LeonV

Some may be interested in a bit of data that I collected yesterday. Ran my Z on the dyno all day, testing various jetting and playing with timing (first with E12-80 and then with 123ignition dizzy). The goals of this project was to learn, as it was my first engine build, try different things even if they go against "conventional wisdom", and enjoy playing in the sandbox that is Z-cars. Ran it on the Dynapack at Works Motorsports, where I used to work (no pun intended). Steve aka Datsuncrush, the owner of my previous 260Z, came by for support and videography! Basic engine specs are: flat-top L28 (0.5mm over), shaved and ported P90, Isky L6 grind cam (.540"/270*), 45DCOE with ported and matched manifold, and MSA 6-1 header with a nice and quiet 2.5" exhaust (resonator and Walker Quiet-Flow muffler) so I can hear those Webers sing. However, I'd like to think the devil is in the detail! Using the OEM head gasket, compression is 11:1. Piston-to-head clearance is .017" (less than 0.5mm!), that's with .021" piston pop-out from the deck. Because of the excellent quench and combustion chamber of the P90, it runs on CA 91 pump gas with 34* of advance all-in! The cam wipe pattern is cheated over to the pivot edge of the rockers. The head was ported by Rebello along with the port-matched and pinned intake. Running Supertech undercut intake valves and OEM L28 non-turbo head bolts on Dave's recommendation. Final jetting was 135/F11/110 (main/tube/air) but it leaves a lot to be desired. The F11 tube is a particularly poor performer in sidedrafts and causes dramatic lean-rich-lean swings (+- 2.5 AFR!) at WOT. I did my best to reduce that tendency by limiting the amount of air drawn into the tube (hence the 110 air jet). Unfortunately, I did not have other tubes on hand to play with. Venturis are 36mm. I plan to correct the mixture and play with cam timing another day but the end result is a good baseline to start from! The yellow line is with stainless steel mesh filters and red is no filter. They were worth ~6hp peak and 1-3lb-ft across the RPM band. And of course, the required video: Overall, I'm very happy with the results and the Z pulls like hell!

Yes on the exhaust studs, NO on the head bolts. The FSM specifies fresh motor oil on the head bolt threads before install to control bolt friction during torquing.

It's a Silvia with an S30 front end conversion, pretty popular in Japan.

The threads are much more likely to be M6X1.0, bolt is probably something like an M6X1.0X16. Getting the distributor out is very easy. Replace the base gasket while you're at it.

Ha, that thing is rad!

I'd guess $25-30k. Good luck!

Commonly referred to as the "Euro lip"

I don't recommend Delta. If you have used Nissan rocker and they don't have a big groove worn into them in the middle of the pad, you're ok to reuse. Much better than reground rockers for multiple reasons. This is coming from a combination of my own and others' experiences, as well as straight from Ron Iskenderian's mouth.

They're fantastic so far, loads of grip on the street! I plan to do some autoX in the near future and maybe a track session if I feel like breaking something, should get a better feel for them then.

Wired backwards? Gap too wide?

My Z is very easy to drive with the 10lb Fidanza, requiring only a bit more finesse than stock when taking off. Stock is around 22lb as site mentioned, so it's a 12lb difference plus/minus a pound. The difference is noticeable but it does not become a pain to drive in traffic at all.

Absolutely. If you're not making way more power than stock, there is no need to spend 4-5x over a perfectly good stock clutch.

Get a big cam and run the triples, you will not regret it. Call and talk to your cam grinder to figure out what profile fits your needs. Regarding compression, I ended up at nearly 11:1 on CA pump 91 and didn't realize my CR was so high until I re-ran the calcs. I haven't noticed any pinging but I'll admit I haven't had a chance to do a whole lot of tuning yet...

Alright, good work Steve! FWIW, I prime fresh motors with the valve cover off (internally oiled cam). Last time I did it, I primed with the rockers removed as to not run them dry. Oil everything up and spin the motor until oil starts flowing from the lobes. It takes longer than you may think.

Take a propane torch to the diff cover, fill plug should come out easy once that Aluminum is nice and hot.

Can you post a good photo of the lobe in question and it's rocker arm?

No problemo!

I believe the N42 head got the new bar, so 75-76 280Z would be the most common application.

Strange... Good work finding the issue.

Why do your carbs have so much varnish in them? What fuel do you use?

I'd guess the loose manifold bolts had opened up an air leak. Glad you got it fixed!

You can also test your clogged jet theory by fully closing each idle mixture screw one-by-one and seeing if it affects the engine.

Vacuum leak is the first thought that came to mind. Vac leaks are most apparent at idle, less so at part-throttle, and essentially unnoticeable at full throttle unless it's a huge leak. I set my floats according to the top-down method, I don't pay attention to how they're actually angled as long as they're all relatively similar.

Both sizes half slim choices for tires. You can get either okay-but-not-great summer tires or aggressive street/track tires. I'd go for the latter but it depends on what you use your Z for...