Why Use A Flat-Tappet Cam When You Know The...
There is a world full of factory hydraulic roller lifter engines in service today ripe for the picking to combine with a good aftermarket hydraulic roller cam.
The trick to building a budget street engine is to use as many production-based parts as possible. Original-equipment (OE) parts are generally well engineered, durable, and in some cases less expensive than aftermarket hot rod parts. This is especially true when it comes to hydraulic roller cams. General Motors and Ford both switched from flat-tappet hydraulic camshafts to hydraulic roller cams in the mid-'80s. While many car crafters initially scoffed at these conservative grinds, the knowledgeable parts swapper can use those now-plentiful and affordable blocks and roller valvetrains to economic benefit. We're going to tell you how to best combine OE hydraulic roller parts with a stout aftermarket cam-for very little cash. We'll look at both the small-block Chevy and the 5.0L Ford, as they are the most common.
The key to a successful hydraulic roller cam conversion is knowing what parts to use and which ones to avoid. If you've been reading the car magazines for a few years, then you've no doubt heard that you should not reuse old flat-tappet lifters and especially not with a new cam. But happily, there's no such restriction when it comes to hydraulic roller components. Because roller lifters don't slide and generate a wear pattern, you can reuse those factory lifters on a brand-new cam and no one will accuse you of being a roller bonehead. This means that the yards are full of serviceable hydraulic roller lifters that can be obtained for pennies, leaving you more money to spend on camshafts, pushrods, and maybe a set of roller rockers. While it's true that aftermarket hydraulic roller cams are more expensive than their flat-tappet cousins, by not having to purchase the lifters the overall price may actually be less expensive. So follow along as we point the way toward budget-building a hydraulic roller cam valvetrain using common sense instead of cubic dollars.
This is the factory hydraulic roller lifter arrangement for an '87-and-newer one-piece rear main seal small-block Chevy. The steel tie-bars keep the lifters aligned in the lifter bores, while the tin spider maintains pressure on the tie-bars to keep them in place.
Where the Chevy Rollers Are
The original small-block Chevy remained basically unchanged from 1955 through 1985. But in 1986 Chevy finally addressed that leaky two-piece rear main seal by making it one piece, and later added hydraulic roller cams to the 305- and 350ci passenger-car engines that retained the same 0.842-inch lifter diameter. The factory conversion to hydraulic roller cam added slightly taller lifter bosses and three small cast-in perches that mount a stamped-steel spider, along with a two-bolt cam retainer plate located at the nose of the camshaft to limit fore-aft movement in the block. While all passenger-car small-blocks from 1987 on were roller-cammed, light-duty trucks used this same iron block but stuck with a flat-tappet camshaft. This means the block comes with the casting provisions for adapting a factory hydraulic roller camshaft. At the most, you may have to drill and tap a couple of holes. We've even seen four-bolt main hydraulic roller cam blocks.
The hydraulic roller-cammed motors also come with a stepped drive face on the cam, which requires a different cam sprocket with a smaller bolt circle. This is the basic difference between a factory-style hydraulic roller cam and the standard early small-block Chevy flat-cam mount. So the idea is to use a later-model, one-piece rear main seal block with the factory hydraulic roller cam configuration. That way you can reuse the factory hydraulic roller lifters and tie-bar arrangement along with the factory-style cam timing gear. It keeps the price down to almost nothing and frees up more money to spend on a good aftermarket hydraulic roller camshaft. This is an especially good idea when stepping up to a budget cast 383-style crank, rod, and piston package.