280zx advance curve question

[doradox]

I can't remember Steve, are those carbs still original? Not remanufactured? In theory, the whole approach of the SU design is to keep the ratio fairly steady through-out the rev range. If the idle mixture is way richer than under load, one thing I'd suspect is a vacuum leak at the throttle shafts. With a vacuum leak, one of two situations occurs: you can tune them either rich at idle/good at speed; or good at idle/lean at speed. If my carbs were worn, I'd want to have mine set like yours rather than lean at speed.

Actually, if you richen the mixture to account for a vacuum leak at idle, which would give you correct mixture at idle, you'll be rich everywhere else. If set the mixture correctly for everywhere else you'll be lean at idle due to the leak.

Steve

[whamo]

Actually, if you richen the mixture to account for a vacuum leak at idle, which would give you correct mixture at idle, you'll be rich everywhere else. If set the mixture correctly for everywhere else you'll be lean at idle due to the leak.

Steve

So what would the overly rich idle mixture indicate? Worn needles? Float level too high?

[Bruce Palmer]

Back to distibutors for a minute, I checked 3 elctronics we'd been playing with on the ball bearing issue and the T-bars read 9, 11.5 & 14.5 degrees and there are most certainly some that are higher than that.

As I said, regardless what's built into the distibutor for advance, it is fixable.

[whamo]

Back to distibutors for a minute, I checked 3 elctronics we'd been playing with on the ball bearing issue and the T-bars read 9, 11.5 & 14.5 degrees and there are most certainly some that are higher than that.

As I said, regardless what's built into the distibutor for advance, it is fixable.

Thanks Bruce, If I send you a distributor can you recurve and rebuild it? Also are the vacum advances available for replacement?

[Arne]

Actually, if you richen the mixture to account for a vacuum leak at idle, which would give you correct mixture at idle, you'll be rich everywhere else. If set the mixture correctly for everywhere else you'll be lean at idle due to the leak.

Oops! You're right. My bad.

So what would the overly rich idle mixture indicate? Worn needles? Float level too high?

Worn, incorrect, bad or improperly adjusted needles, I'd guess. Float levels too high might affect that too.

[jmortensen]

Back to distibutors for a minute, I checked 3 elctronics we'd been playing with on the ball bearing issue and the T-bars read 9, 11.5 & 14.5 degrees and there are most certainly some that are higher than that.

As I said, regardless what's built into the distibutor for advance, it is fixable.

I used to have a chart of the different applications and their advance curves based on the distributor model number, but I can't seem to find it anymore. Regardless, I think you're mixing up 280Z and ZX distributors, or some other L series distributor. There are a TON of different mech advance units out there. The 280ZX distributors only have the two options, and as I recall the automatics had the one with more advance. I'm pretty dang sure I'm right on this one...

[jmortensen]

In fact, 1982 FSM p EL-34 shows:

Centrifugal advance 0 degrees at 500 rpm, 8.5 degrees at 1400 rpm

(that's distributor rpm, double for crank rpm)

17 degrees all in at 2800 is a good amount at a good rpm. I'd say it's about perfect.

[Bruce Palmer]

Thanks Bruce, If I send you a distributor can you recurve and rebuild it? Also are the vacum advances available for replacement?

Arne,

Steve and I keep going round and round on this distributor rebuild issue. He recently ran down to Napa NISSAN and grabbed their distibutor machine with just idea in mind.

We can certainly shorten that curve so you can control detonation and run more initial advance. Both good things.

I'm coming around to the idea that tearing into other people's units will show up those advance plates that are junk (retainers busted and ball bearings missing) and NISSAN showed like 6 anywhere in the world. Once you have a customer's unit apart, I'm thinking you'd best be able to put it back together.

So parts is going to be an issue. I'll do some checking on other sources.