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Mazda Laguna Seca Raceway & Chevy Tech Help - Performance Q&A

Kevin McClelland Nov 1, 2008
0811chp_01_z Mazda_laguna_seca_raceway_chevy_tech_help Chevy_tire_wheel_drawing 2/2

WAJ 2008
It was that time of year again, the Western Automotive Journalist (WAJ) Media Day, when auto manufacturers from around the globe bring their cars to beautiful Monterey, California. They give us media writers the chance to test their wares first on a ride-and-drive around the Monterey Peninsula, then on the Mazda Raceway at Laguna Seca. On day one, there were 32 manufacturers and 89 cars to get a feel for, testing their hardware out on the open road. Day two, four of the manufacturers had dropped out and the number of cars tested around the track was reduced to 57. After a brief chalk talk and a Sedan around-track orientation with driving instructors, they basically turned us loose to choose any of the 57 cars for three laps around Laguna Seca!

Most of the manufacturers that had supercars there made you drive with either a driving instructor or a professional racing driver from the manufacturer. Now, I've been a Chevy guy all my life; I did own a very nice Buick GS convertible for several years, but other than that, it's always been a Chevrolet for me. But those German hot rods really opened my eyes. Anyone who would let a drag racer get in an all-aluminum, handbuilt Audi R8-a mid-engine, magnetic suspension, paddle-shifted street car (the closest to a F1 car I'll ever come)-is out of his mind! I'm still talking to myself after that ride. My son, Daniel, was in the passenger seat, and on our last lap, going into Turn 5 at about 120 mph, I stood on the brakes and downshifted two gears-he said it was slowing down so fast it blurred his vision. Enough said!

Two very cool cars that Chevrolet brought were the Cobalt SS coupe and the HHR SS. Both the Cobalt SS and the HHR SS were equipped with a turbocharged and intercooled, direct-injected with variable valve timing, 260hp 2.0L Ecotec engine. Behind the hot four-cylinder was a Getrag five-speed transmission, which was supported by a new calibration feature called Zero-Lift shifting. With the aid of an electronic throttle control, it allows you to leave your right foot planted during performance driving and modulates the throttle to keep the engine on boost during gear changes. GM claims it reduces the elapsed time during gear changes by 0.10 second per shift. The Cobalt SS rips off a 5.7-second 0-60, and the HHR SS was just a tick behind at 6.3 seconds. Both of them had a ton of beans around that 11-turn road course. Bringing all that speed to a stop on the Cobalt was a pair of Brembo front brakes. Finally, the Cobalt knocked down 30-mpg fuel economy, and the HHR was again right behind at 29 mpg out on the open road. Either car would be really cool to have in the driveway.

Until next year I guess I'll have to stick to the straight-line fun. Yes, it's a blast to drive around a circuit track, but for the dollars, I'll have to stick to my drag racing.

Don't Brake Me
I refurbished a '68 Camaro convertible cruiser last year. It was originally equipped with an inline-six and a Saginaw three-speed manual transmission. I have since upgraded the drivetrain to a mild 327 and a close-ratio Saginaw four-speed tranny. I'd like to update my drum brakes to discs and keep my original 14-inch Rally wheels, only it seems every outfit selling brake conversion kits requires 15-inch or larger wheels. My drivetrain is mild-mannered and the car is for cruising, so I don't need an aggressive brake system, just something that will reduce my stopping distance for normal street and highway driving. Who produces a brake conversion kit that would allow me to keep my 14-inch Rallys? Thanks.
Paul DaSilva
Jacksonville, FL

A Rally wheels are the bomb! I had them on my '67 RS/SS Camaro, '68 SS Camaro, and '65 El Camino. Growing up in the '70s with all the Camaros, early Chevelles, and of course the Vettes running these wheels left a permanent impression on my brain. I've got some good news and some bad.

Let's start with the good. You can keep 14-inch Rallys on your Camaro. The bad: They won't be the ones that you currently have on the car. GM built a disc-brake-specific Rally wheel for the Camaros with disc brakes that were offered in 14x6 and 14x7. I had 14x6 disc brake Rallys on my '67, and 14x7s on my El Camino. These wheels allow you to run 11-inch front rotors and either very rare four-piston front calipers or the common single-piston floating caliper. The front brake system you wish to find is original-equipment '69 Camaro or '69-72 Nova disc brakes.

You can scrounge through wrecking yards or contact Master Power Brake, which offers its GM Four Wheel Power Disc Brake Kit (PN DB1743P). This kit is all-new components complete with 11-inch vented front rotors, 11 1/8-inch vented rear rotors, calipers with pads (parking brake in rear), caliper brackets, a 9-inch dual diaphragm power booster and master cylinder, a combination valve kit, front spindles, brake hoses, bearings/seals/dust caps/hardware, front dust shields, and parking brake cables. This kit comes complete with installation instructions for a painless swap.

Sorry we tricked you into installing new Rallys on your Camaro. Unfortunately, there isn't any way to install disc brakes with your standard drum-brake Rallys. You should be able to find disc brake Rallys easily enough. If not, contact Wheel Vintiques to pick up a set of new Rallys custom-built to your specs. Check out the 34 Series, which is the 14-inch Rally offered in 5-, 6-, 7-, and 8-inch widths. Wheel Vintiques also offers all the accessories, like the beauty rings, Derby caps, and the coveted disc-brake Rally caps.

Good luck on your cruiser convertible. These brakes will give you a very secure feeling driving down the road. My '67 had four-wheel drum brakes, and there's nothing like the sinking feeling that you have in your stomach when you feel those brakes fade.


What Is It?
I got a small-block Chevy, casting number 14093638, from a guy who has no idea where it came from. It runs great and I have it in my '80 Camaro. Is there any way I can tell what the compression is without pulling the heads? I was looking at the Edelbrock top-end packages and they say they get that power level with 10:1 compression. Is there any way to tell if it has a flat or roller cam without pulling the intake? And can you guess the approximate horsepower levels or do you need more info? Thanks.
Paul Head
Via e-mail

A That casting number is an '87-95 350ci small-block with either two- or four-bolt mains, a flat or roller camshaft, and a one-piece rear main seal. This block was used in trucks and cars, carbureted, TBI fuel-injected, and TPI fuel-injected. This block could have been fitted with several different piston designs. To hone in on a compression ratio would be tough. With the standard dish pistons these engines were mostly built with, it will yield a compression ratio of approximately 9.3 to 9.4:1 with 64cc heads and thin (0.026-inch) head gaskets.

To see if you have a hydraulic roller camshaft, you could remove a valve cover and glance through the small holes in the head castings by the manifold flange. Check if you have roller-tappet tie bars and a spider to hold them down. Even if the engine doesn't have a roller in it currently, this casting has the bosses in the center of the valley for the spider. All you need to do is tap the existing bosses to bolt down the spider. You can pick up the roller tappets, tie bars, and spider from a local pick-n-pull auto recycler. Then it won't cost you an arm and a leg to get a roller into your engine.

To break out the famed Air Dyno, we'd need quite a bit more information than you've given here: Which top-end package, compression ratio, camshaft specs, carburetor specs, exhaust system specs, ignition... Only then could we even remotely come close. Looks like you have a nice engine to start your performance build.


Old-School Meets New-School
I bought a set of Chevy aluminum heads for very cheap, but one of the problems that I have is that I cannot place their casting number anywhere. Some say they came from an '89 Corvette, and some say a '96 Malibu. The casting numbers are 10128374 and 10207643 (angle plug, no heat riser). I need to know their whole story before I can do anything with them. I am planning on putting them on a 355 with a high-lift cam-somewhere around a 0.560-inch lift. They will be going in a '89 Chevy S-10 with a 4.56:1 rear, headers, and slicks. The trans will stay with a TH350.

Are they the ones known as the Fast Burn heads? What are their limitations, in the lift part and spring size? What are the cc values for the intake, exhaust, and combustion chamber, in the factory form? What type of head bolts do they take (standard or long)? How about their rocker arm ratio? Head gasket thickness? Or type? As you can see, I am not familiar with aluminum heads; I'm more old-school, iron or nothing (but I'm learning). I need all the information you can provide me with to upgrade them for better performance in bracket racing. Thanks for all your help!
Raul Hernandez Jr.
Via e-mail

A Let us start with our old standby: You need to go to This is by far the absolute best casting number identification Web site we've found, both in ease of use and accuracy. We almost didn't answer this question, but since you are an old-school iron head guy, you really need the straight scoop on these "cheap" aluminum heads.

The casting numbers you provided are heads from a '92-96 LT1 350 engine, very good production heads for a Gen II small-block. And that is the problem: They will only work on a '92-96 Gen II small-block! This is because of the reverse-flow cooling system that GM designed and first released on this engine. As the system is reverse-flow, it forces the cold water from the radiator into the cylinder heads first, then down around the cylinders and off to the radiator to start the whole thing over again. This was a great improvement over the Gen I ('55-91) small-block engines. It helped control detonation and gave a better ring seal by stabilizing cylinder wall distortion. As you noticed, the heads do not have an exhaust crossover, but they also don't have any coolant passages in the front or rear of the inlet manifold surfaces. It would be a little tough to get coolant through the inlet manifold. Also, the inlet manifold bolt holes are not in the standard Gen I location and are at a different angle.

For quick specs, the heads have 175cc inlet ports, 68cc exhaust, 53cc combustion chambers, 1.94/1.50-inch valves, and 1.320-diameter valvesprings. They accept standard-length head bolts and will accept either 1.5 or 1.6 rail-type rockers. To use non-rail-type rockers, you would need to replace the guideplates on the heads with hardened ones. The plates on these heads were only for assembly down the line. They have extra clearance and are not hardened.

Sorry for the bad news, but you needed to hear it. Hopefully, you will be able to sell them and get your money back. Or you could go new-school and get a '92-96 Gen II block for your buildup. They have some unique features and you can make good power with them. Good luck with your bracket-racing project.


Brake Bias
I have been having a problem with my '89 IROC-Z's rear brakes. The car is a four-wheel disc brake system from the factory. The brakes just don't seem to hold well at all in the rear. If I jack the car off the ground and leave it in gear at idle, the wheels still turn. I was restoring the car from the engine back, so I have literally replaced every component on the brake system except the flex connectors to the back brakes at the wheels. I have even tried different brake pads, from regular asbestos to Wagner race brand. I have had the car to a Chevy dealer and a Midas center to fix, with no resolution. When I bleed the brakes, I get plenty of fluid to every wheel. The pedal always has a solid feel to it with no sponge in it. It never bottoms out on the floor, and when I take the caliper off, the pedal pushes the pad out about 3/8 inch with one push of the pedal. I also had this problem on an '88 Z28. I am at wit's end! Any help would be greatly appreciated.
Mike Huelsman
Mentor, OH

A First of all, I think that you're running into a couple of things. Disc brakes are not a self-energizing braking system; they only have the force that the caliper can apply at any given time. Drum brakes have the rotation of the brake drum to force the brake shoe into the drum. The hydraulic force from the wheel cylinder pushes the primary (front) shoe into the drum, and the shoe is rotated, putting pressure into the secondary shoe and into the reaction pin on the backing plate. This is why you have so much holding force with drum brakes. That is why most "foot brake" drag racers will use drum rear brakes, so they can hold the car on the starting line at a higher rpm against the converter. With disc brakes, the rotors and pads must be up to operating temperature before you will have any braking force at a dead stop. Yes, you could increase the line pressure (install an adjustable proportioning valve) to the rear brakes to aid your dead stop issue. The only problem I see with this is when you get the brakes up to operating temperature, you will have way too much rear brake bias and the rear brakes could lock during spirited driving. When going into a turn, that's the last thing you want to happen.

If you would like to do a quick test to confirm this, drive the car and get the brakes up to temperature. Bring it home and immediately jack up the rear of the car and redo your braking test. The rear brakes will hold once they have some heat in them. Also performance (i.e., racing) pads will only aggravate the problem. Most performance-compounded pads need more temperature to create the proper coefficient of friction to perform properly.

One Size Fits All
What size carburetor should I run on my small-block 383 engine? It is a buildup for my '78 Camaro drag car. The car weighs approximately 3,400 pounds and has 13:1 compression, a 0.648-inch-lift solid-roller cam, and out-of-the-box Edelbrock Victor Jr. heads and intake. Thanks for your recommendation.
Roger Ward
Silvis, IL

A We could have used a little bit more information to give you the best recommendation. Things like what type of transmission are you running, manual or automatic? How much stall speed, if it's an automatic? What's your rearend gearing? What size header, and are you going to run an exhaust system? What we will do is give you a couple of selections.

If you use any of the standard carburetor sizing charts at 100 percent volumetric efficiency, you will find that your engine needs 776 cfm at 7,000 rpm. This is a reasonable rpm range for the information you have given us. One thing that you must keep in mind is that a racing engine will achieve 100 percent VE at torque peak; however, rarely will you see the engine carry that high a VE number to horsepower peak.

For ultimate power, we'd recommend an 850- to 950-cfm carb. This is a perfect match if you have a 5,000-stall speed or manual trans behind your little 383 hottie. Also, you will need 4.56:1 to 4.88:1 rear gears. The higher the stall and lower the rear gears, the larger the carburetor can be. For drag racing (accelerating engines) you need a carburetor with enough head room (cfm) to allow the engine to accelerate without creating a restriction. Any time you create vacuum in the inlet manifold below the carburetor, you reduce the air density, which reduces power. If you don't have all the combination to support the larger carburetor, you must Band-Aid the situation with a lower-cfm carb. This will allow the engine to accelerate from a lower rpm without driveability issues. If your Camaro is a true race car, this shouldn't be an issue. If you need a smaller carb for your application, choose between 750 and 850 cfm. This will give the intake system the velocity to create a proper fuel curve at slower engine speeds.

Check with your manufacturer of choice for its recommendation. Either Demon or Holley can sell you an over-the-counter carb that will give you what you need. Good luck with your bracket project and see ya at the races.


LT1 Imposter
What are the differences, if any, between the LT1 swap engines that were put in the '96 Buick Estate wagons and the ones put into the Corvettes? I currently have a wagon that has the swap in it, but I would eventually like to start building a more performance-oriented vehicle. Any advice would be much appreciated.
Trevor Schipper
Kalamazoo, MI

A The LT1 engine was first placed in the '92 Corvette, then released in Camaro and Firebirds in '93 with the introduction of the fourth-gen F-bodies. In '94 the LT1s found their way into the B-body line (Impala, Caprice, Caprice wagon, Buick Roadmaster and Roadmaster wagon, and Cadillac Fleetwood). What many don't know is that GM also released the L99, a visual duplicate to the LT1, except that it only displaces 265 cid! Just think, you get this thing home from the wrecking yard with your prized LT1 only to find out it's a 265. Luckily, if you check on the left side of the rear of the block, just in front of the bellhousing mounting surface, it has either 5.7L or 4.3L cast right into the block. Something to look for!

There are many similarities between the LT1 B- and Y-car engines. The main differences are the cylinder heads. The LT1 iron heads were designed after the aluminum heads were released. Truth be told, the iron heads run better than the aluminum LT1 heads except for the fact that they weigh more, and since they're cast iron, you can't run as much compression. The differences in the blocks are that the Corvette LT1 block has four-bolt mains. The camshaft is slightly more aggressive, if you want to call the Corvette camshaft aggressive. The bottom line is that the B-car LT1 is a great building block for a performance engine. As long as you keep engine speed to a reasonable level and don't run the engine in a boosted condition, you will be fine with two-bolt mains.

Keep your eyes out for those pesky L99 Mouse motors. Any of the other Gen II small-blocks are great cores for performance buildups.

I need some help decoding the transmission I purchased used from the local auto recycling yard. The salesman said it came out of a '92 IROC-Z Camaro. I have talked to Chevrolet parts men and dealership mechanics, including transmission rebuilders, and I keep getting the runaround. All I know is that the transmission is a TH700-R4 automatic MD8-MXO overdrive. I also purchased a catalog that has '67-93 Camaro ID numbers. So here is what I have: 2DDM 164 1 H. What is this transmission from, and out of what vehicle and model?
Richard J. Placek
Via e-mail

A Transmission decoding can be somewhat tricky, and getting all the info can be difficult. We checked with our go-to guy, Ken Casey at Burt Chevrolet, and as we expected, he didn't let us down.

Ken found that this transmission came from a '92 B-car which in the Chevrolet line is an Impala or Caprice with an L05 TBI 350. The car was a four-door with 3.08:1 rearend gears. Your recycling yard man at least had the year right. Unfortunately, it's not from the IROC-Z. However, this is a great transmission core to hop up. It will accept a nice shift kit, and you should replace the Second gear servo cover and piston with pieces from a Corvette. This increases the clapping force of the Second and Fourth gear band for better shifts and durability. TCI Transmissions offers its Trans-Scat Valve Body Kit (PN 376000), designed to deliver a solid shift suitable for towing or a competition-quality gear shift. With most models, you are able to manually shift and hold the transmission in First gear until you shift into a higher gear. The kit vastly improves the Second and Third gear shifts, improves performance, and helps extend clutch and band life. While you're at it, be sure to pick up the heavy-duty servo kit (PN 376003), which will add 300 pounds of force to the band application for extra durability.

We hope this info helps. We know it may have been a little bit of bad news about the trans, but if it's a solid core, you'll have a great trans with the components listed above. By the way, Ken Casey said this is the exact transmission he sells over the counter for people wanting to install overdrives and he has very good luck with it. Good luck and keep on reading.

If you have technical questions for Kevin McClelland, send him an e-mail at



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