You could probably take it up to 125 or maaaaaaybe even 130 with your setup, but if it's vibrating like that and making all kinds of noise I wouldn't push it unless you got some money stashed for replacing stuff. If you want a higher top speed (not sure why you would unless the speed limit in your area is very liberal) then you want the lower gear rear end. The 3.9 will give you much better acceleration and pull, great for around town driving, kinda high revs on the freeway though, and will cut your top speed down a bit. I know my ZX with 5 speed and 3.9 would top out at about 130 before I wouldn't want to push the engine or rest of the drivetrain any further. That was up in the 6k RPM territory, and although I had a good suspension so not too much shaking, there was still this feel about the car, like keep it up and somethings gonna fly off. I say, if you're not looking for better acceleration, stick with what you got. If you want better acceleration and don't want to hurt your top speed or want to keep your freeway cruising revs low, look at maybe raising the boost a tad.

 

I havent looked at the differences in the gear sets between the Nissan trasnny, and the T5, but I have a topend of about 165 mph with the 3.70 gears in the Diff.

 

Yeah, but calculated speed and actual are two different things. There is no way a stock NA 280ZX will get over about 125. It doesn't have the HP. The 5-spd has an overdrive - the aoutomatic doesn't so the 5-spd has that .745:1 advantage for top end and keep engine RPM lower but still not HP advantage.
My '77Z had an '83ZX 5-spd and 3.90:1 and it ran out of oomph at 125. I have an '83Zx with the 5-spd and I'm not sure it will even make it to 100. I don't trust the digital tach and the car gets squirrely at higher speeds.
The new engine and drivetrain I'm putting into my '77 gears out to 220 mph in 6th at 5,500 RPM but it doesn't have the 450 HP necessaryto attain that speed nor does it have a pilot crazy enough to try.

 

Well said, Phantom

I kind of wonder what kind of an answer people are looking for when they ask for quarter mile times for a 'stock' ______Z or ZX (fill in the blank). Like stock times from when the car was new mean anything now that 90% of these cars are 25 or 30 years old with 150,000 hard miles and sagging springs. My 2 cents.

 

If your using a 3.7 gear and a 3-speed auto, that would explain the lower top speed. Figure the 3.55 final drive of the stock 280ZX turbo automatic trans gave it a top speed of between 126 to 131 mph, depending on wind conditions. Sounds very strange to be experience sever vibrations from the driveline. Something is out of balance, could be the reason the differential is howling.

 

only 450hp?

Where did you wome up with that figure? My figuring for an early car with G-Nose was 345 for the 165mph range (Jeffp is right, 162@6500rpm with this gear or that...) HP required rises with the square of speed, my figuring for 200mph with a Zx are a bit more than 450HP. I'm just curious where you got your cd and frontal area numbers.

 

it's a question of $....

Personally, z's are approx. 20-30 years old! that basically puts them out of the super exotic (super expensive) class of cars; if you want to go fast, get a bike, my CBR goes 0-168mph in less time than it would take you to get a z out of 2nd gear, it tops out at around 180mph, and a ferrari would have a **** of a time trying to keep up. Enjoy the Z for what it was designed to do-run great and look neat just simple going 35mph. With the right paint job and ground effects you can get the ladies attention.

 

Be Realistic...

So you are saying your bike goes 0-168 in less than five seconds.
You show me the verification, timeslip, or give me the keys and let me verify it!
That is a ridiculous claim, and you're called out: Prove it.
With a verified time ticket in the logbook from Bonneville at over 167 in a Z, your claim reeks of bombast, sir!