[SuperHart]

Here are some uselful tidbits I picked up from searching for pulleys for my 351W. These principles will hold true even for Ford FE motors. After all, Ford wouldn't bother making up a whole new set of rules for each engine group.

What has been previously said about "underdrive" is mostly correct. Many guys get fancy and use "underdrive" pulleys thinking they are going to gain horsepower by slowing down the water pump and alternator only to later realize that they caused more pronblems than they solved (engine overheating and insufficient alternator output). Most underdrive sets achieve the underdrive by reducing the diameter of the crank pulley. It is uncommon to alter the diameter of the alternator pulley since that one is already rather small. Most Ford FE pulleys will be standard in "offset" or depth and bolt spacing. The differences will be in pulley diameter and number of sheaves on the crank and water pump pulleys.

Don't bother with using pulleys that have more sheaves (grooves) than you need. A Cobra usually uses a water pump and an alternator so a single sheave pulley set will do fine. If you have power steering or (shudder) air conditioning then you will need maybe a two sheave set.

Ideally for street usage, you want the crank and water pump pulleys to be the same diameter or the water pump pulley slightly smaller in diameter, the key word being "slightly". The usual diameter of Ford passenger car crank pulleys is between 6" and 6.5" but truck pulleys may go a little larger. A smaller water pump pulley will cause an overdrive of the water pump which is probably good on the street especially at idle. However, if you choose a water pump pulley that is more than 1/2" smaller in diameter than the crank pulley you will get excessive overdrive (not so good) of the water pump. The pulleys I use are 6 1/8" crank and 5 7/8" water pump and they work very well.

Regarding alignment of the pulleys, install your crank pulley first and then align the water pump and alternator pulleys to that one in that order. Mr. Gasket makes a water pump shim kit just for that purpose if needed. The alternator can be shimmed forward using appropriately sized flat washers. The crank and water pump pulleys are close enough to each other to make alignment simple. The alternator is a little more tricky but a careful eye-balling should do just fine unless you expect to see sustained 7000+ RPMs like most of us do on the street (AHEM). After all, we aren't really talking rocket science here, just some common horse sense. But like my daddy always said, "Common sense ain't common."