December 2012 Chevy High Performance Q&A

Totally Broke(n)

Kevin McClelland Oct 22, 2012 0 Comment(s)

This month’s installment is going to be a two-pronged discussion. If you’re a regular reader, you know that the racing scene in Southern California is quite dismal. We have lost our only quarter-mile track in the Los Angeles area, Fontana AutoClub Dragway, and for a period of time we had also lost our eighth-mile track, Irwindale Dragway. With both tracks closed, the natives have been going crazy to peel out and do wheelies! Well, we’ve got one of our tracks back, as Irwindale reopened for business several weeks ago. This past weekend they were having a Summit E.T. series race to qualify for competition in the E.T. Finals. My son and I had joined Fontana’s team before the closure, but without a definite answer if they were going to reopen or field a team at all, we decided to go to Irwindale and join its team.

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Since the wagon hadn’t run in over four months, and it was well overdue for a good service. I asked Daniel to get it off the trailer, change the oil, and look everything over. I was at work when a picture came across my phone, revealing a very large crack in the transmission case—beginning at the starter and extending all the way around to the upper bellhousing bolt on the driver side. I told Daniel to put everything away. We were done.

Again, if you’ve been a regular reader, you know I’m building an L92 6.2-liter to drop in place of the LT4 350 that’s been in the car for years. It was my plan that when I went to swap the engine out that I would rebuild the A-1 Powerglide and give it a few upgrades for the added torque and horsepower. OK, this is where the “broke” comes into the story. Instead of just fixing the trans, we’ve decided to go headlong into wrapping up the engine build, build a new trans with a Reid Racing case, and knock out the whole enchilada. I’ve been collecting the parts for the engine, as the checkbook would handle it. I’ve gotten the complete camshaft and spring package from COMP with the hydraulic roller spec’d out at 239/251 at 0.050-inch tappet lift, 0.624-inch max lift, and ground on 110 centers. This package utilizes dual valvesprings with tooled steel retainers. Consulting with COMP, this is the largest intake lobe we think will fit without having to cut valve relief in the stock short-block L92. These springs will dress the Lingenfelter CNC-ported LS3 cylinder heads with hollow-stem Manley valves. I’ve also broken down and bought the Victor Jr. manifold to top off the engine. To meet the sub-11-second requirements, I’ve also picked up an ATI Super Damper and an SFI flexplate. To keep the engine cool we’ve dressed the front of the engine with a Meziere electric water pump. I’ve gotten a complete set of ARP fasteners to replace the torque to yield production hardware, an MSD ignition controller for the coil-near-plug system, and a drag-race oil pan. I only have a few more big-ticket items to pick up, like a set of pushrods once the engine is mocked up, CHE Precision bushed rocker arms to prevent losing the pesky needle bearings out of the rockers, and a GM permanent magnet gear reduction starter.

I’ve finally shipped off the Brand-F stock eliminator engine I was building for my good friend Charlie Allen. Daniel’s RX-7 is just about ready to fire; we’re down to the final wiring chores of marrying a GM controller and the RX-7 electrical systems. I guess it’s my turn to dig into our nasty wagon. We’re shooting for mid 10s at 3,200 pounds on a stock short-block on pump gas. Stranger things have happened—we’ll keep you posted.

Balancing Act

Q. You’ve given me some great advice in the past, and I need your help again. What is best location to install a cross-pipe or crossover pipe in the exhaust system? Is it best to place them forward or to the rear of the system?

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Ron Anderson
Westland, MI

A. Glad we can be of service. The best location for exhaust communication between the banks of any V-type engine is as close to the exhaust collector as possible. This is true for either a cast manifold–equipped engine or with headers. The reason that a balance pipe helps performance is the firing order of a 90-degree bank-angle V-8 engine. With any manufacturer’s V-8 engine, you have two cylinders firing back to back on the same bank of the engine. When this happens the exhaust system is overloaded on that bank, and it creates high pressure in the combustion chamber of the first cylinder in the firing order while the exhaust valve is closing. Well, when the exhaust valve is just closing is when the intake valve is opening, and you want the lowest pressure possible (scavenging) in the combustion chamber to aid in pulling the intake charge into the cylinder. On the odd bank of the firing order, the back-to-back firing would be the No. 5 and 7 cylinders. So just as No. 7 cylinder is well into its exhaust stroke, the No. 5 intake and exhaust valves are open during overlap. This causes exhaust gases to rush back up the intake manifold and dilute the incoming charge. On the even bank of the engine, it’s cylinders 8 and 4. If you can eliminate this condition by connecting the two banks of the exhaust system, you have given the excessive exhaust pressure a path to relieve the overpressure condition. With those two cylinders affected during overlap getting full charges of fresh air and fuel, you gain torque and horsepower with the communication.

That said, putting a balance or cross-pipe as close to the collector can be a real challenge. Usually the only things you can do is put the connector as close as possible and take what gains you can get. We worked on one project where we were able to put a balance pipe right between the head pipes, under the oil pan, on a C4 Corvette with an LT1. That engine picked up over 10 hp with no other changes than installing that short communication pipe between the stock head pipes. This was the best packaging of a balance pipe. Usually you have to wait until after the transmission crossmember. Sometimes you can get your communication around the torque converter area on an automatic-equipped vehicle. Give your application a look and get creative. You will love the gains.

Help me Break it in

Q. I have spent a lot of time and money building my first small-block. It’s a 350 0.030-inch-over with a Scat rotating assembly, an Edelbrock billet hydraulic roller, Performer RPM heads, the list goes on. I have filled the oil pan with Royal Purple break-in oil. I have spun the oil pump and have 80-psi oil pressure. After I go buy a battery I am finally going to start the thing. Can you help me out with a good break-in procedure? Thanks! Love the tech.

Mark
Via email

A. Back in the day engine break-in was much more important. With the quality of our machine work today, the cylinder wall finish, and the high-quality, moly-filled piston rings, it’s a snap to break in an engine. Usually, the rings are quite happy after you have turned the engine over during the assembly process—if you have followed clean assembly techniques. Here is what we would do on a fresh engine today.

First of all, you have an easy break-in as you’re running a hydraulic-roller camshaft. If you had a flat-tappet camshaft, you’d need to start the engine and immediately accelerate to 2,200 rpm, and vary the engine speed between 2,000 and 3,000 rpm for 20 minutes straight. This gives the camshaft and lifters a chance to get happy with each other. If you idle the engine from the start, there is a good possibility that you will flatten a cam lobe, as the lifters must rotate right from the first firing, and the only true oiling the lifters and camshaft lobes get is from splash and windage thrown off from the rod journals. Firing the engine and going straight to 2,000 rpm requires that you have everything in order before starting the engine: full of water, oil, correctly timed, and a timing light to set the timing so you don’t burn the paint or coating off your new headers!

Back to your break-in. You’ll want to follow all the previous recommendation of water, fuel, timed, and the ability to time the engine right after firing. After you have run the engine in, checked for leaks, and have everything safely buttoned up, you’re ready for your first drive. If you live in a hilly area, you’re in luck. The best way to break in and seat your piston rings is to apply load to the engine for a short period of time, then unload, and preferable run downhill under compression during deceleration. This will put heat into the rings and pistons. Then turn around and go down the hill at speed with the engine compression braking the vehicle. This draws oil up on the cylinder walls and cools the rings, pistons, and the cylinder walls. Also, the cooling system pulls the heat out of the engine, cooling the component. Continue going up and down the hill five to eight times, applying more load on the engine each time you drive up the hill. Then bring your baby home and let it cool down completely. Check everything for leaks, check all fluids for the correct level, and finish up all the little things you skipped so you could go for your first drive!

When you can’t wait to go drive your new engine again, go give it another round of load then no-load treatment. Do this until you’ve worked your way up to about three-quarter throttle. Also, limit your engine speed to no higher than 4,500-5,000 rpm. After this session, bring it back home and change out the break-in oil, and cut open your oil filter, checking for debris. If everything looks good, top off your engine with your favorite motor oil and enjoy. We’re firm believers that you break the engine in the way you’re going to drive it. Now, we’re not saying that you go out and beat on it, but drive it and enjoy it. If you’ve done your job correctly it will give you many years of service and pleasure.

Crate Expectations

Q. I have an ’87 Monte Carlo SS with 305 H.O. and 160,000-plus miles on the engine. I live in California and have to take it in for emission testing at a test-only station. I would like to replace the 305 with a crate 350, but I was told if the tech notices the heads aren’t center-bolt heads they would fail me. What are my options for a crate motor that will appear stock and still pass the emission test? I have Edelbrock T.E.S. headers and a Hypertech Power Chip for California cars. Thanks for your help!

Keith J Garcia
March ARB, CA Field Services

A. Unfortunately, some of the test-only smog check stations have really thorough techs. If you are caught, you have to go to another shop and keep spending money until someone will pass it. Not to condone this type of behavior, but your ’87 should be on a no-test list, as the politicians guaranteed us they were going to roll the date of the smog check up as the years go by. They haven’t moved the line in the sand from the ’74 model year. Our early performance cars make up such a small percentage (less than 0.01 percent of the vehicles on the road) that they should leave us all alone. Maybe someday. Let’s see if we can come up with a bundle of performance parts that will get past the smog police.

With the advent of Vortec cylinder heads on most crate engines from General Motors, this leaves you with a little problem. Your ’87 is equipped with an EGR valve and requires an exhaust crossover in the cylinder heads to feed the intake manifold. Neither the Vortec nor the L98 aluminum cylinder heads used on the ZZ4 engines have these provisions. We’ve come up with two options using Chevrolet Performance partial engines. This is where GM offers the short-block from its popular crate engines. The ZZ4 partial assembly (PN 12561723) comes with forged crank, powdered metal connecting rods, LT1-style, high-silicon pistons that feature flat-tops and four-valve-relief, four-bolt main block with provisions for a hydraulic roller camshaft and lifters. This is a great foundation for a performance build with a factory warranty.

Next, take a look at the HT383 partial engine assembly (PN 12499106). This fully dressed short-block features the same four-bolt roller cam block as the ZZ4, 4340 forged steel 3.80-inch stroke crankshaft, special powdered metal 5.7-inch connecting rods that feature a stud and nut to retain the rod cap. This gives you the clearance necessary to clear the camshaft in a stroker application. Speaking of camshaft, it comes equipped with the HT383 hydraulic roller that is a short 196/206 degrees of duration at 0.050-inch tappet lift. The short-block is fully dressed with front cover, oil pan, and counterbalanced harmonic damper. Finally, the pistons are a hypereutectic dish design to keep the compression in line. With this camshaft and the proper cylinder heads, the smog police will never be the wiser.

Now to keep everyone happy, check out Dart Heads for its Iron Eagle S/S small-block Chevy cylinder heads. These feature a 165cc intake runner, heart-shaped chambers to improve combustion efficiency, and machined valve cover rails to eliminate leaks, and it will accept both center-bolt and standard small-block valve covers, as well as screw-in rocker studs that won’t pull out. The heads are offered in various combustion chamber volumes (67, 72, and 76 cc) to tailor to your compression needs. They also are offered in both 1.94/1.50- and 2.02/1.60-inch valve options at no additional cost.

First, for a 350 build, we would recommend going with the PN 10021070A, a fully assembled 1.94/1.50-inch valve package with 1.250-inch springs and retainers and 72cc combustion chambers. With the flat-top ZZ4 partial short-block your compression ratio will come in right at 9.4- to 9.5:1. This will be perfect for premium unleaded fuel. For the 383 partial, with its dish pistons, go with the PN 10024365A heads, which feature the same valve and spring package but with 67cc combustion chambers. We’d have the heads surfaced 0.020 inch, which will reduce the combustion chambers down to 64 cc. This, in combination with the dished pistons, will yield a 9.1:1 compression ratio.

With these builds, all the components from your 305 will bolt right on. The inlet manifold, rockers, roller lifters, and pushrods will all be compatible with these buildups. If it was ours, we would upgrade the inlet manifold to an Edelbrock Performer PN 3706. This specific Performer features EGR provisions and the proper inlet manifold bolthole angle to match up with ’87-and-later iron cylinder heads. The four center manifold bolts are stood up at a 10-degree-steeper angle compared with earlier (’86-and-earlier) cylinder heads.

Finally, the ZZ4 camshaft (PN 10185071) would be a great addition to your ZZ4 partial short-block. It would also just get past the emissions test and give you great performance with the rest of the package. The camshaft specs out at 208/221 degrees of duration at 0.050-inch tappet lift, 0.474/0.510-inch max lift, and ground on 112 centers. It was designed for the 350 H.O. emissions package that was a retrofit engine assembly for both the carbureted 305-equipped Camaros and Monte Carlos. This made a great driving package in these cars. Unfortunately, this package has been discontinued or you could have dropped it right in, completely emissions legal.

Hopefully, this has given you some ideas and direction building a great crate for your SS. Either of these packages will have no problem passing the California emissions test-only program. You can expect the 350 package listed above to produce around 330-340 hp with your Edelbrock inlet, T.E.S., and Hypertech chip. The 383 will knock down 350-360 with well over 400 lb-ft of torque to plant you in the seat. Have fun choosing and enjoy your Monte.

Sources: chevroletperformance.com, dartheads.com, edelbrock.com

Belted In

Q. My alternator/water pump belt keeps coming off. This is a street/strip ’68 Camaro, with a 383ci small-block, F-1R ProCharger, and five-speed (GF5R shifted without the clutch at 7,000 rpm), and has run 9.0s at 12748 mph and 7,200 rpm. I have spent many hours making sure the pulleys are in alignment; everything looks great, then about 100 miles and 12 runs later the belt comes off. It is always twisted and sometimes takes out the 12-rib blower belt with it. I always replace it with a new high-quality belt, most recently a Napa Premium PN 25-7445, 13/32x45 1/8 inch.

I am using ProCharger powdercoated aluminum pulleys, a 6.75-inch crank pulley, a 6.5-inch water pump, a 3.5-inch od alternator, and all are 0.5-inch deep. The water pump is a Weiand, long shaft and is tight with a Flex-a-lite 18-inch fan, which never gets hot. I’m running an MSD 130-amp alternator installed on the right head, stock location and hardware install for use with a long water pump. Please help if you can, as this really screws up a nice cruise night!

Bill Unruh
Riverside, CA

A. Beautiful Camaro, Bill! This car was featured in the Feb. ’09 issue of CHP. You have spared no expense building one very trick, very fast Camaro.

From everything we can find, MSD has gotten out of the alternator business, but here’s some very interesting technical information. The production V-belt pulley measures out at 2.64 inches od. The V-groove is machined to accept a 0.468-inch-wide V-belt. Your 13/32-inch belt width is right in there at the proper width for these pulleys at 0.406 inch. Yes, we’ve seen that even with proper alignment the belts can flip at high engine speeds and, soon after, leave their respective grooves. GM had the same problem with the early Z/28s when engine speeds went north of 7,000 rpm with the 302 engines. It remedied this problem with a very deep-groove alternator pulley, and the Corvettes also had deep-groove water pump and crankshaft pulleys. You can try and install a larger-alternator-diameter, deep-groove pulley and see if that takes care of the problem. Or you can convert the water pump, alternator, and crankshaft over to a six-groove serpentine beltdrive. The easy test is to install a Powermaster deep-groove pulley (PN 182). This pulley specs out at 4 inches od and has the unique 0.668-inch alternator shaft diameter. This is quite a unique spec for the shaft that MSD used. We would go this route first and give it a go.

As for the serpentine conversion, we’d recommend checking out what ProCharger has to offer. We’re sure you could pick up a set of pulleys from March Performance but we’re not sure how that would impact your blower drive. Good luck keeping the belt on your charger, alternator that is. It’s really no fun when you lose your only accessory belt!

Sources: marchperf.com, msdignition.com,powermasterperformance.com

Flat or Dished

Q. I see some cylinder heads are available with different-size combustion chambers, and I’m wondering what would be the better way to go, larger chambers with flat-top pistons or smaller chambers with reverse dome pistons? Assuming all else is equal on a pump-gas Chevy small-block. Thanks!

Adam Hubley
Via email

A. Yes, cylinder head manufacturers have come to the rescue and offered multiple chamber volumes to allow engine builders like you to tailor their compression to the application. Common combustion chamber sizes for small-block Chevys are 58, 64, and 76 cc from the factory. There were many others, but you can see that there was a big gap between 64 cc and 76 cc. The aftermarket has adopted 72 cc as another common volume.

As for flat versus dished, we prefer the flat-top piston. With a dished piston you have less quench area to create mixture motion in the combustion space. Also, it’s tougher to completely evacuate the combustion space of spent fuel (exhaust) with a dished piston. That said, that’s volume in your fresh charge that cannot burn again, possibly reducing output. With a flat-top piston you can run a larger combustion chamber and do a better job of unshrouding the valves, which increases flow. You can also transition from the inlet port, across the back of the chamber, and into the cylinder better, which keeps the fuel in suspension with the incoming air. This reduction in separation also increases output by having consistent mixture throughout the combustion space.

We’re assuming you’re referring to small-block Chevy builds. With big-blocks it’s tough to build compression because the standard open-chamber cylinder head has a chamber volume of 119 cc. Even with 454 ci you must run a slight dome to make 9:1 compression.

Look at all the options on the market for cylinder heads and their chamber sizes, and then you can hone in on a piston head design

Officially Jealous!

Q. Keep up the great work with your articles; they are the first thing I flip to when I get my newest issue. I’ve been a Chevy guy my whole life and have spent years restoring many Bow Ties. I have a numbers-matching, all-original ’67 Camaro SS 350. Did this car come from the factory with multileaf or monoleaf springs? All the research I found told me that ’67 Camaros came with monoleaf springs. Mine has multi on it, and I would like to know which spring it came with from factory before I start my restoration.

Dave Bruley
Arlington, OH

A. Yes, all ’67 Camaros were equipped with monoleaf rear springs. The multileaf springs found their way onto the Camaro in 1968, when they also had the stagger shock option to help reduce wheelhop, but it did very little to control the spring wrap that causes wheelhop. In another attempt to control wheelhop, GM added the right rear axle radius rod option on limited L-48 (295 hp/350), and all L-78 (375 hp/396) engine packages. The 350 cars were equipped with a round radius rod, and the 396 cars had a stronger square tubing bar. The two radius rod upgrades were very similar, but on the big-block–equipped vehicles GM added a stop bracket, which mounted below the radius rod on the rear axle. This stop would come in contact with the radius rod when the spring would begin wrapping up and create a nice little traction bar. Unfortunately, GM only felt it needed this on the right side of the vehicle. It would have been very cool on both sides.

If you have multileaf springs, you may have a ’68 or ’69 12-bolt rear axle, as the spring perch brackets on the rear axle are different between the mono and multileaf springs. The depth of the perch accommodates the either four- or five-leaf multileaf spring, depending on the spring option and original build. The monospring perch is very shallow. The bottom line is with the rubber isolators installed between the spring and rearend, and the spring retaining plate, which incorporated the rear shock mount, will pull up flush to the rear axle spring perch.

Enjoy your resto. Send us in-progress photos—we’re still jealous.

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