May 2011 Chevy High Performance Q&A - Performance Q&A

Love It When A Plan Comes Together

Kevin McClelland Mar 29, 2011 0 Comment(s)

Well, it’s been a longtime coming. Today, we finally made it to the track with my super gas roadster. I know, you’ve been reading about it for months. As with any project, it took much longer than expected, and I don’t even want to think about adding up the receipts. I figure this will be the only new race car I’ll ever have. True, it was originally built in 1995 by Don Davis Race Cars and was one of the first ’27 Ford roadsters they built. It ended up being the house carthe one they tried all the upgrades onfor the first several years of its life cycle. Don doesn’t build these cars anymore and has mainly moved on to the Corvette roadster for the aerodynamic advantages. Needless to say, this car has had several sets of interiors in its lifetime, with brackets and tabs welded on and cut off in the process. Now it’s fresh and pretty until I need to make some type of change. Remember, race cars are just tools to win races, not show cars. (My dad will love that one!)

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After many hours of double- and triple-checking everything, it rolled out of the trailer this morning and went through tech inspection without any drama. Not only was the car fresh, I was finally able to reinstall my 524 big-block built from a Dart Big M block and 335 CNC Pro One cylinder heads, Crane valvetrain, CP pistons, and Total Seal rings. It’s completely fresh, and many new tricks went into this pump-gas 10:1 compression race engine. With my change of job several years ago, I lost easy access to the engine dyno that I had the pleasure of running for almost 20 years. I just couldn’t bring myself to pay someone to run my engine. So after running the engine in, and bedding in the brake pads and rotors several weeks ago, it was ready to pull up to the asphalt dyno.

Fontana Auto Club Dragway is the slowest dragstrip in California. There are many reasons for that, but mainly the air sucks (it’s right on the edge of the desert) and the track is slightly uphill! Not knowing what to expect, I put on my wheelie bars and drove it up to the lanes. I was ready to be very happy if it ran in the 8.70s at Fontana. Pulling to the line, setting the transbrake, and letting it rip, it rocked back on the wheelie bars and carried the front wheels just past the Christmas tree! As it blasted straight down the track, I watched the sensor readouts on the RacePak digital dash. It felt good, and just hoped it was really that quick. Pulling to the timeslip booth for my instant report card, I had to give it a double take. I ripped off a 1.229 60-foot, 5.430 at 126 in the eighth, and trucked on through the quarter at 8.560 at 155.56 mph. Well, I can’t wait for tomorrow morning and first round. It’s been almost a year and a half since the last time I’ve raced it. All the thrashing was well worth it, and next up is the Bracket Nationals in Las Vegas. Hope to see ya there.

Valve Clearance School

Can I install a camshaft with 0.533-inch lift into a stock 454 Chevy engine? If so, what type of modifications would I need to make? What selections of valvesprings are available, and will I need to use long slot rocker arms? Any clearance issues between valves and pistons? It’s a ’74 engine with oval-port cylinder heads. Thanks.
Minnie
San Antonio, TX

At least you’re asking all the right questions. Many folks install an aftermarket performance camshaft increasing the lift and duration without ever thinking of the consequences. Yes, lift can be an issue with piston-to-valve clearances, but it’s more about when it happens in the engine cycle. Let’s talk a bit.

Most people think that when you increase the lift you get piston-to-valve clearance issues. Increasing the duration and/or reducing the valve separation angle will cause clearance reductions greater than the actual max lift value. When you’re running a stock-type camshaft in a big-block you have duration values in the very low 200-degree range at 0.050-inch tappet lift. When you increase the duration to, let’s say, 240 degrees at 0.050-inch tappet lift you have started the valve lift event 20 degrees sooner and ended 20 degrees later. This change puts the valves much closer to the piston than the actual max lift. If you have two camshafts with a max lift value of 0.500 inch, the camshaft with 200 degrees of duration at 0.050 will have a piston-to-valve clearance of 0.200 inch at the critical valve-to-piston location, which occurs right around 15 degrees before top dead center on overlap for the exhaust valve, and 15 degrees after TDC for the intake. A camshaft with 240 degrees and the same max lift of 0.500 inchbecause the valve event started 20 degrees soonerthe valve could be open 0.120-inch more than the smaller camshaft at the critical checking points. The main difference in the two camshafts is that the cam lobe dwells at max lift for 40 degrees longer with everything else being equal. Now you throw in the tightened valve separation angles and advanced intake centerline, the piston-to-valve gets even closer.

So a mild-performance camshaft will fit into your big-block without a problem. If you wish to go over 230 degrees at 0.050-inch tappet lift, we’d start checking things. Whatever you do, a safe piston-to-valve clearance will run around 0.080 inch for the intake valve and 0.100 inch on the exhaust. As for the valvesprings, go with the camshaft manufacturer’s recommended valvespring and retainer to ensure that the valvespring pressure is correct for those cam and lifters. The factory stock rocker arms will accept 0.533-inch max lift. Finally, with the cam manufacturer’s retainers in place, make sure you have at least 0.050-inch valve seal-to-retainer clearance at max lift. Many of the cam manufacturers have taken the increased lift possibilities into their retainer designs giving you the maximum clearance between the seal and retainer.

Good luck with the mild hop-up of your big-block. They can be fun, torquey little (big) engines. Many a tire company has made a fortune on BBC-equipped vehicles!

It’s All About The Boost!

I have long been a subscriber to Chevy High Performance and to one of your sister publications. In that magazine, I often see articles on Buick Grand Nationals with turbocharged V-6 engines. It’s hard to imagine a fullsize car running 9s or 10s with a V-6, but they apparently do. Since Chevrolet has always built higher-performance motors than Buick, why don’t we have any Chevrolet V-6 motors pushing Monte Carlos or Camaros into 9- or 10-second timeslips? How do we get big powerand hopefully good mileageout of the Chevy V-6 that is so plentiful? I cannot tell you how much it pains me that Chevy performance is being bested by a Buick!
John Caldwell
Albuquerque, NM

Having owned many of the GM products over the years, we had a ’70 Buick Grand Sport convertible with a 455-cid big-block. The Buicks were always referred to as the Businessman’s Hot Rod, with their upscale appointments and big power. The Stage 1 455 was only rated at 360 hp (far below real output for insurance reasons) and 510 lb-ft of torque. This would move the Skylarks and GSs right with any of the LS6-equipped Chevelles of their day.

Then came the emissions wars and the downsizing of our whole car lines. The Buick Grand Nationals came equipped with a 3.8L turbocharged/intercooled V-6 that when modified would make tons of power. Yes, there are 9- and 10-second GNs around the country, but these are highly modified variants of this animal. A well-tuned GN with minor aftermarket parts will run deep into the 12s, and with the right mods, dip into the 11s. For a period in the late ’70s Chevrolet used the 3.8L turbocharged Buick in the Monte Carlo. This was well before EFI and intercooling. This was a very poor attempt at turbocharged power in Chevrolet cars. The Buick GN V-6 was also used for several years in Pontiac Firebirds in the late ’80s and early ’90s.

Finally, to your question: The Chevy Syclone and GMC Typhoon truck utilized much of the technology of the Buick GN on a 4.3L V-6. This engine was equipped with a Mitsubishi turbocharger and a Garrett water/air intercooler. It featured unique pistons, main caps, head gaskets, intake manifold, fuel system, and 48mm twin-bore throttle body from the 5.7L GM small-block. The power was transferred through a 4L60 transmission mated to a Borg-Warner all-wheel-drive transfer case split torque, with 35 percent forward and 65 percent to the rear wheels. The engine was rated at 280hp SAE and 350 lb-ft of torque. When the truck was new in 1991 it ran a 4.6-second 0-to-60, and would cover the quarter-mile in 13.4 seconds at 98 mph. During testing, the little truck ran a 4.3-second 0-to-60, and 13.06 in the quarter-mile. This was a bone-stock truck, and when you leaned on these machines, they flat flew! Unfortunately, this program ran from 1991-93, only producing around 5,700 of these trucks.

Now for the 21st century power. The new ’10-and-up Camaros come equipped with the 3.6L engine code LLT direct-injected V-6. In 2010, the engine is rated at 304hp SAE and 273 lb-ft of torque, and in 2011 it was upgraded to 312hp SAE, and 278 lb-ft of torque, from 87-octane fuel! This engine has a compression ratio of 11.4:1 and because of the specific engine design and controls and the direct fuel injection. Anyone who says, This isn’t the good old days of engine design needs their head examined!

With boost and design, just about anything is possible. You could outfit a Chevy V-6 with the right components and run just about as quick as you wish. It’s just that you’re doing all the R&D; Buick made it easy for everyone.

Later X-Bodies

Do you know of any good websites with aftermarket parts for ’75-79 Novas. I know they’re odd years and it’s hard to find aftermarket parts for them. There has to be someone out there making parts.
Thanks!
Dustin Sampson
Winifrede, WV

Most parts have been developed and offered for the ’62-74 model years. The ’75-and-up X-body Nova is like a lost stepchild. They had very good points about them, and law enforcement used them quite a bit in the late ’70s. They had some very cool factory suspension packages to make those cars drive on rails.

Classic Industries has a nice offering of body components, emblems, interior parts, and accessories for the late Novas. Not as many as for the later years, but new items are added all the time. Check out the site for more information on the hardware you need.

Source: classicindustries.com

Positively Messed Up

My ’69 Camaro has been modified as a Pro Touring car, and I have a big-block under the hood. My problem is the front suspension. We have added Heidts’ upper and lower control arms, Hotchkis lower springs, Unisteer rack-and-pinion, and poly bushings and endlinks on the factory sway bar. The car aligns great, but after about a mile the tires squeal really bad and the camber goes positive and looks a little high in the front, like something is shifting. Both front tires go positive camber at the same rate and no one can figure it out. I have found that if you back up a bit it will settle back down most of the time. I think it may be the sway bar binding. We removed the suspension and double-checked all bushings and bolts. Any suggestions on what’s going on? It’s destroying my tires and is not driveable! I have every suspension shop in the area stumped.
Thanks,
Bill Hussey
Severn, MD

OK, we’ll give this one a try. Without being able to see the car it’s a little tough, but we’ll throw out a couple of ideas and you guys can check them out.

We cannot see how the camber is changing when you drive the car a mile. We’re sure you’ve heard this from all the shops in the area that have checked out your car. Since it seems the camber is changing after a mile of driving, and when you back up the camber returns to the correct value, it sounds like the alignment is going toed-in and binding up the front end. When you go toed-in the front end plows, the tires squeal, and the front end will appear like it has gone positive on the camber setting. You mention that you’ve swapped out the steering box and drag linkage for a rack-and-pinion conversion. The factory steering was a rear steer, which means that the steering gear is behind the front axle centerline. Incorrect steering arms on the spindles, an improperly mounted rack, and flexing mounting brackets for the rack are all factors that could cause the steering to not control the toe setting. It’s hard to believe that the Heidts upper control arms are moving enough to lose their camber adjustment. Sounds like something is flexing, allowing the alignment to return to normal after you back the car up.

Contact Unisteer to follow up with your installation and the components used to mount the rack to the factory subframe. The installation instructions look to be very straightforward. Your rack is mounted in the factory rear steer position. If the rack is not tightened properly, with the lower control arm bolts and spacers supplied, that could flex, causing toe variations. Also, we don’t know that we agree with their alignment specifications. Everything looks good for the toe-in and caster settings. Heidts recommends setting the camber a quarter degree positive. With the Heidts control arms and Hotchkis springs, you’re setting this Camaro up for performance driving. We’d set the camber to at least a half degree negative, up to as much as 1 degree. It just matters how much long freeway driving you plan on doing. If it were ours, we’d be out throwing this thing through the turns. Check it out, and good luck finding your gremlin.

Source: unisteer.com

Tranny Choice For Minnie Mouse

Which transmission would be better for use behind a 302 small-block Chevy? I have a turbo 400 and a Muncie M21 four-speed to pick from. Now for the engine specs: The block is a ’67 327ci bored 0.030 inch with a 283 steel crank and Scat 4340 steel forged rods connected to KB 11.4:1 forged 302 pistons. The heads I’m using are GM 3991492 casting with 2.02/1.60-inch valves and angled plugs. I went with a Duntov 30/30 solid lift cam for nostalgia reasons. Last but not least, ’69 Winters Z/28 aluminum dual-plane high rise with the casting number 3932472, and topped off with a Holley 800-cfm double-pumper with mechanical secondaries.

This engine has been built to be stuffed into a ’79 Camaro with a stock 350, a Saginaw four-speed, and a 3.73-posi rearend at the present time. This will mostly be used for car cruises and occasional quarter-mile passes. Any suggestions on the engine combination and the type of trans would be greatly appreciated.
Thanks!
Fred Stipkovits
Via email

Many folks are reliving their high school years with Minnie Mouse engine combinations. Your buildup is very cool, but there is one clear choice (for us) on transmissions. The TH400 is a massive transmission that was built to be used in trucks! The thing is heavy, the rotating mass is high, and they eat horsepower. Many estimate the amount of power to rotate one from 20 to 30 hp. All we know is that you’re going to need a four-speed connected to the back of your 302 to keep that little Mouse in its powerband. Anyway, rowing the gears is much more fun at 7,500 rpm than just moving a stick one click! Enjoy the song that your small-block is going to produce. CHP

Technical questions for Kevin McClelland can be sent to him at chevyhi@sorc.com.

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