Free Parts Cost - Performance Q&A

Kevin McClelland Mar 1, 2010 0 Comment(s)

Nothing Is Free
I know I've written this before, but it hit me again: The most expensive parts you will ever get are the ones you get for free. Many times your buddy will help you out with some very cool parts-but they end up being completely wrong for your application and you spend a ton of money to use them. This time, the heads, manifold, headers, and wheels were free so I thought I was safe on this one, but I found a new way to break a lot of parts.

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As you have read in the past, I've had nothing but trouble getting the rings to seal in our Stock Eliminator engine for the wagon. I'm on my fourth build to seal this thing up and I've tried different brands of rings, as well as various cylinder wall treatments to match the "trick of the week" rings. After beating my head against the wall, I've gone back to standard back-cut, low-tension 5/64-inch-wide rings on my pistons. When I was reassembling the engine I was very confident that this was the answer. As I had hoped, the engine sealed right up and all eight spark plugs were dry as a bone. Success ... or so I thought.

We were at the track for our first test day and I noticed an excessive amount of blow-by through the breathers on the valve covers. We made a few passes down the quarter-mile, and it was time to start tuning the engine to find its best performance. With the engine safe on our AEM wideband air/fuel ratio gauge, I decided to advance the timing 4 degrees. The engine has a whopping 9.8:1 compression and is running on Rockett Brand 111-octane racing gas required by NHRA. Past experiences with these engine combinations have shown to make peak power at 42 degrees. So after advancing the timing to 42 degrees we made two runs-with no performance gain. After these runs the blow-by was worse and the engine began to crank through some cylinders. All I could think of is, what have I done now?

On teardown we found that it had broken the top rings on four of the eight pistons! Now, these were standard rings like I had mentioned above. How did the rings break? Sure enough, it came down to one of those free parts. A good friend gave me one of his off-shore SFI-approved lightweight dampers. What I found was that the degreed damper was incorrect. When I build my engines, I set the TDC with a dial indicator on the piston and make a pointer to ensure TDC. However, when I set the timing by the degreed markings on the damper to 38 degrees, it was really 42, which meant I'd advanced the timing from 42 to 46 degrees! All I can figure is that the engine rattled with the 46 degrees of lead and the extreme cylinder pressure broke the back-cut rings.

I thought I'd figured out just about every way to break something, but this was a new one. This is something to think about when you're using off-brand components to save money. If you have to go this route, be sure to always check them over with a fine-tooth comb!

Go Flat When You Can
Q: I have a '70 El Camino with a 350 engine. I had to replace a head gasket and saw it has dished pistons and 187 casting (76cc) heads. I want a bigger cam, but I need more compression. With the compression around 8 to 8.5:1, I was thinking of using ProComp 58cc heads to raise the compression. Which is the better combination: dished pistons with small chamber heads or flat-top pistons with larger chamber heads?
Thanks.

Dennis Stabler
West Hills, CA

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A: We will always go for the flat-top piston and the properly sized combustion chamber for the compression ratio needed for the application. The flat piston crown will give you the most mixture motion when they almost touch the deck surface of the heads at top dead center. The quench area forces the air and fuel into the combustion chamber, mixing the fuel into the air, which gives you a more uniform burn across the chamber.

Does this mean we always do this? Not when you're working around an existing combination like yours. We've built many an engine doing exactly what you are describing with great success. Did it make the most power that it could have made with a properly designed piston? Probably not. But we can't always have our cake and eat it too. Good luck with your little 350.

Solid Bolt-Ons Q: My '71 Chevelle has a 350 and a four-speed. The engine and transmission are out of a '76 Chevy pickup. It's lacking the power I want, so I would like to do some performance upgrades to the engine. I'd also like to use positraction. I would like to keep a budget of around $1,500 to $2,000. Can you help?

Jess Breyer
Madison, MN

A: Your quest is the most popular upgrade around. First, you must have a sound short-block. The short-block of your '76 truck engine must be in very good condition. Also, if there is a ridge at the top of the cylinder bore, you will break the rings when you extend the rpm range of your engine. The bottom end of your engine is built with cast dish pistons and a cast-iron crankshaft. The max engine speed this short-block will live with is about 6,000 rpm. Also, you must keep this engine out of detonation. Nothing kills cast components faster than overspeed and detonation. Please make sure your short-block is a useable victim before installing components that will raise the output by 100-plus horsepower and the engine speed by at least 1,000 rpm.

Once you're confident that you have the building blocks of a nice little small-block, choose your components wisely to stay within your $2,000 budget. Look for an affordable aluminum street head, intake manifold, carburetor, headers, and camshaft package. Your stock truck engine is probably kicking out a whopping 250 hp, and you should get yourself a safe, driveable 350 hp out of the stock short-block. Hopefully, when you installed this engine in your Chevelle you upgraded a few things like headers and dual exhaust. This would save your budget and leave you more to spend on much-needed new hardware.

We've picked a package of components that will not break your budget and really wake up your Chevelle's mild personality. Start with a set of Summit Racing Aluminum Street heads. These feature 170cc inlet ports and 62cc combustion chambers, and are fully assembled with valvesprings that will accommodate a flat-tappet camshaft with a max lift of 0.480 inch. With the 62cc combustion chambers it will kick your compression ratio up to slightly over 9.0:1. These heads matched with a Comp Cams XE268 camshaft and lifter kit PN CL12-242-2, an Edelbrock RPM Air-Gap PN 7501, and an Edelbrock Performer 750-cfm carburetor PN 1407, will round out the top end. To install the aluminum heads you'll need aftermarket head bolts and pushrods. ARP offers a very nice set of affordable head bolts with hardened washers under PN 134-3601. You'll also need hardened pushrods to mate with the guideplates on the new aluminum heads. Check out Comp Cams PN 7812-16 stock-length, 5/16-inch-diameter pushrods. To seal everything up you will need an engine gasket set from Fel-Pro PN QKS2600; this is a complete engine gasket set to give you everything you need for the project at a decent price. Finally, to light your fire, step up your ignition system with an MSD Street Fire HEI PN 8362.

All of these new components come to a grand total of $1,892.70, using Summit's standard everyday prices. From time to time you can find that many of the mail-order houses run discount coupons that can save you up to 30 percent. With the extra couple of dollars you could squeeze in a set of headers and spark plug wires.

For your posi, you'll need to wait and save for the next upgrade. This engine package will give you a very reliable 330-350 hp that will make your Chevelle a whole lot more fun. Enjoy Sources: arp-bolts.com, compcams.com, edelbrock.com, federal-mogul.com, msdignition.com, summitracing.com

Rather Be Blown
Q: I have a 327 small-block Chevy that was built by my local speed shop with a 9:1 CR. I was thinking of installing a blower to the engine, but I don't like the 9:1 CR and would rather go with a 7.5 or 8:1. Other than changing the heads or pistons, what would be a good way to achieve this? The heads are camel-hump 64cc. The shop said the engine would handle the blower, but I have always seen blown engines built with a low compression. The blower I have is a 6-71 with a fuel-injection setup. Before I get creative and do my own thing I would like a little help from you guys.

Freddy Reyes Jr.
Santa Ana, CA

A: First, you didn't tell us what you're trying to do. If this engine is just going into a street rod to impress your friends and have a little fun, the 9:1 compression won't be an issue. Simply underdrive the blower and keep the boost under control. You could easily get away with somewhere around 5 psi of boost with 9:1.

Now, if you're looking to really work the engine, you will want to lower the compression. Yes, dished pistons or larger chambers are the correct way to go. We would go with aluminum heads with 76cc combustion chambers. You will get the added power that a current aluminum head design will give you, plus get your compression in line. This will drop the compression right into the 7.5 to 7.8:1 range. This will allow you to run the boost up and stuff more atmospheres into your little Mouse.

A more affordable way to lower the squeeze would be to go with thicker head gaskets. Cometic will build you custom head gaskets to the thickness you wish. If you used 0.090-inch-thick, 4.100-inch-bore head gaskets, you would pick up 11 cc from the current head gaskets you're probably running. This would be a much cheaper and easier way to lower the compression, but not the most efficient.

The choice is yours. Are you looking for power or pizzazz? If we were building a blown small-block, we'd want our Mouse to roar!
Source: cometic.com

Tale Of Two Temps
Q: My '68 Camaro's 327 engine has a mild build-up of '69 302 heads, a Comp Cams 292 cam, an Edelbrock Performer RPM intake, flat-top pistons, a block deck, balanced, a four-speed, and 4.10:1 gears out back. What is the ideal temperature for the engine for performance and durability? Thank you.

Charles Creed
Mount Airy, NC

A: Great question. For performance you want the engine temps to be low. For longevity and wear you want high temperatures. Go figure. Let's find a compromise.

When you're looking for maximum performance you need to have low engine temps because the heat that is transferred from the cylinder heads and intake manifold into the fresh fuel and air charge lowers the power potential of every cylinder firing. Also, the cooler the combustion chambers, the more spark advance the engine will tolerate before reaching detonation issues.

As for wear and durability, higher engine temps are favorable to boil all the moisture out of the engine oil. When you run lower engine temps and short-duration engine run time, the engine oil doesn't get over 212 degrees F. When the moisture isn't boiled out of the oil it creates acids that attack the metal of the engine and destroy the oil's lubricity. A nice engine oil temp is around 230 degrees F. This is a very safe operating temp for the oil and it can take away the heat from the rotating assembly and pistons. Most of us don't want to know how hot our engine oil is running down the road. A normal passenger car running down the freeway at 70 mph will commonly see a 250-degree oil temp.

For a nice compromise on street driven engines, I like 180-degree thermostats. This is a good balance between engine wear and performance potential. Hope this gives you a little insight into engine temps.

Lacking A Few Liters
Q: I have an '08 Impala with a 3900 V-6. I have been told the police package with the same engine has 300-plus horsepower. Is it possible to get this power out of my engine with some simple modifications, such as a chip? Thank you.

Jim Hershberger
Via email

A: The police-package Impala is equipped with a 5.3L V-8 LS-based engine. This engine produces 303 hp and 323 lb-ft of torque. This little runner is a wolf in sheep's clothing. The Impala SS also has this engine combination and is a very fun car to drive. Knocking down over 25 mpg on the highway and an easy low 15 seconds in the quarter-mile, it's a nice four-door family cruiser. The only thing you need is nice strong arms to hang on to the steering wheel when you stand on the throttle-torque steer can be rather entertaining.

Your 3.9L base engine comes with 233 hp and 240 lb-ft of torque. Very few aftermarket companies offer hop-up components for your powertrain. You can add a K&N air filter PN 33-2334, and MagnaFlow offers an after-cat exhaust system PN 16708 to free up a couple extra ponies. As for performance reprogramming, JET Performance offers a Stage 1 and 2 Power Control Module for your Impala, claiming a gain of up to 25 hp, and it's 50-state legal. Check with JET for more information on these. With these components you'll see a nice bump in your power curve over stock. If that's not enough, trader her in for a V-8.
Sources: jetchip.com, knfilters.com, magnaflow.com

Boy, I've Done It Again!
Q: I'm sure you started a firestorm of controversy about not calling the Gen III/IV "small-blocks." Hopefully, I can help set the record straight.

It definitely was GM's intention to have the Gen III perceived as the next generation of small-block evolution. The catchphrase at the time was: "Maintain the essence of the original SB but do what has to be done to prepare it for the 21st century!" Maintaining the 4.400-inch bore spacing fell into the "essence" category, even though we argued for more. We did manage to sell the bank-to-bank offset change, however, by eliminating the old offset con rods and the left/right piston/rod assemblies.

Your point about the Gen III resembling a Ford Modular was purely coincidental. Our benchmarking group was called the Mona Lisa Project and they did not have a Ford Modular to compare with at that time. I did try to arrange a tour of the Ford Romeo Engine Plant so my team could benchmark their product and processes, but they wouldn't let us in. In the early '90s the Modular was top-secret stuff!

The Gen III was initiated because we felt any further improvements in the Gen I, the Gen Ia, and the Gen II SBs were like picking fly specks out of the pepper. The changes were very expensive and the incremental gains were hard to measure.

It's only a matter of time until the old-style SBs become GM's equivalent of the Ford Flathead.

Don Webb
GM Powertrain
Gen III/IV Design Manager, ret.

A: Many thanks for a very informative letter giving us a view back to the formative years of the LS-based engine family. As we've stated before, the LS-based powerplants are world-class, and we love to make big power with them. We sure wish you guys would have won the battle on the bore spacing. Just think what we could do with, let's say, a 4.600-inch bore spacing!

Yes, the incremental gains that the Gen I/Gen II engine family gave was extremely hard to come by with the emissions requirements and the power bogeys set by the upper management. The Gen III reset the clock on power potential and specific power output.

We're now 23 years since the Gen I was put to bed and 12 years past the Gen II's bedtime. The Ford Flathead was done in passenger car use in the early '50s. The way we see it, we have another 30 years to go before the Gen I makes it to the ranks of the Flattie! Yes, its time will come, and we can't wait to see what "pushrod" small-block The General will have us playing with in the year 2040!

No Replacement For Displacement
Q: How can I upgrade the horsepower of my '03 Silverado 1500 4.8L more than the K&N, throttle body extender, powerchip programmer, and Borla exhaust already on the truck? I know the next step is probably some headers, but what else can I do on a budget? Thanks in advance.

Mike Sullenger
Harlingen, TX

A: As stated in the title, you need some inches. The little 4.8L trying to pull around your '03 Silverado is dying! Adding headers to your small 4.8L engine isn't going to give you as much torque increase as you need to move your truck. We're now about 10 years past the release of the 6.0L truck engine. You can pick up LQ4s and H.O. LQ9s at wrecking yards around the country and drop one in for a little excitement. This would be the most affordable upgrade to give your truck a really noticeable increase. You've added most of the standard bolt-ons. You could add a supercharger, but it would cost more than a used 6.0L engine by a long shot. Also, you could have the swap done in a single weekend.

Check out what's available, and maybe you could find an affordable LQ9. These engines had the highest power rating: 345 hp from the factory. Then you would really have something to build from.

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

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