LeonV

That sounds awesome!

Well said.

This is so awesome, great job!

Check the FSM, download it for free at xenons30.com.

We've already discussed the chain topic, within this thread! The timing chain is not the problem, forget about it. If anything, a slightly worn chain will retard the timing, which would give you a mild improvement in high rpm performance. Advancing the chain to the next position will advance valve timing and move your powerband down, meaning more low end torque as doradox states.

Excessive camber and fiberglass rear quarters equals big collision, in my book.

Your issue is fuel starvation, and it's very likely that the dirty tank clogged your filters. I would replace all fuel filters you have in the system (by the tank, in electric pump if you have one, in engine bay, and at the carb banjos). Again, for those having problems, correct valve lash is absolutely critical. It does not take much effort to remove a valve cover and measure clearances, yet it has a huge effect on the way your engine behaves. Filters first, valves second, then worry about the rest. If your car will rev to redline occasionally, but bogs at constant speed then the problem is exactly what you would think it is, no magic to it.

I just took a look at ZTherapy's site. Here is what they say about their balance tube: Here is their photo (PCV valve front and center): You must have the crankcase breather hose attached to the PCV valve. Otherwise, you have a giant vacuum leak in your intake making you run very lean.

Ok, so the problem from the original post has been partially fixed, correct? I really doubt that ZT would plug the PCV hole (why?), are you 100% sure that there is no hose coming from the block breather that attaches to the bottom of your balance tube as the FSM depicts? If there isn't then check to make sure that you don't have a huge, gaping hole or a PCV valve sitting all by itself in the bottom of your balance tube. If everything checks out, I would move on to valve lash. Check it hot. If that checks out, then make your way to the carbs and make sure the needles are installed properly. If they are, then put in a good set of stock needles and see if anything changes.

All cars sold in the USA since about 1968 had to have a PCV system. Refer to page EC-2 of the 240Z FSM. You've figured out the problem with the "colortune", but here's the thing with round top SUs: you can't adjust the idle mixture without changing the AFR in the rest of its dynamic range. By leaning out the mixture to look good at idle, you have leaned it out off-idle as well. We'll see if making the mixture richer will help, and if turning the knob doesn't work I would take the carb pistons out and inspect needle installation. A wideband O2 sensor is the only good method for finding out what is really going on in your engine.

If you don't care then you can do whatever you want... If you're talking about making an engine run as best as it can (this so called "tuning"), then that's another deal altogether. I'm really curious to see the dyno sheet of the 20hp gain that a header alone got you. Can you post the dyno sheet to substantiate your claims? Okay, the key word here is "seem". This does not quantify anything whatsoever. The EGR valve should always be inspected and replaced if it's malfunctioning. A malfunctioning EGR valve or broken parts is the only reason why an engine would operate better without the EGR system in place.

Vacuum advance is only active at part throttle. At WOT, vacuum advance should not be making a contribution to total timing. Empirically, MBT timing is typically 33-36 degrees on an L-series engine without serious combustion chamber work. If everything else is okay, and your timing is a few degrees off then the engine should still function fine, it will just be slightly down on power. One thing that is apparent to me is that your mixture seems lean. A leaner mixture burns slower, which necessitates an increase in spark advance. You increased advance and the problem shifted to a higher rpm, telling me it's a mixture issue. Also, popping from the exhaust can indicate a lean mixture since incomplete combustion will then cause the unburned part of the mixture to ignite and "pop" within the exhaust. The first thing I would do is check for big vacuum leaks and mal-adjusted valves. Just because they're quiet and were adjusted 2000 miles ago, does not mean that they're okay now. Make sure to include the PCV system during that check as well.

And where did you "see" this 20hp increase? What is the reason for eliminating EGR? EGR has NO effect on power at WOT and also increases your gas mileage at partial throttle. So not only does it not affect max power, but it gives you better gas mileage when you're cruising around while significantly dropping NOx emissions. That's a win-win in my book. So what the headers actually gave you was more noise, more heat, marginal (if any at all) power gain and a drop in fuel economy. You've actually lost power at partial throttle by eliminating EGR. There are no "tuning tricks" unless you consider it a trick to clean electrical connections, adjust valve lash and set timing. You will benefit much more from these three things I just listed, than haphazardly slapping "aftermarket parts" on it.

Concerning the exhaust system, best bang for the buck is to find a good exhaust guy and have him make you whatever you want. If you're after performance, a single 2.5 inch pipe with a resonator and straight through muffler will have great performance and shouldn't cost you much. If you want less noise, get a quieter muffler. My local exhaust guy did a header-back twice pipe exhaust for me, including a total of 4 glasspacks and 2 O2 sensor bungs for $300. Obviously, I can get a single pipe system for less. Find a good local exhaust guy and you won't regret it!

He is an EX-dictator. He has ceased to be!

Sure! Are there car clubs? I did some FSAE stuff but nothing outside of that. Then again, I didn't have a running Z at the time... Heck yeah, Julio! The Hangar is pure bliss for fabrication. I loved Cal Poly, wish I could go back for seconds!

If you're at Cal Poly, I would recommend making friends with everyone that works at The Hangar, especially if you're an engineer! I'm not sure about their current policy on personal projects, but make some friends and see what happens. Take some time to learn some valuable fabrication skills and you'll be able to fix anything on that Z!

Cool, sounds like an awesome project! Definitely post some video when you can!

Just take the wheels off and drop it on the ground. It'll be mad low yo.

Sounds like your countershaft bearing is on its way out.

That guy is so full of BS, I wouldn't believe a thing he says!

Aha, thanks Tom! I thought I had seen Mikunis with the pull towards the cabin, interesting that you can set up for LH or RH positions. I haven't seen that on the Webers, but it may exist as well.

Just FYI, this is not true. Flame temperature is a maximum with a slightly rich mixture (~13.5:1) and gets cooler as the engine is leaned or enriched from there. As far as color goes, I've done lab experiments with a glass engine (glass cylinder, you could see the piston move and combustion happening!) and from what I remember, orange was rich, bluish was probably slightly rich, and light-orange with flashes was lean. Good luck. I'm thinking that installing a WBO2 while also using the colortune may yield some interesting results.

Not exactly. They have cold start enrichment circuits, no choke valves are involved. But yes, they are both cable pull-type actuators. I think the only difference between the two in that department is the direction in which you pull the cable, but I'm not 100% sure on that. If you look at Dave's (cygnusx1) picture, the Weber levers must be pulled toward the hood. I think the Mikuni cables are pulled towards the windshield. Someone with Mikunis can chime in to confirm.

I like your solution, Dave! I chose to remove my choke lever when I put in a new center console.