. Having friends is always a help in a situation like this. You never know when you'll need a part that a friend has no use for, so it's always a good idea to spread the word and maybe save a few bucks like we did.
Once all our parts were gathered, our engine went together without a hitch. The small-block Chrysler engine is easy to build, and when properly assembled will give many years of great service. Follow along as we show you how to perform all the steps to properly assemble a small-block Mopar engine.
