Davey G

My '78 280Z is my daily driver, and already had a valve job when I bought it 10,000 miles ago. It always starts, reves to 6K, runs great. Stock the car is 150 HP (170 S.A.E. HP) and at 2900 lbs any additional HP or weight reduction yields good results. It seems to me like 40-50 extra HP would go a long ways with a 2900 lbs car toward making the car more fun, less sluggish around town and on the freeway. So to my questions: Can 40-50 HP gains be had with bolt on equipment without tearing into an otherwise great and dependable engine? I'm thinking headers, exhaust, mufflers, K&N filters, etc. or are those add-ons only going to net around 15 extra HP? Or am I going to need head work, triple ground valves, flat top pistons, lighter flywheel, etc., etc., to get there and maybe more? I thought I'd ask the guys who know..........................dg

The other thing I did was change to a new 180 degree thermostat to keep the car running warmer, as in doing so will send a message to the computer to let the car run leaner.

The car was running decent before. It had a valve job 9 months before I bought it, but all is still stock (so far). I also replaced the AFM-to-Throttle body boot which had dry-rotted and was leaking air, and had the AFM adjusted. I then replaced the exhaust donut between the exhaust manifold and downpipe. But it was still running rich. I did a lot of reading - first "Brapp's L6 EFI-induction advice and tips" from the Nissan L6 Forum, then further on the links he provided on there. One is a 70+ page document on Z EFI and troubleshooting the same. Both are fantastic. Part of that reading helped me to understand how an injector works, and I realized that if it did not get the same current to every injector because of crappy connectors the injectors would not consistently open up the same or for the same duration, thus different amounts of fuel getting mixed with the air before getting compressed into the combustion chamber. Yes, the car runs better, smoother. It also runs cleaner. I still wish to replace all vacuum lines as well. It's very dependable, and my daily driver, 50 miles per day, 5 days a week. I love the L6 engine! One day I'll rebuild that thing, but from the way it's running it may be a while.

Well I finally got around to replacing the connectors for the injectors. It still had the original connectors on it when I purchased the car in February. I don't think any manufacturer got the connectors right until the late 80s. I went with AC/Delco connectors and they worked out great. I took a short overnight road trip, only a 2 hour drive one way, and by the time I had gotten back I had averaged 23 mpg. Previously I had only gotten as much as 21 mpg. While my mechanic was doing the connectors he also found a radiator leak. I had told him of a small 2" puddle of water/coolant I found on my garage floor, but he found the crack where it was coming from. Though planned for the future, I got to put the aluminum radiator in now instead of later, even though it hurt the pocketbook a bit more than planned. Next on the horizon are: a/c & heater work new blower motor weld 4X12 rust area in floor pan replace floorpan support rails And if I can just figure out how to get that interior overhead trim (that houses the dome light) to quit squeeking...!

Round port or square? Coated or non-coated?

What type and brand header did you use? Are there good ones and ones I should try to avoid?

Guys The suspension part is done, including bushings, no vibration even at speed. I replaced the AFM-to-TB boot since it was old and cracked, had the AFM adjusted and timing set - made a huge difference in the engine's ability to climb thru the RPMs. Runs well all the way past 90 mph, though slower getting there than I'd like. The brakes are done, albeit stock. Replaced bushings on shifter, new carpet, new vinyl, new tach. I get about 21 mpg with freeway/town driving, everyday driver. What size wheels/tires work well for street performance? I have some 15" alloys with Michelin 60-Hs on it now. Good tires but probably not the profile I eventually want. I also have an exhaust leak at the donut joining manifold to downpipe. Is it time for those headers, or just get that fixed? Davey G

I have an exhaust leak where the exhaust manifold joins the downpipe (bad donut?). Headers are part of my future mods, and will get the 2.5" exhaust at the same time. Will the combination buy me anything, or do I have to switch to a MAS and larger throttle body to gain anything? Just wondering how to prioritize the mods. I'll probably upgrade the sway bars to 1" front, 7/8" rear soon. I've also finished interior refurb (except the cabin light), carpet, and polished out the paint in the meantime. The car also runs great since replacing the AFM-to-throttle body boot. New connectors for the injectors soon also.

It's a bone stock '78 280Z right now that runs great and I use it as a daily driver. Since it's running well I have considered a Phase 1 of making the stock engine breath better with higher volume cold air intake, headers, and 2.5" exhaust upgrade, then down the line do Phase 2 with head work, flat top pistons, clutch, and an appropriate cam for street performance. But I've been told I would waste money on the headers because I need to go back with an N42 head for Phase 2, and they need a square port compatible header. Is the N47 so lame that if I'm aiming at an eventual 230-250 HP I'll need the N42? I'm getting conflicting stories from different Z motor builders. Either way is fine; I just want to use my car funds wisely. Any experienced guidance would be welcome. Thanks

Thanks for the guidance everyone! I will formulate a plan and proceed. Davey G

Since the 280Z is fuel injected I want some help with knowing how far I can go with the stock EFI engine. As the paint and suspension work are finishing up I'm wishing to formulate some engine upgrade strategies for street performance in phases. Mr. Cerutti's 280 mods is on the far end of my thinking (and pocketbook) - computer programmed 280 ZXT, raced out suspension, etc., so that might be considered a Phase 4 with an EFI engine (might decide on carburetors before that point). That said, what would be Phase 1 with the stock engine? My inexperienced thinking says K&N intake, 6-into-1 headers, 2.5" exhaust, electric engine fan, etc. Then at Phase 2 (rebuild time) perhaps a lighter flywheel, higher flowing oil pump, bigger AFM, etc. Thoughts, opinions?

Well, after all that I've determined the tachometer is screwy. Today it would not register anything above 3900 RPM, though I had the car up to 100 mph (if the speedometer is correct), and it ran well, even if not perfect. I'll have to do a little electrical troubleshooting I guess.

Since the engine feels strong it may be that the tach is wacky. I'll check the fuel filter and pressure also.

It got the tuneup before I bought it, at which time it got new cap and rotor, new wires, new plugs, new air flow meter, and timing. It has new tires. I've replaced the air filter since buying it.

Help! Total noob here, with my first Z bought a week ago, currently doing suspension, weatherstrip, and interior redos. Engine has had a top end rebuild within the last 10,000 miles, and runs good. I know these L28s are torque monsters and this one pulls strong as well, but this thing struggles to want to climb above 4500 RPM or so, even in 2nd. This was originally a 4-speed, now with a 5 speed, so is the original rear end not a good match, and holding it back? Or could I be looking at other problems?