July 2011 Chevy High Performance Q&A

Kevin McClelland Jun 6, 2011 0 Comment(s)
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LS Engine Heaven

1107chp 01 O  July 2011 Performance Q A Engine Drawing 2/2

Last month I wrote about finally finishing my Super Gas roadster and having a great first outing at a local race in Fontana, California. Now, the garage is full of LS engine parts. As I mentioned several months ago, my son, Daniel, is installing an LS2 in his ’94 Mazda RX7, but the motor was dead on arrival. We were originally hoping to swap out some performance parts and drop it right into his car; the engine was from a 42,000-mile ’06 GTO that looked like the oil had never been changed, and it was on its second set of tires that were bald when we got it. Once we pulled the engine apart, we found that the top of every cylinder was out-of-round and was letting a tremendous amount of cylinder pressure past the rings; not only were compression gases going past the rings, a ton of oil was getting into the combustion chamber.

To remedy this, we picked up a complete 4-inch stroker kit from Livernois Motorsports. They use only high-quality Callies forged crankshafts, H-beam rods with ARP 2000 bolts, Diamond pistons, Total Seal rings, and Clevite Tri-Armor Coated Bearings. We’ve mic’d all the critical dimensions and everything was dead on spec. We’re currently in the process of fitting the rod and main bearings to bring the oil clearance at 0.0025 inches on the rods. We did experience a minor setback when we went to set up the mains. After installing the ARP main stud kit and torquing everything, we used our dial bore gauge to make sure that the main housing bores were within spec. We should have expected it since we knew the condition of the GTO, but the main housings were 0.001 inch over the maximum tolerance and worse yet, the rear main was over 0.001 inch out of round. We ran the block out to Jim Grubbs Motorsports last week for a quick align hone to bring the main bore into spec and to hone the block out 0.005 inches to match the oversized pistons. At JGM, they have gone through the expense and trouble to use two torque plates on all eight cylinders to fully stress the tops of the cylinder block before honing to ensure perfectly round cylinder walls for great ring seal.

With my roadster out of the way it’s time to get the 6.2L L92 into our Malibu wagon. I’ve already ripped the heads off, picked up a full set of Manley hollow stem valves, and sent the heads off to get CNC ported; we baselined the stock heads on my flow bench and I can’t wait to see the increases with the porting. I have the engine swap kit and headers coming from Muscle Rods, and all the oil system components needed coming, so between Daniel’s engine and the wagon repower, we’re going to be burning the midnight oil. Come by and check to see if the lights are on.

Too High

Q: I am swapping out my 396 ci with a 496ci big-block in my ’69 Chevy Camaro. The old engine header tubes on the driver side are partially collapsed to allow clearance from the steering box. I decided to buy new headers for the fresh engine and was informed that the headers should not have to be modified whatsoever to clear the steering box. As a side note, I think the original engine was a small-block. I was also told that the current 396 ci is probably using the small-block motor mounts that came with the car. That said, I purchased new engine frame mounts and made sure they were correct for the big-block. The old frame mounts are in a different set of holes and I see the hole that lines up with the new frame mounts. My question, or problem, is that the new big-block mounts are two different sizes; one is taller than the other that mounts to the frame of the car. What side gets the taller mount? Is it the driver side or the passenger side?

Dave Mock
Via email

A: The difference in heights moves the engine over to the right side of the engine bay for header clearance around the steering box and clutch cross-shaft. The taller frame mount is installed in the left side (driver side). This gives you the correct header clearance. The engine isolators (motor mounts) are both the same thickness for the big-block. The frame mounts may look like they are two different heights, but when bolted in the engine bay and the engine sitting on them, the height difference just moves the engine over; the engine will sit level in the car.

Good luck with your Camaro. The first thing that I would do as soon as it’s running is buy stock in your favorite tire company. The rear tires aren’t going to last long my friend! Good luck.

Source: summitracing.com

Go Stock

Q: I hope that you can give me a little help on figuring out what the estimated horsepower would be and what I will need for a torque converter. I have a ’68 El Camino SS 396 with 350 hp and 415 lb-ft of torque big-block. The engine was rebuilt to stock specs about 3,000 miles ago. Here’s what I’ve done so far: Edelbrock 2161 intake, 1411 carb, 2162 cam, 5895 valvesprings, and 7810 timing chain, DUI HEI distributor, Hedman 68196 headers with 3-inch Flowmaster stainless exhaust, and TCI 700-R4 trans (rated for 450hp max). The rearend has 3:73:1 gears, posi, and Strange axles with C-clip eliminators. I don’t plan to race it; I built it to show off at our local cruise nights.

Martin Walter
Griffith, IN

A: What a nice cruiser! The ’68 was the first year of the new Chevelle/Malibu body style for the A-bodies. The Chevelles really grew up from the ’64-65 and ’66-67 body styles. I was lucky enough to have a ’69 SS 396 Malibu convertible for several years. To this day, my wife still reminds me that we should have never sold that car, but that is another story.

Your engine build will give you years of service and the Edelbrock Power Package that you’ve installed will give you great torque and horsepower to the 5,000- to 5,500-rpm range. The Performer 2162 camshaft specs out at 218/228 degrees of duration at 0.050 inches tappet lift, 0.500 inches max lift on a 114-separation angle. This camshaft will deliver a very smooth idle and great torque from the crack of the throttle. That said, a stock stall speed converter or the tightest performance aftermarket converter will give you excellent driveability with your low 3.06 first gear in the 700-R4.

As for horsepower, I assume you’re running the stock closed chamber oval port heads with the slightly domed pistons, which gave you 10.25:1 compression ratio from the factory. With the addition of the Edelbrock Power Package, Hedman headers with 3-inch Flowmaster exhaust, I would peg your horsepower right in the 400hp range. The torque should come in right around 410 to 420 lb-ft of torque, and the torque curve should be about as flat as a tabletop. Don’t be afraid to stop by your local dragstrip and make a few passes. You will really enjoy the rush and you won’t have to worry about any red lights in your rearview mirror! Enjoy!

On Your Own or With the Pros?

Q: OK, I have a few questions to ask the pros. I’m currently deployed in Iraq and have a ’72 Nova sitting at home. It has a tired two-barrel two-bolt 350 in it. Of course this won’t do, and I want a replacement. My question is should I go long-block GM crate and Vortec heads with the addition of my cam and intake? On the other hand, should I buy parts and have a local machine shop throw together a 383 with parts I have selected? Going that route would be cheaper, but I’m not sure which one will last longer. Lastly, the YearOne $3,000 small-block looks like it would be a good contender. Please, any and all advice on this would be greatly appreciated.

CW2 Bryan Bartucci, UH-60 Pilot
Balad Air Base, Iraq

A: Bryan, thank you for your service to our country. I am sure that you have plenty of time to think up all kinds of horsepower packages. From the way you asked your question it sounds like you would be completely comfortable screwing together your own small-block. There is a lot of satisfaction in building your own engine and the thrill of standing on the throttle for the first time. Yes, you can build a very high-quality 383 on your own with the help of a quality machine shop. The parts are readily available for any power package you can dream up. On the other hand, many very high-quality rebuilt crate engines are on the market.

You mentioned the YearOne crate engine, which is one of the better ones. This crate is based on a four-bolt main 350 block, nodular iron crank, powdered metal rods, hypereutectic aluminum pistons that spec out at a pump gas–friendly 9.5:1. The cylinder heads are Vortec casting, which have been ported featuring 2.02/1.60-inch valves, 1.6 stamped steel rockers, and heavy-duty valvesprings to control a hydraulic roller camshaft spec’ing out at 218/228 at 0.050-inch tappet lift and 0.520 max lift. The engine comes complete from dual plane air-gap–type manifold to oil pan. The engine is dyno tested and comes with a dyno sheet from your engine. These engines produce over 400 hp and 400 lb-ft of torque. I’ve run similar engines that have easily made upwards of 415 for horsepower. You would be hard pressed to rebuild your own engine with all of these components for its $2,989 selling price. You can pick up this outstanding bargain under PN CT350PC1. YearOne offers many crate small-blocks, ranging from this economical stormer up to 383s producing 500 hp and 480 lb-ft of torque for just under $5,000.

It’s all up to you. If you have a machine shop in your area at home that you trust to produce high-quality machine work you just may have to build your own engine. Before you take the plunge, make sure that you’ve sharpened your pencil and done the math on every part you will need. YearOne builds these engines in quantities that really bring the price down. Get home soon safe and sound to inject some power into your Nova.

Source: yearone.com

Early Start for the Apache

Q: I am 16 and want to pump up my 327 in my ’56 Apache. I am on a very tight budget here, but don’t want to cut corners. I just need some help picking out some major parts, like the rotating assembly, heads, and valvetrain components. I’m looking to make around 400 hp and plan on using a factory block. For a rotating assembly, I’m looking at Eagle Specialty Products PN 1310200 from Summit, and for lungs, I plan on using a set of Competition Products aluminum heads that you guys tested a while back. This is where I’m a bit confused. I want a really nasty-sounding idle, but I do have to run power brakes and steering, and, if it helps, I have a 700-R4 auto trans. I am willing to put any stall converter to accommodate the cam. So I am a little lost on what I should buy. Lastly, what size carb should I have on top of my Edelbrock RPM Air-Gap manifold? This is mostly going to be a street motor and will see the dragstrip occasionally. I would love to run down those Mustangs without a sweat. If you can help me out that would be awesome and thanks for your time!

Griffin
Via email

A: Adding ponies to your Apache truck is the easy part. Now, making it stop and turn is a whole other topic. The straight axle front end and drum brakes all around make quite a ride. Don’t just spend all your money in making the thing a rocket. As I said earlier, it’s easy to buy parts and make them fly. Just remember that you need to stop somehow, and you don’t want it to be a tree!

First of all, the Eagle rotating assembly (PN 1310200) that you listed above is for increasing the displacement of a 305-cid small-block. It uses a stock 305 bore of 3.736 inches and adds a 3.75 stroke (400 small-block) crankshaft to produce 329 cid. Your 327 comes with a factory bore size of 4 inches and swings a 3-inch stroke. Your 327 Eagle has a complete forged rotating assembly under PN 12040030 that is equipped with SRP flat-top forged pistons. They also offer a kit (PN B12041030) that comes with an SRP forged 7cc dome piston that matches the original 10.25:1 compression ratio for the 327. Unfortunately, these kits are quite a bit more expensive than the cast component equipped assembly that you’ve been looking at. They are great packages that come with all components youwill need with bearings, file-fit moly rings, H-beam forged rods, and a two-piece seal forged crankshaft.

If you’re looking to wring out 400 ponies from your 327 you can get there with some of your stock components. Most of the early 327s came equipped with forged cranks from the factory. You could pick up a set of Eagle 5.7-inch rods and a set of SRP forged pistons for the price of the engine kit you listed. The machine work will be the same with this route or the Eagle assembly.

Since we’re talking about machine work, cutting 0.030 inch off the deck may be a little much. You will need to mock up the rotating assembly after the block has been overbored to your new piston size. Slide in your crank and a rod and piston in the four-corner cylinder numbers 1,2,7, and 8. With these pistons installed, rotate the engine to top dead center on the four corner cylinders and measure down to the piston from the deck. You should see that the pistons are somewhere around 0.015 to 0.022 inch down in the hole. By measuring all four corners you can give the machinist those depths, and they will be able to square up the deck height. We would cut the deck to bring the piston right up to the deck surface. This, with a 0.041-inch-thick head gasket, will give you the best quench.

A camshaft with a really nasty-sounding idle and idle vacuum cannot be used in the same sentence. To give your little Mouse a nasty idle you will kill the idle vacuum down to the point that the power brakes are pointless. Years ago, we did a little test to see how much torque it took to drive all the power accessories on the front of a small-block installed in an ’87 Camaro. It was driving the water pump, alternator, P/S pump, and the A/C pulley that wasn’t engaged. We also had the transmission in drive range sitting still. At 650 rpm the engine had to produce 45 lb-ft of torque to maintain 650 rpm. We measured this with an engine we had installed in the Camaro that had too much camshaft. We measured the idle vacuum at 650 rpm. Then we removed the engine and installed it on an engine dyno. To find the torque required we ran the engine up and applied load to the engine at 650 rpm until we reached the vacuum that we saw in the vehicle. With this amount of load, it required the engine to produce 45 lb-ft of torque. When you think of that amount of load at 650 rpm you can see why a large camshaft can cause havoc.

How about we reach a compromise? Since you’re running a smaller (by today’s standards) engine let’s go with a less aggressive camshaft. The Xtreme Energy 268 (PN 12-242-2) would be a good compromise for your little 327. It will give you a nice chop at idle and just enough idle vacuum for your power accessories. The camshaft specs out at 224/230 duration at 0.050 inch of tappet lift, 0.477/0.480 inch max lift, and is ground on 110 centers. This is the max that I would recommend for your little Apache.

Finally, a nice 2,400-stall converter would work just fine with this camshaft and your 700-R4 trans to get into the meat of the torque curve. As for a carb, I recommend going with a Holley 650 double-pumper carb. (The list number for this carb will be a 1-4777.) You may be able to pick one up at a swap meet or from one of your friends. They have been around forever and with a quick rebuild, they will give you many more years of service. Good luck with your Mustang-hunting Apache.

Sources: compcams.com, holley.com, summitracing.com

It’s a Drain

Q: I have a ’68 small-block in my ’55 Chevy. I am using a recently rebuilt Q-jet from around 1973. I am using a stock fuel pump and have changed it, but I am still getting the same results. What happens is when the car sits for several days the gas drains back to the tank. I disconnected the fuel line, and it doesn’t drain from the carb. I am using a stock fuel tank. Any idea why the gas drains back? It requires extra cranking each time. Thanks for any help.

Jim Baker
Dover, OH

A: Fuel drain back from the Rochester Q-jet has been a problem just about from their first introduction. The fuel isn’t draining back through the fuel pump; it’s draining through the carburetor. There are “Well Plugs” that are in the bottom of the main wells and secondary feed wells on the bottom of the main body of the carb. These plugs are made from lead on the primary main wells, and aluminum on the secondary side. These plugs are driven into the main body at the factory and over time they become slightly loose and leak very small amounts of fuel past them. Usually they don’t leak enough fuel to affect the performance of the engine. However, after the vehicle sits for several days the fuel will slowly drain down into the intake manifold and evaporate. Between natural evaporation out the main bowl vents and the slow leak, there is no fuel for the engine to start on until the fuel pump can fill the float bowl.

You can remedy this problem by rebuilding your carburetor and lightly peening the well plugs back into place with a small ball-peen hammer. You will then want to seal them with a coating of either epoxy or JB Weld. This will help seal up and keep the plugs in place. If you’re not comfortable doing this yourself you can ship your Q-jet out to Jet Performance in SoCal and have them do a performance rebuild. They correct this drain back problem with their standard performance rebuild.

Source: jetchip.com

Too Cool For School!

Q: I’d like to run a quad exhaust on my Chevelle. I found an Australian site that goes by cross-sectional area. If my calculations are correct, does that mean for a 21/4-inch single pipe after muffler I would want dual 13/4-inch pipe on each side of the car? Any information would be much appreciated. I just don’t want to plug the engine up.

Jason
Phoenix, AZ

A: You’re spot-on by using the cross-sectional area to calculate the area needed to evacuate one larger pipe with two smaller pipes. The formula to find the area of a tube is pi r2 (the radius—half the diameter—of the inside of the tubing, squared and then multiplied by 3.1416). This will provide you with the cross-sectional area in square inches (in2).

Most muffler tubing in 2.25-inch od is 0.065-inch wall thickness. You need to subtract the 0.130 inches of wall thickness, which brings you down to an id of 2.120 inches. This gives you a true area of the inside of the tube at 3.53 in2. You mentioned using 1.750-inch tubing for your quad tailpipes. Most 1.750-inch tubing you will find will be 18-gauge wall thickness. This has a nominal wall thickness of 0.049 inch. If we do the area calculation on the 18-gauge 1.750-inch tubing, you come out with a cross-sectional area of 2.14 in2. When you double the area (because of the dual tubes), you have an area of 4.28 in2. As you can see, this is well over the single pipe feeding your dual tubes. If you go with 1.625 × 0.049-inch tubing for your duals, you have a combined area of 3.66 in2. This would support your 2.25-inch feeder tailpipe with no problem.

Building unique cars is what this hobby is all about. Making your car different from the other guy’s or gal’s is where the fun is. Enjoy your peashooters! CHP

Technical questions for Kevin McClelland can be sent to him at chevyhi@sorc.com.

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