Perserving Your Classic Corvette Engine

There's no way I would ever change my classic Corvette, but if I did, I would do something with the engine. The words are the same from a number of my clients, but their reasons for saying them vary. If you've just tuned in, this is the second in a series of articles. Your author is a Corvette restoration shop owner and longtime NCRS member. The National Corvette Restorer's Society is dedicated to the restoration, preservation, history, and enjoyment of Corvettes-a credo that I am honored to be a part of and bound to help promote. This series is designed to show Corvette owners how they can enjoy their classic, but at the same time preserve it. I was inspired to write this series after talking with a number of people (some of my clients included) that have achieved a Top Flight or Duntov award, and are now afraid to drive their car for fear of hurting an original component, especially an original numbers-matching engine. So they don't, and their Corvette sits in their highly decorated garage shrine and gets a new desiccant bag inserted into the hermetically sealed car bag every month. This is not, in my opinion, what Corvette ownership is all about. This segment also addresses the questions an owner has prior to the restoration of his or her Corvette that is, something we can't deny, outdated. So ride along and look at some options that will help inspire you to pump up your tires and wad up your car cover. If you couldn't care less about originality and numbers, climb aboard as well; maybe you'll see something you haven't seen before. A word of qualification: There is nothing here that can't be put back to stock should you wish to.

The first segment of this series focused on the installation of a five-speed transmission, something that will certainly enhance the drivability of your car as well as help to preserve your engine by slowing down the highway rpms. We'll now look at more direct ways of preserving your original engine either through substitution by actually putting your entire engine into storage, or by installing more modern up-to-date parts into it to add to its life. Such parts will deal with the changing environment of today. How can a true NCRS member tout anything about changing parts on a true Top Flight car? That's like the chairman of Ford motor company driving a Corvette to work every day. Well, my guess is that Bill Ford wishes he could. Read on and I'll explain. The "bag and tag" approach is the answer to the owner that has a very valuable engine and cannot risk a failure that will render it inoperable, or worse, unrepairable. I have heard the stories, and maybe you have too, about a 283 that was cruising down the highway at 65 mph when suddenly a rod went through the side of the block. That original code-correct engine just became a doorstop. I had a rocker stud pull out of my '63 340 horse engine while driving down the highway-same type situation, but at least mine was repairable. We can preserve history and still enjoy our classic cars with replacement engines under the hood while we sock away our originals.

Difficulty Index NNN

Many times a restoration project will come into my shop that doesn't have its original engine, so we're forced to install a replacement of some sort. The GM crate engines make a great choice because they are readily available at a decent price point for all that you are getting. The versatility is impressive because they can be dressed to the nines for show, or disguised with a vintage look with the proper parts installed onto them. the internals are new, strong, and will withstand some moderate street abuse. And they will out-perform many of the stock engines installed in our beloved classics. I've heard from the group that are tired of driving dated technology-so dated that a four-door Honda can beat them from traffic light to traffic light. It's sad but true, there was a time when the base V-8 engine in the Corvette offered a dismal 165 hp, whereas the 3.5-liter V-6 Honda rental car of today boasts 268 hp. The pair-up on the boulevard would be a bloodbath. I've also heard from the group that simply wants a more efficient and powerful engine for no other reason than because the technology is there. Well, the technology is there, and we can make it look period-correct. I'll share that with you too.

The other side of the coin takes your original engine and not only replaces the worn-out parts (some of which may not be evident), but also updates it with some of today's current technology. If you stand still in a changing environment, you're dead. This will certainly be evident if you rebuild your engine the same way as you have in the past because if you do, you will more than likely experience a failure. You can no longer afford to make the assumption that your pressed-in rocker studs are ok, or that the connecting rods are pretty strong, and, therefore, fine. You have too much at risk to gamble this way. And how about another new twist: With the advent of roller cam technology, oil companies have been able to reduce the zinc dialkyl dithiophosphate (ZDDP) in today's motor oil. This reduction protects the catalytic converters on all our everyday grocery-getters where some oil is seeping past the rings, but the trade-off is that it eliminates some of the lubricity of motor oil under extreme pressure situations. What does this mean to you? This extra high-pressure lubrication is exactly what is needed for a camshaft to survive with a flat-tappet lifter grating against its lobes. What has happened is this: stories have circulated from all over about how someone else's brand-new camshaft is wiped out before it ever sees 20 minutes of operation during the break-in period. The engine drops a couple of cylinders, the cam lobes are flat, and the oil is black from the metal floating around in it. How do new cars get by with this oil? Because flat-tappet technology is a thing of the past. Your new camshaft for your engine rebuild will come with multiple warnings to this effect, and a statement of voided warranty if strict procedures are not followed. These procedures call for special light-pressure springs to be installed on the valves for the break-in process, along with additives to be put in the oil. What is your outlook for long-term survival? Well, you can put additives in your oil, try to find some CI-4 spec diesel motor oil (not CJ-4), or look at a couple of other options we'll talk about in this segment.

We Corvette owners are a die-hard bunch. We meet the problem head-on without flinching, we don't take no for an answer, and some of us anal NCRS-type guys even consider it a challenge when someone says "that can't be done."

One excellent choice of a replacement engine for your original is a Chevrolet crate engine from GM Performance Parts (www.gmperformanceparts.com). This is the ZZ383 crate engine shown as it comes, whereas the ZZ4 comes a little more complete with an aluminum intake manifold and H.E.I. distributor or as a "turnkey" engine ready to run. They both come with a warranty.

Beneath the skin of the 383 is where the real beauty is-with a full-roller valvetrain, nearly bulletproof balanced lower end and high-tech aluminum Vortec heads with taller intake ports and a swirl-inducing design built to make horsepower and torque-425 hp and 449 lb-ft of torque-on pump gas. The stock hydraulic roller cam needs no upgrading, and has a nasty get-outta-my-way personality to it. The full-roller rockers are strong, lightweight, and designed to rev freely.

Look at the big picture before starting a project like this. For instance, this '67 is getting this powerhouse GMPP ZZ383 small-block and a Classic Motorsports Group Tremec TKO 600 overdrive transmission with a .64 Fifth gear. This engine/transmission combo is a great match because the engine makes big torque numbers at low rpm, which is where this engine will reside while in Fifth gear on the highway. It's important to match the power curve of the engine with gear ratios in the transmission as well as the final drive in the rearend, and all of this according to the type of driving you'll be doing, along with accessories you will need to run, such as power brakes and A/C. Knowing what transmission you'll be running makes installation a lot easier by installing the two as an assembly.

Planning starts early on a full restoration with questions such as: where are you going with it? how do you want it to look? what are your performance expectations? This '65 is a full rotisserie restoration with the original transmission and rearend, but with a ZZ4 crate engine up front. We've installed crate engines to preserve the original engine, or where there wasn't an original engine in the first place.

It's a marriage of disciplines-the NCRS-type restoration on the better part of the car, but updates and upgrades blended in either on the surface or in a stealth way beneath the skin. My philosophy is to burn no bridges in the restoration process-allow the car to be put back to stock should the need arise. Someone down the road may want it back the way it was, and it just makes good sense to leave that option open. In the meantime, enjoy your car your way. You would be amazed at the number of enhancements available that will simply bolt on.

The WOW factor under the hood of this '65 is unbelievable. This is the ZZ4 with glitz to the Ritz, and 355 hp on pump gas. We've upgraded the hydraulic roller cam so it has more attitude and speaks of presence with headers and under-car chambered exhaust.

This is the ZZ383 making its home in the engine compartment of the '67. It's a direct bolt-in, but know how you want to build it from here before you commit to the project. The Vortec heads are taller, as are the intake runners (.64-inch) and require a Vortec-friendly intake manifold. GM offers two carbureted Vortec manifolds: a tall one that won't fit under the stock small-block hood, and a shorter one that will. This car has the small-block hood, so we better go with the short one.

Naa. How about the Accel Street Ram tuned port injection made for the Vortec heads, with Accel's own runners, throttle body, and redesigned air plenum. The unit comes from Don Sutherland at Fuel Injection Specialties in San Antonio, Texas, (www.fuelinjection.com), who specializes in fuel-injection electronics, computers, harnesses, and all that makes fuel-injection work on any engine.

The beauty in the ceramic coating of these Hedman Elite Hedders is how they accentuate the aluminum heads, but it's also in the way they fit. There is plenty of clearance for all things concerned, even the rack-and-pinion steering system we have outlined for this '67. And with their 15/8-inch tubes going into a 3-inch collector, they will extract exhaust gasses quite nicely. And, after all these years, they're still made in the U.S.A.

As with any "aint quite stock" application, make sure you have room to do it. The stock small-block Corvette hood fits over the tuned port injection just fine almost. With the throttle body (not shown) installed to the front of the air plenum, we'll be into hood center brace territory. We knew this going in and will make provisions for it by "windowing" the center brace: cutting the fiberglass to make a recessed area for the throttle body, but preserving the strength of the brace by boxing it. This modification borders on burning a bridge, but it won't. We can always put it back to stock.

Stick to your master plan by installing the right pieces to achieve your final goal. This '67 is all about setting aside the original powertrain for preservation and installing a high-performance system that will bring this car into the 21st century. On the way out is the original 350hp carbureted small-block; on the way in is this 425hp fuel-injected small-block. We do this engine justice by installing high-performance components to complement it, such as a high-performance fuel-injection system to feed it, a high-performance exhaust system to efficiently extract exhaust gasses, and, yes, even a high-performance cooling system starting with this beautiful Weiand polished aluminum high-flow water pump from Holley Performance Parts. One look at this swirl-patterned casting and you know something is different about this pump.

With headers, there will always be a little custom exhaust work needed as shown on the bottom of our '67 full restoration coupe. Pipes will have to be fabricated to join the collectors to the openings in the crossmember because the system is obviously a different configuration now. Sometimes we run a stock system from this point back, or we like to run a 21/2-inch undercar chambered exhaust system from there to the back of the car-sounds kind of like side exhaust, only it's out the back instead of in your ear. With a high compression engine, it still annoys the neighbors. Yes!

Now we go from the beautiful to well, these valve covers that come with the crate engines. We wanted to use the chromed aluminum GM Performance Parts covers on the ZZ383 like we did on the ZZ4 in the photo at the bottom-right of page 32, but they won't fit beneath the power brake booster. The Vortec heads are just a little taller-enough to kill the deal. The good news is that these Vortec heads support either the center bolt variety of valve cover or the old perimeter mount covers, so there are lots of options to replace these black pseudo-finned Medusa valve covers. Man, are we glad.

Let's turn the page now. Suppose you're sitting there reading all this, and you're thinking this is all nice, but I really don't want to deviate that much from a factory, period-correct look. But you do like the idea of a crate engine to thrash-around without the worry of launching a 40-year-old rod out the side of your original block, thereby rendering it totally worthless. The ZZ4 is a great choice and can easily be disguised to look like a vintage Corvette engine. But just to put a little challenge-type spin on it, let's say you also like the idea of a stroker small-block with a full-roller valvetrain and Vortec heads. Well, I'm always pondering the means to an end, so I got with my friend and fellow NCRS member Steve Salley of Salley Tool and Die and presented him with an idea and a model. Steve turned my crude model into what you see here: the first-run of a 6061-T6 aluminum adaptor plate that will allow an early intake to be used with the Vortec heads of the ZZ383.

The plates cover up the four-bolt Vortec intake bolt pattern and leave the six-bolt pattern of the early small-block intake. But, more importantly, they bridge the 0.64-inch increased intake port height to allow for the fitment of an early intake and stock intake manifold gasket. In effect, they become the new head surface. The Vortec heads are a dual-bolt pattern design to also accommodate the early intakes, but only if they have the extra tall ports.

Here's the difference between the head surface of the ZZ383 (on the left) and with the aluminum adaptor plate in place (on the right). If you were to try to install your early intake manifold and gasket set right to the Vortec heads, it would bolt up, but you'd have an incredible vacuum leak.

With the intake gaskets in place, you can see the final alignment of components. The shiny aluminum around the inside of the dark gray gasket is not our adaptor plate, but the machined surface of the aluminum head. Our plates follow the shape of the intake gasket. If you want to do some port matching, you'll need to pull the heads.

This is what we're after: an early Corvette engine look from a ZZ383 high-tech crate engine. Lose the lift hooks, replace the long water pump with a correct short one, paint the block, heads, and adaptor plates orange, and you're getting there. Your tach-drive distributor will work with a replacement steel-cam friendly gear, and all your ignition shielding will fit, even with angled plugs.

The dual-bolt pattern at the top of the heads allows for the use of perimeter-mount valve covers, like the aluminum Corvette covers. You'll want to run the 21/2-inch solid-lifter engine exhaust manifolds because the 2-inch just won't flow enough exhaust out of these Vortec heads. Exhaust port alignment isn't perfect with the manifolds, so you can do a little shaping to the inside of the reproduction manifolds from Paragon Reproductions. And you'll have to make provisions for a PCV system to vent the crankcase. There's no way I would ever drill a hole into a perfectly good Corvette aluminum intake, so my first choice would be to install a '66-'67 oil fill tube with the provision to screw in a PCV valve. Bring clean air into the crankcase through the rear china wall of the block with a fitting, internal baffle, and a tube connecting to the bottom of the air cleaner. Everything is pretty well hidden under the intake manifold and at the back of the block.

OK, another turn of the page. Suppose you want to keep your original engine intact, but are interested in improvements that will not only help its performance, but also its survival. You've heard horror stories about today's gasoline, and now motor oil, and are almost afraid to even run your engine. Here are some of the things you can do. Starting with the distributor, the Lectric Limited Stealth SE electronic ignition conversion system is among the best going, and is my favorite because it has only one wire (a black one) coming out of the body of the distributor, just like stock. The Hall Effect system is completely concealed beneath the stock distributor cap, so you and I are the only ones that know you've changed anything, and I'm not talking . . . for a price.

Probably the most pronounced improvement you can make to your engine is through the installation of a roller valvetrain, starting with the roller cam. Because of the aggressively quick ramps of the roller camshaft lobes, improvements are made in horsepower and torque over a much broader rpm range than ever possible with a flat-tappet cam. The added bonus: the lifters roll over the lobes of the cam rather than grate against them like the old flat-tappets do. This means lower engine temperature, less drag, and no need to worry about oil additives, lack of zinc, finding the right diesel oil, or the possibility of wiping out a brand-new camshaft in 10 minutes. This is the Comp Cams Retro-Fit hydraulic roller camshaft, made to fit the stock Gen 1 Chevrolet engine lifter bores.

Again, a means to an end. Turns out the culprit is the poly-lock nut that stands up too high for the valve cover to fit. The Restoration Station cured this little problem by having their own nuts made out of annealed 4150 steel, blackened and hardened to 44 Rockwell. Unbeknownst to us, Comp Cams had already addressed this problem with their own line of short nuts listed as High Tech under part number 4600-16. These may be the best kept secret in their catalog. These nuts are designed to fit either the Comp Cams 8650 chrome-moly Pro Magnum roller rocker or the Hi Tech stainless steel roller rocker in small-block or big-block Chevrolet applications. If you have an engine with the aluminum covers and drippers formed into the roof of them, roller rockers will not fit without modifying the drippers.

Here's the difference in rocker height with the original poly-lock in the background, and our new nut in the foreground. It's also the difference in running aftermarket or original valve covers. You can also run roller tip rocker arms with stock valve covers since they use the standard self-locking stock variety hex nut. That's better than the stock stamped-steel rocker, but it's kind of like driving all the way to the pool on a hot summer day, but never getting wet.

If you insist on rebuilding your engine with an original-type, flat-tappet cam, do it wisely. If you simply build the engine, pour in the oil, and fire it up, you will likely wipe out your new camshaft in a matter of minutes due to the lack of zinc in today's oil. Here's a Comp solid lifter cam with a warning tag attached to it with strict instructions about camshaft break-in procedures. Also shown are two must-haves: Comp's assembly lube in a pouch (PN 103) that comes with every new cam, and oil additive in a bottle (available separately, PN 159) to compensate for the lack of zinc in today's motor oil. The camshaft shown here has been nitrided-an extra hardening procedure available from Comp Cams for about a hundred bucks. There is no way I would install a flat-tappet cam today without stepping up for this additional procedure. Ask them about it at www.compcams.com

The proof is in the pudding. Here's a full-roller, 390hp, '67 big-block, and, except for a couple of Corbin heater hose clamps and one or two other details, it's ready for NCRS judging. It is totally stock on the outside, but it has longevity and performance-enhancing details on the inside that will help preserve this valuable engine.

Another small-block version, this time a '69 350/350hp beauty that is, once again, a full-roller on the inside. This information and these ideas are presented to you to be thought-provoking, but also to help keep your classic Corvette on the road-something that will benefit all of us in the hobby.