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Performance Tech Questions - Performance Q & A

Kevin McClelland Aug 1, 2009
0908chp_01_z Performance_tech_questions Water_pump 2/2

Where There's Smoke
A good friend of ours had the misfortune of running into some serious heat. I could change the names to protect the innocent, but you know me: If you break it, you own it. Charlie Allen decided he had enough of Super Gas racing and sold the Vega wagon he'd raced for many years to build a Stock Eliminator car. He chose to build an off-brand car to this book, but his challenges fit any make or model.

At the first race of the season, he brought out his new car and was having a great day. After winning the first round, he was back at the trailer, checking the weather and filling out his log book, when a young kid came up and said, "There is a car on fire out here!" Well, it was an electrical fire burning up the interior of Charlie's new race car. It took three dry chemical fire extinguishers to put it out. The dash was toast, and the windshield was black. The cluster was melted, and all the vent controls were gone. What happened was that when Charlie installed the aftermarket gauges and switches for the electric fan, he had not installed a relay for the load of the cooling fan. The switch overloaded while he was cooling it down, and it caught fire!

This past weekend he was back at the track after many trips to the local Pick-and-Pull for interior parts and pieces. I felt so bad for what happened that I gave our friends at Painless Performance a call and picked Charlie up a six-switch panel and wiring harness. This is a killer wiring kit for race cars and has lit, fuse-protected rocker switches. We also spec'd out a couple of 30-amp relays for the water pump, electric fan, and fuel pump. Most of these power accessories take a good amount of amperage to run, and as temperature goes up, so does amperage demand. Any switch should only be used to trip the relays and let the relay carry all the load of the circuit.

This could have happened to any of us. I know that back in the day I built many cars using switches to carry loads. Over the years we've become accustomed to using electric-powered drives for fans and pumps. Detroit has also made the electric load conversion. You can pick up used relays and connectors at your local wrecking yard; they're all over late-model vehicles, feeding the electric fans, A/C blower motor, and other high-load accessories.

Protect yourself and your car with power relays. The last thing you need is Smokey the Bear to visit your toy with a three-alarm blaze. Be safe out there.

Free And Clear
Q: I love your magazine and the honesty and detail of your answers to readers' questions. I just read the Feb. '09 issue and was interested in a little more information on the roller rocker upgrade. I've got a '68 Camaro with a stock GM crate engine (330 hp, 380 lb-ft), Hooker headers, 21/2-inch exhaust with Flowmasters, a Tremec five-speed, an Edelbrock 600-cfm carb, and 3.07:1 rear gears. I took it on the Hot Rod Power Tour this year and averaged 23 mpg! Would the rockers mentioned in the article work on my engine without fear of hitting the pistons? Also, what improvements would I see in power and torque? What else can I do to the engine without pulling it apart to get me up around 345-350 hp? Thanks!
Duane Courteau
Dayton, MN

A: Nice mileage! Years ago we stuffed a ZZ4 in a '67 Camaro Pace Car Convertible with 3.08s and a TH700-R4. It knocked down 21 mph on the Power Tour without even trying. This was with a Holley 750 double-pumper right out of the box! There are some easy ponies to be had out of your engine. Let's talk.

The 1.6 ratio roller rockers will increase the max lift around 0.030 inch. This would put the exhaust valve max lift on your engine at 0.490 inch. The factory dish pistons with valve reliefs in your engine will accept this with plenty of room to spare. Max lift isn't where the problem lies with increased lift. It's right around top dead center (about 12 degrees either side), when the engine is in overlap. This is between the exhaust stroke and the intake stroke. When you increase the duration or tighten the lobe separation angle, this is when the valves get closer to the pistons. Increasing the duration opens the valves earlier relative to the piston location. Using the stock 330hp camshaft with its 212/222 degrees of duration at 0.050 inch lift is very mild, and you have a ton of piston-to-valve clearance.

We really like the GM Performance Parts 1.6 ratio rockers (PN 12370839 for the kit). The rocker body is the same design that GM used on the one-year LT4 Corvette engine. This is the only production small-block that came with aluminum roller rockers. The body was a proprietary extrusion, and the machining of the slot in the body for the rocker stud was kept to a minimum to reduce flexing. These rockers will only accept a max lift of 0.570 inches before the rocker body will crash into the rocker stud. They are perfect for mild street camshafts. It's important to note that they are a self-aligning design, which works perfectly with the Vortec cylinder heads. Also, they have a special posi-lock that is very short and will clear the stock valve covers. This rocker swap will give your 330hp engine an extra 10 ponies easily.

As for the extra 5 or 10 hp, the 330hp deluxe engine comes with a GM Performance Parts inlet manifold that is great for low- and midrange torque. If you swapped to an Air Gap-style, high-rise dual-plane you'll find your other 10 hp. Both Edelbrock and Weiand have great manifolds to choose from. Either the Edelbrock RPM Air Gap Vortec PN 7516 or the Weiand Stealth Air Strike PN 8502 will give you the extra power you're looking for as an easy bolt-on.

Both these modifications will help the power without killing the great gas mileage you knocked down on the Power Tour. Simple bolt-ons are always a great addition to any crate engine. Have fun with your Camaro.Sources:,

Double Trouble
Q: Over the years you have spoken of the good luck you've had with a 502, and it prompted me to write. I have purchased a 502 H.O. for use in my motorhome. Previously I had a 496 with very good results, until an intake valve broke and trashed the engine.

What kind of oil do you prefer? Petroleum or synthetic? Straight weight or multi? Ask 10 people and get 10 different answers! I want the best for my new engine! The motorhome is 18,000 pounds and I tow a 4,000-pound Jeep. The engine lives at 3,200 rpm at 65 mph, and I only use it in the summer, no cold weather. Also, the engine is being broken in and tuned on a dyno, and my guys says Joe Gibbs break-in oil is the best for break-in. What do you think?

Finally, what causes a valve to break? The stem is still in the head with spring and keeper in the same place? My mechanic says valves sometime break. Never heard of this before! Thanking you in advance.

Oh, and a word from my wife. Prior to rebuilding the stock 454, which lasted 120,000 miles with little trouble, we spent $5,000 for the 496ci. With good components, including valves, rings, sparkplug wires, heads, and manifold, the 496 lasted less than 10,000 miles. Talk about modifications! Can all that hurt reliability?
Kitty and Will Grosse
Ingleside, IL

A: First of all, I've felt your pain. We've built up engines that should have been bulletproof and run forever. I've built engines for my friends before, and one in particular ran for about 5,000 miles in his 1/2-ton work truck before breaking the crankshaft! The engine still ran, and he drove it to my house just fine but with a loud knock. Pieces can and do fail without warning. Can we push them too far and cause them to fail? Absolutely! Mixing the wrong components can cause parts to fatigue and break before their time. With your 496 it sounds like it was purpose-built for RV use and mild components that were properly utilized. As the mechanic said, sometimes valves do break.

The 502 H.O. should be an interesting engine for your motorhome. If you purchased the engine new it will be a Gen VI big-block with the hydraulic roller camshaft. These engines have been durability-tested back in Detroit, and the components will live a long and happy life.

Since the engine has a roller camshaft, you have some latitude on your oil choice. Joe Gibbs is a very good break-in oil with high-shear additives for break-in. I've been really happy with Delo 400 LE 15W-40 Chevron diesel engine oil for my engines for performance use. This new engine oil was released in 2007 with the advent of low-sulfur diesel fuel and the low-emissions diesel engines. Its applications have spread from diesel-only oil to high-speed four-stroke gas engines. It has an API (Automotive Petroleum Industry) rating of CJ-4. Even though the oil is low in emissions, it still carries a good amount of phosphorus and zinc, the high-shear additives that have been stripped from our standard gas motor oil. These levels aren't as high as previous Delo oils but help with flat-tappet camshaft wear and sliding contact components. It will take the high loads and temperatures of your motorhome use.

A couple of tips for your installation. First, you must us a melonized steel distributor gear on your HEI ignition. This gear must be used to mate with the billet-steel hydraulic roller camshaft in your 502 H.O. This gear has very close tolerances on its machining and has a secondary coating operation to prevent wear. These gears were used on all GM roller camshaft engines. You can pick one up from any GM dealer under PN 10456413. Second, keep the engine speed to a minimum until the engine oil has come up to temperature. There is a great amount of load on this gear during cold starts, when the oil pressure is highest. Third, keep that thing cool. The 502 blocks are a Siamese bore design, which means there is no coolant passing between the cylinder bores. These blocks have thick cylinder walls and will run cool as long as your system has the capacity. Finally, your motorhome should have had some type of engine oil cooling system. Either the engine oil was plumbed through one of the radiator tanks or had an external cooler. We would look to install an external cooler to keep the engine oil at a nice 200 degrees. Getting that cooling load off the radiator will free up some capacity for the engine coolant. Check with Fluidyne for very nice air-to-oil coolers that will pull the heat out of the oil; you can plumb the universal kit into your system.

Good luck with your traveling home. Hope the new 502 power will pull your 22,000 pounds down the road like you expect.

Roller Tappet Swap
Q: My '66 Chevy II SS bracket car is equipped with a moderate 383ci small-block featuring a forged Eagle rotating assembly with 6-inch rods, 10.3:1 forged flat-top pistons, fully massaged 186 casting heads, a port-matched Victor Jr. intake, and a 750-cfm Holley double-pumper. The cam is a solid-lifter Lunati that specs out at 0.530/0.550 inch max lift with 242/244 duration at 0.050 inch lift. I want to "detune" the car enough to be able to drive and enjoy it during the off-season.

Can I successfully replace the solid lifters with hydraulic roller lifters, install hydraulic-compatible valvesprings, and tweak the carb to accomplish a drivable tune-up? The car weighs approximately 3,000 pounds and has a TH350 and a 2,800-stall, a 4.88:1 posi, and MT 28x11.5-15 ET Streets. Is this approach practical? Thanks.
Randy Rowland
Via e-mail

A: Nice plan, but tough to execute. The cast iron that your flat-tappet camshaft is made from would be torn up by the hardened hydraulic roller tappets. Mechanical roller camshafts manufactured by Crane are commonly made out of 8620 billet steel and then Carburized, which means heat-treating the camshaft cores in large ovens to 1,650 degrees F over 46 hours in a high-carbon-content atmosphere. Then the camshaft is air-quenched for eight hours. This raises the hardness of the material to a 58-62 Rockwell "C" scale hardness. This makes the lobes very hard, but have you ever noticed there is a copper color between the lobes? This copper coating is on the shaft to protect the core of the cam from the Carburizing, allowing the shaft to flex without breaking.

I know this sound like a lot of work, but have you thought about building a nice 350hp small-block 350 to swap into your Nova during the cruising months? If you think about it, replacing lifters, swapping out springs, and retuning the car for different driving can take a bit of time. If you dress both engines with the components needed to do a quick swap, it could be less time to switch out the engine when needed. This is what we've done with our Malibu Wagon. We have the Stock Eliminator-legal drivetrain (engine and trans), and we have our bracket package (pump-gas small-block and Powerglide). Switching over the drivetrains takes less than a day and keeps the wear and tear to a minimum on the Stocker pieces. That engine combination has a set life expectancy, and the bracket 350 should give us at least 10 years of trouble-free racing.

Initially, having two packages sounds like a lot of money. But over the long haul it will save you time and money on your race engine. Look into it; you may be able to pick up someone's crate 350 lying around for the right price. Just another idea. Good luck.Source:

Missing Something
Q: My '91 RS Camaro needed a trans, so I picked one up from a bud for a buck! It was out of a '91 Caprice. I installed it without realizing the Camaro had an electric speedometer and the Caprice is cable-driven. I don't want to swap out the trans again, so is there an easy fix? Thanks.
Richard Gall
Palatka, FL

A: A buck? I want to know where to find deals like this today. Fixing this is as easy as can be. To install the Caprice trans in your Camaro, you must have swapped out the extension (tailhousing) off your original Camaro transmission. The torque arm that comes from the rearend connects to the transmission at the tailhousing. The Caprice trans wouldn't have had the bolt holes to attach the torque arm mount. The electric speedometer signal generator is installed into the extension housing, and there is a matching 17-tooth Red speedo gear on the output shaft to drive this generator. All you need to do is remove the speedo drive gear from the original Camaro transmission and replace the drive gear on your Caprice trans output shaft. Once you mate up the correct speedo drive gear with the signal generator in the tailhousing, you should be back in business. If you've tossed the original trans and you don't have the drive gear needed, it is sold under PN 1246221.

H2O Pump
Q: I'm building a 383 stroker for my first engine build and looking to make just over 400 hp/torque. What factors dictate whether to use a long or short water pump? I can't find an answer online in my short search. The engine is going into a '82 Camaro. I'm planning to have some fun with the car, but it will also be my daily driver. Thank you.
Perry Evison
Abbotsford, British Columbia, Canada

A: There is a very short answer to your question. You will want to use the pump that matches your accessory drive system. The '82 Camaro front dress utilizes the long-style water pump. GM switched from short to long water pumps back in 1969 on small-block engines. The only vehicles that stuck with the short pump were Corvettes and pickup trucks.

The only other hiccup you may see is when you run serpentine beltdrive accessory drive systems. All the factory serpentine systems on small-block engines used a reverse-rotation water pump. If you were unlucky enough to install the wrong pump on a reverse-rotation system, you would have major heating issues. Stick with the pump that the General designed the system around, and you won't have a problem. Enjoy your 383!

Fuel-Sipping Small-Block
Q: I am looking to replace the 350 engine in my street rod. I drive the car on long trips and would like to build an engine that will give me better gas mileage. I want to build a one-piece rear main 265 small-block to put in a 3,000-pound street rod with a TH700-R4 and 3.42:1 rear gears. I have an excellent source for good engine cores. I recently purchased a 3.00-inch-stroke crank, 5.94-inch-long rods, and flat-top pistons out of a '94 L99 LT1-type engine. I also have a nice 305ci one-piece rear main block (the same bore as the 265ci engine). The heads I'm planning to use are casting number 471513 with 1.74/1.50-inch valves. I have opened up the combustion chambers around the valves to end up with 55cc chambers, which should give me about 8.8:1 compression with thin head gaskets.

I also have several stock roller camshafts to choose from: 350 ramjet, L99, stock 305 Vortec, stock 350 Vortec. I'm leaning toward the RamJet cam with the 109 LSA. Is there an aftermarket roller cam that will work well? I have an Edelbrock Performer intake or an Edlebrock SP2P economy intake, with which I plan on using a 600-cfm 1406 Edelbrock carb. Would a Q-jet or 500-cfm Edelbrock work better? I will use 11/2-inch Block Hugger headers and will not need to spin the engine over 4,500 rpm.

Another thought I had was to build a 302ci using a 350 one-piece rear main block. Will I lose much mileage over the 265 engine? I don't remember anyone building a 302 for low-end torque and mileage. Thanks for your help.
Jim Martin
Hutchinson, KS

A: No, we can't think of anyone building a high-torque 302. Many people have built up engines by swapping out parts from all the engines that Chevy built over the years. Let's take a look at a few specifics.

First, the stock bore on a 305 is 3.736 inches, while on the 265 it is 3.750 inches. You can take your good core 305 block and have it overbored for the 265 pistons. This will give you a fresh cylinder wall for the new rings to seat against.

The rest of your plan is quite solid. The cylinder heads you've chosen are from a quite rare 267 small-block built only for the '79 model year. This was GM's test at making a very clean smog engine for the lightweight Monzas. The engine was weak in every respect! It had a very small 3.500-inch bore with the standard 305/350 stroke of 3.48 inches. Choking the engine down with such a small bore was its downfall. If you are going to use these heads, we suggest having the ports massaged in the bowl area and the short side. This won't increase the port size by much but will pick up the flow by 10 percent. This will help efficiency in every way from mileage to making power.

From the camshafts you listed, we'd go with the RamJet camshaft also. The cam is relatively short at 196/206 duration at 0.050 inch tappet lift, 0.431/0.451 inch max lift with 1.5 ratio rockers, ground on 109 centers, with the intake installed at 104 degrees. The tight centers with the advanced intake lobe will build good cylinder pressure, with your little engine giving it some snap.

Where on earth did you dig up an SP2P inlet manifold? I spent a lot of time with this manifold back in the day at Edelbrock. We designed that manifold with cross-sectional area runners of two different sizes to broaden the torque curve. The upper plane is the small runners, and the lower plane is the larger. Don't go and port-match the runners because it will just shorten up the length of the small runner. These manifolds were designed to run on 305/350-cid engines and will feed your 265 quite well.

As for mixers, we'd choose one of the later (late '70s, early '80s) 650-cfm Q-jets. They have very small primary bores and venturies. This will work well with the signal from your baby Mouse. If you can keep your foot out of it, you should see the best mileage from the Q-jet combination.

Building compression is always tough in small-displacement engines. Once you have unshrouded your valves by opening up the chambers, clip the heads to get the chambers back down. We'd shoot for 9:1, or more if you can. Increasing the compression is going to be free mileage, and you would be safe up to 9.5:1.

Hope these tips give you some ideas for your Mouse. Make sure you go out and stretch its legs every once in a while. You will be surprised how well this engine is going to run. Good luck and happy cruising.

Technical questions for Kevin McClelland can be sent to him at



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