The point of diminishing returns......

No matter how fast our cars are, hot rodders are always looking for "Just a little More." However, especially if your planning to drive the car at all-i.e. it's not a show car or a race car-sometimes you hit the point of diminishing returns. This is where the gain in power or drop in 1/4 mile e.t. isn't justified by the loss of idle quality, or driveability or smooth ride or whatever. Here's a few good examples. # 1. My own car-a 1973 Hurst / Olds 442. After blowing the crank out of the 455 3 times, I put the numbers-matching block and BOP bolt-pattern TH400 in plastic bags in my garage and installed a ZZ4 Chevy crate engine and Chevy bolt-pattern TH400. For those of you that live in a cave-the ZZ4 is GM's best-selling crate engine. It's a 4-bolt main 350 block with a steel crank, "pink" rods, Keith Black Hyperuetic flat-top pistons that give 10:1 compression with the aluminum L98 Corvette heads, a hot hydraulic roller cam, and an aluminum intake that's an exact replica of the original Z/28 / LT1 manifold. It's rated at 355 hp and 405 lbs ft of torque. What makes it such an awesome street engine is the fact that it has more than 350 lbs ft of torque from 1800-5200 rpm. It has 17 inches of vacuum at idle, works with a stock torque converter, idles at 800 rpm, and pulls hard to 6,000. The car runs mid-13s on street tires through the mufflers, and gets 16 mpg, which isn't bad for a 3,731 lb musclecar. Anyone that drives it thinks it still has the 455 in it. No one believes that a small-block Chevy has that much torque. Of course, some of my friends have great advice on how to make the car go faster. I'm not being a wise-ass; the advice is sound. Yes, the car would run faster with a bigger cam and maybe a single-plane intake and a bigger carb. But that would mean decreased idle quality which would also necessitate a higher-stall converter, and probably stiffer gears. Now the car would be running in the 12s, but it's wouldn't be nearly as pleasant to drive, and would get 8 mpg instead of 16. See what I'm saying?  If I wanted a race car with liscence plates, I'd have built one in the first place.  # 2. A friend has a 1966 GTO with a 400 out of a '74 Gran Prix and a TH350 that replaced the  two-speed ST300 ( Read Powerglide ) tranny. The short-block is stock, but he has Edelbrock aluminum heads, and a Performer intake and matching 750 cfm carb, and matching Performer cam, as well as Hedman "shorty" headers with stepped primarys. This car will literally spin it's tires as long as you want to stay on the throttle. It's an absolute blast to drive, has 15 inches of vacuum at idle, and purrs like a kitten. Until you hit the loud pedal. Edelbrock claims 387 hp and 439 lbs ft of torque with this combo. Since he often gives 400 hp modern Camaros, Mustangs and Chargers fits, I'd say this is about right. Another friend suggested he "upgrade" to the "Performer RPM" package which has a taller dual-plane manifold and a much hotter cam that's actually an exact copy of the legendary factory Ram Air IV cam. The "RPM" package makes 422 hp and 441 lbs ft of torque.  A gain of 35 hp and 2 lbs of torque. However, this gain is all above 4,500 rpm, the cam has only 10 inches of vacuum at idle, has a very rough idle, and actually makes LESS power and torque than the other one under 4,000 rpm. Your giving up quite a bit of bottom end and mid-range torque for top-end rush. He'd definitely need a 2,500 or higher rpm converter, and he'd probably need to change his 3.23:1 gears for something stiffer.  There's a reason the factory only offered them with 3.90:1 or 4.33:1 gears!  And honestly- without slicks or traction aids-how much faster is the car REALLY going to go with 422 hp as opposed to "only" 387?  Not too much, maybe 3 /10s. Which in my mind is not worth giving up the glass smooth idle, and easy freeway cruising of the 3.23 gears and broad torque range of the "base" Performer Package for a choppy idle, LESS power under 4 grand, and  and the motor buzzing at 3,500 rpm on the freeway because of the 3.90:1 or stiffer gears, so I can drop 3/10s at the drags and gain  35 hp between 4,500 and 6,000 rpm!  "Bigger" is not always Better! So think carefully before you go for the "Max" on everything. You might not like the results. Mastermind