Troubleshooting performance

[soundmasterg]

If I went to the Pertronix and a Crane PS-40 coil, should I increase my spark plug gap also? I tried it before I put the coil in and it ran better at .032 than above .040.

Greg

[sblake01]

If you "up-grade" to the ZX distributor - you have to also supply it with a ZX spec. coil. Otherwise you can suffer from too weak a spark, to jump that larger gap consistantly.

The car will run with the 240-Z coil - it just won't run as well...

FWIW,

Carl

And lose the ballast resistor......

[DeesZ]

Years ago I did some work on diesel engines for Uncle Sam. At high altitudes in S-W Cambodia, say 5000 feet, our compression levels would drop. What should have been around 500psi at 0 altitude was coming in with about 450psi at 5000 ft above mean sea level, and these things were new out of the crate. We also found that cutting the fuel back by about 10% made a good overall improvement. Now, that's diesel stuff and I'm going back on 35-year-ago recall. Not certain how this would translate for internal combustion. We also converted over some types of internal combustion applications to turbine engines because the IC engines' performance suffered terribly at high altitudes. It's all old technology now, but the basics are likely the same.

Edited September 26, 2008 by DeesZ

[Pop's Z]

Just had to respond on the Z Therapy jets and needles. When I got my carbs "Z Therapy-ed" the sheet they sent back said I had .100 nozzles and

N27 needles. I told Bruce that I lived at 5000 feet and that most of my driving was at even higher elevations. I have a ZX dizzy and a Crane PS20 coil. I eliminated the ballast resistor from the system. I gapped the plugs (NGK BP6ES) at .043. I consistantly have a nice light brown residue on the plugs and the engine (a stock 2.4L) runs very well. That being said, I'm about to install an

'82 280 ZX motor with 132,000 miles on it. I'll transfer the carbs and dizzy and see what happens.

Cheers, Mike

[dcraigbrown]

Ya, I think I'll try the smaller nozzles and see which needles go with. Eventually I'd like to drop an L28 in it but $$ are tight these days. Is the swap pretty much plug and play, or some modifications required? I'd be interested to hear how your'e goes.

[dcraigbrown]

Refering to the other posts concerning the electronic ignition and losing the ballast resistor, I did both. I bought a stock zx coil and bypassed the ballast. That brought a huge improvement. I might just be dealing with a false perception now. I am curious though why just leaning out the mixture won't do the same as installing a smaller nozzle?

[Bruce Palmer]

Refering to the other posts concerning the electronic ignition and losing the ballast resistor, I did both. I bought a stock zx coil and bypassed the ballast. That brought a huge improvement. I might just be dealing with a false perception now. I am curious though why just leaning out the mixture won't do the same as installing a smaller nozzle?

What a great question. Let me see what I can do with it.

Say you run the nozzle up to where you've gained a thou on the needle. I think what you have is a one point improvement on the needle by closing down that gap. What you are left to deal with is the profile on the rest of the needle, all of which are different. In essence you've introduced a new needle to the deal.

By going down in size on the nozzle the full range of profile on the needle remains useable as if they were stock. This way you are working with a needle profile that was at one time derived for a particular engine through a full range of RPM. I think running the nozzle up a known needle introduces new characterisitics for that needle across the RPM range which may or may not be right at the new setting.

Does that make any sense to ya all? It's early, I tried. Feel free to ask for your money back....

[dcraigbrown]

Fair enough. My mechanical ability stops at knowing the engine needs a good air fuel mixture but short of knowing all the nuances between the needle and nozzle. I have no doubt that a lot of guys on this forum would verify the smaller nozzles would be a good option in my (high altitude) situation.