As you look at this shot of a beautiful red on red '67 Corvette convertible sitting atop a rollback, you have to wonder what its story is. The wheels and tires are probably the first thing to get your attention, then your eye picks out the subtlety of other replacement bits like the seats, rockers, and the exhaust system that exits out the center of the rear panel, just before you reiterate the obvious that it's sitting on top of a rollback. As the story goes, the build is completed at this point and this project '67, which started life as a numbers-matching 350 horsepower convertible, is on its way to the dyno to have its new fuel-injected 425HP crate engine setup.
The GMPP ZZ383 has a proven combination of technology with its roller drivetrain, pump gas friendly requirements, and sheer performance with 425HP and 449 lb.-ft. of torque. These impressive performance figures are due in large part to the taller Vortec heads this engine comes with, with their larger intake ports and specific chamber design. The spec sheet states these figures are achieved with a high-rise aluminum intake manifold and a big Holley carburetor on top. Problem: We couldn't use a tall aluminum intake because it wouldn't fit under our stock small block hood, and we didn't want a carburetor anyway. So we began our research of fuel injection. We knew that we didn't want T.B.I., or any port injection that would require an air cleaner sitting on top of a throttle body on top of the intake manifold. Nothing against it, we just didn't want that look with this project. GM tuned port injection seemed to be the answer, but we had some reservations about how much a stock tuned port would flow. Remember, we have some killer heads on this engine, which leads us to another speed bump. A stock (normal) GM intake manifold, be it carbureted or injected, will actually bolt to these heads via their dual-bolt pattern design, but it won't cover the extra-large intake ports. Can you say massive vacuum leak? This led us to Accel, where they advertise a "special" tuned port setup called the Street Ram with oversized runners, a larger throttle body, higher flow rate injectors, and a manifold that fits the Vortec heads. The manifold was actually Edelbrock's High-Flow T.P.I. Vortec baseplate, but worked very nicely for this application, and is one of the few T.P.I. intakes for Vortec heads. And, dimensionally, it looked like it might even fit under the small block hood of a midyear Corvette.
We're glad you could join us for this final segment of the Reconsidering Your Line in the Sand series, where we have showcased the installation of today's advancements on several classic Corvettes, but mostly on this '67 convertible. The scope of this series has been to illustrate that you can have an NCRS hat and a SEMA hat hanging on the same rack in the corner of your garage. That is, you can satisfy two disciplines and do everything outlined in this series of articles without, as I've said all along, "burning any bridges." By this, I mean that after enjoying the fruits of today's advanced technology and improved comfort, your classic Corvette can be put back to stock to take its place on the judging field once again, should you ever wish to.
In this segment, I've been asked to answer some detail-oriented questions by a few folks as to how things worked, how they fit, whether they were compatible, what I would do differently, and so on. In other words, to get to the specifics of what I will call the peripherals of this project. It's one thing to write a short discourse on a given work, but our learnedness will benefit by knowing what happened behind the scenes, or "between the sentences". Jump in and take one more ride with me on this subject, but don't be surprised if we hit a bump or two.
It all starts with a plan, just like any project. The primary focus of the plan should be "Where you want to end up?" instead of "How are you going to get there?". The latter is something that needs to be engineered, modeled, tested, scrapped, re-invented and rebuilt once you have your focus-the business model if you will-in your mind. In the case of this '67, the new road wasn't a huge departure from the 6-lane highway of stock, but it nevertheless was a road less traveled. Not for any one reason, but likely because of its uncertainty as to where it leads, or the possibility of some speed bumps and potholes to be navigated. Our instructions from the car owner were; at least four hundred horsepower, pump gas friendly, a rowdy personality, fuel injection, and-oh yeah-it all has to fit under my small block hood. Where the hell do you find that road on a map? We thought, of course,about the LS series engines with their proven performance and reliability. But the only engine that came to mind with the rowdy personality-and able to deliver that kind of performance-was GM Performance Parts' ZZ383, with an idle quality that speaks the language of potato-potato-potato.
Research is a wonderful tool, and is the first tool you should pull out of your tool box before starting any project. Speed bump: This particular engine and induction combination hasn't found a lot of ink in the media - especially under the hood of a Corvette. It isn't something you'll likely read about in the "how to" sections of other car magazines, or get a lot of hits with your search engine on the internet. I'm not saying it hasn't been done; that would be stupid. It just hasn't been written about very much-at least that I've been able to find. It's something that we researched as independent components - that is - the 383 crate engine here, and the Street Ram fuel injection there. But not the two as an assembly. Research led us to emails and phone calls to suppliers, and interestingly enough, it was split about 50 / 50 as to "Yeah, you can do that" to "No, that won't work". The ones that said it wouldn't work were just too negative for me, so we went for it.
With the crate engine sitting in the engine compartment of our Corvette, we pulled the pre-assembled Street Ram Injection System out of the box from the supplier. Man, it looked mean with the over-sized runners and larger throttle body. We sat it atop the crate engine and located the mounting bolts for it. Pothole: The injection needs to be disassembled so the intake manifold can be installed to the Vortec heads' bolt pattern. No big deal, except that the $40 Accel gasket set will tear when you pull these assemblies apart-an added expense. Why an Accel gasket set? Because they are e-x-t-r-a thin, and the stock tuned port gaskets won't work. OK, the intake manifold is installed, new gaskets are in hand, the runners and air plenum are installed. Pothole: The oversized runners won't bolt up until you relieve the right front and left rear manifold bolts and make room to the extra fat runners. Has anyone done this before? The bolts are now relieved, the air plenum and runners are installed, and everything looks great. Fast forward to our initial startup. Another pothole is encountered as a small vacuum leak was evident from the get-go, and was traced to an E.G.R. port on the bottom side of one of the runners, partially covered by the gasket. Down goes the assembly again, and another $40 gasket set is procured after we seal up the hole with a pressed-in welch plug.
I had read before that the chrome plated GM Performance Parts aluminum valve covers won't fit the tall Vortec-headed engines when the Corvette is equipped with power brakes. I just figured these guys didn't know what they were doing. After all, we've put them on the ZZ4 engines with power brakes (ZZ4 engines have shorter aluminum heads). As Bugs Bunny said to the Gremlin; "Hey Mac, let me take a whack at it". Well, ok, they won't fit. So instead of losing the chrome plated beauties that we had already installed and running the Medusa snake-head lady models that came with the engine, we decided instead to change the power brakes. Not to delete them, but to change them. A supplier with a direct link to the manufacturer got us this street rod booster that's 7-inches in diameter, will give us the clearance we need for the good valve covers, and has been converted to mount up like a Corvette booster should. That should work beautifully. Pothole: The actuator rod in this street rod booster is like a turtle that won't stick his head out of his shell; it's too short to actuate our Corvette master cylinder. So it's off to see Jerry Rose, a client and fellow Corvette owner that owns Rose Grinding and Mfg. in Miamisburg, OH,to have a stock Corvette master cylinder actuator rod turned down and threaded to match the installed end of the wimpy actuator rod. All is well again.
Brackets were no big deal, but as you already know; when you add headers to the equation, the picture changes for mounting up the engine accessories. It is important to have proper belt alignment for our drive belts, so we opted to make some of our own brackets,and then we sent all of the brackets out to the chrome shop for some added bling. This decision came after we had decided to go with the March billet aluminum pulleys, which was a decision we came up with after investigating a serpentine belt drive system. Now we already have aftermarket air conditioning on this car, so it seemed only natural to contact the same company that made this system and talk to them about their serpentine drive system. Makes sense, right? Speed bump: It seems that in order to use their serpentine belt drive system, you have to use their 'serpentine belt drive system air conditioning compressor' instead of their 'regular v-belt drive air conditioning compressor.' Really? How does the compressor know what kind of belt is making it spin? Anyway, it is what it is, and we couldn't feel the love or see the reasoning in trashing a perfectly good compressor just to change the belt drive system, so we did the very best that can be done with standard v-belt drive pulleys with the polished billets from March.
How about something that went just as planned, without a hitch, with no surprises? I'm not sure that exists. Actually, it does. I ordered the radiator for this project from DeWitt's, as I always do for our restorations. This aluminum radiator with the dual Spal fans will cool the earth's core, so it can easily handle this big crate engine. The beautiful thing about it; it drops right in. I've got DeWitt's on my speed dial.
Every project starts with a vision before it comes together as a plan - a virtual look at its end result after its metamorphosis. We were directed to exit the exhaust of this '67 out the center of the exhaust panel - kinda sorta like a C5 or C6, but not really. Speedbump: Immediately behind the shiny red exhaust panel is the spare tire bucket. The spare tire bucket will have to go, which means we either run four run-flats on the ground, or we pack a tire repair kit in the storage well. Building a custom exhaust system is as much about the sound as it is about the look. It was to have an aggressive high-compression big block side-exhaust kind of sound to it, though exit out the back instead of ahead of each rear wheel. This means chambers instead of mufflers. With a build like this, you start with the "starting point" and the "ending point" of the exhaust system, then fill in the blanks in the middle. Starting at the header collectors, we have a fairly straight run to the rear spring, where custom bent tailpipes will bring the exhaust out the center of the exhaust panel. The "straight" section of floor will be where we run our chambered sticks; two 21" sections off the headers, and two 25" sections from the frame crossmember to the rear spring. These chambered "power sticks" came from Classic Chambered Exhaust Inc. in Milford, Michigan, with the rest of the piping fabbed up to our specifications at our local muffler shop. Aesthetics enters in where we built a curved fiberglass wall into the rear panel in the area that we cut out to make room for the exhaust tips. This is all about making it look like it came that way, and not an afterthought. With Vortec heads ramming exhaust gasses into headers and then four chambered sticks, this Corvette doesn't ask you for its attention, it hits you square in the back of the head with a sledgehammer. The exhaust note on acceleration makes the hair stand up on the back of your neck, but there is no objectionable drone while cruising down the highway. Perfect.
With everything installed in the engine compartment and the hood ready to be set back on the car, we hold our breath as to whether or not the hood will fit over the top of this new setup. And it does! And it almost closes! Actually, we knew this going in. We need the center bridge section of the inner hood brace removed for adequate clearance over our throttle body. Now, we don't just hack it away and call it a day. Instead, the area of interference is surgically removed, the remaining brace sections are boxed, and it's finished off as if it came from the factory that way. This is as close to burning a bridge as we have come to on this entire project. The bridge isn't burned, but the boards are a little charred and the ropes are singed, but we can fix 'em. Ok, maybe the ropes are burned off.
Which brings us up to date with this Corvette sitting on the rollback. Phasing the distributor, setting the timing and firing up our new engine is just step one of the set-up process. From here, it goes to Jeff Wightman's Precision Autosports in Beavercreek Ohio for a tune. Jeff will strap our Corvette down on the dyno and run it through the gears while he analyzes the data and adjusts the tables to sweeten the performance and driveablity of our project. Most of what we're driving today could benefit from a proper tune, with the timing and air/fuel mixtures very adjustable and performance and fuel economy standing to benefit from it. We didn't run any hard pulls this time around, but will later on-after we get some break-in miles on this engine.
As our ride comes to a stop, let me leave you with a thought. If your classic Corvette is tucked into its garage bed without ever seeing the light of day, be it for reasons of comfort, reliability, or fear of losing original components, today's technology has the answer. Through parts and component substitutions, a "bag and tag" philosophy can make your car more comfortable, more reliable, more powerful and more enjoyable. And the real payoff comes with the fact that you are preserving your original components while enjoying your classic once again. This is something we can all benefit from.
|Difficulty Index - 3 Wrenches|
|Anyone’s Project: no tools required||1 Wrench|
|Beginner: basic tools||2 Wrenches|
|Experienced: special tools||3 Wrenches|
|Accomplished: special tools and outside help||4 Wrenches|
|Professionals Only: send this work out||5 Wrenches|