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Chevy Tech Q&A - May 2014

Kevin McClelland Mar 7, 2014
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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.

 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.


Lose the Clutch Pedal

I have a 235 Stovebolt six-cylinder Chevy engine in my ’49 Chevy Truck. I want to convert it over to an automatic transmission. What type of transmission will I need to do this, and can it be done? I have looked all over for info and could find nothing in this sea of Internet misinformation! Thanks.

David Sanford
Chatsworth, GA

Back in the day, the only automatic transmission you could hang behind the second-generation Stovebolt 216, 235, or 261 was the original cast-iron Powerglide. You could just about kill yourself rebuilding one of these gems; they were so heavy you really had to be careful. The cast-iron Powerglide was introduced in 1950 in GM passenger cars a year ahead of Ford’s automatic, and Chrysler didn’t have an automatic until 1954. This gave GM a distinct advantage, as the customers were really pleased to lose the clutch pedal.

To move your Stovebolt into the 21st century, get in touch with Langdon’s Stovebolt engine company, specializing in GM six-cylinder performance parts. One of those is a very nice adapter plate and flexplate, which adapts aluminum Powerglides, TH350s, TH400s, TH700R4s, and TH200R4s to the back of your six. With these choices you should be able to fit in your framerails whichever trans tickles your fancy. You’ll need to fabricate a transmission crossmember to hold up the back of the engine and trans, as your current engine/trans is attached by bellhousing side mounts. The adapter is sold under PN 56-3001 and includes a billet-machined adapter plate and hardware to mount to the back of your 235 and give you the six bolt holes and dowel pin locaters for the above transmissions. It also has a re-machined flexplate to adapt to the specific bolt pattern on the back of your 235 crankshaft. Finally, Langdon’s recommends purchasing its starter that matches up with the billet adapter plate and is aligned properly with the supplied flexplate. The prices are very affordable and could save you many headaches during the install. Check with Tom at Langdon’s at 586.739.9601 for more information before you order.

Good luck with your swap. Yes, weeding through the info on the Internet can be daunting if you don’t know specifically what you’re looking for. This is why we’re here.


Really Blown!

I’m hoping you can help me out. I recently came across a 10-71 blower off a late-’50s GMC diesel. Is this supercharger worth rebuilding to put on a gas engine, or would it be better to get a more common 8-71 or 10-71 for the engine? If it would be a good candidate for rebuilding the blower, where would I be able to find parts for it? Thanks.

Liverpool, NS, Canada

ANice find. This would be a very cool display piece in your man cave. As for using it on your performance gas application, it’s a long way from being ready to rumble. The changes required to this early piece would be more expensive than starting with the blower of choice for your application. The 4-71 and 6-71 blowers were sized for specific four- and six-cylinder diesel engines displacing 71 ci. Above the 8-71, the first number was just an expression of added capacity. Seeing that it’s a 10-71 application it’s not really size-appropriate for a small-block, and with a big-block you’ve got to work out the ignition issue for street use. Again, you didn’t tell us enough to give you application info about this blower.

Now, when you’re ready to upgrade to a Roots supercharger for either street or race use, check with Blower Drive Services, The Blower Shop, and Weiand. These are three of many that offer very high-quality superchargers for both street and strip use. They may also be able to tell you if your find would be worth rebuilding, or going with one of their specific casting that have been upgraded over the past 60 years.


Missing Bumpstick

In your Jul. ’12 Q&A, you recommended a camshaft for a 1-ton dualie Crew Cab 496 big-block. I have been unable to locate that cam—has the part been discontinued or the part number changed? I was wondering if you can help. Thanks!

Lowell Breiter
Hurricane, UT

ASorry for any confusion. We’ve gone back into the archives and pulled up the issue. The camshaft we recommended for your Gen VII 496 big-block dualie application was a standard 454/502 H.O. hydraulic roller direct from General Motors. The part number in the edit (PN 24502611) was correct and it hasn’t changed. If you pop that part number into Google the first dealer that comes up is Pace Performance, then GM Performance Motors. Give it another try; they are out there, and it will kick ass in your application. Good luck.


Roller Locater

I have a question on Cam Retainer Plates. I have a ’71 small-block Chevy which had a solid flat tappet cam in it, but the cam went bad due to moving back and fourth in the block, wearing the lobes resulting in a chewed up distributor gear. I have a Dynagear timing set with a cam button. I’m stepping up to a solid roller now and I had seen in your latest article on moderate mouse about the retro roller with retainer plate and I was wondering if I should do that too, so the roller cam doesn’t move on me again. However, my block doesn’t have a spot to drill for a plate. I would appreciate any tips and/or options. Thank you!

Trevor MacNeill
Lincoln, MI

Your flat tappet camshaft should have never had an issue with “Cam Walk” because the camshaft lobes should have had a very slight taper ground into them. This taper constantly puts force pushing the camshaft back into the block. This keeps tension on the cam and loads the thrust surface between the camshaft gear and the block. If your cam manufacturer didn’t have their camshaft grinder set up with the proper angle on the lobes the camshaft will walk. We’ve only seen this a couple of times.

Now moving onto roller camshafts, they do not have any taper ground into the lobes and they will definitely walk. When this happens it gets real ugly as the lobes can run into the roller lifter next door sending hardened metal shavings throughout your engine. The late model thrust plate option is very cool if you can run a camshaft with the machined features from an ’87 and up roller camshaft master. Getting a performance solid roller profile ground on a late model blank could be expensive and isn’t really necessary.

For your street build, we would recommend going with a cast aluminum front cover that will prevent any deflection of the front cover. This front cover in combination with your camshaft thrust button will prevent camshaft walk. When setting up your cam endplay you will want to use the front cover gasket that you’re going to run, and torque the front cover into place to 80-inch pounds of torque. The target end play you’re looking for is 0.005 to 0.015 inch. You may have to either shim behind your thrust button and camshaft, or turn off a few thousands from your thrust button to achieve this tolerance.

As you stated in your question, your early block doesn’t have the retainer attaching features like the ’87 and later blocks incorporate. With your application, the thrust button is the way to go. Following these instructions above should give you a drama free solution. Enjoy your new roller cam power!




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