Of all the segments of the automotive hobby, one of the fastest growing is the custom rod contingent. There are a host of reasons for the increase in interest in '49 and later cars, certainly price, availability, and unique styling are at the forefront. But they have another thing going for them as well, and that is they are inherently good cars.
When compared to their '48 and earlier street rod brethren, the '49 and later variety, no matter what the make, require far fewer modifications to make them into fun, safe, and reliable drivers which also makes them easier, faster, and far less expensive to build. And while it is true that many custom rod candidates can benefit from some updated components, such as disc brakes, power steering, or comfort items such as air conditioning or a contemporary sound system, more often than not the original running gear, particularly the engine, is worth saving. A case in point is our very own '60 Dodge Dart station wagon.
Although our trusty Dodge ran great and produced respectable mileage with reasonable power, the blue smoke out the tailpipe and the metallic rattles from within suggested the original 318 Polysphere was at the end of its road. Our first impulse was to yank the tired motor and replace it with a late model 318, 340, or 360 small-block Mopar, but then we had a change of heart. A little investigation revealed that all the parts necessary to freshen our engine were still available through Kanter Auto Products, Weiand still stocked an aluminum four-barrel manifold, and Chris Nielson Cams had performance grinds in stock. It was as if the forces of nature were telling us to leave the Polysphere in place.
Rather unique designs, Polyspheres were produced by Chrysler as an alternative to the more expensive Hemi. Like the Hemis, the valves of the Polysphere were still laterally opposed, which offered many the advantages of the hemispherical combustion chamber. But by using single rocker shafts, reorienting the valves, and moving the sparkplug outside the rocker cover, the heads were much more compact, which lowered costs.
All Chrysler divisions used Polyspheres, they were identified as Plymouth Hy-Fire, Dodge Red Ram, and Chrysler Spitfire. First introduced in 1955, there were actually two versions of the Polysphere, one series was based on the Hemi block and were built in displacements of 241, 259, 270, 301, 315, 325, 331, 354 cubic inches. (These engines can be converted to Hemis by substituting the necessary parts). The second version of the Polysphere, referred to as the A series, were built in displacements of 277, 301, 303, 313 (Canadian), 318, and 326. This series was built through 1967 and can be identified by numbers stamped on the front of the block under the head on the left side; none of this series can be converted to Hemis.
While parts are readily available for Polyspheres, the potential for confusion exists, particularly with the 318. With the introduction of the new LA engine family in '67, there were now two 318s to deal with when it was time to buy parts. The new engine shared little with the older design, about all that can be interchanged are rod and main bearings, timing sprockets and chain, valve springs, oil pump driveshaft, and distributor. As a means to distinguish between the two, many parts suppliers began referring to the A as the "old style" 318 and the LA as the "new style" 318.
Making Everything Old New Again
While all the operations shown here were performed on an early Dodge 318, any engine from an Auburn to a Zephyr can benefit from the same treatment. Granted, parts for some engines are hard to find, and that can obviously complicate things. But as far as the machine shop operations go, the processes used to bring virtually any engine back to life are the same.
For those who may have heard some of the common terms that relate to building an engine, but may not be exactly sure what they mean, here is an overview of the operations involved in rebuilding any engine.
Line Honing: The first thing that should be checked on a block is the alignment of the main bearing bores. For the crankshaft to rotate with as little loss to friction as possible, it is critical that they be in perfect alignment. Normally alignment is checked in a special fixture or with a precision straightedge. If the alignment is as it should be, leave it alone, there is no advantage to honing a block if it's not necessary. However if the block has been damaged due to a spun bearing, as an example, or the alignment is not perfect, line-hone as required. The process consists of taking a few thousands off the surface of the main bearing caps, then they are reattached to the block, and the main bearing bores are honed to the proper diameter, and as a result are in perfect alignment.
Decking: It is not unusual for the deck height (the distance from the centerline of the crankshaft to the head gasket surface of the block) to vary from side to side on a V-8 as well as from one end of the block to the other. The result is the pistons come closer to the deck in some cylinders that others; that means there is a difference in compression and power production between the cylinders. Decking insures the block's surfaces are flat to facilitate head gasket sealing, and parallel to the crankshaft centerline.
Boring: When cylinders and pistons wear the clearance between them becomes excessive. To reestablish proper tolerances, the cylinders are bored oversize and fit with larger diameter pistons (this also increases displacement slightly) and rings. Pistons for some engines come as big as .125-inch oversize, but here's a valuable tip. Never bore an engine until the pistons are measured. Some manufacturers figure clearance in to the finished size of the piston, others don't.
Honing: This process establishes a pattern in the cylinder walls to hold lubricant and help the rings seat. There are three types of rings: cast, chrome, and moly, and each require a particular cylinder wall finish. Cast rings break in fast and are good for less than perfect cylinders, often these are the only type available for older engines. Chrome rings are best suited to dirty environments but can take a long time to break in, these were once considered "performance" rings, and may be found for some older engines that were commonly hot rodded. Moly rings (called that because the face of the top compression ring has a groove filled with molybdenum disulfide) break in fast and provide excellent sealing but have limited applications for older engines.
Connecting Rod Preparation: One of the most critical components in an engine are the connecting rods. Few things are more catastrophic than a rod failure, so special attention should be paid to them. Prepping rods begins with Magnafluxing to check for cracks, next the diameter of the small ends are checked, and the big ends are resized by removing a small amount of material from the rod and cap mating surfaces, bolting them back together, then honing them to the proper inside diameter. This insures proper bearing crush, which is what prevents the bearings from spinning in the rod. Finally the rods are checked in a special fixture to insure they are straight in all planes. If possible it's always wise to install new rod bolts if replacements are available. Check with ARP for high-strength bolts listed by size as opposed to application, for oddball engines.
Crankshaft Grinding: Generally considered a repair procedure, grinding the crankshaft journals undersize (normally .010, .020, or .030-inch) removes any imperfections and ensures the journals are smooth and round. The appropriate undersize bearings are then required. On any vintage engine, check bearing availability before grinding the crank.
Balancing: This is the key to a smooth, long-lasting engine. Even if you're building an absolute stocker, invest in balancing the crank and everything that attaches to it, including the flywheel/flexplate and vibration damper.
Heads: Generally speaking every early engine will need to have the heads rebuilt. This consists of replacing/bushing the valve guides to prevent oil consumption; checking the strength and height of the valve springs and shimming and replacing as necessary; and grinding the valves and seats to ensure a good combustion chamber seal. Another suggested modification is the installation of hardened exhaust seats (some early engines are already equipped with them). When an engine designed for leaded gas is run on unleaded it is not unusual for the exhaust valve seats to wear prematurely. The reason is that the lead once found in gasoline not only raised octane, but served to cushion and protect the valve seats. When lead was eliminated, auto manufacturers used induction hardened valve seats, older engines can simply have hardened seats installed.
While there are many reasons to build a custom rod, one of the motivating factors is to be different and have something unique. So why spoil that with another run of the mill small-block under the hood? If the engine in your '49 or later whatever is savable, think about giving it a new lease on life. While it may take some sleuthing, there are still an amazing number of rebuild parts available for even the most obscure engines, and there was a surprising amount of speed equipment available in the Fifties and Sixties that can still be found at swap meets today. But if you can't find vintage hop-up parts for your oddball engine, get creative. Slip in a reground performance cam, bolt on an aftermarket fuel injection system, and add an electronic ignition system. Then go somewhere, pop the hood, and just sit back and watch everyone scratch their head.