wheee!

As for the stock ecu, I agree I may have to stay with the stock motor config for now, but with two motors I may be able to source a triple weber carb setup for the P90 head combo. Again I appreciate all the feedback guys. I am a member of the local z car club and have a lot of experience with 370's. The long winter an short driving season here have prevented me from taking advantage of a ride along in another members 280. Sent from Canadia

From another head thread... I expect the same compression with a head shave. WHAT DOES THIS RAISE THE COMPRESSION TO? After running it for a year, I had the machine shop CC it when I had it off for my newest engine mod. They got exactly 46cc. That equates to 10.06:1 on a L28 with flattop pistons. At 500 miles my new motor showed 210-215 psi on each cylinder(!) But remember... this P79/P90 head mod is meant for flattop piston L28 motors only. If you use a dished L28, the compression will only be in the low 9s which won't be worth the trouble. Sent from Canadia

I guess so. I'll get the head shaved and do the porting and polishing first. I plan on doing the body restoration first so I have about a year before I need to worry about the motor. With two complete motors, I can play around a bit. Sent from Canadia

Picked up my P90 yesterday! I am still thinking a mild shave, flat top pistons, stock cam and ecu. 10:1 compression with a 1mm gasket. Port and polish while I'm at it. Thoughts? Not worth it? Sent from Canadia

The sad part for me is that I have never driven a 280Z and have no baseline. I can't compare it to my 370Z! I just want it to be a fun, safe, spirited driver. The aesthetic mods like a shaved intake and fuel rail are more for the OCD part of me. I hate a cluttered engine bay. My big advantage is that I am doing a complete restoration much like Hazmatt has done. I don't need it as a driver and I will take my time doing it right. Sent from Canadia

SO I guess the question now becomes, should I leave the engine stock and just do a rebuild and header back exhaust (147,000 miles) or should I modify the engine slightly by going flat top pistons and the P90 head with headers and exhaust? I am seriously thinking of leaving this engine stock at this point unless someone can offer me a better solution for a mild performance build. Triple webbers would be awesome but are extremely hard to come by up here in Alberta. I know I can order a set from a dealer with intake for a couple thousand dollars, but that seems a little steep for a street dd build. I also have the extra L28 engine that I can build on the side after the stock motor is finished. Experiment with it so to speak.

But will the smaller combustion area and better quench with flattop pistons be better than the stock configuration on the 76 N42?

So is going the route of removing the FI and installing an older carb set up better? Or a four barrel carb manifold? I thought the fuel injection would still be better than carbs....?! As for the P90, I am under the impression is is a solid lifter head, unlike the hydraulic lifter P90a head... Or am I wrong? I thought the P90 was similar to the E79 only better?? Excuse my cylinder head ignorance please.... edit info from web: Nissan made only three US 280ZX heads from 1981-83, the P79, P90, and P90a. - The P79 came on the non-turbo L28s - The P90 and P90a came on the 1981-83 turbo ZXs. All three heads used the same valve diameters (44m intake/35mm exhaust), combustion chambers and intake runners. While I don't have numbers, one would have to assume that Nissan designed its turbo heads for one thing: to flow lots of air. The important difference was that the P90/P90a came with square exhaust ports instead of the lined "diamond" shaped ones on the P79. The P90a is identical to the P90 except for it's unique feature of having hydraulic lifters under the rocker arms which no other Z head had. This made for a nearly quiet engine needing no valve adjustment, but could not use high-lift aftermarket cams because of the lifters and was costly to rebuild. P90a replacement lifters were about $50 each, but have been unavailable for years. This made the P90a a great head, but not the best choice for modifying. Keep in mind that the a P79/90/90a on a flattop piston L28 will give 8.8:1 compresion, on a dished piston motor 7.4:1. THE P90 PROFILE - square exhaust ports with no liners (like the N42/E88/E31 heads) - .100" deeper chambers than the N42/47 - nearly straight exhaust runners and high-quench/swirl combustion chambers - steel valve-seats INTAKE RUNNERS The P79 and P90/P90a combustion chambers are deeper than other L28 heads. By making the chamber deeper, it lines up the valve bowls with the intake runners and greatly straightens out the short-side radius "bump". N42/N47 heads have a sharper "bend" as the runner transitions to the bottom of the intake valve. FUEL PUMP HOLE Strangely, while the P79 has the mechanical fuel pump hole sealed over, the P90 actually still has it, the ZX power steering pump flange covers it. I'm guessing the same casting dies for the square port N42 were used by Nissan. Why else would they leave the hole there?

Good points.... I am liking the input here and I am realizing I might be better keeping the engine fairly stock. I can port match and redo the seats for sure. The lightened flywheel concerns me as clutch engagement is different and can sometimes lead to stalls at low rpm's. My wife tends to shift a little heavily... Plus the chatter. Clutch, not her I already have the early 5 spd and R200 3.90 lined up for the build. That should help too. Thanks for all the tips!

So would you recommend sticking with the N42 head, swapping to flat top pistons, and keeping the stock exhaust manifold as the best route to go? Small increase in compression and no changes to the EFI? I still have an extra L28 that I can use the P90 on later if I go all LD28 crank and overbore on....

Thanks for the input! I am not familiar with the stock ECU (I actually have 4 of them now, ). I was under the impression that the larger cc injectors will operate at the factory pressure/volume based on the ECU output. The advantage being that later on I might be able to upgrade the engine without having to replace the fuel rail/injectors (for a megasquirt system for example). Which aftermarket ECU should I be considering? I run UpRev tuning on my 370Z... Thicker gasket was in relation to having to shave the P90 head down and adding the flat top pistons. I was trying to stay around 10:1 compression and assumed I would need a thicker head gasket or have my pistons machined to avoid valve collsions/too high compression. Again, I plan on running 94 octane in the motor when it's done. Headers for the wife? Ha Ha! Funny thing is I put the HKS and berk exhaust on the 370 and now she hates the sound... (I love it). But the exhaust headers were to clean up the engine bay/cylinder head area and gain a few HP. My wife drives sports cars and is used to over 300HP so I wanted it to have a little more oomph and headers are usually an easy gain for cars. Performance exhaust will of course be part of the plan but I may slip a small Cat in there to eliminate any fuel smells from the exhaust. A 200 cell unit should do the trick and keep the sound down a bit too. She is aware the 76 Z is going to be a little louder than her Turbo Veloster... Thanks for the excellent feedback guys! I am learning a lot on this forum!

I would like to see a reasonable gain in HP & torque with a slightly higher CR, but I am not looking for huge gains. I know the stock configuration with N42 head has a lower CR mostly to combat emissions during the production era. The higher quench and better flow of the P90 head should make for a small gain in performance I would think. The flat top pistons I thought would raise the CR enough that all I would need is Premium fuel in order to avoid detonation. The P90 is in need of a milling and I was assuming that I would be able to take off .080 without too much of an issue. I am not sure if the head has been milled before, but I will confirm that before re-milling. A thicker head gasket could solve any issues there I would assume. The fuel rail is more to clean up the engine bay than anything else. I like the look of the shaved intake and Pallnet fuel rail. The 14mm injectors are so I can use the low resistance Audi style 14mm injectors that have the same harness connections. Performance there is not really a concern and I would hope that the stock FI computer could manage that. Having said all of that, I am starting with two complete '76 L28's with N42 heads and all accessories, so I have two of most everything. The solid lifter P90 is coming from a friend who has a spare early 5 spd and 3.90 R200 for me as well. In the end I would like a spirited driver that has a small bump in performance over stock.

Hi! I am going to be rebuilding my 76 L28 this year and would like to know what pitfalls to be aware of in the process. I am planning on using a P90 solid lifter cylinder head and flat top pistons. I would like to end up with between 10:1 - 11:1 compression. We have 94 octane fuel in my area. This will be a daily driver for my wife and will not be raced or tracked. Aftermarket Exhaust headers will be used and probably a Pallnet fuel rail with 14mm injectors. Thank you in advance for your tips and help. This forum is full of very helpful people!

subscribed for future use... thanks for the research!

Just curious... what has your timeline been? When did you start and how many hours/month have you put in?

Well, that's what I thought.... but upon doing a small test area for paint removal over the rear quarter i encountered 4 layers of paint and primer and some heavy bondo around a replaced lower quarter panel.... This is not a "virgin" restoration apparently!! Your thread will be my bible for restoring my Z. A million thank you's for documenting your extremely well done project! ....and if you ever feel like coming for a drive north, you will have a warm reception at the Edmonton Z Car Club!

Now come work on mine....

I just have to say, this thread is epic!