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1967 Chevrolet Corvette - Reconsidering Your Line In The Sand, Wrapup
No Way Would I Ever Change My Classic Corvette, But If I Did...
Nov 2, 2009
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1967 Chevrolet Corvette - Reconsidering Your Line In The Sand, Wrapup
As we strap this killer '67 Red/Red roadster to the rollback for a trip to the dyno, let's review some of the interesting points it took to get it here.
At the heart of this midyear is this ZZ383 GM Performance Parts crate engine, not with a carburetor on top, but with a warmed-over Street Ram tuned port injection system from Accel. Advertised output of this crate engine in carbureted form is 425HP and 449 lb.-ft. of torque.
You might remember the engine segment with this picture of the crate engine upon installation. It comes with these lovely pseudo-finned stamped sheet metal valve covers that you have to look at in the mirror to avoid turning to stone. They're gone, plain and simple.
Enter these chromed aluminum beauties from GM Performance Parts-and a knot. These valve covers, along with the factory brake booster, are trying to share the same space at the same time. Won't happen-not with raised Vortec heads. Sooooo, we replaced the factory brake booster with a 7-inch hot rod booster that's been adapted to fit a Corvette. Problem solved.
Bzzzt. Wrong answer. The wimpy little brake rod that's threaded into the street rod booster is something like one third as long as it needs to be, and won't actuate our Corvette master cylinder. So, we took a correct factory booster pushrod, and had our machine shop turn it down and thread it so it could be installed in this booster.
Brackets hold all the accessories to the engine and everything works in harmony-until you add aftermarket air, headers and a later model alternator to the mix. Some of our brackets are factory, and some of them are shop-made, like this AC bracket.
Here is a C4 Corvette alternator installed with one mount bracket and two adjustment brackets for more stability. We converted the internal regulator so this now becomes a one-wire alternator. With battery juice available to it at all times, it turns on when it starts to turn, and turns off when it stops.
Accel sends you this DFI ignition coil and says "here, put it somewhere." Well, with firewall space completely taken up with relays, junction blocks and wiring, we made some mounting brackets and installed it to the top of the intake manifold, hovering over the valve cover.
Here are some of our brackets laid out on their way to the chrome shop. Some are factory, and some are shop-made. It's a good idea to draw diagrams and stamp witness marks on the spacers and bolts so you know which ones go with which brackets, the accessory they hold on, and the order of assembly. After all, it'll be at least a month, more like two, before they come back from the chrome shop.
We installed these March pulleys because-for one thing- they are very cool. We had looked into a serpentine belt system, but we would have had to change the AC compressor to another model, essentially throwing a perfectly good one away. The serpentine belt system that we looked into, and the compressor that is already on the car, are from the same company-and they are not compatible.
This 425 horsepower crate engine needs to be cooled. This was a no-brainer, because whenever we need a radiator, we call DeWitt's. Tom runs a first-class company with a first-class product. We got the twin Spal fans with this one.
Installation is drop-in, just like it came from the factory. The fan-control temperature sender mounts in the radiator near the hot water inlet.
We made up these Aeroquip stainless steel braided fuel hoses for fuel supply and return because they're clean, proven, and will last for years. We've joined them to the steel supply lines that we ran along the frame.
These are the 3/8-inch steel supply and 5/16-inch steel return lines prior to our application of gravel-guard. It doesn't look like it, but they are actually tucked nearly out of harm's way over the top edge of the frame rail. The gravel-guard will give them even more protection from that rogue flying stone while hazing the rear tires. The alternative is to pull the body off the chassis and run two lines where one line originally ran on top of the frame, and inside the frame rail at the last couple of feet.
We insulated the fuel pump with rubber, and mounted it to the frame cross member just behind the differential. The wiring (not yet installed) runs through 1/4-inch steel conduit along the inside wall of the framerail.
A new gas tank was used because we have to do a little soldering, and don't need to risk the job with some old gas fumes in the old tank. Fuel injection needs to have a fuel return, so we have to make one.
We made this fuel nipple for the fuel return, an installed it in the recess of the gas tank. It's a press-fit here, but now it's just a matter of flowing a little solder around the nipple to secure it and make it leak-proof. This little recess is a perfect location for it.
OK, so the owner of this '67 comes to us and says he wants at least 400 horsepower, he wants it to be rowdy, and he wants it to fit under the small block hood. He doesn't want a big block hood cause it's a small-block car. Sounds reasonable. We're in luck, because this engine / injection combination just fits under a stock small block hood. Almost.
You might remember this shot from the engine segment of this series showing the air plenum with the throttle body removed, and the closed hood hovering just above. It's easy to see that once the throttle body is installed, we'll be into the cross brace of the hood big time.
Something's gotta give. In this case, it's the center section of the hood brace. We have to take the center bridge of the cross brace out to make enough room for the throttle body, or we will have to have a big block hood. The owner doesn't want a big block hood since it's a small block car. I remember that.
If you're gonna do it, do it right. Make it look factory. We boxed the cuts in the bridge to not only strengthen them, but to give them a clean look. Speaking of bridges, we didn't burn one here, we just warmed it up a little. We're a restoration shop; so we can always put this back later.
Success. It's clean, strong, looks like it came that way, and will give us the clearance that we need over this tall fuel injection system.
We experimented with different exhaust tips before ending up with these Hookers. Exhaust tips that is. Two large outlets vs. four smaller ones-it's purely a matter of taste.
The advantage of four smaller tips is "fitability" beneath the license plate. We cut out the exhaust panel to fit the pipes, and then built a curved fiberglass wall in the cutout for a molded look, and for structural strength.
The chambered exhaust sticks were installed with maximum road clearance in mind. The forward sticks negate the downward direction of the headers and allow the exhaust system to pass through the frame crossmember as it should. The rear sticks continue to hug the floor from there and join in to the tailpipes that exit at the center of the exhaust panel.
Accel markets this clean little billet aluminum dual-sync distributor for their fuel injection systems. With the cam and crank triggers built into the distributor, there is no need to have them installed anywhere on the engine.
Because of this, however, it's very important to properlyphase the distributor prior to startup. With the GenVII computer connected to your laptop, phasing may begin. Red and blue LEDs built into the distributor signal the falling edge of the cam and crank trigger positions as you rotate the distributor body.
This is the Accel Thruster DFI startup screen on the laptop. Follow the instructions to get things properly set-up so the engine's computer knows whether to fire a plug or an injector.
With the distributor phased and the base timing set, we have run the engine. From here, it's time to load the car up and get it over to the dyno for some fine-tuning.
It's one thing to statically set-up an engine management system, but it's something else again to tweak it while running under a load with an exhaust gas analyzer connected to read the air-fuel mixture.
Jeff Wightman at Precision Autosports is an old hand at tuning, and runs the 383 through its paces to get everything right. Want more performance or more economy-he'll tune it your way.
After collecting data, Jeff reviews and makes the proper adjustments to dial-in this package to deliver what we're looking for. He hasn't "hammered" the throttle or redlined the tach, he has simply initiated a load while running the transmission through the gears for real-world testing. After some break-in miles, we'll be back to trim it in a bit more.
Which leaves us here-with the hood back on, the stickers and labels all removed, and the road calling out to a beautiful midyear to be driven. It will be a pleasure to accumulate those break-in miles before another trip to the dyno.
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