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Chevy Tech Q&A - June 2014

Kevin McClelland Apr 9, 2014
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Our Track Is Back!

Hopefully, by the time you're reading this, we've been peeling out and doing wheelies at our home track: Fontana, California's Auto Club Dragway. As you may know, Fontana closed more than two years ago because of issues with local neighbors and organizations over noise. About a month ago the Auto Club Dragway and local homeowners came to an agreement. This past week the final OK was given and the construction of a 1/2-mile-long sound wall began to protect the local neighborhood from the music that comes from our internal combustion engines. This was the final requirement from the San Bernardino courts to get us back to racing. This wall reaches almost 30 feet into the sky and wraps around the staging lanes, behind the tower, and well past the 1,320 mark at the top end—at a cost of more than $1 million!

The decision to move forward with the construction and expense of the wall didn't come lightly. This facility is owned by NASCAR, and the bottom line is that the track must be a profit center. With this track being the only 1/4-mile track in Southern California that is operated on a regular basis (Pomona is open twice a year for NHRA Nationals), the aftermarket, SEMA, Auto Club of SoCal, and NHRA came together to support the track with fundraising and support. With Southern California being the home of the drag racing, we must retain at least one active 1/4-mile racing facility.

The track is also a major help to the local Southern California area to give the young people a place to race that is off public roads. Auto Club believes in the "Street Legal" program, which runs once a month and attracts more than 500 cars per event with everyone coming together with a common passion of having fun and going fast safely.

What this means to our local racing community is huge. The tentative 2014 schedule has been set with eight Summit ET series events, four PSCA, two NMCA, an NHRA National Open, and four association weekends. These association weekends will include SoCal Pro-Gas, SoCal Super Street, SCEDA, and SoCal Super Comp. SoCal Pro-Gas is the longest-standing private racing association in the country, and my family is one of the founding members. We attended and participated in the first event, back in 1975! In the late 2000s it wasn't uncommon for us to have 60 to 70 cars for a race, paying great purses for a local event.

If you're ever in our backyard, please come by and check out our track. We'd love to see you and talk about racing and how to be good neighbors with your local community. We need to stop losing racetracks around the country. We're very lucky that ours is re-opening. This is not the norm. Wish us luck. I'll keep you posted.


Q I believe your column is the best in the magazine industry. Your depth of knowledge has amazed me for years.

I just installed a new Dart-based 421 small-block making 581 hp at 6,400 rpm and 549 lb-ft of torque at 4,700 rpm in my street/strip '67 Camaro. I'm looking for advice on chassis setup for my drag racing adventures. The Camaro is equipped with a 10-bolt diff with a spool, 4.11:1 gears, an aluminum support cover, Strange 33-spline axles, and 275/60 M/T Drag Radials on 8-inch rally wheels.

It hangs on CalTracs bars and split-mono leaf springs. A 350 Turbo with a 4,000-stall converter transfers the power. To tie the car from front to rear, I've got bolt-on subframe connectors to offer support.

Up front, it's got unknown coil springs with one coil removed, stock control arms with urethane bushings, three-way adjustable shocks, and the stock sway bar. The battery is in the trunk.

It's a 4-mile drive from home to the dragstrip, with my priority being dragstrip results over street manners. I really look forward to your recommendations. Thanks in advance!

Jim Baylor
Catawissa, PA

A Wow, thanks for the kind words. Yes, drag racing is our passion, but we hope we can keep it mixed enough for everyone to take something from each column.

Your new small-block is making some good power for a street/strip combination. If we were to venture a guess, we bet it runs on pump gas, too. A man after our own heart! Getting the power to the ground with the least drama possible is our goal. Most of your suspension package is spot-on and will work well in a street/strip application. First, we would swap out your front springs for a set of Moroso Trick front springs. These tall, small-wire-diameter front coil springs have a spring rate of 213 lb/in on the small-block applications, and 240 lb/in on big-blocks. They hold a great amount of stored energy for instant weight transfer, placing the load on the rear tires, where it's needed. These springs are listed for racing use only, as they will not last forever with such a low spring rate, and can be a handful to drive with shocks set for weight transfer. The springs for your small-block application are PN 47150. Your polyurethane bushings will allow the control arms to move freely. Also, install polyurethane sway bar bushings with your stock front bar.

You need a good set of racing shocks all around, for the adjustability to fine-tune the suspension and control all the torque you'll be throwing at those rear tires. The 4.11:1 gears, with the 2.52 First gear in the TH350 gives you a First gear ratio of 14.47:1! This, in combination with your 4,000-stall converter, is going to hit those 275 drag radials. Unless you control the extension of the rearend, you could hit the tires and then blow them off with wheelspin. Regular three-way adjustable drag shocks won't give you the control needed for this type of power. To give you the adjustability you need, we recommend AFCO double-adjustable racing shocks. This will give you independent adjustment for both compression and rebound. Most single-adjustable shocks give you rebound with a fixed compression. With your high power and running stock type suspensions, you'll need to stagger-adjust the shock rates from side to side on the rearend to control the torque rotation of the rearend housing. This is something you just can't do with a single-adjustable shock. The AFCO shocks are PN 3840F (front) and 3870R (rear) in your application. As for a baseline setting for the rear shocks, we would set the compression at two clicks off full soft, and the extension around the midpoint of the adjustment. This will give you a tuning point to gauge from. Also, if the double-adjustables are just too spendy to put them all around, the rear shocks are going to be the more important. Up front you can deal with a standard three-way in a 90/10 setting at the strip, and the 70/30 for extended street use.

The bottom line is we dig your package. It's been years since we've had our '67 and '68 Camaros. We raced the '68 for the five years before we sold it. Those were the days. Enjoy your toy, and hope you find some serious daylight under your front tires. Hanging the fronts is very cool.



Q I have an '80 Malibu Wagon that I am turning into a "ProSleeper" (you heard it here first). It's a cross between Pro Touring and a sleeper. It's running a Hotchkis TVS system, Wilwood replacement front calipers, and a ZZ383 crate engine with a 350 Turbo and 2,000-stall. I have added a 650 mechanical secondary double-pumper carb from a previous project. The jets are 68 and 72. I'm using a Holley 12-834 mechanical pump, rated at 80 gph. My objective is great throttle response for street driving and occasional drag racing (for test and tune). Am I leaving power on the table with a "little" 650-cfm? Back when I bought it 10 years ago, the 650 seemed to be very popular and in keeping with the "smaller is better" concept so widely promoted. I am also running an HEI, which I have locked out the mechanical advance to 36 degrees and ditched the vacuum advance, along with a spring weight swap.

Also related to the above is my rearend. It has a stock 7.5-inch posi with 3.08 gears. I'm going to try it as is until budget allows an upgrade. Besides, I'm real curious about the top-end capability and fuel economy with this "highway" gearing. The car weighs in at around 3,200 pounds, so I'm hoping I can keep decent acceleration and highway ability with this gearing. But if I have to, I'll bump it up to 3.42-ish. People tell me this rearend will grenade very quickly. I'm only running a 245 street tire, so traction will be limited. Is it worth investing any money into an aftermarket posi and axles? (Still way cheaper and lighter than a 9-inch swap.) Will the 7-5/8-inch ring-and-pinion fit the 7.5-inch (from a Monte Carlo SS)? What's the breakaway torque rating on this unit before service? Thanks!

Tom Silver
NL Canada

A ProSleeper, is it new? Surely someone has uttered these words at one of the Hot Rod Power Tours. Now, since you're from Canada, it's the first time in the great North! We like it! Especially since you've converted your wagon into one.

The 650-cfm carburetor is plenty of air for your ZZ383. If anything, you're giving up a few ponies at red line. All the rest of the time driving your package you're building the best torque curve to move your wagon. Locking out your advance in your distributor will give you great throttle response and part-throttle snap. With only 2,000 rpm of stall speed you'll be able to put too much load on the engine at slower speeds (2,000-2,800 rpm) with the advance locked at 36 degrees. Be careful and pay close attention to spark knock and detonation. Also, having the spark locked at 36 degrees isn't going to give you the best fuel economy. At part-throttle cruise, driving down the freeway your combination will probably be around 44 degrees total timing. This is where the vacuum advance comes into play to increase fuel economy. You may want to rethink your advance package and reinstall your mechanical advance weights and springs. Limit the mechanical advance to around 8-10 degrees total in the distributor, which will be 16-20 degrees at the crank. This advance should be all in by the 3,000-rpm range, and you will want to set the initial spark timing at 14-18 degrees, based on how much advance you set up your distributor to have. This will put you in the 34-degree total range, and then throw around 10 degrees of vacuum advance. This will give you a well-rounded advance curve and the best fuel economy you're going to achieve with the ZZ383.

As for the 7.5-inch diff, yes, the 7-5/8-inch gearset will fit into that housing. We agree with your buddies' opinion of the 7.5-inch diff. You can spend a bunch of cash hopping it up, and it would probably live, but it's still a 7.5! We would ditch that rearend and look for an 8.5-inch unit out of a Buick GN Regal or a Hurst Olds. The SS Monte Carlos still have the 7.5-inch diff. Don't know why GM cheaped out on the SS Monte. You can still find the 8.5-inch diffs out in wrecking yards. This is a direct bolt-in into your '80 Malibu wagon. You can find a complete selection of gears and posi-tractions to choose from. The production 8.5-inch would live behind your ZZ383 without a problem. We've got a Buick GN rearend in our Malibu wagon race car. It's filled with Strange gears, axles and spool, ARP studs on the caps, and an Unlimited aluminum rear cover with load pins and back brace. This rearend has given us six years of service without a whimper. We're even throwing 600-plus horses at it and it's gone as quick as a 1.41 60-foot. The 8.5-inch would be a much cheaper way to go than the 9-inch route. Also, it's all GM and it's a bolt-in.

Have fun with your ProSleeper! To each their own, and we love wagons. They make very cool performance cars, and you always have a bedroom!

New Idea for Clearance

Q I read some articles in your magazine about the SBC 434. I have a new Dart SHP block and a new Callies CompStar 4-inch-stroke crank. I have read many articles, and each one seems to use a different rod and has a different view on how they fit. I don't want to have to grind a bunch on the block. The Callies Ultra XD rods are supposed to be the best fitting, but they are $1,500. Do you have any real-world ideas on which 6-inch-stroker-friendly rod to use? Thanks!

Dave Snyder
Via email

A Thanks for the question. It gave us the opportunity to look into these Ultra XD connecting rods, and the really trick application of canting the rod parting line. Callies has a patent pending for this technology. Let's look at how it picked up clearance between the block and camshaft in stroker applications.

Stuffing inches of stroke into any engine has been a popular performance option since the internal combustion engine was invented. When the GM engine designers laid out the crankcase, they never imaged we'd be stuffing 4 inches of stroke into a Gen I small-block. The placement of the pan rails, camshaft, and cylinder walls assumed a max stroke limit. When the Gen I small-block was conceived, it started as a 3-inch stroke engine, then pushed to 3.25 inches for the 327, and then to 3.48 inches for the 350. We believe this is where the original designers had given the engine its limits. Then along came the 400s with their 3.75-inch stroke. GM had to go back to the drawing board and shorten the connecting rod to 5.565 inches, shorten the rod bolts to clear the camshaft, and to keep the wristpin in a production-happy location. Also, they needed to increase the main journal diameters from 2.45 to 2.65 inches to ensure production integrity of the crankshaft. When you extend the stroke out to 3.75 inches, you lose pin overlap between the rod and main journal. This is where the two journals share common material and you're not relying on the counterweight material to transfer all the forces down the crankshaft to the flange. All of these changes were put in place to stroke an engine properly.

As we have written, small-blocks have ballooned in displacement to unbelievable levels. The performance of these engines is incredible with the selection of cylinder heads on the market. However, with any stretch of design there are compromises. Dart has accommodated many of these compromises in its SHP small-block castings. This block has been relieved for cylinder wall and pan rail clearance to fit a 3.75-inch stroke without any clearance issues. Even with this block you still have to be mindful of connecting rod clearance to camshaft. Going another 1/4 inch further on stroke will require grinding of the pan rail and cylinder walls. To minimize this—and to gain the needed camshaft clearance—the Callies solution is right on point, with the slightly rotated connecting rod parting line to rotate the bolt area away from the block and camshaft side of the connecting rod. This not only alleviates camshaft clearance issues, but it also gives you more clearance between the block.

Another major benefit of the Callies XD Ultra design is that you can use a standard base circle camshaft. When you reduce the base circle of the camshaft to gain connecting rod clearance, you lose rigidity of the camshaft. With the camshaft lobe designs, and the spring pressures required to control the valvetrain at engine speeds of today, the reduced base circle camshaft turns into a wet noodle in operation. No one ever talks about the performance loss of camshaft flexes, which creates cam timing variations and lift losses. Now, this is why we use raised camshaft locations in stroker applications, and large camshaft journals to increase the base circle in all-out racing applications.

In our opinion, you'll be dollars ahead using the Callies-innovated design. Sure, cost a few bucks, but the benefits out weigh the cost. There's the XD Ultra design in 5.7-6.25 inches for small-block Chevy applications. The two rods that you should be looking at are the 5.85-inch (PN U14130) and the 6.0-inch (PN U14135). Give Callies a call for more information at 419.435.2711.

Finally, you mentioned using 6.0-inch rods in your application. This will leave you with a compression height of 1.00 inch for your wristpin placement in the piston. You didn't mention what power level you plan on for this build, but that's rather tight. If we were building this package we'd go with the 5.85-inch rod to give you a 1.150-inch compression height. Your piston and ring manufacturer will love you, and with a 4-inch stroke that rod ratio is so blown up that the additional 0.150 inch of rod length isn't going to be the difference. The 6.0-inch rod combo gives you a rod stroke ratio of 1.5, and the 5.85-inch rod comes in at 1.46. As stated above, stroking engines is all about compromise. Picking the right ones is the difference between a good packaging, and well you know. Good luck.




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