bearcat

I don't know how much a stock Datsun 2.4 liter engine weighs, but an all-iron Chevy small block is about 550 pounds. Aluminum heads removes about 75 pounds from that. I replaced the 750 pound 235 straight six engine from my '52 GMC pick up truck and replaced it with a lighter 550 pound 350 V8. So in my case, it was less weight on the springs.

Just thought I'd add, I'm the original owner of this particular Shelby Charger. That's my son standing in front of it. He knows I'm giving it to him, so he's all smiles. This car is in need of a restoration but it's extremely straight. Anyway, the purpose for this pic is that this exact car went 140 mph on a turbocharged 2.2 liter 4-banger. This was right after I intercooled it and got it up to probably between 180 and 210 hp. I don't know for certain. But originally, they were 147 hp and they weigh 2450 pounds. So power-wise and weight-wise, they are near twins to the Datsun 240Z. When I did my 140 mph run, it was at 5000 ft ASL, in Fort Collins, Colorado, on I-25. I had a taller geared transaxle in it while my original was being built (3.07:1) and decided to see what it could do with the right gearing. I hit 138 very quickly, but those last 2 mph took about 3 miles to reach, and then that was about it. As you can see, not all that aerodynamic, with headlight pockets and hatchback not much different than a 240Z either. But with a turbocharger, 15 pounds of boost, and an intercooler off of a Mitsu Eclipse, it acheived an honest to goodness 140 mph, and to this day, I'm proud of that. Please note the ground effects and rear spoiler. They WORK too. At that speed, the car just sucks down to the ground and is very smooth. That's why I think simply turbocharging a 2.4 Z engine would vastly help.

Hoov100, I'm in Taos, New Mexico. But I might be moving further south...hopefully! If the job I want there opens up. You are both right. Hoov, the bigger hammer, downforce and stickier tires only goes so far. You usually can't have both downforce AND great coeff of drag, because downforce USUALLY means greater drag. But this doesn't stop NASCAR racers from going 200 mph. They use the bigger hammer approach too. A bigger hammer DOES work to a point. And this is where JMortensen is correct. He and I agree on that. The Corvette body can go faster, because a 427 has enough balls to allow it, if the gearing is there. And that's the problem. I have a close ratio Muncie 4 speed with a 1:1 fourth gear and a 3.36. Although the 3.36 is not optimized for drag racing, it will allow a 165 to 170 mph top speed. But I'll be gear-limited, and I'll probably be using about 400 hp to travel at that speed. I have higher power than that, but not the gearing. I did deep research on the available 5-speed overdrive trannies out there and most of them will actually make me less quick while improving my top speed. I finally came to the conclusion that because I live in America and we don't have autobahns, what do I need an overdrive for? Guys, I actually built my car to race in the Silver State Classic. It has the gonads to do it, but I can't race the unlimited class for two reasons. #1, I don't have the gearing to keep up with those 230 mph monsters, and #2, I don't want to basically destroy a valuable classic Vette by permanently altering the car for all the safety requirements the sanctioning body has for that class. In all likelihood, I'd probably realistically race in the 120 mph class, which won't require me to dedicate my car to a race-only configuration. I have always admired the first gen Z-cars and would love to own one, but at the present time, I don't. Maybe someday. But when I do, I'd like to keep it stock-appearing, but have a nice big turbocharger on the straight six. I do miss turbo cars.

A 3.70 gives nice acceleration and is usually the perfect blend of street and performance. Limits your top end though.

That's a really NICE one. I like that! Very smooth and the NACA duct will work great, as long as the boundary layer isn't too much; and I don't think it will be because the scoop is raised up a few inches above the rest of the hood. Nice and very clean design that will work very well with the Z's bodywork.

I will try to post pictures. This is a 1968 Corvette. The scoop on the hood is from a '67 Stingray, and I grafted it on. It is both ram air and cowl induction. There is a wall which redirects the ram air flow down over the top of the engine and bathes the carburetor in cool air. When the car is idling in traffic, it also provides a heat escape from the top of the engine bay. The cowl induction portion is what's used for intake air into the engine. There is a custom air box that fits over the air cleaner when you close the hood. I fabricated that out of fiberglass. Then I use a K&N top-breather lid on the 14"x3" K&N round filter to help get as much air as possible. It's a little hard to see the details in this picture because the air box is painted black. But hopefully it turns out.

Yes I understand. With a 2.4 liter engine, the coefficient of drag is much more critical. With a 7 liter engine, a brick wall could punch a hole in the atmosphere at over 100 mph. That's all my point was. I was suggesting more power. For example, a turbocharger would give a lot more top end and still keep it at 2.4 to 2.8 liters. My point was also that it is a lot more important to keep the car from flying off the ground than it is to be more aerodynamic.

There is a junkyard here in Taos, New Mexico that has two 280Z's from the looks of it. I drive by it frequently. Tell me, what are you looking for? I'll check it out and see if I can get prices.

First thing I would look at here is your squirter size. Seems to me you're just not getting enough of a shot of fuel when you romp on the throttle. That's usually the simplest cause. You could also change your accelerator pump cam, that little colored plastic piece on the throttle plate's lever arm, held in by one screw. They have different sizes, and you have to experiment between cam profile and squirter size. Your motor wants more fuel and is not getting enough out of the squirters. If you go up in squirter size, jump a couple of numbers. For example, if you have #30, try #33. This is a trial and error adjustment, and it is part of the tuning.

Good to see you here, GrumpyVette. I remember you from the Chevy Talk forum. I'm a big block Vette owner, but I'm trying to get myself a little Z. Don't think I'll V8 it though, I've got lots of those. Might turbocharge it though. Cheers.

And I don't think you grasp how much power 631 hp really is. L88's built to similar but lesser levels (due to technology) hit that speed routinely. The '68 L88 427 Corvette won its class in the 24 hours of Lemans many times throughout the 70's, hitting speeds in the high 160's and into the 170's. All you need is a bigger hammer. Do the research, it is historically recorded. I'm not makin' this up. Maybe I should start by asking, what are your goals here? You have a car which has roughly the same coeff of drag as my Corvette. At the legal speeds encountered in the US, this isn't an issue at all. If you're racing your Z, and you have limited horsepower, then yes, CDA is more important. But honestly, dudes, if you've got a big block Chevy that can hit 7000 rpm, the point is moot. If you want to hit 160 in your Z, install a bigger "mallet", because there's only so much you'll be able to do to improve the CDA of your car. Absolutely no offense intended. Just trying to help, Cheers.

I'll weigh in. Let's move away from raindrops and airfoils for a minute and talk about cars. Because I have a '68 Corvette which I've owned for many years, I'm most familiar with that. When the Vette evolved, the C2 (1963-1967) used to experience severe front end lift at about 152 mph, to the point where you couldn't steer it anymore. The C3 was designed with a much sharper front nose and longer, smoother body. It's beautiful to look at, but actually wasn't that aerodynamic either. The C3 Vette, (1968-1982) had almost the same CD as the 240Z in fact. But it did reduce lift significantly over the C2, for a higher top speed, approaching 170 mph, so it was an improvement. The Kamm tail of the early C3 was actually more aerodynamic than the smooth taper tail of the later C3. So they brought it back starting with the C4. The wedge shape of the C4 (1984-1994) was a big improvement. The C5 was the best, aerodynamically, but it's not nearly as attractive. So my point is, the C5 and C6 have more of a rounded nose, not unlike a teardrop. But unlike a teardrop, the abrupt end to the tail was found to be far better. The Corvette was designed as an early attempt at aerodynamics, but on paper only. Through trial and error, they finally learned what to do. Just like Nissan has also learned what to do, and has improved their Z aerodynamics through the years. The new 350Z is far more rounded than the much more beautiful 240/260/280Z. Thing is, what works at very high speeds is different than what works at lower subsonic speeds. That is why supersonic jets have sharp noses. The behavior of the slipstream becomes much more fluid as speed increases, and the rules change. Simple as that. I really don't worry about the coefficient of drag on my '68 Corvette. It has a 427 race motor in it. I figure if I need more power to hit 170 than a later generation Vette, I just hit it with a much bigger mallet. What is much more important than maximizing your CD is maximizing your ground-sticking ability. The C3 Vette had almost a 20 mph higher top speed than the C2, because they may not have fully understood how to build a lower CD, but they very much did know what worked on the race track. You can always install a bigger hammer, guys. Then it doesn't matter how low your CD is. Cheers.