Transformation

There's a lot to be said for building a nostalgic hot rod with vintage parts. Of course, one of the things that can be said is there's a good reason we stopped using some of that old stuff. Simply put, better stuff came along. Certainly, transmissions fall into that category.

While many vintage engines--Hemis, Cads, Olds, Buicks, and yes, even the venerable Flathead--are capable of providing reliable propulsion for a street rod, the same can't always be said for the transmissions they were mated to. The standard shift versions generally have just three forward speeds, with syncromesh on the top two cogs only. Most early automatics offered disappointing performance while giving the driver the feeling that there was no direct connection between the engine and the wheels. Fluid leaks to rival the Exxon Valdez were also common. But then, just because you want to use a vintage engine doesn't mean you have to be stuck with a lousy transmission.

Transmission swaps have been part and parcel of hot rodding for a long time. Gearboxes from Lincoln Zephyrs, Packards, and Cad/LaSalles were routinely installed in place of weaker stick shift components. And when heavy-duty components for GM Hydramatics and Chrysler Torqflites came along, things really changed. But today there are even more and better choices with the contemporary crop of four-, five-, and six-speed manuals, plus the array of overdrive automatics. All that's required is an adapter to bring old and new together.

When selecting an adapter there are a host of things to take into consideration. First to examine is space. Is there room for the transmission you want to use? With manual transmissions the location of the shifter has to be considered, as on some five- and six-speeds the shifter will end up under the seat unless it can be moved forward. For automatic transmissions a custom flexplate maybe required while manuals may require a custom flywheel. In addition, stick shift adaptations may require pilot bushing adapters, combining clutch components as well as special throwout arms and bearings (a hydraulic throwout bearing often solves a variety of problems). And, of course, there is the starter to be concerned with. In some cases the stock starter will work, in others a substitute will be required. All these items should be addressed when selecting an adapter.

This month we've rounded up a variety of adapters for both manual and automatic transmissions that make it possible to do everything from bolt a 700-R4 to a Buick straight-eight to backing a Hemi with a six-speed. Next time around, we'll show how to proper fit an engine, adapter, and transmission together. Let the transformation begin.

ADAPTER ADVICE

By Pat McGUire, Wilcap Company
The name Wilcap has been synonymous with hot rodding, as well as with transmission adapters, for decades. Until recently the company was run by Lloyd Capanna, son of one of its founders, the legendary Tony Capanna. Sadly, both Lloyd and Tony have passed away, but the company lives on. Now in the capable hands of Pat McGuire, Wilcap is up and running producing a line of Wilcap adapters, flywheels and Hemi components, as well as Sharp speed equipment for Flatheads. An avid hot rodder, McGuire brings a rich background in aerospace manufacturing to two of the most famous brand names in the industry. --Ron Ceridono

The biggest thing to keep in mind about adapting an engine to a transmission is that it's a big project. It's easy to find brand-new adapters that have never been installed at a swap meet--somebody bought it thinking it would be an easy project, only to find out that it wasn't. My job is to make mating the engine and transmission as painless as possible. I think our products do a good job, but it's only half the job. In a lot of adaptations, everything from the radiator to the driveline has to be changed. When building from the ground up you're ahead of the game as long as you start out with the engine/trans assembly and work from there.

The first popular engine/transmission adapters were built to put all kinds of different motors in front of the '32-48 Ford three- and four-speed transmissions. Part of the reason these were the favorite transmissions for rods was because the enclosed driveline on the early Fords was a chore to change. Adapters were built for Buick, Cadillac, Chrysler/Dodge/DeSotos, and even Studebaker engines to go in front of the early-Ford/Mercury transmission. The thing to remember about these adapters is that they use the engine's flywheel with the rest of the assembly (pressure plate and cover, friction disk, throwout bearing, and linkage) coming from the transmission OEM.

Although many hot rodders prefer to use the same make engine and transmission, from my point of view the transmission should enhance the engine just like the induction system or exhaust. That means bolt in the best transmission for your application, which often means adapting a contemporary overdrive automatic. The most popular adaptations are the various GM automatics--the 700-R4 being the most common. (However, for the purpose of bolting the engine to the transmission there is no difference between the 350 or 400 transmissions and the 700-R4.)

Another option is one of the modern four-, five-, or six-speed manual transmissions. Whichever one you pick, keep in mind that the adaptation of the engine to the transmission gets twice as complex when you go to a manual transmission. The reason is that if it's done wrong, a manual transmission adaptation is downright dangerous. I strongly urge anyone who is doing a manual adaptation to do two things: 1) Never use a spacer between the crankshaft and the flywheel and 2) Buy an "explosion resistant" (no such thing as explosion proof) bellhousing, or at the minimum, a scatter blanket. Why the caution? The first time you miss a shift and the tach goes to 8,500 rpm you're going to find out one of two things: 1) You did a good job on buying, assembling, and installing your adapter, flywheel, clutch, and transmission or 2) You might find out what 30 pounds of steel sounds like exiting the bellhousing at an equivalent speed of about 290 mph. An automatic transmission is a safer design; the front hub of the torque converter rests in the end of the crankshaft, or in the hub spacer if it is an adapted assembly, and this "captures" the torque converter. If a failure does occur, it is not likely that the torque converter is going to escape the bellhousing.

If the adapter is a "plate"-type adapter the flywheel needs to be fabricated for that particular adaptation. The extra length that the plate adds between the crankshaft and the input shaft should be made up by the thickness of the flywheel. This doesn't mean that the flywheel is heavier than stock, just that the contact surface of the flywheel is closer to the input shaft. The other factor with a manual transmission adapter is the transmission to bellhousing alignment. If the input shaft of the transmission and the crankshaft are not in line or concentric, the resulting "bind" will cause the input shaft to continue to rotate with the clutch engaged and the transmission will be difficult to shift and the syncros will wear prematurely. More importantly, the resulting bind on the friction disc will cause it to drag and wear at its outer edge prematurely and could cause a failure of the hub (center plate) of the friction disc.

Traditionally, the correct alignment is accomplished using offset dowel pins and shims. These can be purchased in different increments (.007, .014, etc). First, the "out of square" condition is corrected with the shims and then the "out of concentricity" condition is fixed with the dowel pins. Make sure the bellhousing surfaces are flat and parallel. Consider regrinding or replacing the bellhousing if it's more than .020 out of parallel or out of flat. Once the bellhousing is determined to be okay, check for the "out of square" condition with the bellhousing in place. First, bolt the bellhousing (and the block plate if your using one) to the engine starting at the bolts closest to the dowel pins and working the final torque in a star pattern. Using a dial indicator attached to the crankshaft and taking the endplay out of the crank, rotate the crank until the low spot is found. Make an appropriate thickness shim for the transmission to bellhousing bolt nearest to the low spot.

When checking for concentricity, first see that the bellhousing transmission register or pilot diameter is round. There's nothing like spending half an hour screwing around only to find out that the diameter was .010 out of round to start with. Once you've measured the "out of concentricity" the fun begins. Pull the engine dowels and put the correct offset dowels in. Put the bellhousing on and run the bolts down "snug." Rotate the dowels together with offset toward the "low" or tight condition. Once you've gotten it into tolerance, torque the bellhousing bolts to spec and recheck.

It is possible to align an automatic trans to the block. First take an old transmission to a shop that has a jig to rebore and sleeve the automatics' dowel pin holes. Once that's done, gut the transmission and cut the case to gain access to the front pump bore from the back. Once the case is aligned to the engine's crank, mark which way the offsets were and install your working trans with the offset dowels. While it's more trouble than most people want to go through, the process does guarantee accurate alignment. In any case, boring and sleeving the dowel pins on the case of your automatic should be done if the dowels are loose.

One word about the back of the block, and this goes for any assembly, but especially for a "plate"-type adapter; clean and prep it like you would any engine gasket surface. Chase the bolt holes, replace any deformed dowel pins, and remove and burrs or dings with a fine pitch file. The crankshaft flange should get more attention than any engine gasket surface. Flat and clean. All of the power from your handbuilt, high dollar motor is going out that end, so don't neglect it.

One more thing, "dowel pins" are a misnomer. They really are "alignment pins." They are there to align the engine to the transmission as there is too much clearance between the bolts and the holes in the transmission case for proper alignment. The pins of the correct size must be in place to get the alignment correct. OEMs use soft steel pins for a reason; they are softer than the engine block--never use hardened dowel pins.