Chevy Tech Q&A - May 2014

Kevin McClelland Mar 7, 2014 0 Comment(s)
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Lucky Number 13

The number 13 has a different meaning to each and every one of us. If you step onto an elevator in a high-rise building, I defy you to find button for the 13th floor. Most references to 13 are in some way unlucky. Well, for the Mac family, the number 13 comes up quite often in our lives. Thinking back to my first day of classes at Los Angeles Trade Technical College, I was student number 13 of 30 in Mr. Bryan’s Carburetion class, probably having to do with my last name starting with the middle—or 13th—letter of the alphabet. And then back in my Kart racing days, I ran number 13.

KevinMac 2/3

Fast-forwarding, I come to the latest brush with lucky 13 for the Mac Family. Back in 1997 I was lucky enough to win the NHRA Winternationals in my good friend Tim Moore’s Super Gas Brogie Roadster. This was the first national I had won, and the first national I had raced in over 14 years. At that time, Jeff Smith was the editor of this fine publication (he’s now the Senior Tech editor of Car Craft) and I was writing the Performance Q&A column for him. He was so proud of our accomplishment that he put it right on the cover of Chevy High Performance that “CHP Wins Pomona” with the attending story inside on Tim’s car and a round-by-round account of the race.

Well, two weeks ago, Daniel and I were in Las Vegas racing the NHRA Jeg’s Sportsnational. Daniel lost a very close race in the third round in Super Street, and I was able to make it all the way through the field and be the last man standing with the Wally in Super Gas! This would mark my fourth National win and the first since my last at the 2000 Autolite Nat’ls in Sonoma, California. This again would be 13 years since my last National win! With as few Nationals I get to run because of our busy schedule, and the lack of races out on the west coast, I didn’t really know if it would ever happen again. Also, with the influx of technology packed into these new Super Gas cars, it sometimes makes you think if you have a chance.

As with any index class, the objective is to, “kill the tree, drive the stripe, and run the index.” How you choose to do that is your choice. With the latest technology, or doing it old-school, it really doesn’t matter. All I know, I hope that it’s not another 13 years before another one. You may need a crane to get this old guy in my car!

Many Inches

I have a 502 Gen VI big-block Chevy that has been overbored by 0.120 inch. Can I re-sleeve this engine? Thanks.

502 Gen Vi Big Block Engine 3/3

Deon Roodepoort
Johannesburg, AK

Wow, that’s quite an overbore for a production Gen VI big-block. The factory bore on your engine was 4.470 inches. Going a-buck-20 over brings you to 4.590 inches. The production blocks can handle 0.030-0.060 inch of overbore without much worry. Going any larger, you must sonic-check the cylinder wall thickness to ensure that you have enough meat.

Yes, you can sleeve all eight holes, but with the machine shop expense—and the chance of water leakage—we would look for another block. GM has sold a ton of Gen-style 502 big-blocks, so you should be able to find used ones out there on the market. Hope you find one.

Junk in the Trunk

I’m in the process of relocating the battery to the trunk with a disconnect switch on my ’78 Chevy Malibu. I want to keep the original Delco 3-wire 10si alternator, but I’m not quite sure how to wire it up so the engine shuts down when you turn the disconnect switch off. Do I have to install a high-amp alternator shutdown relay? Any thoughts, advice, or recommendations will be greatly appreciated.

Brandon Foot
Via email

By the NHRA rulebook you must be able to kill the power to all devices, which will separate all loads from the positive battery lead. When you add alternators into the mix, things can get a little strange. This is especially true when you’re running “one-wire” alternators, and alternators in which once the alternator field current is established it will continue to charge until it stops being turned. Even with a battery disconnect in place, if the alternator load (charging) wire is connected to a common bulkhead feeding accessories, the engine will continue to run on alternator power. Let’s talk about your options.

You mentioned installing a high-amperage relay between the alternator and the load. This can work, but you must be careful when wiring the relay that it will lose 12 volts when the battery disco is turned off. Again, if it’s connected to a common lug with alternator power, you won’t be disengaging the alternator. Next, and the truly legal way to do this, is to check out the Flaming River Combination Battery/Alternator Kill Switch (PN FR1013), designed just for this issue of self-energizing alternators on race cars. The switch features 2,000-amp surge capacity on the high-amperage terminals, 150-amp continuous on the high-amp, and 120-amp on the specific alternator disconnect. These switches are a little pricy, next to a standard 2-pole disco, coming in right around $100. Check out all the disco switches offered by Flaming River.

Finally, let’s talk about having a heavy-gauge, full-time hot lead running the length of race cars. The way we wire our personal cars is using an 8-gauge wire directly from the alternator and runs the length of the car straight to the positive battery lead. To protect the vehicle from mishap with the heavy-gauge wire going to the alternator we install a 10-gauge fusible link in the 8-gauge wire right at the battery. This prevents issues with grounding, the alternator shorting out, or in a crash having a hot lead grounding out. Should this 8-gauge wire be shorted to ground, the fusible link would immediately melt and protect the car. Is this totally legal? Possibly not, but it’s an elegant solution to the issue of killing all accessories in the vehicle. This allows you to use a standard 2-pole disco switch and put all accessories and load to the disconnect and remove the load from the battery. The alternator is a charging device that is isolated directly to the battery.

We hope these options help with your decisions to separate your battery from your car. Good luck, and make sure you mount the battery very securely, as that’s about 40 pounds of mass that can easily come loose in a shunt.


Manual Conversion

I’m trying to convert an ’89 Chevrolet Stepside 4x4 from an automatic trans to a manual. I have a five-speed Getrag to put in—is there a mounting bracket or a conversion to mount the trans to the transfer case? The guy I bought it from said he’s seen a mounting bracket but couldn’t remember where. Please let me know if there is something available. Thank you.

Kevin Lemire
St. Joachim, ON, Canada

Can you even believe your truck is 25 years old now? It’s hard to remember late-’80s vehicles are as old as they are. GM is required to offer service parts for its vehicles for 10 years after release … so you can probably see where this is going.

The adapter you’re looking for on your Getrag transmission is the extension housing of the 4x4 transmissions. There isn’t an adapter to bolt a 2x4 gearbox to a 4x4 transfer case. Also, the only way this 4x4 tailhousing was serviced through GM—when it was available—was on the re-man transmissions. GM didn’t offer the tailhousing separately. To make this conversion, you’ll need to find a 4x4-specific trans and choose which trans is in better condition. The one you find may be in better condition than the one you purchased from your buddy.

Finally, after talking with our pal Ken Casey at Elway Chevy about your swap, he suggested that you look into the NV4500 gearbox. He said that the Getrag trans wasn’t the best and that people have much better luck with the New Venture 4500 five-speed in the trucks. New Venture came from a merger of the GM Munice and the Chrysler New Process gearbox programs. The NV4500 five-speed was introduced in ’93 Chevy/GMC trucks in both 2x4 and 4x4 applications. For adapter help, check with Novak Conversion, which specializes in conversions into Jeep vehicles, offering adapters and components to adapt these transmissions to multiple engine families and transfer cases.

Sorry to ditz your Getrag trans, but if Kenny says it’s the wrong direction to go, we’re taking his advice. He sees this stuff every day, and like us, he’s an old guy with many years under his belt.





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