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January 2013 Chevy High Performance Q&A

Kevin McClelland Jan 28, 2013

L92/Wagon Marriage

As I mentioned last month, I thought I would get some quality time with our wagon and the L92 small-block destined to fit between its framerails. Well, since we last spoke, I’ve put all my time into getting the engine together and ordering the last components necessary to drop the engine in. If you recall, I said that we had spec’d out a COMP hydraulic roller that was just small enough to fit without intake valve reliefs in the pistons. That was my first challenge. Probably, if I’d have gone with production LS3 hollow-stem intake valves over the Manley racing hollow stems, we might have made it. The production valves you could shave with the margins, and the Manleys have a good, safe margin of approximately 0.060 inch. The production valves have a nasty habit of dropping the head of the valve when pushed into racing applications. Better safe than sorry. When I degreed the cam and checked the valve drop, the valves were hitting the pistons by 0.038 inch. We reached for the Isky catalog and purchased the pilot and a 2.250-inch cutter to cut the small valve pockets in the pistons as needed. It was a little bigger exercise than I expected, but that’s done now.

chp 01 O January 2013 Chevy High Performance QA Kevin McClelland 2/3

I was going to go with the complete Muscle Rods engine swap with Hedman Hustler headers, which make the installation a snap. Well, after installing the Milodon racing oil pan, which has a widened sump for added oil capacity, and the pan dropped away from the rotating assembly to reduce windage, I decided to make my own mounts. Also, with making my own mounts I may cut the main crossmember to lower the engine and get a better driveline angle. I did order the Hedman headers and they just came in this week. Hedman puts together a beautiful set of 13/4x17/8-inch step headers that I went with. My plan is to make killer torque and shift at 7,000 rpm and gear the car to go through the lights at 7,000 rpm. These headers should give me both great torque and outstanding power to the upper-rpm range.

My concern with lowering the engine is that the car currently launches off of a 3,000-rpm chip and will pull the front wheels around 10 inches to a foot. Adding around 100 lb-ft of torque on the launch and taking at least 100 pounds off the front of the car (50 pounds for the engine and a fiberglass cowl hood) I’m worried that the front end is going to go skyward. Not that I don’t like a good wheelie every once and a while, but what’s the name of the game? Win lights!

Finally, with the way projects go around the McClelland household, you buy parts when there is money in the bank, so this project has been moving along in $300 to $500 chunks. Some parts, I purchased well over a year and a half ago and put on the shelf until needed. Today I opened something I purchased at least a year ago, and one of the components was machined incorrectly, and the part is scrap! Mind you, I work for a large performance aftermarket company, and it is a challenge supplying quality components to our customers every day. My take on this is that we should all inspect our parts as soon as we get them, making sure it’s what we ordered and that it’s perfect. It will prevent delays like mine. I guess it will be another weekend until the engine is complete. Until next month, wrench safely.

Resto Stuff

Where can I find parts for my ’67 Chevy Chevelle 300 deluxe two-door post. I’m looking for a window to trunk panel, inner front fenders, all glass window felts … I need lots of parts. Please help.

chp 02 O January 2013 Chevy High Performance QA 67 Chevy Chevelle 3/3

John Vieira
Manteca, CA

Rear window to trunk panels loved to rust out in the second-gen A-bodies. Check with Goodmark for all your sheetmetal needs. The window to trunk panel you’re looking for is called the Deck Filler Panel, PN 4031-710-66. This fits all hardtop ’66-67 Chevelles. For new front inner fenders, check out PN 4031-350-67L and R. These are exact replicas of the factory pieces. Goodmark also offers many of the trim and window seal pieces for your Chevelle.

For the glass felt, window seals, door seals, and rubber parts, check out companies like Classic Industries, National Parts Depot, and YearOne. We’ve been very pleased with all of the parts we’ve used from these companies, and they all have great customer service. Check them out online and see who works out best for you.

Enjoy restoring your ’67. You couldn’t have picked a better time to start your restoration. Almost everything has been reproduced to bring your Chevelle up to better-than-new standards. Good luck with your project—hope your checkbook holds up!


Steer in the Right Direction

I’m the proud owner of ’64 Nova SS, white with red interior. I can’t find the original red steering wheel anywhere. Can someone please point me in the right direction?

Rick Barber
Brooklyn, NY

What Chevy II owner wouldn’t be proud? We dug around all the reproduction houses and no one we could find offers original reproduction wheels for anything earlier than ’67 models. A quick search on eBay Motors yielded a perfect-condition ’64 Nova wheel with the horn trim ring and everything. The money wasn’t that bad at $150, either. The only issue is that the wheel was white. The restoration houses offer special paint to refinish steering wheels, and the base color white is easy to refinish.

Also, you should network with your Nova brethren. There are many Nova clubs around the nation, but check out the National Nostalgic Nova Club. They have free classifieds to their members, newsletters, and events around the country.

Unfortunately, used and refinished may be your only option. We have to remember that our early Chevys aren’t getting any younger. Yours is right at the half-century mark. Take care of her and enjoy!


502 for the Masses

We have a 502hp/502-cid GM crate motor with an 850 Holley. It runs with 10-10.5 inches of vacuum at 800-850 rpm idle. Is that enough vacuum for power brakes? At higher rpm, 1,500 and up, the vacuum runs about 14-15 inches but does not go up when you quickly let off the throttle. Our power brake booster is in the trunk, plumbed with a hard line. The engine only has an hour of run time on it (in the shop, not highway). It also runs rich. We have not done an air/fuel mixture test yet, but it is definitely rich. Any suggestions on jet sizes? I enjoy your magazine, and it has a great Q&A section. Thank you!

Ed Jacobson
Port Angeles, WA

A Chevy 502 crate engine is one of the best choices for great performing street machines. They are not too radical to drive power accessories and power brakes. Yes, the 10-10.5 inches of idle vacuum is right at the low side for power brakes. You mentioned the idle speed, but didn’t give an idle spark advance spec. We would shoot for 16-18 degrees of initial spark advance at idle, and 32-34 degrees at 3,200 rpm. Then add vacuum advance on top of that. This will give you the best idle quality and vacuum you’ll see out of this package. As for the rich idle, we assume this carburetor is the GM-tuned 850 supplied with the Deluxe engine package. If it is, it’s already jetted properly and all you need to do is set the correct float level, then adjust the idle fuel screws to the lean best idle. Remember, with the overlap of the 224/234-duration camshaft at 0.050-inch tappet lift, you’ll have unburned hydrocarbons at idle, even when the carburetor is adjusted properly.

If your engine is equipped with a standard list number 4781 850-cfm Holley double-pumper, the factory jetting should be very close. These carburetors have four-corner idle, course-threaded feed screws. Very slight adjustments change the fuel flow significantly. Again, first adjust the float levels to their appropriate levels, then adjust the idle fuel screws to your lean best idle. With this type of carburetor, you want all four idle feed screws to be adjusted to the same point. This will take some finesse, as you should start with all of them about one turn out from fully closed. Then choose one screw and turn it in (leaner) until the idle speed begins to drop. Once you find where it’s sensitive, say, a half turn out from seated, go back to one turn out and close all the screws, say, an eighth of a turn. Then return to the screw you started with and lean it again. Now it only goes another eighth to a quarter turn before the idle begins to drop. Repeat the procedure and slowly equalize the four screws to your lean best idle. You know it’s right when you can just tap the accelerator pump arm and squirt in a slight amount of fuel and the idle won’t climb. If the engine speed goes up with a slight squirt of fuel, the idle fuel adjustment is too lean. Repeat your idle fuel adjustments until the accelerator test causes no change in engine speed.

Enjoy the ton of torque these engines have on tap. Down the road, when you’re tired of the power, you have a great foundation to kick it up a notch. These short-blocks will handle just about anything you want to throw at them. We’ve enjoyed many a dragstrip lap behind a 502 short.


Geared Up!

I have just swapped a brand-new 357-cid small-block into my ’83 4x4 truck, and am now wondering about gearing. The engine has 10:1 compression ratio and 230/236 degrees duration at 0.050-inch lift, with a max lift of 0.490 inch. The engine is in front of a 700-R4 transmission, and I have 33-inch tires. The truck will be driven on the street, but driveability is of no issue to me. What torque converter and rearend gears would be desirable? Thanks for the great magazine.

Thomas Quinn
Via email

Getting almost 21/2 tons of fun moving can really put a load on a small-block Chevy. When you install taller-than-stock tires, you just kill the gear multiplication—that’s the only thing your little engine had going for it. The 700-R4 First gear of 3.06:1 gave it some low-end grunt. Let’s take a look at the gearing choices that won’t make your truck fun to drive yet unusable.

Luckily, with the 700-R4 you can get pretty silly with the rearend gearing yet still have a very streetable truck. The 0.7 overdrive and the lockup converter really gives you a nice driver. Your truck probably came with 3.73:1 rear gears from the factory. The original tires on your truck were 29 inches tall. With these tires and gearing, your truck is loafing down the freeway at 2,000 rpm at 65 mph. By throwing your 33-inch tires on the truck, the 65-mph engine speed drops down to just above 1,700 rpm.

Now, let’s have some fun. By dropping your gear ratio down to 4.88:1, you still retain a 65-mph cruising rpm of 2,250, which is a great range for your mild cam 350. Also, with the very low 3.06 First gear in the 700-R4 and the combination of the 4.88 rear gears and 33-inch tires, the truck will still pull 40 mph in First at a redline of 6,100 rpm. It would really wake up the acceleration of your rig.

As for the converter, a mild 2,400 stall would give you one hell of a launch with the combination of low gearing. Check with Monster Transmission for its Punisher Pro Street lockup converter. The 2,300-2,500 lockup converter (PN HD7730) features furnace-brazed impeller fins. Also, we wouldn’t recommend going away from the lockup feature. With the weight of your pickup, even with the low rearend gears, you would be right at the edge of your stall speed at freeway cruising speeds. This will cook the trans fluid and eventually the transmission. Check with Monster at 800.708.0087 for more information.

We hope this all makes sense. Let us know how the truck launches after these mods. Also, watch it when you put this puppy in four-wheel Low. With the gear multiplication of your transfer case, your driveshafts may want to leave the truck!


Drivetrain Losses

I have a question that’s been bugging me since I tried to figure out how much horsepower I needed to run in the 140s at 10.90. It seems that chassis dyno operators are always quoting a drivetrain loss of anywhere from 15 to 35 percent compared to crankshaft horsepower. Is there a sliding scale for horsepower output? In other words, all things being equal, why would a 1,000hp engine lose 150 horses to the drivetrain and a 100-horse engine loses only 15, assuming a 15 percent loss? Am I missing something or is friction the culprit? Thanks!

Gary Thompson
Pahrump, NV

For all you readers, Gary has a C4 Corvette that he runs in Super Street with a small-block Chevy. This is why he would be asking how much horsepower to run 10.90 e.t., but at a much faster 140 mph. A car running flat out will cover the quarter-mile at 10.90 seconds at around 122-124 mph. The e.t. for a car traveling 140 mph from a standing start is in the mid 9-second range. In the Super classes we run throttle stops to adjust the performance of our vehicles to hit the magic 10.90, 9.90, and 8.90 seconds, respectively.

To your specific question first, all things are not created equal when you’re talking about the driveline to harness 100 ponies and 1,000 hp. To transmit the power produced by a 1,000hp big-block you need much larger parts; e.g., transmissions and differentials. If not, you’d end up scattering the parts all over the strip if you used the clutch, trans, and diff from a Chevette behind that 1,000 hp! Yes, it is frictional differences and rotating mass that cause the greater losses. Also, the more load that you apply to the transmission and rearend gears, the more power is converted into heat and frictional power loss. The lowest percentage of driveline losses will be with a front-wheel-drive vehicle, since they don’t change the direction of rotation 90 degrees as with a hypoid gear arrangement in a standard rearend. Most front-drive transmissions and differentials keep the rotation of their components going the same direction as the crankshaft. These types will commonly come in at around 10 percent loss. Next would be your manual trans–equipped vehicles, at around 12 percent best case, to an average 15. Then you would have your standard automatic non-lockup–equipped vehicles. These start in the 18 percent range and climb from there. In performance vehicles, Powerglides are king at stealing the least power from your engine. Inversely, the TH400s rob the biggest chunk because of the sheer weight of their components and drive direction within the trans. Luckily, the performance aftermarket has built components that will withstand the abuse in a Powerglide since they were originally intended to be behind 250 hp tops. The worst crank-to-tire loss we ever saw on the dyno (first dyno’d on the engine dyno, then in the car on the chassis dyno) was 25 percent. This was a Brand-F car with a four-speed overdrive transmission, P/S, A/C, Alt., six-blade steel fan, and a 9-inch diff. We swapped out the fan and water pump to electric units and gained 6 percent at the rear tires.

Now that we’ve gotten past the loss factor, let’s talk about one more issue on chassis dyno testing race cars. Stall converters basically make it impossible to accurately dyno race cars. You can use them, but the torque number is pretty useless. If you are to test on a chassis dyno, you must bring the vehicle speed up to your stall speed in High gear. You can figure this out by calculating the vehicle speed in High gear at your stall rpm. This may sound crazy, but you may start your test around 100 mph, and take your car to redline, which would be in the low 140s. If you start the test at a much lower speed, your engine will sit in the stall of the torque converter and cook the fluid, and also give you a greatly inflated torque number. Torque converters multiply torque when they are in any type of stall condition below 1:1 engine speed and input shaft speed.

So how much horsepower do you need to push your Corvette to 10.90 at 140 mph? If you were to run 140 at that e.t. and then you ran the car wide open with no throttle stop, you should see between 142 and 143 mph. This would be combined with a 9.40-9.50 e.t. We’re making a couple of assumptions. We know your Vette is probably close to the Super Street minimum weight of 2,800 pounds, with driver. For your Vette to run 143 at 2,800 pounds, it’s going to take approximately 730 hp. (Now all you keyboard hot rodders are going to go online to a site like Wallace Racing, which has all the performance calculators you could ever wish for.) From years of experience, automatic transmission race cars usually eat up 75-100 more horsepower than the e.t. predictors on the market. These prediction formulas are very accurate with a fully vetted manual trans, unlimited race car. They are spot on in applications like NHRA Pro Stock–type cars. Everything we’ve ever had consumed the extra power listed above, perhaps because we don’t have the lowest friction driveline, or our vehicles are less than desirable, aerodynamically.

Good luck finding a few more ponies for your Vette. See ya in Vegas.


Fire in the Hole, Rewind

In the May issue, you advised Betty about her hard start problem. I may have a solution. I had a similar problem with my ’87 Cavalier Z24. It turned out to be the fuse for the fuel pump start circuit. Cranking the pump got no power. Once the engine delivered enough oil pressure and I released the ignition switch, the engine fired.

There are two circuits for the electric fuel pump: one for starting and one for running. When cranking the fuel pump, power was routed through a different circuit to bypass the oil pressure switch. She may have a similar problem with her pump. The run circuit works but the start circuit has no power.

John McGibney
Via email

You’re spot on, as the fuel pump must be energized during the crank event. Usually this is taken care of by the ECM, which sends out a signal to the fuel pump relay based on the crank voltage being fed to the ECM from the ignition. We experienced this once, where the crank voltage was omitted. I would never have thought to look if it weren’t for the message board,

Great tip, checking all fuses when running into these types of problems. Yes, some GM vehicles have a crank fuel fuse, and others just send a signal directly from the computer to the fuel pump relay.


60-Foot a Little Slow

I have a ’63 Vette with a 98-inch wheelbase, mild steel tube chassis at 2,450 pounds, with a four-link suspension, antiroll, rear wishbone, and struts. The engine is a 565-cid, producing 1,007 hp, with a Powerglide transmission, a 9-inch 5,600-stall converter, 4.57:1 rear gears, 50-inch wheelie bars, and 16x33 Hoosiers slicks running 9 to 91/2 pounds of air. I launch the car off a transbrake at 4,400 rpm and shift the car at 7,000.

I don’t know the instant center of the rear suspension, but the antiroll and chassis were set up by Ken Kier. I’m located on the East Coast (Maryland) and race from New York to Florida.

My problem is it doesn’t seem to 60-foot very well, the miles per hour doesn’t match the e.t. Could the rear coilovers cause this? I have single-adjustable QA1s. I’m considering double-adjustables and 66-inch wheelie bars.

Here are some runs in varying weather conditions:

April, 68 degrees: 60-foot: 1.265; eighth-mile: 5.491 at 128.96 mph; quarter-mile: 8.501 at 164.17 mph

July, 90 degrees: 60-foot: 1.295; eighth-mile: 5.567 at 128.18 mph; quarter-mile: 8.604 at 163.02 mph

October, 60 degrees: 60-foot: 1.256; eighth-mile: 5.483 at 130.20 mph; quarter-mile: 8.479 at 165.80 mph Thanks for any help you can give.

Kevin A. Banks
Via email

Very cool Vette. You’re making some good steam with your big-block. It’s just that some of it is being eaten up as you’re going down track.

First, let’s take a look at your runs. I wish you’d sent the density altitude of the three different runs. We’d have to wager that when you ran in April and October they were within about 1,000 feet of each other. The run in July was at least 2,000 feet higher than the other two runs. The drop-off in performance in July is directly related to the lack of horsepower because of high temps, humidity, and possibly low barometer. Also, when the track temps climb, as with the July runs, you expect to lose some 60-foot time because of wheel slippage. The variations in the 60-foot times and the performance changes down track don’t look out of line for a gasoline-fueled race car.

We took a look at your pass on “Pass Time”, on YouTube. It offered some insight into how your car is set up. Now, as for your 60-foot performance, you didn’t mention if you’re at 2,450 pounds with driver or not. On “Pass Time,” you said it’s 2,600 pounds with driver. With that weight, the tall 33-inch tires, and your relatively low launch rpm, the mid 1.20s isn’t out of the question. We’d expect your car to 60-foot in the low 1.20s if you turned up the steam on the starting line by raising your launch rpm. Now, what is the name of the game? We’re all about the win lights. If you pour the coals to the car at the hit you may kill your consistency. Unless you’re spinning the tires at the launch, you should be able to get the car moving quicker. Have you tried lowering your tire pressure as a test? Have you raised your launch rpm to see if it’s sensitive? From the video, it looks as if the instant center is a ways out on the car. It barely lifts the left front tire. This is why we would love to see the launch at, say, 5,000 rpm.

You asked about installing a set of double-adjustable shocks. These shocks will give you much more flexibility to adjust your car’s suspension. Again, it seams to work well with the power you’re giving the car now, based on the video. Once you hop the power up, you may need to adjust the compression and rebound independently to optimize the grip you have available.

Finally, yes your e.t. and mph are a little off, given the power you’re producing. This is back to the cars that eat 100 more horsepower than is predicted. Your car, at 2,650 pounds, needs 917 hp to go 165 mph. The eighth-mile and quarter-mile e.t.’s correlate perfectly. If you work on your 60s, you’ll be right in there with picking up your quarter-mile times. You should see a 2:1 correlation between the 60-foot and quarter-mile e.t.; a 0.01-second improvement in 60s should help the quarter by 0.02.

If you really want to try something, borrow a buddy’s 8-inch converter and give it a try. The 9-inch converters are great for efficiency, since they are usually in the 5 percent range, but they lack in torque multiplication. An 8-inch will lose efficiency at the top end to the tune of 9 percent, but it’ll really wake up the car on the starting line. It would be worth it to answer the question. Good luck on your quest for performance, but always remember the name of the game, win lights!



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