LeonV

Correct. Or rather, they attempt to equalize. One 140 treadwear tire will differ from the next, depending on manufacturer. This is due to the way that the treadwear rating is determined. Treadwear ratings are something that can be played with and this is actually somewhat described in the TR article. To truly equalize tires, everyone would have to run the same tire. With that said, none of this matters much if you're not trying to win National Championships.

The best advice I can give is it's somewhere on the sidewall. Usually doesn't take long to find it unless the tire is caked in dirt. If you're buying new tires, that information is available to you without having to look at the sidewall.

This should be interesting as I plan to get some machine work done on a block and head. The default suggestion is to go to Rebello, but not everyone needs that. Piggy-backing on this thread, has anyone used any machine shops on the Peninsula with success?

It's on the sidewall, they are talking about 140 treadwear tires. This is not complicated. The Tirerack article does a pretty good job of explaining things. EDIT: We posted at the same time, looks like you figured it out. The TR article describes what the temp and traction ratings signify.

BTW, I played with the Z a bit last weekend. Switched the hypojets from H223 to H221, meaning the smallest air bleed hole. H22 denotes a .022" orifice, the third number is air bleed size with 1 being smallest and 4 largest. A smaller air bleed enriches idle while leaning transition. You can look at the hypojet as a "teeter-totter", which balances out idle and transition mixtures. It's an awesome tuning feature of the hypojet, essentially making 1 idle jet into 4 (e.g. 50F8, 50F9, etc). Therefore, moving to the smallest air bleed enriched my idle while simultaneously leaning out transition/cruise. The Z ran even better! Idle was rock solid at ~14.5:1 at about 1 1/4 turns of the mixture screw and cruise mixtures were leaner, in the 13:1 range. Testing was done on a relatively cool day so I'd like to lean out cruise mixtures further. Keith recommended blocking off a hole in the e-tube to see if cruise mixtures get leaner (part-throttle AFR is controlled by a combination of the idle jet and e-tube), although it may have an adverse effect on transition. If this experiment doesn't give good results, going to a smaller hypojet should do the trick. The only real issues I still have are my carbs not always going back to idle (mechanical issue), hesitation when suddenly jumping on the pedal at low rpm, and going too rich at WOT. New internal throttle return springs and 110 mains are on order from Pierce Manifolds which should help the throttle return and going rich issues. I'm working with Keith to solve the sudden WOT hesitation and will be putting in stiffer accel pump springs as soon as he gets them in. That should strengthen the pump shot. I checked and have size 40 pump jets, but did not check bleed back. Keith believes that the springs will have a bigger effect than changing either the pump jet or bleed back jet. One other benefit I noticed last weekend, the car starts much easier when it's warm. I no longer have to crack the pedal to start it. Cold starts require pumping since I don't have my cold-start units connected, which I never needed before since I was running so rich.

That about sums it up. Enough flow as to keep the floats filled and enough pressure to get the fuel there. I agree that if you don't have starving issues, you're likely ok. I would put a fuel pressure gauge either after the carbs or between the 2nd and 3rd carb and make sure there is some pressure there, if you're really curious. I've taped a fuel pressure gauge to my windshield to test this. Not my fault if your car burns down. I'm still using the stock mechanical pump, but I did block the return line when I was tracking starvation issues. Turns out it was a bad fuel filter, but I never got around to unplugging the return line since it was running well. I should unplug it one of these days for curiosity's sake.

Well put, took the words right out of my mouth! (Except the "Spec tator" bit, nice touch )

I recommend reading for a few months before touching the car. Buy some books on automotive maintenance and fundamentals and go from there. Taking some basic auto tech classes at a nearby community college would help greatly as well.

Agreed.

What, doesn't everybody track their commutes by spreadsheet to find optimal routes and departure times? LOLLOLLOL Yup, you're right! However, SF must still be tackled as I have to drive across the city to get to the Golden Gate. There is no freeway that accomplishes this. With SF done with in a timely matter, it's about an hour from my driveway to the parking stall at work. Looking at my (ahem) spreadsheet, the quickest I've ever driven through the length of SF has been 11 minutes and the slowest at over 40 minutes.

Nice to hear, Julio! Your job description sounds eerily similar to mine. I'm an automation/tooling/anything else engineer at a medical device company and I commute to Petaluma 5 days per week, but live in San Bruno. You'll get used to it, just figure out the best time to leave the house. Certain times of the morning can be great, but rush hour sucks, especially when school is in session. I drove the Z in to work today, made the Friday drive a little more tolerable. What's your commute looking like? If your going up north, I have a spreadsheet.

Sweet S2000 Phil! I like the Silver/Red combo. Sounds like some grand plans in the works, good luck!

Ah, that's right! It was Bill that said he exclusively tracks his Z. Ooops!

I'll report back with my findings once I get things dialed in. You can see first hand whether it's worth it or not!

I definitely agree with the rich-running sentiments. Getting a carb to run an engine is one thing, getting it optimized is the challenge. You're definitely on the idles at low-speed cruise and I remember Keith saying that you're about 50/50 on the idles and mains at high-speed cruise, say 75mph. Mine came out running a lot better than it was but there is definitely work to be done! I'll be getting some 110 mains and a set of internal throttle return springs (mine are dead) soon. Keith's Elan (400cc cylinders, 30mm chokes, same as my Z) runs the O3 tubes and only needs 110 mains. Besides Rob, my Z hasn't seen a track yet. My goal is for someone else to be able to drive the car and not tell it's carburetted. Your Z is almost exclusively a track car, so as long as tip-in and WOT are set, you're ready to roll! Of course getting better mpg on the way to the track is always a good thing as well. I need to get my Z out there with you guys.

Thanks for the reminder!

Oh man, this discussion could go on for a loooong time! A good start would probably be buying Obert's book. But to sum it up, of course there is the precautionary warning of making sure all other systems on the car are functional, ignition, charging, etc. A dysfunctional engine will make it impossible to tune and will frustrate you to no end. Once you're ready to tackle the carbs, the fuel levels must be set accordingly. Keith has found that to be 2mm below the brim of the passageway to the aux venturi. Then make sure your carbs are in order: no leaks, barrels flow equally, throttle returns correctly, linkage set up properly. Once that is set, you're ready to "tune". Ensure throttles are positioned correctly to the progression holes, sync at idle and high rpm, play with the jetting... Keith is working on a paper to detail all of this, hopefully he'll have it up soon. We had some very interesting discussions on the physics of what is really going on inside those carbs, and I'm sure he will be covering that in the paper as well. As far as venturi-to-engine size question, that is a good one and not simple to answer. Venturi size would be best determined empirically. The goal would be to go as big as you can without sacrificing driveability, and this depends on parts availability and the skill (moreso patience) of the tuner. Intake length sizing is its own discussion, and I've made some fairly detailed posts on it on HybridZ. In a nutshell: Use air horns, or at least have some sort of radiused opening at the inlet of the carb Longer intake valve-to-carb inlet length is more efficient at lower rpm Shorter intake valve-to-carb inlet length is more efficient at higher rpm Have as few bends as possible and try to make it a straight shot into the cylinder I've designed a spreadsheet that is supposed to predict intake and exhaust lengths according to RPM but I've yet to test it. I'm sure Obert's book has the details on it. Internal Combustion Engine Fundamentals by Heywood has some very good sections on intake and exhaust design. I've recently bought Obert's book, and in some respects it's outdated (which makes it cheap ), but most if not all of the information will be very relevant to the L-series engine.

My setup: L24/E88 with stock cam 40DCOE18 Webers with 30mm chokes Nissan Motorsport header with dual 2" pipes all the way back Started with: 50F9 idle jets (too rich) F11 e-tube (junk) 170 air corrector 125 mains (bit rich) *** I need to track down accel pump specs Performance resulted in really soggy idle and cruise mixture and some bogging on aggressive tip in at lower rpm. WOT above 3500rpm was good, no matter the gear or how aggressive I was with the throttle. After tuning day: H223 hypojets (.022" orifice, 3rd air hole) O3 e-tube Custom air corrector for O3 tube 125 mains Idle is way better, less soggy but no flat spot. Cruise mixture is better but still rich. I plan on going to a smaller hole on the hypojets, which would enrich the idle but lean out cruise. I think the H222 or H221 setting will get me close but we'll wait and see. At WOT, my mixture still tends to go richer as rpms climb. I'll talk to Keith and see what he thinks. I'm thinking this may require a different e-tube, perhaps an O2, as it has less holes to lift the fuel up. However, low and midrange is fantastic. The mixture is spot on with much less jumping around as shown by my wideband. I still have an initial hesitation issue when quickly going WOT. It'll hesitate and then pick up, so this points to an accel pump issue. I need to investigate this further, as I don't know how much bleed-back I have and don't remember the size of my pump jet (40 or 45 I think). One other thing I discovered a few days ago is that my internal return springs need replacement. I was doing idle-sync and decided to see how well each carb returns. After disconnecting the linkage, I blipped each carb independently to see if it had the same airflow before and after. Each carb was flowing more after I blipped the throttle, indicating that it is not fully returning. Pierce Manifolds has the right ones for a good price.

FWIW, Bryan Blake goes by "1 fast Z" on hybridz.

Man, what an awesome day! Throttle response has never been so crisp before and the idle is so much cleaner. I love how my mixture got steadier too. This is just the beginning, I'll be playing with the hypojets to find the optimal ones as well as increasing my pump shot and possibly upsizing the chokes. Achieving Weber nirvana is a (big) step closer! Big thanks to Rob for setting this up, Keith for the time, parts and knowledge, Original Customs for hosting, and Glenn, Patricia and Bill for coming. It was a blast!

Heck yeah I'm still in! About to print directions actually.

Carefully apply heat with a heat gun and see if it loosens up. Don't melt anything.

Download the FSM from the "Reference" section of xenons30.com, everything you need is in there. The Haynes book is woefully underwhelming.

You can always leave it as is and hope for the best! The way I justified it to myself is that the engine spins counter-clockwise when looking at it from the driver's seat, thus the header will move away from the floor under torque. The only time I can hear my header tap is during a bumpy, hard right corner and I attribute it to poorly-done exhaust hangers.

Ah, the machine shop ground the washers. Shims would be a different issue altogether! I can see your concern, although I'm not at all worried about my floor (more about the header, really) if contact is made. Since you don't want to clearance the floor and don't want it to have a chance at tapping it, bending the pipes would be your best solution unless you want to put a dent in the header where it is closest to the floor (I wouldn't). Wrapping the area may help with heat, but it also expands the effective diameter of the piping, meaning that the wrap will be even closer to contacting your floor.