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Q&A - March 2014

Kevin McClelland Feb 5, 2014
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Bed Time

I know I've been here before, as have most unsuspecting upgraders. We build up our project car over the period of a couple of years, adding new components from stem to stern. Finally, we start our freshly completed restored or modified toy and want to go out and beat on it, and we take careful precautions breaking in the camshaft properly to ensure a lifetime of trouble-free service. But what else needs to be broken in properly and carefully in your driveline? Certain clutch packages take very specific break-in procedures, based on the friction material and their mating surfaces. There may be specific techniques needed for your transmission and differential run-in. In an automatic trans, you will definitely want the clutch friction material and fresh steels to have time to burnish themselves into a nice relationship—and for the frictions to have plenty of time to absorb ATF fluid. Whoever built the trans for you should have soaked the frictions in ATF for at least an hour before the build. Finally, for manual gearboxes and hypoid differentials, you need to give the gearsets time to welcome their new friends that they need to transfer torque through. This should start on stands with running the car though the gears and letting the differential run through the motions without putting load on the gearset. After you put the vehicle into service, you should be nice to it for the first 100 miles. This early attention will go a long way in protecting your upgraded ride.

This past month I finished and tested our wagon with its new Strange Drag Race front brake kit. And just yesterday, I replaced the front rotors and pads on our daughter's, Ashley, Mazda wagon. Road-racing folks will be very familiar with this process of bedding in several sets of pads at a time, since you need to replace pads throughout a race. If you haven't bedded in the pads properly and put them into a racing environment, they'll immediately glaze over—and your driver wouldn't be too happy with you. Worst case, the car would come back on the wrecker after being put into the wall or another competitor.


The bedding process cooks the manufacturing glues and resins from the new brake pads, and seasons the new rotors with a layer of friction material from the brake pads. In street-performance applications, this bedding process is a series of six to eight braking events from about 60 mph down to 10 mph, without stopping. Each of these braking events should be made at moderate to high rates at about 75 percent of the braking force required to lock up the brakes. These six to eight stops should be made one after the other without allowing the brakes to cool between stops. After this procedure, either drive the car for some time to allow the brakes to completely cool, or park the car until the rotors are cool to the touch. This is considered one bedding cycle. For most street applications, you are ready for years of trouble-free braking. For race-specific pads and applications, the bedding process is just more aggressive, mainly in speed, and in amount of heat cycles. For racing applications, make sure that you follow the manufacturer's recommendations for break-in because it will be pad specific.

So remember, when you finish up your build, make a plan of what needs to be broken in, and in what order. When you pull out of the driveway the first time, you need to bed in the brakes. If not, you may be chasing your tail for years asking yourself why your cool big brake kit doesn't whoa down your hot rod.

Wish In One Hand

A As a longtime reader of your column, I know you've answered some pretty tough questions, and I hope you can help me with mine. I bought a nice 1993 Corvette Coupe cheap. Why cheap? It had no engine, trans, or rearend. I found a good LT-1 to build into an LT-4 and have the heads and intake from an LT-4. I have a fully rebuilt T-56 that RPM put its magic touch on. Also, I have a Dana 44 with 370 gears. After scouring everywhere, I can't find a Maggie-style blower and intake to fit this engine. I did find several guys online who have cobbled something together, but most have had less than stellar results. I have even thought about taking my spare LT-4 intake and having the top cut off and having a plenum to put a Maggie-style blower on top. Sure, with enough dollars anything is possible, but I hate to reinvent the wheel. Any help would be greatly appreciated.

Bob James
Franklin, IN

A. The first GM vehicle Magnuson built complete supercharger kits for was with the release of the C5 Corvette and the LS1 engine. Then in the late '90s, Magnuson continued and offered complete kits for the 1500 and 2500 trucks with the LS engine family, and the rest is history. Magnuson builds complete emissions-legal, OE-quality supercharger kits for almost any performance-base domestic car released today. Unfortunately, as you have found, there is nothing for the Second Gen small-block Chevys. Yes, you could cut and weld into your LT4 manifold, but that would be quite an exercise.

Check out what ProCharger offers in its centrifugal blower kits, like the kit for 1992-96 Corvettes that features its P-1SC blower and a two-core intercooler system, which produces 8 psi boost. The P-1SC is a self-contained supercharger with its own oil sump, which contains special synthetic oil that keeps the 4.1:1 gearset cool and lubricated. The service interval for the supercharge oil is 6,000 miles. The nice thing about it being self-contained is you do not have to use the engine oil to lube the blower and the attending plumbing required to get the oil to the blower and back into the pan. This kit mounts the blower to the front of the passenger-side cylinder heads with an arrangement of billet aluminum brackets, and it allows you to keep the stock hood with no modifications. If you were able to mount a Magnuson you would have to modify your hood for additional clearance.

With the 8 psi of intercooled boost you can expect a 55- to 60-percent increase in baseline N/A horsepower. Let's say you build a production LT4 with no upgrades. This type of gain would give you 510-530 SAE crankshaft horsepower. Since you're building this up from scratch, we don't see the N/A power at 330 hp. No, the centrifugal superchargers don't give you that instant full boost torque rise at slower engine speeds, but they do help keep the tires hooked up and allow you to put that power gain to the ground. Check with ProCharger at 913.338.2886 for exact specs you need to put your blower kit together.

Sorry we couldn't help with your quest for a Maggie-style blower. You had already found that it was going to be tough. But if you have the tools and skills, Magnuson has the parts. Good luck with your huffer project!

Swirl Tune Port

Q I purchased a new 12568758 GM crate engine. What can I do for a street-performance cam and heads? It has a Tune Port injection setup with the computer. It thinks it is a '92 Z/28 Camaro. Should I swap out the heads and cam, or just the cam? Any help would be greatly appreciated.

Rick Cross
Champaign, IL

A The GM crate engine you've listed is a replacement engine for 1987-95 Chevy and GMC trucks with VIN code K. This is the replacement engine up to 7,200 GVW. It's a solid short-block with a cast crank, powdered metal rods, dished hypereutectic pistons, 9.25:1 compression, and a high-volume oil pump. The short is rounded out with a hydraulic flat-tappet camshaft that specs out at a teeny 166/175 degrees duration at 0.050 inch tappet lift, 0.382/0.402 inch max lift and is ground on 112 centers. The best thing about this short-block is that it's machined for production hydraulic roller tappets if you wish to upgrade.

Now, this is where it goes a little downhill. These engines are equipped with "high swirl" cylinder heads. What creates the high swirl is a ramp that is casted into the roof of the exhaust side of the inlet port bowl. Essentially, it blocks off half the bowl, which kills the airflow potential. It gives you serious mixture motion, which boosts slow-speed torque, but kills the top end. These heads, with the really short cam and your TPI injection setup, probably give you enough torque to boil the rear hides! However, when the tach hits around 3,800-4,000 rpm, the fun is all over. Let's pick a couple of parts that will work well with your TPI injection.

First, let's look for some affordable aluminum cylinder heads with 58cc combustion chambers. With the dish pistons, thin head gaskets, and the small chambers, we can get you close to 9.8:1. After searching around we've even found a great choice for your little TPI runner using the TFS Super 23 175 aluminum cylinder heads. These heads were developed for small-bore small-block engines with a 56cc combustion chambers and 175cc inlet runners. This will put your squeeze right at the 10:1 point. These heads have TFS's "Fast As Cast" technology on its intake runners, which give you a cast-ported head. They feature 1.90/1.50-inch valves and come fully dressed with stainless valves, and 1.250-inch valvesprings that accept up to 0.480 inch max lift. They are topped with steel retainers and locks, and screw-in 3/8-inch rocker studs and guideplates. The fully dressed cylinder heads are sold under PN TFS-30310001 and you can pick up a set from Summit Racing. Install these heads using factory GM head gaskets PN 10105117, which come in at a very thin 0.028 inch.

Next, because your crate engine is equipped with iron swirl-port cylinder heads, and you state that you've got a (1992) Camaro TPI system, we're going to assume the center manifold bolts are at the skewed angle of 72 degrees. Only the factory Corvette engines with the aluminum L-98 cylinder heads had the standard 90-degree-to-inlet-surface bolthole angle. You will need to either pick up a Corvette TPI base, or you could go with an Edelbrock High Flo baseplate PN 3861. This base is designed to be used with '85-and-earlier small-block and aftermarket cylinder heads. One benefit of going with the Edelbrock base is that you've taken the largest restriction out of the TPI system by upgrading the base. Then you have the option of going with aftermarket runners in the future for a staged build-up.

Finally, you need a suitable camshaft that stays within the bounds that the TPI system sets, and would give you strong power to the mid-5,000 rpm range and outstand torque. The largest camshaft we would try to run in a TPI application would be the Comp Cams Xtreme 4X4. These camshafts have a very broad torque curve with a decent idle. Check out the grind number X4254H, which specs out at 210/218 degrees duration at 0.050 inch tappet lift, 0.447/0.462 inch max lift, and is ground on 111 separation angle installed at 107 degrees intake centerline. This camshaft will complement the cylinder head flow specs of the Trick Flow Super 23s, and the lift of this camshaft will work perfectly with the 1.250-inch performance valvesprings on the cylinder heads.

These upgrades will completely change the personality of your crate engine. You'll lose some of the very slow speed torque you currently have, but when the tach hits 2,800 rpm, hang on! It's going to hit you with a surge of torque that will keep you in your seat well in to the 5,000 rpm range. Enjoy your upgrades.

Sources: chevroletperformance.com, compcams.com, edelbrock.com, summitracing.com

Keep On Bumping

Q In the November 2013 issue there was a question, "What Was That Bump?" The reader had a van what wouldn't shift out of First gear. I once had an old (about 1970) Jeep Wagoneer with a TH350 transmission that sat in the yard all winter because it would not shift out of First until about 55 mph. Through a friend, I found out that the problem was a stuck kickdown switch located under the accelerator. After spraying some lube and working the plunger in and out a few times, it worked just fine.

Terry Hertz
Hopewell, VA

A. Thanks for the quick tech tip.

Back in the day, before Chrysler purchased Jeep, it would pull from many manufacturers' parts bins to build its vehicles. In an automatic transmission configuration, most Jeeps, especially the fullsize Wagoneer, used the TH400 gearbox. Just to clear things up, the TH350 transmissions have a kickdown cable, which attaches to the carburetor and controls the kickdown valve in the valve body of the transmission. As for your Jeep, it was equipped with a TH400 trans. The 400 uses and electric kickdown solenoid on the valve body to kickdown to a lower gear. GM used switches either in the engine compartment by the carburetor, or at the throttle pedal, to control the electricity to the kickdown solenoid.

Going Direct

Q My question regards the direction. I have read that some early direct injected engines have had problems with oil cooking up on the top of the intake valves due to the lack of washing from the fuel. Jimmy, a wonderful performance machinist at Napa Auto Part in Vacaville, California, suggests that there may be enough air velocity to keep the intake valves clean. Is this further evidence for my theory that they put the red mark on the tach so we can know where the needle should be pointed? Is there anything other than keeping the needle pointed at the fun mark to keep the valves clean?

And how about the fuel? Chevy suggests that the car will be happy on regular gas even with 11.5:1 compression ratio. Will this engine respond to premium fuel like my big-block crew cab? I have been a big believer in the name-brand additives like Chevron to keep by injectors and valves clean. However, with the direction, do these have any advantage anymore? If not, can I save a few bucks by just burning the base stock fuel from Costco?

Dan Johnson
Vacaville, CA

A As we all know, direct injection is the wave of the future. We really like your recommendation of keeping the engine at its red line to keep the intake valve free from deposits. It's amazing what the OEs have done to control the oil in our engines. It wasn't too long ago when you would regularly check the engine oil in our street-driven vehicles. Both of our family vehicles, equipped with four-valve, four-cylinder engines, go easily 5,000 miles between oil changes without burning a measurable drop of motor oil. Even Daniel's 2003 LS6-powered Z06 goes 5,000 miles without needing to add oil. That's saying something for an aluminum LS engine.

Basically, some of the deposits we've seen built up on the backside of the intake valves have been reduced dramatically from the improvements in oil control. The only oil that is getting to the valves is the small amount leaking past the valve seals, and the mist of oil vapor being introduced into the induction system by way of the positive crankcase ventilation. The harder you run your engine, the more blow-by and oil vapor can be introduced into the induction system. You're spot on about detergents in our motor fuels help to prevent deposit buildup. These detergents have aided the cleansing of the carbon buildup on the backsides of the valves in standard port injection. With DI, you don't have the fuel to carry the detergents to the backside of the valves. GM released a technical service bulletin on August 19, 2013, number PIP5029D, "Engine misfires due to Major Carbon Deposits on the intake and or exhaust valves." This covers all DI engines that are in the GM arsenal, from the 2.0L Eco-Tech up to your 3.6L V-6 in your Camaro. Illustrated in the bulletin is the effect of the carbon buildup, but GM did not give a specific reason for the problem. Currently, its only solution is to treat the engine with Upper Engine and Fuel Injector Cleaner. The application of this cleaner is a little different procedure, in that this cleaner must be introduced through the throttle body since it can't be introduced with the fuel, and it requires some very specific equipment. It's a "dealer only" procedure, and it could be that this should be a preventive maintenance procedure to keep the stems of the valves carbon-free.

Now, some manufacturers have adopted the strategy of injecting a slight amount of fuel during the overlap event to wash the backside of the intake valves with fuel. The amount of fuel injected is not nearly enough fuel to give you a burnable mixture, so it doesn't affect the combustion process. Diesel engines have been dealing with this problem for a long time. The secret is to control the amount of oil that is getting back into the induction system via the crankcase vent. If we had a DI-equipped vehicle we would add an auxiliary oil separator in the crank vent line between the crankcase and intake manifold. It could be something as simple as a catch-can positioned in the engine bay away from the engine, which is lower than the valve cover and manifold. This would give the oil time to fall out of suspension and collect in the can for drainage. The only issues are that when we do things like this, the Smog Police get unhappy, and it may void your vehicle warranty. Check with your local Chevy dealership and see what they have to say about adding such a device.

We also followed up with Tony Knight at Cylinder Head Exchange; as he touches more cylinder heads in a day than most of us do in a year. He said the Mazda DI engines are the worst, and he didn't think crankcase vapor is the main culprit, that because of the small-displacement engines, and turbocharging, the combustion heat is way up there. Without the cooling affect of the fuel going across the intake valves, the combustion heat is traveling up the valve stem and killing the valve guides in the cylinder heads. Once this has occurred, the valve seals don't have a chance and next comes the oil. From the photos in the GM bulletin, you see that the major carbon buildup is right up where the stem mates with the valve guide. This is why the carbon buildup is causing misfire by preventing the valves from closing. Back to your engine, the 3.6L V-6, he did say that he sees it the most in four-cylinder engines, and the V-6s are not as prone. This is most likely due to how hard the engines are taxed as the little four-cylinders are expected to pull around 3,000-pound platforms.

These same detergents that help keep your high-pressure injectors are being introduced to the flame front of the combustion process every other piston stroke. Also, down here in SoCal, our local Costco station has just upgraded its vapor recovery system and was advertising that it was about to release an additive package to its fuels. Time will tell.

As for using 91-octane fuels in your 11.5:1 high-strung six-cylinder and seeing big-block Suburban, we believe big power gains are things of the past. The DI really helps as you're able to properly time the injection of the fuel into the combustion space preventing pre-ignition. Also, if the engine has been calibrated from the factory to perform properly on 87-octane, you're just throwing money away. Back in the day, when we were doing EFI tuning for GM project cars, we found that there was tons of room to pick up power by adding timing and leaning out the fuel mixture. This is where the aftermarket tuner market came from. These days it's not uncommon to find that the engines are right at best power timing, and lean best torque from the factory and the manufacturers rely of the knock sensors and O2 sensors to keep the thing safe. Again, it's all about what the factory has originally tuned your vehicle to run on.

Source: cylinderheadexchange.com

142 Blower Opportunity

Q My 1985 Monte Carlo SS has a 358 small-block covered by ported and polished S/R Torquers 67cc chambers. I have a Holley 750 3310 on top a Weiand dual-plenum tall-platform intake. Valves are opened via a Comp Cams 12-243-3 dual-pattern. The exhaust exits via Flowtech Afterburner headers and old-school, three-chamber 50-series Flowmasters. Finally, the power is transfered through an Art Carr 700r4 rated at 800 hp and 3.73s to both wheels, thanks to Auburn Gear.

I purchased a rebuilt B&M 142 supercharger kit that I'd really like to bolt on my powerplant. I have planned on installing thicker head gaskets to reduce my compression a bit. I am concerned about my ring gap. I read an article in which a 142 Weiand blower was bolted to a 383: "1972 Chevy Nova Weiand 142 Blower Upgrade - Boost Machine, January 2009." The engine was built for an alternate purpose. The engine was reused for new article. The article did not say anything about ring gap. I want to know if piston ring gap was opened up for the additional blower pressure or not. My top compression rings come in at 0.018 inch gap. Can I run my 142 blower with my engine as is? I have planned on installing thicker head gaskets to reduce my compression a bit. How would my Torquers react to the blower addition? What would be a good cam and head setup? This is a street-driven car that I take the kids to baseball in. It also gets me to work when the weather is good. Thanks, and keep up the good work!

Norm Crawford
St. Joseph, MI.

A Great job keeping us honest. On that specific 383 engine with the Weiand blower install, the ring end gap was not increased for the blower installation. We're glad to see you have your thinking cap on when considering the blower install on your small-block. Let's talk through a few things—we think you're going to like the answers.

First, we're going to assume you have either forged or standard cast pistons in your 358 if you built your engine with a 0.018-inch ring end gap. If you were running hypereutectic pistons, your engine would have already butted the rings with the above spec. As for your build you've used the standard street performance spec of 0.0045 inch gap per inch of bore. This is a relatively safe spec for most performance applications. When you start throwing large doses of nitrous or boost at the engine, you need to open the top ring gap up into the 0.006 inch per inch of bore. Again, that's large doses of nitrous or boost.

Your 142-cid B&M blower will probably give you 6 to 8 psi of boost at full song. The larger the displacement of the engine, the lower the boost will be. At these boost levels it's completely safe to leave your ring end gap where they're at. All the aftermarket blower companies sell blowers to the masses and they pop them on top of stock short-blocks with these types of boost levels. Again, we believe you're good to go with your short-block.

As for your camshaft and cylinder heads, the COMP Cams' 12-243-3 is the Xtreme 4X4 X4270H, which specs out at 226/234 degrees duration at 0.050 inch of tappet lift, 0.480/0.498 inch max lift, and is ground on 111 centers. This is pretty aggressive for stable idle with the 226 degrees intake duration, and the relatively tight separation angle for a supercharger application. Obviously, you've been happy with this engine combination with the rest of your drivetrain. The converter in your TH700R-4 must be enough to handle the duration and overlap that this cam has. Swap the blower straight onto your current long-block and see how you like it. The Torquers will work just fine as you will be pushing the air into the cylinders.

If the cam gives you fits trying to control the idle once the blower is installed, swap it out for the COMP Cams' Nitrous HP cam, NX262H. This shaft specs out a 218/230 at 0.50, 0.462/0.480 inch max lift, and is ground on a wider separation angle of 113 degrees. We really like the 12-degree spread on the dual-pattern, which favors the exhaust side. When you boost the power by either nitrous or aupercharging, you need more exhaust event. This camshaft would really make a snappy throttle response, and make good power to 6,000 rpm.

Your kids are going to like their ride to the baseball games—that ride's about to get faster! Good luck with your swap and enjoy the power.

Source: compcams.com



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