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

Under Pressure Round II

Kevin McClelland Feb 11, 2011
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If you were reading last month, you heard about Daniel’s LS2 and the high oil consumption we found after taking it apart. The theme of the last column was to resist the pressure to throw a project together, and well, we took our own advice after fully disassembling the engine and finding heavy carbon deposits in the ring lands of the pistons. The cylinder bores had evidence of combustion gases blowing past the rings at the top inch of the bore. This isn’t that uncommon for the LS-based aluminum engine blocks. They have gotten much better with time, but we got lucky. Daniel has decided to jump in with both feet and enlarge the engine out to 404 cid with a Livernois Motorsports stroker kit, which features a Callies 4-inch stroker crankshaft and H-beam rods, fully coated Diamond Racing forged pistons, and Total Seal piston rings. This kit is packed with quality parts, and the folks from Livernois have been great to work with.

chp_01_o January_2011_chevy_high_performance_q_and_a Editor 2/2

As if this isn’t enough for a very full plate, I got my Super Gas roadster chassis back from the powdercoater! It was killing me to break away from the car and sit down to write this month’s column. I want to have it back on the track so I can tell you all about it next month. As with Daniel’s project, we have to slow down to make sure the car goes together the way we want. I’m completely rebuilding the car from stem to stern, including all-new plumbing for both the fuel and braking systems. I’ve already replaced the battery cables and rebuilt the steering; it’s going well, but my checkbook is dropping like a rock. One of the best upgrades I’m doing is installing a Racepak UDX digital dash and a Sportsman Data Logger system. This digital dash is the bomb; it replaces all analog gauges in the car. With the combo of the Data Logger and dash, I’ll be able to monitor in real time the rpm, water temp, transmission temp, oil pressure, fuel pressure, crankcase vacuum, and oxygen sensor. Another really nice feature is that you can program any warning lights from the channels you monitor. From shift lights, to max temps, to low fuel pressure, you can concentrate on winning the race instead of scanning the gauges for problems.

And on a bragging note, Daniel and his wagon won the Stock/Super Stock Series put on by the Southern California Drag Racing Association. This was an eight-race series; now with the season wrapped up, we’re moving on to our bracket combination and getting ready for a big bracket race in Las Vegas. Don’t work too hard this month, guys and gals!

Gold Filter

Q: I recently built a 388 stroker with an Eagle Street performance-balanced rotating assembly. The assembly came with a cast-steel crankshaft, SIR 5140 steel connecting rods, and FM244 aluminum alloy hypereutectic pistons with Perfect Circle piston rings and Clevite 77 bearings. A local machine shop came highly recommended and did, from what I can tell, a fine job. They bored, clearanced, and machined 0.005 inch off the deck. They installed ARP main bolts and said the mains were within spec. A Melling high-volume oil pump and a Summit stamped-steel stock replacement oil pan seals it up. I’m running a COMP Cams valvetrain with a small-base-circle Thumper camshaft, Magnum roller rockers, and Magnum double-roller timing set. I had the 350 Turbo tranny rebuilt, and he included a rebuilt 2,200-stall converter. I hope this is enough information for you to point me in the right direction.

I removed the oil filter to find brass shavings that looked like glitter. I have built several engines and have never seen this before. Is this bearing material? I was told the torque converter might have ballooned and pushed the thrust surface of the crank into the thrust bearing and this is the material I’m seeing. The rods are bronze bushed for floating pins. Could this be the material from the small end of the rod? A couple felt a little tight but assembled without any problems. The only other bronze/brass-colored materials used were the valve locks.

The engine has about 5-10 miles on it. Please let me know what you think before I rip it apart and start over.
David LeGrand
Arnold, MO

A: The first oil change on a fresh engine is always an aha moment. When you find the oil clean and the filter perfect you’re totally relieved. When you find material in the filter, or on a magnetic drain plug, your heart drops and you question where it came from. Sometimes it is quite easy; other times it’s like this couldn’t be inside this engine!

We highly doubt you have a ballooned torque converter after 5-10 miles of driving, unless those first few miles were repeated power brake launches. We don’t think your little 388 has enough torque to balloon the converter. You’ve listed the few sources your brass-type shavings in the oil could be from. The wristpin bushings are usually out, because if the bushing locks up, they rarely shed much debris, and the pin continues to rotate in the piston. Yes, over time it wouldn’t be happy because the rod couldn’t float from side to side with the pin locks retaining the wristpin. Some timing chain sets use a bronze thrust washer between the camshaft gear and the block, but the COMP Cams Magnum series timing set doesn’t. Finally, if you were running a roller camshaft, you’d be using a bronze distributor gear and they have to wear in from initial start-up. They are a service item, and you need to keep an eye on them over the lift of the engine. However, you’re using a standard cast camshaft and shouldn’t be running one.

This brings us back to the rear main thrust bearing, because it’s usually the culprit. We had a battle with our little 305 eating rear main thrust surfaces. After going through two bearings (slow learner) we finally figured out what it was doing. When the machine shop align-honed the mains, they cut the rear main cap on an angle. This caused the hone to cut a taper in the rear main that was slightly tighter in the rear of the main saddle. This, in conjunction with the cap being slightly cocked on the block, reduced the thrust clearance. We then sanded the rear main thrust surface to achieve 0.004-inch crankshaft endplay, assembled the engine, and thought we were good to go. Well, that slight taper in the rear main would allow the oil pressure to exit the front of the rear main and not lubricate the rear thrust surface of the rear main. Within about 20 dragstrip runs the endplay was about 0.020-inch and guess what we found in the oil filter?

The first thing we’d do is check your crankshaft endplay. If it’s still within spec, put a fresh filter and oil in the engine. Put some more time on the engine and give it a good break-in cycle. Service the engine and check the filter for debris. Check the endplay of the crankshaft to see if the clearance has moved. Sometimes on a fresh build things need to get happy with each other. You’ve identified where the material could come from. Good luck with your break-in.

Super Mixer

Q: I built a 372ci small-block with a B&M 420 Mega Blower and outfitted with two 750-cfm Edelbrock carbs. Out of all the Hot Rod and Chevy High Performance magazines I have read and I have read many I have never seen an article on tuning a 2-4 engine. What concerns me is, remember the old Torker manifold from Edelbrock for a big-block and how the carburetor was turned at an angle for fuel distribution? GM printed info on stagger jetting for this engine, but can you imagine all the mumbo jumbo it will take to get the plugs to read right? Dealing with eight carb holes! Could you please help me on this?
Charles Guarisco
Silverhill, AL

A: The Edelbrock Torker manifolds did turn the carb at an angle to help fuel distribution, but also to help equalize the runner lengths. This helped the distribution of fuel and also the air feeding into each cylinder. As for jetting your blown baby, you have two big mixing rotors directly below the carburetors. These rotors are going to mix the air and fuel and steer the mixture. There isn’t anything you’re going to do with the jetting of your two four-barrels above the blower that will make much difference in the intake manifold. When you do get down to jetting your engine, you’ll want to stay to the safe rich side of the fuel curve. A 12:1 AFR is a safe fuel mixture for your supercharged engine at wide-open throttle. As for part-throttle cruise conditions, you can shoot for 14.7:1, but with the volume of the blower and all the distance from the carbs to the cylinders, you may need to run it slightly on the rich side for good driveability. If you have an issue with distribution, this will cover up most of them. The last thing you want a boosted engine to do is go lean. A quick lean period at full throttle could spell disaster for your engine.

Your best investment would be a wideband air/fuel ratio meter for your car. They have really come down in price and will give you instant feedback on the fuel mixture going into your engine. We’ve now used about four of the AEM Digital Wideband Air/Fuel UEGO Gauge kits PN 30-4100 in our own race cars, and several of our friends’ cars. This completely takes the guesswork out of dialing in the fuel mixture of either a carbureted or EFI system. We prefer the digital gauge, because at a glance you can see the air/fuel going down the track. They utilize a very quick-responding Bosch wideband oxygen sensor for optimum accuracy and reliability. Another really nice feature is that the sensor has a 0-5V output to be used with data loggers, so that can interface with your race car data logger or laptop EFI tuning software.

A Little Spin?

Q: I just finished building a ’69 Chevelle and have a 598 big-block backed by a Tremec TKO II five-speed with a Ford 9-inch rearend and 3.73:1 gears. I have ladder bars, Hotchkis 11/2-inch drop springs, QA1 double adjustable shocks, and I’m running a P295/65R15 Mickey Thompson drag radial.

I had it dyno’d, and it generated 631 hp at 5,600 and 647 lb-ft at 4,500 to the wheels. I’m having a little trouble hooking up coming out of the hole and was wondering if I took the ladder bars out and installed a sway bar, would that help or do you have any other suggestions for this situation? This is a full body car with factory front suspension.
Via email

A: A little trouble hooking up? You’re trying to control 647 lb-ft of torque with a TKO II five-speed with a 2.87 first and an M/T drag radial! That gear ratio, coupled up with your 3.73:1 rear screw, gives you a total First gear ratio of 10.70:1. That’s a lot of power for a stick-shifted A-body, and it must be an absolute blast to drive. Have you ever tried to take off in Second? The 1.89 gear drops your launch multiplication down to 7.05:1. Yes, that’s very high, but 650 lb-ft of torque is a lot to hit on a small street tire.

Alf Wiebe sells race-only rear suspension designs for NHRA Stock and Super Stock cars that would make the car hook. However, it’s a race-only suspension that would put tremendous strain to the rear axlehousing and mounting during street operation. Wiebe won’t even sell his system for street use because it will only break parts. We assume you’re running bolt-in ladder bars with the factory four-link rear suspension? If this is the case, the rear suspension is in a complete bind. The suspension is trying to move across two different instant centers, and the car must be very stiff (little or no movement). Yes, remove the ladder bars to allow the factory four-links to apply the torque.

Now, let’s look at some four-link systems on the market that will allow you to continue driving your monster on the street and give it some more teeth. Check out Wolfe Race Craft, specializing in stock-suspended, small-drag-tire cars that really fly. Wolfe’s adjustable four-link suspension bolts into your factory mounting points, and the complete system (PN AWOLDK) comes with adjustable upper and lower control arms and a weld-in double sway bar, which gives you infinite tuning of the rear body roll. Wolfe also offers a very trick set of billet aluminum holders that allow you to install spherical rod ends in the rearend upper control arm pick-up point. Give Wolfe Race Craft a call to spec out a specific rear suspension package for your Chevelle. You have one unique application that will need direct attention from the experts!

After you get your rear suspension freed up, you will need to install some new front springs to aid in getting the vehicle weight moving to the rear tires on the launch. You cannot rely on the rear suspension lifting all that nose weight of your big-block. A little help from some Moroso Trick front springs will get the weight transferring to the rear. The springs for your heavyweight are PN 47200, listed for drag race use only because of the energy they have and the ability to control the suspension with the shocks. You will need to be honest with yourself about what your car really is, either a very quick street car that is an absolute blast to drive or something to refine for the quickest timeslip possible. Pick your parts wisely and have a blast!

Leaving Me Stranded!

Q: Hi, great magazine! I purchased a ’67 GMC truck from a guy several years ago and wanted to turn it into a weekend driver. Seven years later, it looks fantastic but I have a starter problem. I know every square inch of the truck except for the engine. The person I bought it from said the motor was rebuilt with zero miles on it. I, unfortunately, lost contact with him shortly after and did not get all the specs on what was done to the motor. It’s nothing wild, just a 350, intake, a Holley carb, headers, and a wild cam. It has a very rough-idle cam and the engine will barely idle, but it sounds great. When the engine is cold, it turns over great, but when it gets up to temperature and you shut it down, it’s nearly impossible to get it to turn over. You need to wait at least 20 minutes before you try it again; even then, it’ll barely turn over, but it’s enough to get it started again. Recently, I was running it on a hot day, turned it off, tried to start it 15-20 minutes later, and there was nothingnot even a click of the starter and it seemed dead. I left it for an hour, and it fired up with ease. The starter is a regular over-the-counter heavy-duty starter. Thanks.
Don Castor
Alberta, Canada

A: Your problem is a classic early model GM starting issue. This can stem from a lack of voltage getting to the energize terminal of the starter solenoid. Heat soaks into the very large starter housing from close proximity of the headers. Also, undersized, poorly routed battery cables or very bad ground path can’t get all that amperage back to the battery. Let’s take a look at each one.

First, the voltage getting to the starter solenoid is usually the main issue with an early GM product. The 40-plus-year-old wiring and switches have built up resistance over the years. The gauge for the energize wire is 12. The power on your truck comes from the battery across the core support to the voltage regulator. From there it travels from the regulator through the firewall bulkhead connector and then out of the fuse block to the ignition switch. Then, it goes through the neutral safety switch and back through the firewall bulkhead connector en route to the starter. The power for the starting circuit goes through no less than eight connections and two switches from the battery to the starter. The voltage that reaches the starter solenoid must be at least 9 volts for the electromagnet to pull in the plunger and make contact with the high-amperage connectors in the solenoid. If it can’t pull in the plunger, the starter won’t even try to turn. If it comes in slowly and just can’t make the connection, you will have a nice arc welding session in the solenoid. Exhaust header heat only magnifies the problem by increasing the resistance in the wires to transfer voltage. There are many helper solenoids on the market that use a full 12V shot going straight to the starter solenoid, which covers up most of the problems with the car, and they start. Check out the complete Start ’Em Up solenoid kit from MAD Enterprises, with the Ford-type remote starter solenoid to boost the energize voltage.

If the starter engages and cranks slowly, this can result from a number of situations, including undersized battery cables, overheated battery cables, or a poor ground loop back to the battery. On all of our projects, we upgrade the battery cables to 1- to 1/0-gauge wire to prevent any starting issues; with these cables, the starter will sing. A lot of the quickie auto parts store battery cables are undersized and will overheat in an instant when high loads are thrown at them. MAD can also help you with 1/0 battery cable and connectors to upgrade you entire starter power circuit.

Finally, we really like to dump the early, large electromagnet starters in favor of the late-model, permanent magnet-style gear-reduction starters. They give you increased clearance between headers and allow the starter to keep the motor cooler. They are not as susceptible to the heat because the poles of the starter are permanently magnetic and do not require voltage to create the magnetic field to drive the armature of the starter motor. All power is directed to the armature and creates a very strong magnetic field to rotate the starter. On small-blocks we’ve been very happy with the standard 153-tooth flywheel starter (GMPP PN10465143) that comes on the fourth-generation LT1-equipped Camaros. For big-block applications or anything with a 168-tooth flywheel, go with the starter (GMPP PN 12606096) off a ’96 L-29-equipped big-block Chevy truck.

Do You Want To Compromise?

Q: I’m looking to build a 383ci stroker for my ’94 Camaro Z28 with an LT1. I want to build a separate short-block so I can still drive the car while I build it. I’m just extremely confused right now about what block I can use and still keep the LT1 intake, heads, and rest of the parts. Do I have to use another LT1 block, or is a Gen II Chevy small-block the same exact thing as an LT1 block, with no changes needed? Also, I’m building it forged because I will add a turbo down the road, but that could be a year after I finish the 383. So how low should my compression be, and would it be safe to have low compression and still have good power without the turbo on yet?
SW Ranches, FL

A: Over the years, we’ve done just what you’re trying to do. We build the engine with a future goal in mind. We’re currently doing that with an LS2 that we want to turbo in the future. It’s always a compromise either way you build the engine; the camshaft and compression aren’t going to be right for a naturally aspirated operation and you’ll be driving it around for at least a year like this. Will it hurt the engine? Absolutely not. However, you will get very tired of the lack of performanceand more often than not, you never get around to finishing out that planned upgrade. Anything can happen.

How about you build this short-block for a max-performance NA engineand later rebuild the short out of your car for the turbo application? It will cost more, but then you have the opportunity to build it in the future. You may be very pleased with the 383 you build up and never turbo this car and move on to some other project.

Getting back to some engine specifics, you need to pick up a Gen II short-block for a core. The Gen II engines were built between 1992 and 1997. The ’97 Camaro had both LT1s and LS1s. There should be plenty of blocks in the wrecking yards, as the LT1s were an option in the Impalas, Caprices, and Caprice wagons (’92-96) and were standard in the Buick Roadmaster wagons and Cadillac Fleetwood Broughams (’94-96). In the Chevy products, there was the L99 265-cid Gen II that looked just like the Gen II LT1; the way to make sure the car is LT1-equipped is that in the eighth digit of the VIN will be a letter P. Also, cast into the cylinder block right behind the driver-side cylinder head on the bellhousing flange will be the 5.7L. In the Buick and Cadies alone, GM installed more than 135,000 LT1s between ’94 and ’96. Look for the oddballs to pick up a core at a screaming price.

You could build your short at 8.5 to 9:1 compression ratio for your turbocharged build. You could go with a nice naturally aspirated camshaft and swap out the cam when you stick the turbo on it. If you do build the engine with this low of a compression, please stay very conservative with your camshaft selection. If you go with an aggressive profile, you will hate the car until you add your hair dryers. Good luck with the planning and execution of your project.

Let It Bleed

Q: Performance Q&A is one of the first articles I read each month. Can you help me find information on air bleeds and emulsion holes? I have a QFT 750AN DP that gets lean up top. It is on a 383 with an Extreme Energy 274H cam, cleaned up Vortec heads, and a Performer RPM intake. The bottom end is forged, but I am running hypereutectic pistons so I keep the rpm to around 6,000. It is in an Austin Healey kit car used for track days, kind of a Cobra for a Chevy guy. For tuning, I installed an Innovate wideband and disconnected the secondaries. Accelerating at moderate throttle I jetted for 14.5 to 15:1. I then adjusted the power valve restrictors to get 12 to 12.5:1 at full throttle up to 3,000 rpm (half the rpm for half the carb). When I reconnected the secondaries, it was rich so I started dropping secondary jet sizes. When I get it right in the 4,000-5,000 rpm range, it leans out to 13.5 or so at the top. I think I need to reduce the main air bleeds, but I’d like to read up on the subject. When I called QFT they said any good Holley book would help. I currently have an old HP Books Holley Carbs and Manifolds by Urich and Fisher, a newer Super Tuning and Modifying Holleys by Emanuel, and now Hot Holleys by Walordy. They touch on air bleeds and emulsion holes a little, but mainly say, Don’t screw up your carb by messing with them. Can you guide me to a good source of tuning info to minimize my cut and try? Thanks,
Kenneth C. McDonough
Hillsboro, IL

A: Austin Healeys are very cool cars. They have a very nice size engine bay in a small package and were built to have small-block Chevys swapped into them. You’re off to a great start with your Innovate wideband O2. I like your solid tuning foundation working out the primaries first and then moving on to the secondaries. With it going lean at higher engine speeds, we will assume that you have plenty of fuel pressure and volume and that your float levels are correct. Our first recommendation was going to be that you contact Quick Fuel Technology, but you’ve been there, done that. All the books you have listed are great reference material. They give you a clear understanding of the role of the air bleeds as a timing tool more than an enrichment tool, timing when the circuit will become active, and how much air is emulsified into the main well before going through the boosters. When you reduce the size of the air bleed, the circuit will come in sooner and be slightly richer.

To get you closerwithout having to change out the air bleeds more than necessarywe like to use either stainless safety wire or warranty tag wire (attaches most warranty tags to new parts). This is just a fine (0.018- to 0.025-inch stainless) wire that you can install down the main air bleeds and run under the air cleaner base to hold them in place. This will restrict the size of the air bleed and change the fueling. You can then see how sensitive the carburetor is to changes in the air bleeds. If the wire brings the jetting in line, work out the area of the bleed hole and the wire diameter. This will give you the final size of the air bleeds you need to install in your carb.

We know of no other shortcut than to cut and try. At least with adding a restriction to your factory air bleeds you can figure out the final size and change them once. Good luck with your metering and be safe on those track days. Watch out for the hero drivers!

Posi Minded

Q: I am 17 and my ’68 Chevelle currently has a 10-bolt rear, open-ended, with highway gears. It has a mostly stock 350hp, 327ci small-block up front with an M-20 behind it. I recently purchased a ’68-72 Chevelle 12-bolt rear at a swap meet; this rear is open-ended as well, and I believe it has 3.07:1 gears.

How do I figure out what series the rear is? I found CY 0618B on the axle tube and NF X 3917124 on the pumpkin. Depending on what series the rear is, what posi would you recommend for a street and strip application? I’m looking at putting 3.73:1 or 3.90:1 gears in the rear.
Jacob Hill
Via email

A: Identification lies in the ring gear carrier that the rearend is equipped with. This will give you the gear range that can be installed with that specific carrier. The two-series carriers were used for the rearends equipped with 2.56-2.90:1 rearend gears. The three-series ranged from 3.08-3.90:1, and the four-series was 4.11s and up. The series of the carrier is specifying where the ring gear flange is located. With a drop in gear ratio (higher numerically), the smaller the pinion gear gets in diameter. With this drop in pinion diameter, you must move the ring gear closer to the pinion or make the ring gear physically thicker. On the market, blanchard ground spacers can be used between a three-series carrier and four-series gears. We don’t like using spacers because of the chance of ring gear runout.

The selection of posis on the market include disc-type clutch, cone-type clutch, the traditional locker, and newer air lockers. The factory posi that GM/Eaton designed back in the ’60s is the disc-type clutch, which we prefer. One of the major issues with the factory posi is the strength of the side and spider gears, but Moroso redesigned the GM posi back in the late ’70s, and it’s still hard to beat for strength and performance. The spider and axle gears are made from forged H-11 aircraft steel bar stock, and Moroso increased the friction disc count from the factory 18 to 22. Between this count change and the increased spring pressure on the clutch pack, the posi gives you a 100 percent increase in breakaway torque. Now for the downside: Moroso only offers the posi carrier in a four-series design. Also, they can be quite aggressive for street use. We had one in our El Camino for 10 years and it will give you a good deal of chatter when turning slow-speed corners when the diff gets hot. If you stay up on the gear oil with friction modifiers added, you can minimize this issue. The bottom line is you’re not going to break this posi! The Brute Strength posi is sold under PN 83000, and the Moroso Climbing gear lube is PN 34800you can also check out the GM Posi Lube PN 1052271

To find a gear ratio that works for you, check out Precision Gear, which offers a 3.73:1 gearset (PN GM12/373C, specifically designed to work on a four-series case. This gives you a gear range from 3.73:1-6.10:1 on a four-series case. Precision also offers specialty gears that allow you to use 4.10s and 4.56s directly onto a three-series carrier without the above-mentioned blanchard ground spacer. CHP



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