What air intake should i use?

[McGuinn]

I have a 1971 240z and I drive up to the mountains frequently but when I go up to the 5000-foot level and higher the engine seems to lack power do to the thinning of the air. For instance, I have to push on the gas more to keep the RPM, it basically feels like a power loss. I have the old stock air intake and was wondering if I had to change it to help the engine breath a bit better. I recently changed the filter but to no avail.

I just started restoring this Z and I am a rookie when it comes to engine work. Any help would be much appreciated.

[Bambikiller240]

What you are describing is fairly common for carburated cars. The thinner air changes the Air to Fuel ratio significantly. The computer controls for fuel-injected engines seem to be able adjust very well to compensate for the altitude, but carbs cannot. Most folks with carburated cars travelling up to the mountains for a brief stay just live with it. If you're going to be there for a longer period of time you might consider adjusting your carbs to operate properly in the high altitude environment. You could start you leaning out the mixture some, though (depending on the altitude and what needles are in your carbs) you might end up needing to change needles to get it running well. I'm doubtful that you could ever get it to run as well in the 5000' mountains as it could nearer to sea level. (but I'm no SU guru, that's for sure)

[McGuinn]

Makes perfect sense, I'll have to give that a shot.

Thanks

[ZmeFly]

bambi, elevation reaks havick with a carbureted engine, like bambi said fi systems seem to take up for this failing. simple adjustments should be your only need.

by the same token opening up to the k n n style filters and letting your engine breathe a little better cannot hurt at all.

[240ZMan]

I live in Colorado at about 6500 feet elevation. I've got a 73 with 3 screw round top SUs. As I never go lower than Denver (~5000 feet) my tuning is optimized for altitude. But when I had the car in the Bay area where I used to live, it certainly had more power. At this altitude the general concensus is that an engine makes about 20 - 25% less power - that's both torque and HP.

At first it's frustrating, but eventually you get used to it