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February 2013 Chevy High Performance Q&A

Kevin McClelland Mar 6, 2013
1302chp 02 O  Chevy High Performance Q A 2/2

Back in the Day!

When we sometimes refer to the way it was “back in the day”, we often remember things better than they actually were. We polish up the past for our memories. But in some cases it really was that good.

This past weekend I had one of those moments that truly was a great time in the performance aftermarket. My wife, Lisa, and I took an R&R three-day weekend in Las Vegas. When we were on our way up, I remembered that my good friend Les Figueroa had moved his business Figspeed from Lake Havasu up to Henderson, Nevada, a little over a year ago. Figueroa has operated Figspeed for many years as trackside racer support with a full trailer of performance parts to keep the racer going down the track. He and his team come to most PSCA, NMCA, and NHRA divisional events, in Division 6 and 7 out here on the Left Coast. When he moved his performance operation up to Henderson, he set up his shop to support racers with a complete speed shop. Now, I don’t know how many of the youngsters out there ever visited a local speed shop, but back in the day, this is where we learned about the latest and greatest performance offerings and could order them for our builds. There was no Internet. There wasn’t Jegs or Summit. There was, of course, the J.C. Whitney mail-order catalog, which would carry some of the good performance stuff, but the speed shop was where you could hang out with your gearhead buddies and pick the brain of the counterman. The counterman was usually one of the top racers at your local track and was pretty hip on the latest performance parts.

When my family moved to Southern California back in 1971, the killer speed shop in our area was Glendale Speed Center. My dad and I would frequent this haunt for gaskets, hardware, and parts when we were assembling our Fiat Altered car, powered by an injected big-block.

Walking into Figueroa’s place was like I was stepping back in time 40 years ago. The store is filled with the latest tricks from ARP, ATI, B&M, Holley, Jesel, Milodon, Moroso, MSD, Strange, and many more performance companies just waiting to offer instant gratification. Check out the shop at Yes, our days of Jegs, Summit, and even Amazon are great, but sometimes you do get stuck and need that one part to get your project going. This is one of the things your local speed shop is great for. Also, again as back in the day, most of the people working in these shops were racers themselves and could steer you right to the parts you need, the first time.

There will always be the online deals, but sometimes you can’t beat the face-to-face transaction of building speed. Search out your local speed shop and support them in every way you can. It will bring you back to a time in our history that we need to cherish.

Trans-Am Racer

My ’69 Z/28 is patterned after a Trans-Am car of the era, as I have watched them race in person and have always enjoyed them. I built the car with a NOM 383, a COMP XE268H hydraulic cam, a Performer RPM Air-Gap, and aluminum heads to have a broad torque curve and good street behavior. That it has in spades, up to about 6,200 rpm, but now I’m interested in a higher-revving combination more in character with the original 302 but with (of course) more horsepower and torque.

I am considering a 377 (4.155x3.47) or a 427 (4.125x4), as it seems the new generation of hydraulic roller cams rev to 7,000 easily and that would suit me fine. In addition, I have wanted a cross-ram (yes, I know they are expensive) to go with it but am concerned about streetability and performance, as no one ever seems to use them. I must admit, I really only prefer the cross-ram for appearances unless there is a sound performance gain that can be achieved. As a follower of your column, I will pay close attention to your advice. Thank you.

Tom Purtill

Richmond, TX

Your 383 sounds like a perfect combination that gives you trouble-free enjoyment. Stepping into a new, higher-revving combination will give away some of your street manners. If you go with the large-displacement 427 you’ll get the bump in horsepower and torque you’re looking for. Pushing that combination to 7,000 rpm could be a challenge unless it’s a true race-type build. Our vote is for the large bore with the relatively short-stroke 377. These engines have always had a soft spot in our heart as they would rev quickly and make great power with that large bore for breathing.

You reference the revving potential of the hydraulic rollers. One of the issues with a complete hydraulic roller setup is the valvetrain mass. Keeping this under control at 7,000 rpm could be challenging. If you decide to go this route, please work with your camshaft supplier of choice and communicate your goals. You’ll want to keep the valves, springs, and retainers as light as possible, as they are the hardest to control. If this is your weekend warrior, look into a high-quality mechanical roller setup. Small-block engines don’t have the lifter wear issues like the big-block engines. Also, if you went with the Isky EZ-Roll lifters you wouldn’t have to worry about it at all. Opening up the valve events to a mechanical roller design will give you the limiting speed you’re looking for with no issues.

Now, back to your desire to use a cross-ram intake manifold. GM did offer these manifolds in the trunks of the Z/28s, as they wouldn’t come from the factory installed. This intake system was sold as an option, but the only problem is that it was installed in the wrong end of the car. These manifolds look very cool, but they are also very challenging to get to perform well. They have mixture distribution issues at slow engine speeds. They will puddle fuel in the manifold between the runners and in voids in the plenum, which would lead to bad habits at idle and part throttle. Once the engine was at full song, they would run well, but they don’t perform better than a single four-barrel, single-plane manifold setup. Yes, the long runner lengths do boost the torque at slower speeds, but rarely were they fueled correctly at these speeds. Several aftermarket suppliers released their own version of the cross-ram with some success of improving the distribution issues. These manifolds still couldn’t keep up with the current offerings of single-plane performance.

Keep us posted on your progress for power. We’d be very interested to see the finished product and what you decided to go with. Good luck, and long live the high-revving small-block.


There She Blows!

My son and I installed a freshly rebuilt 0.030-inch-over 350 engine in his ’78 Camaro. He ran it for about a week and he noticed that one of his lifters kept tapping. He removed the valve cover and adjusted the rocker arms, but in a day or so it would return. Upon removal of the valve cover, he noticed that a couple of the studs in the heads seemed to be pulling out. That’s when we decided to change the heads.

This is where the issue begins. We had a stock set of 882 heads that had been worked on, sitting on a shelf in our shed, so we disassembled the engine and purchased a new head gasket set. We put the car back together. When we started it up, we noticed quite a bit of blow-by and thought maybe this was oil burning off the heads, or maybe some oil had gotten on the headers. Well, it got worse. We told a friend what we had done, and he recommended we check the part number on the head gaskets to make sure we had the right ones. He seemed to think we had the wrong head gaskets and the compression was getting under them, therefore causing the blow-by. We pulled out our receipt and they had sold us head gaskets for a 305. We called the parts house and told them of this mistake and they agreed they had given us the wrong ones and replaced them. So we tore it back down and installed the new head gaskets for the 350 bore; however, now we still have a massive amount of blow-by. I asked my friend again, and he feels that since the head gaskets were for a smaller-bore engine, it caused the fire rings to hang over into the cylinder walls, and this increase of compression caused the compression rings to collapse. Would the smaller-bore head gaskets cause this problem?

Al Roofer

Via email

Your friend has his thinking cap on! He’s had some great suggestions and got it right on the 305 head gaskets. Unfortunately, the difference in bore size on the head gaskets makes very little difference in compression ratio. Most replacement head gaskets on the market for the small 3.736-inch bore size of the 305 is in the 3.800-inch range. The replacement gaskets for the 350’s 4.00-inch bore is 4.100 inches. The compression difference between these two gaskets is in the 0.1 to 0.02 of compression ratio. For example, you probably went from 9.0 to 9.2:1. This small change wouldn’t have hurt the ring lands.

Now, what would have easily cracked the ring lands of your rebuilder, cast pistons would be if the pistons came out of the deck any amount. If the engine had been decked when it was rebuilt and the pistons had a tall compression height, the pistons could be coming slightly out off the bore. It wouldn’t take much to crack the ring lands of the pistons if they came in contact with the fire rings of the 305 head gaskets. You would see witness marks on the heads of the pistons on teardown where the gasket was coming in contact.

With the engine fully assembled, the best way to test the integrity of the pistons and the rings is to perform a leakdown test. This is where you put the cylinder you’re testing at top dead center on the firing stroke. You then apply air pressure to that cylinder with a special leakage tester. When you apply air pressure to the cylinder you’ll have some amount of leakage. With racing engines we shoot for the least possible leakage. On street engines it’s not uncommon to see the cylinder leakage in the 8-15 percent range when the engine is cold. On really sealed-up street engines we’ve seen the leakage in the 2 percent racing engine territory. Maybe your friend with the great answers can help you with a leakdown test. You can pick up a tester from most any tool truck, Sears, or online. In a quick search we found low-dollar testers out there in the $70-$80 range. Remember, you do get what you pay for, but if this is a one-time diagnosis you may want to go this route. Maybe you can find one to borrow. Good luck finding your leaky rings.

305 vs. 302

I have a 305 small-block out of a ’92 Caprice with engine code E. Why can’t you build respectable power out of a 305 like you can a 302 out of a (gag) Ford. I’m putting it in a ’91 S-10 and don’t need a lot of power, just want the sound of a V-8. I just have never understood why they are so unbuildable. Thanks.

Mike Moriarty

Via email

For anyone who has spent any time trying to build decent power from a 305, “unbuildable” is perfect! First of all, we don’t have to compare the 305 Chevy to a (gag) 302 Ford. We can take the same architecture of the small-block Chevy 302 versus 305. The 302 bore/stroke is much more desirable for performance with its 4.00-inch bore versus the small 3.736-inch 305 bore. The performance aftermarket hasn’t really built a small-bore Gen I small-block cylinder head for performance, so you’re stuck with replacement heads and what GM offered. Also, with the 302’s large bore combined with its relatively short 3.00-inch stroke compared to the 3.48-inch 305 stroke, the 302 loves to rev! Enough said.

Back to your S-10 build. Your E engine code 305 is an L-03 TBI engine. These are great workhorses but will build no power, as the cylinder heads have a swirl vane in the intake port to create mixture motion. They work great at building slow-speed torque and helping fuel economy, but they kill top end horsepower by killing the airflow potential of the heads. If we were building your engine, we would swap out for a set of the 416-casting GM cylinder heads, then step up the intake valves to 1.94 inches and pocket-port the intake and the exhaust bowls. This will give you the best chance in building decent performance from GM heads.

Next, you’ll need to kick the TBI to the curb. This system is very reliable, but not very performance orientated. We’d recommend an Edelbrock Performer PN 2101 intake manifold with either a Rochester Q-jet or the Edelbrock 600-cfm Performer carburetor PN 1405. This package, with your upgraded GM cylinder heads, will give your 305 a fresh breath of air. If you wish to stick with a throttle-type EFI, look into the FAST EZ-EFI, the MSD Atomic, or the Professional Products Powerjection III. Any of these auto-learn EFI systems are a snap to install and enjoy.

Finally, to continue with the theme of conservative torque-producing components, go with a relatively small hydraulic roller camshaft. Check out the Crane hydraulic roller (PN 104225), which specs out at 208/214 degrees of duration at 0.050-inch tappet lift, 0.438/0.452-inch max lift, and is ground on 112 centers. This cam will give you a slightly noticeable idle, but makes outstanding torque and horsepower to 5,500 rpm where all your components are matched to top out. This package will produce somewhere around 325 lb-ft of torque with headers, and 275 peak horsepower. For a mild 305 this isn’t bad when the base engine you’re starting with was rated at a whopping 170 hp! This might not sound like a ton of power, but it will pull your S-10 around nicely. Good luck with your swap.


It’s only a Name

I read CHP each month and see many articles mentioning LS-type engines. I hope you’ll excuse my ignorance, but what exactly does LS mean? I sort of get cubic-inch numbers, but LS? No clue. Can you help me out?


Erial, NJ

Unfortunately, we refer to all Gen III and Gen IV small-block engines as LS series. This is because the engines are built on the original architecture that was launched with the LS1 engine. As we’re sure you know, earlier small-blocks went by many other designators, and one of the most confusing could be the LT engine family. There was the Gen I LT-1 back in 1970, the Gen II LT1 (without dash!) that came out in 1992, and then the LS engines starting with the 5.7L LS1 in 1997. This was the birth of the LS lineage with the Gen III LS2 coming in the ’05 Corvette displacing 6.0 liters, and the current Gen IV 6.2L LS3 that was debuted in 2008. There have been many engine designators for the LS engines as the L-99, L-92, LS6, L-76, and many others.

B-Car Boogie

I want to add a six-speed manual transmission to my ’96 Impala SS. Could you guys help me find a main pedal bracket kit or give me advice on the best way to go? Thank you, and love your magazine.

Jamario Walker

Columbus, GA

Jamario, you know why GM designated the Impala a B-body? It’s because that they are big, bad, and bodacious! They didn’t come from the factory bodacious, but you can certainly make them that way.

You’re asking for one tall order since GM never offered a manual transmission option in the late B-cars. A few guys have built their own swaps, but we’ve found a company that has done all the hard work for you. Check out B-Body High Performance, which offers a complete trans swap kit that includes the clutch pedal mount for the hydraulic clutch, a clutch pedal, and a modified factory trans crossmember. These components are laser-cut and TIG-welded in fixtures for repeatability. They also include firewall reinforcement brackets to support the added load of the clutch pedal operation. Give B-Body High Performance a call for more information at (941) 6SPEED-1 or check it out online, as B-Body has a ton of photos of the components and swaps preformed by both the company and its customers. Good luck with your Imp!


Pressure Equals Work

I have been pondering this engine setup for years but I want to know if I am correct. I want to build a very high-revving engine with a turbo. It doesn’t matter if it has no low-end torque. The high revs thrill me.

If I take a large-bore block and throw in a very short-stroke crank, using long rods should give a slower piston acceleration while the wider pistons should decrease the chance of detonation because of a lower combustion chamber pressure (at normal atmospheric pressure, no boost).

It seems counterproductive when many stroke their engine to the max. Drive it like you stole it!

Todd Kibbe

Providence, RI

The bottom line is cylinder pressure is cylinder pressure. The larger the bore, the more surface area there is that the same amount of pressure has to push down against the piston crown. The motoring (no cylinder firing) cylinder pressure will be dictated by the swept volume of the cylinder and its parts. The ratio among the swept volume and the combustion chamber, combustion chamber floor (piston crown), head gasket volume, and ring land area around the piston sets the compression ratio. When you then add fuel, air, and spark, you increase the cylinder pressure by extracting heat from the fuel and expanding the air. If you have 1,000 psi of cylinder pressure on a your large-bore/short-stroke combination, versus a small-bore/long-stroke combination, displacing the same cubic inch you still have 1,000 psi in the combustion space. The power will be close in both combinations except for the frictional differences. You could build your combination for your high-revving thrills, but don’t look for reduced detonation threshold from your large bore exercise.

Now for your “counterproductive” statement about stroking your engine. Yes, there is a feasible displacement limit for any engine design. Increasing the displacement on a boosted engine is a great way to make outrageous power. Remember, every time you double atmospheric pressure going into the engine you basically double the output of the engine in a boosted application. Of course, you must control charge temperature, and don’t overstress components to failure. In other words, if you push 14.696 psi of boost into your engine you should expect close to a 100 percent increase in power. This is with a turbo compressor arrangement. With a supercharger you must drive the compressor with power from the engine. It’s going to steal some of your gains.

Let’s just say for numbers you build a 302-cid small-block. At 1.5 hp per cube it will produce 453 hp, naturally aspirated. If you stuff 14.7 psi of boost down its throat, with the proper configuration, you could expect around 800 hp! If you build a 377 small-block with the 4.155-inch bore and 3.48-inch stroke at 1.5 hp/cube that equals 565 hp. Now throw the same one atmosphere at it and you will yield 1,018 hp!

This is a very simplified example of the power potential of boosting an engine. We’ll take the displacement every time if you have the package to control the power. Great questions, and keep on thinking!

Multi-Coil Benefits

I read several magazines every month, but I enjoy your technical question section the most out of any of these. I really have no personal project that caused me to raise this question, just the thoughts that came from all my sources.

I was under the impression that one of the benefits of the LS engine was the individual coil pack for each plug. I have read how having such a setup allows the coil to have longer to recover between fires, which sounds very logical and as a great gain. However, I see some building very aggressive LS motors, but using a Ford distributor and returning the engine back to a single-coil configuration. I was hoping you could shed some light on why this is being done to what I thought was a superior design. Thanks.

Randy Ranloachi

Via email

You’re spot on with your assessment of the multi-coil features and bennies. The coil-near-plug arrangement gives the coils 610-plus degrees of crankshaft rotation to saturate with a fresh 12V charge to be ready for its next high-voltage discharge. It also eliminates the issues with secondary voltage across the distributor cap, rotors, and the long plug wires that have a bad tendency to leak voltage when the load goes up. Electricity will take the easiest path of flow, and if it’s easier to flash voltage over the plug insulator, or around a boot to a header when the cylinder pressure gets high, it will. Also, with individual coils for each cylinder you can control the spark advance to each cylinder. When the detonation sensors see spark knock, they identify which cylinder is having the issue by using the crank position sensor and the cam sensor and pulls out the spark to that individual cylinder until the cylinder has recovered.

Now, back to the engines you’ve seen that have reverted back to a distributor and single coil. Chevrolet Performance designed a front cover assembly to run a standard distributor and mechanical fuel pump for limited stock car application. To this day, some sanctioning bodies are scared of electronics and their inability to police what the competitors are doing with them. The way GM got around this was to create the ability to run a distributor for the carbureted LS engines. Its LS front distributor drive cover is sold under PN 88958679. Using this front cover requires the use of a small-block Ford-style distributor, mechanical fuel pump, special water pump, accessory drive, and damper.

To retain the eight ignition coils on carbureted applications, you can also run an MSD 6LS-2 Ignition Controller for carbureted LS engines. MSD offers two different controllers based on if you have a 58X or 24X crankshaft reluctor ring. These systems are very cool as you can use pre-programmed ignition curves that can be changed by swapping out timing modules, or you can create and download your own custom ignition curve based on your application. The software is supplied with the ignition controller as part of the package.

Thanks for the question; surely you’re not the only one who has noticed a distributor on LS engines. Unless it’s needed to meet some rules requirements, or you’re completely put off by electronics, we would retain all those lovely coils on the valve covers.




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