Chevy Performance Tech Questions - Performance Q&A

Kevin McClelland Aug 1, 2008 0 Comment(s)
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Trick Part Of The Week
In racing, we're always looking for a performance advantage over our competition. This can come in the form of driver aids, such as special colored glasses to see the tree better; the newest, hottest set of tires; or the latest in torque converter technology. Sometimes it's really tough to get the straight scoop about some of these new parts. Lessons are often learned hard and at quite a bit of expense. Getting someone to share this type of information can be downright impossible at times.

This is where I've been with my Stocker adventures this past year. I've just spent six weeks getting the engine ready for our local National event and my son Daniel's first major NHRA race. With an empty checkbook, high hopes, countless hours on the flow bench, and all the latest tricks in cylinder block preparation, my horsepower goals were far from obtained! "Hey, don't you do this for a living?" I'll tell you what I told a camshaft manufacturer this last week: I can build Super Gas Tractor engines all day long, but these Stocker engines are a completely different animal. I've gained newfound respect for the Stock and Super Stock engine builders around the country. I believe I have not read between the lines enough in the rule book. I keep telling myself that this is a baseline engine and the other guys out there have been doing this for years. Needless to say, we've learned a lot and already have more parts on order. What did I say earlier about my checkbook?

I guess what this ramble is all about is this: Be cautious about the "trick of the week" and make sure you have investigated every angle; it'll save you a lot of pain, both physically and mentally. I'll keep you posted on our National event debut in Stock Eliminator.

The Way The General Should Have Done It!
Q I own an '01 Chevy Crew Cab 4x4 S-10 with a 4.3L engine and an auto trans. I want to swap a 5.7L Vortec engine from a '97 Chevy 1500, complete with the computer and wiring harness. Will the computer from the '97 work with my trans, because I have a 4L65E (I think) and the '97 has a 4L60E? Can you think of any other problems related to the computer swap I might have? Also, if this will not work, what about swapping a 5.3L from a newer-style truck? Thanks for your help.
Edward Hall
Via e-mail

A What nice trucks like that need is more power. When you have a lightweight 2x4 standard-cab S-10 and a five-speed, the 4.3L V-6 has respectable power and is a quick and fun little truck to drive. When you load down the truck with four-wheel drive, a crew cab, and gear, it can turn into a real stone. It's a great swap, but let's look at some of the issues.

The transmission in your '01 S-10 is a 4L60E. The 4L65E was phased in around the '03 model year and featured five-pinion planetaries, a higher-capacity input housing, and an induction-hardened input shaft assembly. These improvements were to withstand up to 380 lb-ft of torque. A new 300mm torque converter with improved, higher-capacity internals was also introduced on select engine models. The control logic is the same as with the 4L60E transmissions.

To swap the Vortec 350 into your little 10 we recommend getting in contact with the guys at Jaguars That Run. Yes, I know you're working on an S-10 pickup, but Mike Knell and his folks have been building engine swap kits for many years, starting with a nice small-block conversion for the Jaguars. They also offer swap manuals and components for Datsun Z-cars, Chevy Astro vans, and Volvo 200 and 700 models. The S-10 V-8 conversion manual is now on its 14th edition and runs more than 200 pages. It guides you through the pitfalls of emissions legalities, wiring and computer selection, and cooling system recommendations. The manuals are incredibly complete with GM part numbers for everything from exhaust manifolds to sensors and connectors, and also proven aftermarket components that they have tested.
Source: jagsthatrun.com

Stock Head Holdout
Q I want to build my '66 Chevy Nova two-door sedan to do a little weekend racing and street bullying. Currently I have a 383 stroker bored 0.030 over with Keith Black Hypers, forged 5.7-inch rods, a cast steel crank, '71 camel-hump heads with 2.02-/1.60-inch valves (ported and polished), and 1.5/1.6 all-steel roller rockers. The cam specs are as follows: 334/334 advertised duration, 238/238 degrees duration at 0.050-inch tappet lift, 0.498-/0.498-inch max lift, 108-degree LSA ground on a 104 intake centerline. This is confusing to me, as my engine builder/machinist failed to come up with an adequate cam card. I really don't know what is in this thing. I'm hoping to reach 425 hp and a lot of torque. Any help would be appreciated. Oh yeah, I'm running a TH350 trans with a shift kit and a 3,000-stall converter, a 750 Holley mechanical secondary carb, and a 3.73:1 posi rearend. Thanks for your help.
Ben Harrison
Via e-mail

A Why are you stuck on production cylinder heads when the market is filled with killer low-cost aluminum heads? I know you have already prepped your 492 or 186 castings. However, you're leaving a ton of power and torque on the table. You could drop them on eBay and use that money to move up to some real power.

Your camshaft specs are not really confusing. The only numbers that look somewhat suspect are the advertised numbers. One thing you don't know is the checking clearance for the advertised duration. Early production GM performance camshafts were checked at the first motion of tappet lift. Contemporary checking clearances fall somewhere between 0.004 and 0.006 inch of lift for hydraulic flat tappet camshafts, which lowers the advertised number quite a bit. If you used 0.006 inch of lift to check the advertised duration, you'd probably come in around a high 290-degree duration. Everything else sounds like a rather aggressive camshaft for street performance. With the relatively tight 108 LSA, you will have quite a bit of overlap, giving you a very aggressive idle, and the powerband will be pushed up significantly.

The rest of your street bruiser package seems to be quite solid. Your stock heads are going to need to be quite good to reach your horsepower bogey. If you went with a set of 190cc inlet-port performance aluminum heads, you would easily reach your 425 goal. It is your choice. Good luck with your Chevy II.

Tooooo Much Cam
Q I have a GM crate engine, PN 12499529, with 290 hp and 326 lb-ft of torque. I have had two of these engines; both required approximately 30 degrees of initial advance to run properly. The first engine was replaced under warranty by a GM dealer, but nobody could explain why this engine needed so much advance. Any idea? Thanks.
Ike Byers
Butler, PA

A When GM combined a pile of off-the-shelf parts to create the 290hp crate engine, it picked the L46/L82 small-block hydraulic camshaft, developed back in '69. The L46 was released for Corvette use at 350 gross horsepower. This engine was equipped with very good (for the time) 186 casting heads and 11:1 compression. Then GM used the camshaft in the Corvette again in the L82 smog-era 350s. They also had decent cylinder heads and a true 9:1 compression. The L82 was rated at a whopping 250 net horses before the catalytic converter years. Now, let's talk about the 290hp crate engine on the market today.

The base long-block is derived from the solid foundation of the GM Goodwrench replacement 350 engine. In its stock form (with stock inlet and exhaust manifolds), the engine produces 230 hp and 330 lb-ft of torque. The engine is a replacement for the GM LM1 small-block and is rated at 8.5:1 compression; however, every one I've disassembled and cc'd came in around 8:1 compression. The 290hp GM Performance Parts crate engine starts with this base Goodwrench engine with the L46/L82 camshaft. As I said above, this camshaft was designed back in the '60s to run with much more compression. The camshaft specs out at 222/222 degrees duration at 0.050-inch tappet lift, 0.450-/0.460-inch max lift, ground on 114 centers. Why your engine likes so much timing is because it has very low cylinder pressure at low engine speeds. These engines are great for stick shift, lightweight vehicles and for light street rods that want a cool cruiser engine.

If you swapped in a Crane Powermax 260 or a Comp Cams Xtreme Energy EX256, you would have a much happier engine. This engine, with either of those camshafts, will still make 290 hp with a street-performance inlet manifold and a set of 15/8-inch headers. This is the gain of current technology in camshaft lobes. Is there something wrong with your engine to make GM warranty the engines? Absolutely not. It's just a case of misapplication. Good luck.
Sources: compcams.com. cranecams.com

Water Shaft
Q I am going to put a '90 Corvette L98 engine in my '87 Chevy pickup. I read in your Jan. '07 column about a marine roller camshaft. Being a marine technician, I have a couple of these cams. Will this cam work well with a TPI engine? Also, would a Fel-Pro head gasket (PN 1003) at 0.041 inch compressed thickness work well on this engine? Thanks.
Charlie Anderson
Via e-mail

A The Mercury Marine hydraulic roller is a very mild performance camshaft. This cam will produce tons of midrange torque and run out of air at about 5,000 rpm. GM uses this camshaft in its Ram Jet 350 and HT383 crate engines. The torque curves of these engines are just about flat from 2,200 to 4,700 rpm. This is right where the Tuned Port Injection (TPI) inlet track is tuned to run on the 350. If you wish to step up the runners or inlet base, it will only boost the upper-rpm power potential. This, in conjunction with 1.6 roller rockers, will give you a very nice, mild 350. The camshaft you're looking for is sold under PN 14097395. It specs out at 196/206 duration at 0.050-inch tappet lift, 0.431-/0.451-inch max lift, and is ground on a tight 109-degree LSA. The tight centers work out because of the small duration lobes and low overlap area. Cross-reference the camshaft to make sure you have the small Mercury Marine camshaft. GM builds several power levels of the marine engines for Mercury. The camshaft listed above is the mildest engine package offered.

When replacing head gaskets in the L98 aluminum-headed engines and the ZZ small-block family of crate engines, you must be very careful. The Fel-Pro head gasket has a diameter of 4.166 inches. This large diameter gets very close to the water jacket feed on the spark plug side of the cylinder head deck. With this gasket, you have less than 0.050 inch of sealing surface! It's very easy to knock the gasket out in this area. This is why we recommend sticking to factory head gaskets that have a diameter of 4.100 inches. The production gaskets are 0.052 inch thick for the aluminum heads, and 0.026 inch thick for the iron heads. I use the 0.026-inch-thick gasket exclusively for my performance street buildups. Most of the GM short-blocks have the pistons somewhere around 0.020 down in the hole. The iron gasket at least gets you in the ballpark for a decent quench. Pick up a set of the iron gaskets under PN 10105117.

The L98 TPI engines have been pushed to the side by both the LT and LS engine families. The long-runner TPI system will pull your truck around quite nicely. Good luck with your swap and enjoy the great gas mileage.
Source: gmperformanceparts.com

Take The Boat
Q I have a '69 SS Chevelle with a '70-model 408. It has closed-chamber heads with recommended valvesprings and about 9:1 compression. Now my problem: I have put two Xtreme Energy flat tappet cams in that went flat. Then I went with a 270 Magnum cam, which also went flat. The last cam was installed by a professional mechanic, the engine was pulled and all the metal cleaned out. This cam lasted less than 500 miles. Now I am going with a hydraulic roller. It has a performer intake and a Q-jet carb. I would like to get about 400-425 hp. I don't mind changing intake and carb. I have also bought a TH700-R4 core. What are your thoughts on this trans with a Corvette converter to put in place of the TH400? The rearend is a 3.31:1 posi. Any help in cam selection and trans selection would be appreciated. Also, I may have the opportunity to buy a rebuildable marine 454ci long-block for $1,000. Would this be a better alternative to the 408? This car is driven on weekends, weather permitting, with some freeway trips.
J. White
Benton, AR

A OK, where did all the boat parts come from? If you can scoop them up, go for it. The marine components take way more of a beating than standard passenger-car or truck parts do. They are tested to a much higher durability level than the production stuff. The 454 marine short-block should have four-bolt mains, a forged steel crankshaft, and possibly forged pistons, based on the power level of the original engine. Another added benefit would be the almost 50hp/ci bump.

Sorry about the camshaft pain. You can thank all the new emissions regulations that have taken the zinc and phosphorus out of our engine oil. The sliding contact of a flat tappet lifter to the lobe is the highest sheer contact in the whole engine. Without these additives in the oil, the lifters and camshaft really don't have much of a chance. Comp and all the other camshaft manufacturers offer oil additives to fortify the current engine oils, but they still come up a little short. Some of my dyno buddies have told me about Joe Gibbs racing engine oil, with two products that really help out with our flat tappet dilemma. First is a petroleum-based break-in oil, which isn't under the DOT regulations that kill our oil. Next is a synthetic engine oil specially blended for older engines, sold as Hot Rod engine oil for hot rods, street rods, and classic and vintage cars built before 1997.

Moving up to a hydraulic roller package is the right direction. To reach your 400-425hp goal, go with a Comp Cams Xtreme Energy hydraulic roller. Check out grind XR276HR, which specs out at 224/230 at 0.050-inch tappet lift, 0.510-/0.510-inch max lift, and is ground on 110 centers. This cam will work with either your 408 or will make a ton more torque in your 454. As for the inlet and carburetor, I really like Q-jets, and if yours is in good condition and performs well, stick with it. Go with an Edelbrock Performer RPM 2.0 Q-jet. This manifold will accept the Q-jet carburetor with no adapter plate, and it also accepts a square-flange carburetor on the same manifold. PN 7164 will match your oval-port cylinder heads.

The TH700-R4 transmission is probably one of the best upgrades for any big-block-equipped performance car. Lowering the cruising speeds of a big-block will lower engine temps, fuel consumption, and noise considerably. A performance rebuild and the Corvette torque converter will be a perfect match in your Chevelle. Then you can enjoy the cruiseability of your SS.
Sources: compcams.com, edelbrock.com, joegibbshotrodoil.com

Things That Go Boom
Q I have a Chevy 383 with an all-cast bottom end. The cam is a Comp Xtreme Energy with advertised duration of 270/278 and a max lift of 0.482/0.489 inch. I have a fresh-worked set of 041 Chevy castings with 2.02-/1.60-inch valves and Crane Gold Billet 1.6 roller rockers, Edelbrock Victor Jr. intake, out-of-the-box Holley 750 double-pumper, MSD Pro Billet distributor, 6AL Box, and Blaster 2 coil. It has an adjustable NOS two-stage dual-shot cheater plate system. I've only sprayed 150 to the engine. The system can go 50-175 on the first shot and 150-250 on the second. The drivetrain is a TH 350 trans, an 8-inch Vega converter, and a stock rearend with 3.73:1 gears. The '87 SS Monte Carlo cruises on the stock fuel pump, but at the track I run two Holley Blues and a 5-gallon fuel cell feeds it. Its best was 11.13 at 123 mph. I'm working on an S-10 with the same build except for the heads and cam and 4.10:1 gears. Would a set of 220cc Motown Street heads with 64cc combustion chambers and 2.08-/1.60-inch valves help the power? What if I added a Comp Cams Nitrous HP with 284/305 duration with 0.507-/0.525-inch lift?

You have to love technology, I'm sending out this e-mail to you out of my backyard and under a tree!
Bobby Baxley
Via e-mail

A Have you ever heard that the fuse is lit and you better run? To move your Monte that fast, you're making well over 600 hp and a ton of torque with the nitrous. We've seen things live for much longer than they should, but we wouldn't recommend building on this combination any further. You may have lucked into something that will live for now.

Adding the above components to your current engine package will only raise the engine speed. Larger cylinder heads, added duration, and lower rearend gears are a recipe for disaster. Cast cranks and cast pistons have a limited engine speed life. If I had to guess, your Monte Carlo is going through the lights around 6,500, based on a 26-inch tire and the slippage of the Vega 8-inch converter at the 123-mph speed. The components you have listed will push the horsepower peak well over 7,000 rpm. Will your cast components take that type of abuse? We think not.

Remember, when it kicks the rods out in the lights, oil under the tires isn't much fun. I've seen tons of race cars wadded up each year. Luckily, when it happened to me, I was able to keep mine off the rail! Be safe.

Throttle Body Follies
Q I recently blew the stock 305 in my '88 Chevy Cheyenne. I then bought a 350 four-bolt-main short-block already bored 0.030 over. I had a local speed shop build the engine with my 305 heads from my previous engine. They are bone-stock valves and ports. I also had the shop install a Hypertech Stage II Thermomaster chip to correct the PCM settings from 305 fuel settings to 350 settings. Shortly afterward, my TBI had one of the injectors stick wide open so I just replaced the whole unit. Here lies my problem: I bought a remanufactured TBI from O'Reilly's Auto Parts. They all have had problems running either too rich or too lean (meaning I have warrantied it out several times, five to be exact). I have now managed to get one that performs OK, but I have to have my EGR or it runs too rich. If I drive on the highway it sends a lean code, and when it is cold the engine surges on warm-up at idle. What are my options for this small but irritating problem? Should I buy a brand-new TBI? I found one at Scoggin-Dickey for a decent price. It's a Holley PN H502-6, but I don't want to make another mistake. Any advice would be greatly appreciated, so please help!
Carmen Napieralski
Springfield, MO

A We have written about this 305-to-350 swap many times before. However, it sounds to me that you have a problem with mix-and-match parts. It's great that you went with the Hypertech chip to move your calibration up to the 350-cid engine. Is it a custom chip or an off-the-shelf chip for a 350-equipped '88 Chevy truck? This makes a huge difference when you go to order any TBI unit. If the Hypertech chip is an off-the-shelf '88 350 chip, it is calibrated to the LO5 350 TBI injector size. The injectors in your throttle body are different sizes between the 305 and 350. The proper PN for the 350 injectors is 19110538, and you will need two. You can easily swap them out, and this should take care of your cold start surge (lean condition) and your lean "check engine" light going down the highway.

The Holley 502-6 direct-replacement TBI unit is a great piece for modified TBI engines. It flows 670 cfm, and the injectors are sized for the stock calibration on a 350 engine. Holley also provides a distribution ring to steer the fuel into the intake manifold to improve cylinder-to-cylinder distribution. The only problem with this TBI is that it uses 2-inch throttle bores. The factory manifold is sized to 111/16-inch bores, and without modifying the manifold you will have a large mismatch.

Make sure your Hypertech chip is calibrated for 350 injector sizes, and the new injectors will straighten out your fueling issues. Good luck.
Sources: holley.com, sdparts.com

If you have technical questions for Kevin McClelland, send him an e-mail at chevyhi@sourceinterlink.com.

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Trick Part Of The WeekIn racing, we're always looking for a performance advantage over our competition. This can come in the fo...
Kevin McClelland Aug 1, 2008

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