Ask Away! with Jeff Smith: Roller Upgrade for Small Block Chevy 350

I am considering buying the basic Chevrolet 350 c.i.d. crate engine. I’ve heard lots of good things about it. I’d like to upgrade to a hydraulic roller cam at the same time. Rather than buy the more expensive roller cam Chevy crate engine, why can’t I just use that Chevrolet Performance hydraulic roller lifter kit — PN 12371042? It seems that adding the roller cam would be the least-expensive way to go. Thanks! — T.M.

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Jeff Smith: This is a great question.

Unfortunately, the short answer is that this approach will not work.

We’ll go into much more detail so you know why and which engines would benefit from a conversion like this. The hydraulic roller cam conversion kit that you mentioned is intended to upgrade Chevy’s one-piece rear main seal small-block engines. A little history on the small-block Chevy is in order here.

The least-expensive and still popular small-block Chevy crate engine is a built-in-Mexico hold-over from the traditional two-piece rear main seal engine configuration that started in 1955 and ran until 1985. It is listed under PN NAL-12681429 at Summit Racing.

In 1986, GM upgraded the small-block in several ways. Among the changes was a one-piece rear main seal and, in passenger cars, these engines received hydraulic roller camshafts.

The block was modified to accept a hydraulic roller cam arrangement using what are called dog bones to retain the hydraulic roller lifters. One dog bone was used to retain a pair of hydraulic roller lifters to prevent the lifters from rotating which would destroy the camshaft. All eight dog bones were held in place by a large steel spring fixture retained in the lifter valley with three bolts using eight legs (also known as a spider) to hold the dog bones in place.

You didn’t mention which hydraulic roller crate engine you were interested in, but the least expensive small-block Chevy crate engine in the Chevrolet Performance catalog with a hydraulic roller camshaft is the SP350/357 long block (PN 19367080). This engine comes with a hydraulic roller camshaft with 215/223 degrees of duration at 0.050-inch tappet lift with 0.473/0.473-inch valve lift.

The problem is that the factory-style hydraulic roller camshaft will bolt into an older, two-piece rear main seal block but the block isn’t machined to accept the dog-bone style lifter retention configuration.

In order to use a roller camshaft in the older, two-piece rear main seal engines, you will need to use what are called retro-fit style hydraulic roller lifters that use a tie-bar between each pair of lifters. This tie-bar keeps the lifters aligned relative to the lobe. This is a very popular conversion for the older small-block Chevy but, unfortunately the retro-fit lifters are usually more expensive than the factory versions.

We did some investigating and found a set of Howard hydraulic roller lifters for a small-block Chevy (PN 91164N) that are priced very near the cost of the GM hydraulic roller lifter set. These are retro-fit tie-bar style hydraulic roller lifters that enjoy a good reputation for quality.

This would be the best approach for upgrading to a hydraulic roller cam in an older two-piece rear main seal small-block Chevy.

However, there will be other changes you will have to make.

The most important is that an aftermarket roller cam button will have to be used with any roller cam in an older two-piece rear main seal engine. This is necessary because thrust inside the engine tends to push a roller camshaft forward.

This does not occur with flat-tappet camshafts because each lobe on a flat tappet cam is ground to offset this forward thrust. This offset machining also induces the lifters to turn in the bore to improve wear.

A roller cam lobe, however, must be machined perpendicular to prevent damage to the lifters, so the forward thrust motion must be limited. If a cam button is not used, the cam will move forward and ignition timing will retard as engine speed increases.

We won’t go into all the details on how to create the proper clearance on a retro-fit roller cam as this information can be found in magazine articles and online. The easiest way we’ve found to limit the cam movement is to use the Cloyes aluminum timing cover (PN CLO-9-221).

The Cloyes cover has a built-in easy-to-access eccentric that will contact the cam button and can be quickly adjusted to 0.005-inch of endplay. This adds to the expense of the conversion, but adjusting the endplay is simple and easy. We mention this because we’ve spent an hour or more trying to set endplay with a cam button and spacers and epoxy-gluing shims to the back side of the stock timing cover. It’s a pain.

Another point worth mentioning is that hydraulic roller lifters are taller than traditional flat tappet lifters. This means the pushrod length will need to be reset using shorter pushrods.

Again, the process for establishing pushrod length has been covered in other places so we won’t get into that here. But you will need shorter pushrods.

One last point, the hydraulic roller cams intended for factory roller cam, one-piece rear main seal engines will use a stepped nose camshaft to fit behind the limiter plate bolted to the front of the block. Do not use these stepped nose cams in older, non-roller cam engines.

Yes, for you knowledgeable small-block fans,  there is a way to use these step-nose cams in a two-piece rear mains seal engine but we won’t go into that as it has a very limited appeal — so please don’t send us emails telling us it can be done — we already know.

Stepped nose roller cams also use a different cam gear bolt pattern. The traditional timing set and cam for older small-blocks will work for a roller as long as a cam button is included and properly adjusted.

This was a longer answer than what you were probably anticipating but we thought the question was good and deserved an expanded answer. As it turns out, your idea is really pretty solid and since the Howard lifters are about the same price as the GM lifter kit, the conversion won’t be that expensive.