AZJoe

A 500CFM 4bbl is WAAAYYYY too big for the engine. I've got my 2.8L setup similarly to what you've described: 10:1 compression, performance cam and valves, 6-1 headers, AZC intake and Holley 390 carb. I'd have to wind the engine up to 8,000 RPM to pull 390CFM. As it sits I top out at about 340CFM, and I've had to reduce the jets to 47 main and 49 secondaries. With all of that what I've got is around 160HP at the wheels, or close to 200HP at the crank. If you put a 500CFM on there you'll barely ever get the secondaries open and drivability is going to suffer. Bigger isn't always better when it comes to carbs.

Private Pilot. Hi-perf and complex endorsed. Current working on Instrument & Commercial & Multi. Own a 172.

Dyno Results I took my Holley 390 280Z to the Dyno last week. I rebuilt the engine about 4 years ago but never had the time to get to the dyno - life got in the way. A quick summary of my Z: 1977 280Z 274/274 Cam, performance springs Flat top pistons, ~10:1 compression Arizona Z cars 4bbl intake and 6-1 headers 2.5 inch exhaust, straight through muffler Holley 390, 47 main jets, 7.5" power valve, metering plate secondaries, short white spring on the secondaries Running 100LL Summary of the dyno run: way too rich at WOT. I'm running about 10.5:1 A/F. Even with that I'm pushing 155HP/162ft-lbs at the wheels. I'm happy. I've got a metering block on order for the secondaries. The plate is equivalent to 53 jets, we believe that putting in 47 or 49 jets in the secondary will bring up the A/F ratio and give me even more power. Once I get the carb reconfigured I'll be going back to the dyno. The 4bbl setup works VERY well! Here's the run: