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April 2012 Chevy High Performance Q&A

Kevin McClelland Feb 22, 2012

We love letters, especially technical questions. Submit your tech questions to Kevin McClelland at Regular shout-outs and good tidings are also always welcome.

Winning’s Everything!

We got a call this week from our good friend Ian Smith in Australia. You may remember the name from previous columns. He came up over the Thanksgiving holiday last year to go to the Las Vegas ET Bracket Nationals. He experienced racing with the McClelland clan and sponged up information on how they put on such a large bracket race. Ian and his son, Warren, also race a Super Gas Beretta at their meetings in Australia. Back to the call: Ian could barely contain himself. They had just won the Fuchs Australian Nationals in Sydney! For them, this would be like winning the U.S. National in Indy! In 2003, Warren won the National Championship in Super Gas, but they had never won a race. Ian has been racing for over 39 years, and about 15 years ago Warren took over the helm of the race car. Ian served as the Australian National Drag Racing Association Chairman for 10 years, and as Calder Park Raceway’s meeting director during the sport’s heyday through the ’90s. Ian was recognized in 2000 by the government when he was awarded an Australian Sports Medal.

The bottom line is you won’t find a more deserving bunch on the planet. You might think it’s an easy feat to win a National in Australia. Well, Warren was the number-one qualifier, and in the final round won on a holeshot with an e.t. of 9.908 to his opponent’s 9.903! That, my friends, is some tight racing, I don’t care which side of the planet you’re on. I’ve had the pleasure of helping them with their racing endeavors since 2002. We were put together by the NHRA just as Ian had retired from the ANDRA. Ian and Warren were just learning about throttle stops and the finer points of racing Super Gas.

chp 02 O  April 2012 Chevy High Performance Qa Drawing 2/2

Their car is a righthand-drive Chevy Beretta that was originally built for their competition eliminator class in Australia. The car was a roller when they picked it up; the previous owner was running a blown small-block and a clutchless manual trans. Ian quickly purchased one of the first Reher Morrison Super Series crate racing engines in the early ’00s. The car runs 9.90 at 148 mph.

Talk about die-hard racers. We complain from time to time here in the States about the amount of travel for us to follow a series. For Ian and Warren to follow the racing circuit in Australia, they regularly travel a 1,000 miles to hit a race. The closest eighth-mile track to their house is over three hours away. They are a dedicated racing family who I’m very proud to know. Enjoy the afterglow of your win, Ian and Warren!

Engine Dyno Information

I enjoy reading your tech articles and thought I would ask you a few question. My ’68 Chevelle has undergone various stages of builds, since I was 16, to my current build at age 56. I am probably one of the few who actually kept their first car. As I have aged, so has my taste; I went from an eight-track tape player and air shocks to a Pro Touring street car. I have gone from a 307ci two-speed auto trans to a 327 ci with a four-speed to a 377 ci to my current build 434ci small-block with a planned five-speed and a 3.55:1 rearend gear, turning a 28-inch tire.

I have several questions about my dyno results. I dyno-tested my 434ci build and noticed the horsepower and torque curves cross at approximately 5,300 rpm. I asked my builder about it and he said it’s true for all engines. I have read articles with true values, not inflated torque and horsepower values and found this to be true. Why is this?

With regard to inflated dyno numbers, my operator said his machine is very tight. If I wanted higher numbers I should go to a shop, [a name he gave me], and I can expect much higher readings. Isn’t horsepower and torque the same no matter where you go? Horsepower and torque are mathematical formulas with set parameters—there shouldn’t be a difference.

I am curious on my cam choice. I purchased a solid roller cam from Crower (PN CA-56171) with 230/238 degrees duration at 0.050-inch tappet lift, and 0.340/0.355-inch lobe lift. I used 1.6:1 rocker arms. This is set on top of 210 AFR heads with a 10.6 COMP ratio. The intake is an Edelbrock Victor with a Holley 750-cfm mechanical secondary double-pumper. It has 13/4-inch headers, and the car is approx 3,500 pounds. The majority of my driving will be below 5,000 rpm. Would changing lifts or duration have helped with more torque and horsepower? My dyno numbers are as follows: at 2,700 rpm, 498 lb-ft, to 5,100 rpm, 494 lb-ft; max torque was 528 lb-ft at 3,700 rpm. Max horsepower of 483 occurred between 5,300 and 5,500 rpm.

H. LeRoy Thomas
Chico, CA

Let’s go in order with your questions. Most engine dynos use a water brake to apply load to the engine to either control the acceleration of the engine or hold the engine speed at a fixed rpm. Whichever style of testing, there is a strain gauge attached to the brake that reads out the amount of torque applied to the brake. This measurement is expressed in lb-ft. To derive a horsepower number from this, you must do a little math. The formula for horsepower is: torque × 5,252 ÷ engine speed = horsepower. The 5,252 is the constant in the equation, and this is why horsepower and torque always cross at 5,252 rpm on a dyno test.

Next, you can manipulate the dyno results in many ways on both engine and chassis dynos. The strain gauge must be calibrated to a specific amount of load. In 20 years of running an engine dyno, we’d always calibrate the dyno near the peak torque of the engine that was going to be tested. If it was a performance small-block, we would use the proper amount of weight to equal around 430 lb-ft of torque. For a pump-gas big-block race engine, it would be calibrated in the 700 lb-ft range. This would calibrate the strain gauge closest to the projected power output of the test engine. Let’s say you’re calibrating the dyno to run your engine. You could hang around 500 pounds on the calibration arm and tell the dyno it was 530 lb-ft! This would give you a fudge factor of 30 lb-ft. This is just one way you can fool the numbers. The easiest way to play with the numbers is to enter the incorrect atmospheric conditions into the computer for its correction factor. If you put in a low barometric pressure reading, or a high inlet air temperature, this will kick up the power with the correction factor.

Finally, have you driven your Chevelle yet? The horsepower and torque numbers sound really nice, especially the torque curve, its width, and where the peaks occur. Don’t worry about the hero horsepower numbers. You hit the nail on the head when you said that 98 percent of the time the car will be driven below 5,000 rpm. Yes, you could have gone with more duration on your camshaft and picked up the power well over 500 hp, but you’d have given up that really nice, fat torque curve. Remember, torque is what moves the car. Horsepower is just how many times you hit the crankshaft per minute.

Fuel Economy Testing

My ’69 Chevelle currently has a 454 bored to 4.280 inches, a four-bolt main, Eagle SIR rods, and Federal-Mogul pistons, L-2349F 030 with 0.210-inch dome. The heads are GM 781 castings, ported and polished, with 112cc chambers, and 2.19/1.88-inch valves. The compression with this combination is 10.2:1. I’m using a COMP Cams XE 294H Xtreme Energy hydraulic flat-tappet that specs out at 250/256 duration at 0.050-inch lift. It has a max lift of 0.588/0.593 inch and is ground on 110 centers. The intake is Edelbrock Pro-Flo injection. The engine builder estimated horsepower about 550. Would that be close?

This is a 100 percent street car. Isn’t the cam a little steep for street use? I’m currently running a vacuum pump for the four-wheel power disc brakes. Also, the engine shop told me to use only Pennzoil 25W-50 oil. Why that particular grade? I have to order it as no one stocks it. Can I use another grade?

What size exhaust should I be running on this car? I currently have 2-inch Flowmaster dual exhaust on it. When I removed the tailpipes I saw a big difference in power.

Also, gas is coming out of the gas tank vent lines—it doesn’t start right away and after driving it 10-20 minutes the leaking starts. It is a stock-style tank with sender mods for the return line for the EFI. I thought at first it was due to the O-ring seal leaking at the sending unit. It has slowly gotten worse in the last year, and now I am losing about a half cup fuel per minute out the vent lines! I contacted Edelbrock, and they had no real answers to my problem. I switched to a vented cap and it barely helped, and I even ran without the cap. I removed the tailpipes, thinking that maybe it was super-heating the tank somehow. That made the biggest difference, but I still needed the vented cap. When there is more than a half tank of gas I would still leak, but nowhere as much. I installed new vent lines and believe that they are 5/16 and 1/2 inch. I extended the lines further up in the tunnel hoping that would help. I have the purge valve but just found out that the flapper is missing. Could that be the whole reason behind the leaking? I checked the fuel pressure and return line pressure, and they both checked out, even though Edelbrock doesn’t have specs on return line pressure, mine is 3-4 psi. I only checked the pressure while idling. I would have to get a fuel isolator to check while driving. I went to different forums and no luck. I have been fighting this for four years now and not really getting anywhere. Any help would be greatly appreciated.

Michael Labus
Menomonie, WI

Your nasty Rat can’t be getting great gas mileage to start with. Then dumping a half-cup of fuel on the ground every minute must really shorten your driving range! You’re lucky you haven’t caught the thing on fire if you’ve been dealing with this problem for four years. Hopefully we can give you a few tips to remedy your problem.

Yes, you should change the purge valve out, but this isn’t a likely reason for the leak. When you stated that the sender has been modified for the return line, you didn’t mention if the return extended down into the tank. The fuel is returning at a high rate at idle and no load operation. The fuel pressure regulator must bypass most of the fuel volume that the pump produces to control the fuel pressure to the correct amount. There should be no restrictions in the return system or the fuel pressure regulator can’t control the fuel pressure. Let’s get back to your return line in the tank. If you just put a fitting into the sender lid, the fuel is coming out of that fitting at a very high rate and can spray all over the tank. The tank is baffled across the top of the tank to prevent fuel from escaping from the vent lines. Without a line extending down from your return line fitting below the level of the fuel in the tank, you’re creating a heavy mist of fuel in the upper part of the tank. This could be causing most of your headache. We’d drop your tank down and check for any cracks in the top of the tank, and double-check all the connections for your vent lines at your tank. We hope that not installing a tube down into the tank below the fuel level is the answer. When installing this line, make it long enough that you have to get below a quarter tank before it becomes exposed to open air.

Now that’s what we call a “bottom of the page” camshaft selection. Your Xtreme Energy camshaft is the largest COMP offers. Your engine combination should easily produce 550 hp. We can see where you must have a vacuum pump to operate your power brakes. We’d recommend reducing the camshaft duration by a good 20 degrees. Going with either a XE268H or a larger XE274H would be a much better choice for a 100 percent street car. The increased torque will completely outweigh the loss in top end horsepower in the performance feel of your Chevelle.

For an engine of this power, 21/2-inch exhaust is the bare minimum. This will be a restriction at high engine speeds, but again, like your smaller camshaft, the power loss will be minimal compared to the noise of 3-inch exhaust. Replace your full exhaust system with a quality 21/2-inch system from Flowmaster. The American Thunder PN 17119 true dual exhaust features Super 40 mufflers for a great deep tone with very low backpressure. The full 21/2-inch mandrel-bent head pipes and tailpipes come complete with all the factory hangers to bolt right into your Chevelle.

Finally, the recommended Pennzoil SAE 25W-50; this is a race-only oil recommended for its antiwear properties for the flat-tappet camshaft in your engine. Yes, it’s tough to come by, but replacing your flattened camshaft because you didn’t use the correct oil is much worse. Other oils on the market have the correct levels of zinc and phosphorus to protect the sliding surfaces in your big-block. COMP Cams offers a specific break-in oil to protect its camshafts from failure. You can pick up these oils from any of your mail-order outlets. The 15W-50 break-in oil is sold under PN 1591. We would use this oil to break in the camshaft for the first 500 miles. Then you can switch to a quality grade of diesel motor oil as they still have some of the zinc and phosphorus that the government required removed from motor oil. We have had great luck with Chevron Delo 400 15W-40 oil in all our flat-tappet–equipped engines. COMP also offers a 12-ounce bottle of break-in additive (PN 159) that we’d use as an oil supplement to the Delo 400. This will give you great protection and is easy to locate.


Chevy II Cowl Decode

What number in the vehicle identification number tells if a ’66-67 Chevy Nova is an SS or not? This would be either a Chevy II or a Nova. If not in the VIN, where would you look to find the number? Thanks!

Rick Cross
Via email

Many of the early Chevys don’t designate if it’s an SS or not. For instance, the ’67 Camaro has no designator in either the VIN or on the cowl tag to call out if it was originally an SS. You must evaluate all the information you can glean from the cowl tag and the VIN to see what options were placed on that vehicle. Then you can only guess if it was truly an SS or an RS.

As for the Novas, they had clear identification in the style code in the cowl tag. In 1966 and 1967, there was never an SS Chevy II produced. Only Novas were optioned with the Sport Coupe designator. For both 1966 and 1967, the SS six-cylinder cars had a style code of 11737, and for the SS V-8 cars they used 11837. In 1966 there were a total of 21,000 SS’s built, and in 1967 they finished off the first-generation Novas with 10,100 SS cars built.

If you’re serious about decoding your early Chevys, you need to pick up Mark Allen’s Chevy Decode books. The information above came from the Chevy Cowl Tags 1950-1975 decode book. These books are invaluable when identifying your prize Chevy, or when you are trying to protect yourself on a purchase. Give Allen a call to pick up a full set of pocket decode books for your flavor of General Motors vehicles. Happy decoding!


Simple Crate

I have a daily driver ’87 El Camino with a tired 305. I’d like to put a crate 350 in it. Nothing radical, just a stocker with maybe 200-250 hp. It also must pass California smog. I remember reading an article (four to five years ago) about a crate motor with an Edelbrock manifold, carb, and a 305 cam, but I no longer have the magazine. Any suggestions? Thanks,

Doug Cole
Via email

Doug, for a simple crate 350 engine swap we recommend going with a factory GM Goodwrench crate engine. GM has been offering this engine forever. They were originally called the Target Master Crate engine and were renamed when GM started branding itself Goodwrench. GM has built millions of these engines over the years, and we’ve used them for truck and passenger car replacement engines, and whipped them on the dyno for run after run, without even a whimper. Give our good friend Ken Casey a call at the new John Elway Chevrolet (800.345.5744) for pricing and freight for a 350 Goodwrench engine (PN 10067353). This is a direct replacement engine for ’71-85 applications. This will drop right into your ’Elco and all you’ll need to pick up is a standard-balance 153-tooth flexplate (PN 471529). Yes, you will need to truck the engine out from Colorado, but Casey is very competitive with his pricing, we’re guessing under $2,000 for a brand-new engine. All this and a factory warranty on the engine for two years and 50,000 miles!

As you said, you had a story of a crate with a simple camshaft swap and manifold. We’d go with an Edelbrock Performer EGR manifold (PN 3701), and the matching camshaft (PN 3702). This camshaft shaft specs out at 194/214 duration at 0.050-inch tappet lift, 0.396/0.442-inch max lift, and is ground on 112 centers. You will notice that this is a very short camshaft. It was originally developed back in 1985 to work in the LG4 305s, which were computer controlled. Oh yeah, that’s the engine that’s in your ’Elco. This camshaft will work in concert with your factory computer calibration and pass emissions in the state of California. The short nature of this camshaft will produce great throttle response and make outstanding slow-speed torque. The engine will make strong power to 5,000 rpm and produce about 250 hp through the stock exhaust manifolds and cat.

If you wish to step up to headers, you could also add the Edelbrock TES system, which is emissions legal in California and will boost your peak horsepower on this package by around 20 hp. The TES system for your LG4 305-equipped El Camino is PN 68783. This kit will bolt right in to your El Camino’s factory 21/4-inch catalytic converter. If you wish to step up the exhaust to the high-flow Corvette four-bolt–style converter, go with PN 68793. This, in conjunction with a nice after-cat exhaust, will round out your emissions-legal engine swap nicely.

We know this engine won’t turn the world with its sheer power, but it will give you a great daily driver that will get decent gas mileage and produce over 100 hp more than the stock 305! This will make a big difference in the fun factory with your ’Elco. Good luck! CHP




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