Getting more out of my Z

[Mudge]

Tripple carbs would be nice for all out race, but those other upgrades are going to net more power for you overall, the fuel system is not all that bad stock.

Take some time to learn about the cars and you can do those upgrades that seem obsqure to you now. Header and exaust would maybe be a good place to start, when you have some cashola.

[Dan Baldwin]

What year 240Z do you have? If it's a '73, then a set of older dome-top carbs (the '73 flat-tops are universally reviled) would likely do you some good, as would swapping in a '70 E31 or '71-'72 E88 head. The '73 E88 head has lower compression. The E31 would get you ~9.1:1, earlier '71/'72 E88 would get you ~8.8:1. '73 E88 would have you at 8.3:1.

Generally, the best thing you can do for a street NA engine is to maximize displacement and compression ratio. This will give you a bigger shove in the back all the way through the rpm range. Putting a '81+ 280ZX engine with a '75-'77 280Z N42 cylinder head would get you 2.8 liters at 9.8:1 compression, which would give you a big increase in performance. And if you REALLY want to get some torque, get a Maxima diesel crankshaft (one at zcar.com right now for $250), and bore any L28 (2.8 liter) .120" over and install KA24 pistons, and N42 head. This'll get you 3.1 liters and 10.1:1 CR. Tire-boiling torque, and the same or more rev potential (same peak piston acceleration at 7340rpm as a KA24 engine has at its redline, 6900rpm) than an L24.

Headers:

I know of dyno results that showed ZERO loss of low-end torque with headers and a 3" exhaust on a stock-cammed L24. Of course the 3" is overkill, but 2.25 or 2.5" should give a bit more high-end breathing without costing you any low-end. Use a header if you want, but be aware it won't buy you much if any over an L28 exhaust manifold (won't cost you anything, though).

A K&N filter in the stock air box should be fine on the intake side, but if you want to spend some money, twin ITG filters would be better. Just be sure to use some sort of radiused inlet, be it the stock air horns, aftermarket, or "stubbies".

Oh yeah, get thee to a dyno to optimize ignition advance and fuel mixture. Baseline on ignition advance for a stock distributor should be 10 degrees initial, 35 max mechanical+initial (more with vac advance). Mixture is easily adjustable on the SU carbs, just turn the doohickey on the bottom of the carbs.

Have fun!