The Point of Diminishing Returns

As I have touched on before I have a GMPP ZZ4 Chevy crate engine in my Hurst/Olds. I love it, because on street tires, through the mufflers, at my local strip which is at an altitude of 5,200 feet, it runs consistent 13.9s. Corrected for altitude, that would be more like 13.40's. It idles at 750 rpm, has 17 inches of vacuum at idle, pulls hard to 6,000 rpm, and gets 16 mpg even with 4.10 gears in the rearend. It's so smooth, that if the engine didn't have headers on it, you wouldn't be able to hear it run. Driving it, it feels like any other exceptionally well-maintained 70's Cutlass, until you hit the loud pedal, at which point Dr. Jekyll definitely turns into Mr. Hyde! Being the most popular crate engine in history, just about every enthusiast mag on the market has a ZZ4 powered project car, or runs dyno tests on how to get even more power out of one. A buddy showed me one recently and suggested I make those changes to my car. If you don't know, the ZZ4 is pretty hopped up in the first place. 10:1 compression, aluminum heads, roller cam with .474/510 lift, aluminum Z/28/LT-1 style intake, performance curved HEI distributor, etc. The factory rating is 355 hp and 405 lbs ft of torque. What makes them such an awesome STREET engine-not race motor-is the torque curve. According to the dyno sheet, it makes more than 350 lbs of torque from 1800 to 5200 rpm! In this article the magazine got 117 more hp by adding a different carb and intake, larger aftermarket aluminum heads, and a bigger cam. If it's a drag racer or circle-track racer, by all means this is great, because every last ounce counts. But if the car is a daily driver, or weekend cruiser, not a "trailer queen." then you hit the point of diminishing returns. Here's why: In the dyno test, they swapped the stock intake and vacuum-secondary 770 Holley carb for an "Air-Gap" Performer RPM and a mechanical secondary 750 Holley double-pumper. This was worth 28 hp. However, after this article came out, a bunch of readers from mid-western and rocky mountain states wrote in complaining that in cold weather-5 or 6 months out of the year-the "Air-Gap" manifold caused carburator icing! The car either wouldn't start at all, or needed to run for 10 or 15 minutes, before it would make it out of the driveway without the engine dying! Yes, those mechanical secondaries and double accelerator pumps will cover any "bog" you might have, especially in a low-geared car with a stick, or an auto with a high-stall converter, but every time you look at the throttle it's like flushing a toilet-instead of 16 mpg, you get more like 9-11 mpg, and if you have an automatic with a stock-type converter they don't launch nearly as cleanly as a vacuum secondary carb. At this point, when your late for work, that 28 hp doesn't seem so attractive! The bigger cam was worth 55 more hp, but now the engine only had 12 inches of vacuum, and a noiticeably rougher idle, which in reality, would probably need a higher-stall converter, which would hurt driveability and gas mileage even more. Plus, with street tires, the bigger converter would just blow the tires off. I know, as my car is quicker with a stock converter than it was with a "Streetfighter". Doubtless, with slicks or drag radials, the car would be quicker in the 1/4 mile, but how nice is it to drive now?  The bigger heads were worth another 40 hp, but in a 1,400 rpm window- from 4,700 to 6,100 rpm. And they cost $1,400!! Further, the "antiquated " L98 heads that came on the engine were equal to or within 5 hp and 5 lbs ft of torque at every rpm up to 4600! At some speeds there was no difference, or only a gain of 1-2 hp and lbs ft of torque. If you drive the car at all, honestly-how often are you above 4,700 rpm?  That's what I told my pal. Yes the car woukl be way faster, probably even dipping into the 12's, but it wouldn't be nearly as nice to drive, or be as much of a "Sleeper" as it is. So think twice before you decide to put that 720 hp 572 in your Chevelle or that 610 hp 528 Hemi in your Charger. Before you send the nasty letters calling me a candy-ass, yes, anything is drivable, depending on what the driver is willing to tolerate. If you want a race car with liscence plates, build one. A buddy of mine bought a Cobra replica kit car a few years back. It had a blown 514 inch Ford in it. Was it fast? It was ungodly fast-he ran something like 9.90 on his first pass down the strip and then got kicked out for not having the proper safety equipment. ( Anything that runs faster than 11.50 has to have an 8-point roll cage and a driveshaft safety loop )  Did he drive it on the street? Of course he did. Was it pleasant to drive, even around the block? Not only no, but Hell no!!  You had to crane your neck to the left to see around the blower to drive, it had no power steering, no power brakes, no heater, no radio, no roof, no side windows, it needed two cans of octane booster per tankful while getting 5-8 mpg, if it idled for more than a minute and a half, it got hot, which turned the cramped cockpit into a sauna even in the winter, drivers and passengers alike constantly banged their heads on the shorty rollbar and burned their legs on the sidepipes, and about every 6th time he got on it, it would spit a half-shaft out the Jag rear end and have to be towed home! A beefed-up Mustang 8.8 rear solved that problem, but it still had all the others! Did he love it? Of course he did. But he sold it in a year because after the initial "Oh, my god, I've never driven anything this fucking fast" rush wore off, it was more trouble than it was worth to even try to drive to the local Cobra clubs "Show and Shines" or "Cruise-ins".  Not trying to tell anyone what to do, but like the old saying- "Beware of what you want, because you might get it."  Mastermind