DAW

I'd opt for a factory OEM cyl head in good used condition anyday over a rebuilt cyl head; at least you know the geometry is as-engineered and designed...a rebuilt unit is only as good as the replacement components and the rebuild technician, both of which are often inferior to Nissan factory production. I think you're making a good move with the head you picked up. For best performance on an L28, have the intake valve seats replaced with new L28 ('75-'78) seats, and take the intake valves out of the L28 head you removed from the dished-top piston engine and have them ground or lapped to the new seats. Transfer the L28 intake valve springs also to the Maxima head. Transfer the L28 cam, rockers, and lash pads to the Maxima head and keep them in the order they were with respect to L28 cam. If your L28 head is an N42 ('75-'76) then you'll need to transfer the cam towers too because they are spray bar-type cam oiling and matched to the undrilled cam. (later L28 cyl heads (and Maxima L24) have camshaft-drilled oiling; no spray bar). You should be able to leave the Maxima exhaust valve (including valvesprings) as-is. Providing there aren't definite signs of a burnt ex valve, just leave them alone. If you're shopping for a machine shop to do the intake valve job only, and you find a machinist who can't comprehend what it is you're doing and for what reason, and tells you that he will only do a complete head rebuild, then walk away and find one who will. The first guy is also the type who will sell you additional "necessary" parts&labor once he has the head torn down. This is not a complicated swap and you will definitely notice increased performance. Leave the dished-top shortblock alone and use the Maxima cast-iron exhaust manifold (as you're planning) instead of the 280Z manifold when you reassemble. Good Luck! DAW

If the turbo uses the knock sensor and the na not, then that's a great reason to go with the turbo ECU...in fact knock sensing could be useful if harnessed in a hi-performance na engine. DAW

The 8mm bolts use a 13mm nut, and the 9mm bolts, a 14mm nut. If you can put a 13mm socket on the nut it's an 8mm. DAW

You'll need to make a trip to a JY or two and harvest the pedal assy from a M/T car of same/similar yr, clutch slave cyl, clutch master cyl and all lines/hoses for the clutch. Try to take things off in as big an assembly as possible...which means you'll also be able to retro-install it on your car quickly. Get a clutch off a 2+2 rather than a coupe if you have a choice, it's stronger and the same as a turbo clutch in a few cases. Get the rear crossmember and rear engine mount, take notes from underneath on the donor cars as to where the factory-placed hole is in the floor (shifter); it may be essentially a punch/cut-out piece of sheet metal that you'll need to make on your car once you're at is out. One thing you might consider is replacing your A/T with a far superior, higher/newer tech A/T. Yours is a 3N71B three speed , non-lock-up torque-convertor and no overdrive gear. If you're going to performance-mod your car, you could use an A/T from an '85-'89 300ZXTurbo, they have a higher stall speed torque-convertor, which has lock-up, and the trans has a 4th gear. This set-up would be easier and faster to do than the M/T conversion. Oh, if you do this you'll need an A/T bellhousing from an '84 Maxima L24. An even easier quick upgrade would be to take an '81-84 Maxima trans; L3N71B. Not all cars used the "L" (lock-up; hydraulic (vs electric, used later)). That's a bolt-in and when the convertor locks-up it feels like the trans just shifted into a higher gear and it's quite a difference in driving the car, better mpg too. DAW

...OK, so then you place the assembly of air-to-freon intercooler into a bath of something, maybe some sort of gel of a material with a specific heat value that soaks up a ton of thermal energy without itself increasing its own temp too much, taking up much space, or being corrosive; something that absorbs the heat and transfers it to it's finned aluminum case which radiates it into ambient temp air (quickly if the car is in motion or has a fan). DAW

Another budget way of increasing the performance for the minimum $ into what's in it now would be Sterling Piston #12149P which has about 1cc dish, relatively cheap @ $30ea., uses an L24 rod (133mm, 9mm bolts, abundant), and could probably use the ringset you have (and rod bearings) if you're in a pinch (double check on the rings #). If a buyer didn't like the c.r., at least you could provide this info for an inexpensive route to a lot more hp. DAW

I think the O2 sensor gets into the circuit after warm up but check the temp sensor and TPS and the fuel pressure regulator diaphram. You may just be smelling SO2 from the convertor if the above sensors are bad and its dumping raw gas into the exhaust system. Is your convertor plugged up? DAW

I agree with Shane, there's more to it than the hardware store valve description, foremost is that it has no bleed orfice. When boost pressure actuates the wastegate and the boost pressure drops accordingly and the checkball reseats...it leaves a column of air filling the space between checkball and actuator diaphram..which holds the wastegate open indefinitely. The bleed orfice size is one of the means of controlling the opening action of the wastegate because it weakens the boost signal (e.g. a 10lb signal the wastegate sees to open it is actually coming from a 12lb boost signal that's been weakenned by the bleed orfice). I've been playing around with this type of boost control device a bit and I think I can come up with one allows adjustability by adjustability of its internal spring pressure (not by stretching the spring); and by changeable brass caps with slightly different bleed orfice dia. Meanwhile, for $50, the Hallman device is clearly the way to go for an effective, budget-minded control device and is the best balance between spending hundreds of $ for an electronic controller, and blowing up your engine with a makeshift hardware store gizmo (or making it slow by inadvertantly holding the wastegate open). DAW

Ouch! No wonder you're pulling the engine...the best thing at this point for the engine would be to have the piston tops turned down until the edge of the 10.9cc dish is cut down flush with the floor of the dish (making the piston a flat top with a decreased compression ht), then substitute L24 rods for the L28 rods. The result will be a strong na L28 with an improved rod/stroke over stock specs. Otherwise it's anemic...it just won't perform without a higher compression ratio or forced induction...but with the cam, headers, etc., you should stay na. You would be amazed at what increased c.r. will do for that engine. DAW

John, which pistons does it have? (i.e., what c.r.?) DAW

An A/C system compresses gaseous freon which changes state to liquid and creates heat into the freon which is radiated off to air by the condensor (I think; correct me if wrong)...the freon passes through an expansion valve, the resultant pressure drop causes temp drop in the evaporator and the aluminum evaporator absorbs heat from its surrounding air (transferring it across the aluminum). This source of cold air could be used to accelerate the heat transfer of an air-air intercooler, but heat is going air-to-aluminum-to-aluminum-to-freon. I'm wonderring if there's a more efficient/effective way of transferring the intercooler heat using a freon medium...it seems like using an evaporative-type element built inside of an air box could cause a lot of restriction and disruption to airflow if it were large enough to be effective in any volume. What if instead, an encasement box were constructed closely around an existing traditional air-air intercooler core such that the box itself is the vessel into which an expansion valve introduces freon onto one side of the intercooler fins (like a very flat end tank for freon), and the suction port for the freon is in another plate-like freon end tank on the opposite side of the intercooler fins. This system would allow good airflow for the induction charge while eliminating one (air-aluminum)thermal interface. This may already be what's being discussed vs chilled air across a conventional IC; but regardless, a question for this system would be: if a leak springs in the IC, what would freon do when it goes into the combustion chamber?? DAW

Just drop in a complete L28ET and the entire fuel mgmt system from a wrecked 280ZXT, add an intercooler, block off the emergency relief valve, add a BOV valve, and raise the boost a bit. All '81 280ZXTs had A/Ts and in general an A/T donor car may have less wear and tear than a 5spd. The road tests of the 280ZXTs often showed the A/T cars to be faster than the M/T cars (stock), and the dated 3spd A/T they came with could be retrofit with a 4spd A/T from a 300ZXT. Better yet, sell your car and buy a nice 280ZXT so that you get the bigger front sway bar, CV rear end, etc. DAW

I'm confused about the swap because a '90 Maxima already has a VG30 engine. I'm not sure if the Maxima VG30E evolved to VG30DE in '90 as the 300ZX did, but regardless I'd lean toward converting your engine to turbo using VG30ET or VG30DETT factory parts. You'd actually be better off if yours is VG30ET and not the newer DOHC engine because the c.r. is lower to start with. The conversion would not entail using a turbo bottom end but would have to be a low-pressure (ala Volvo) turbo system. Use the complete ECCS, injectors, fuel pump, etc, from a Z31 and change the cams if they're different (or just swap in VG30ET heads with the turbo manifolds on them already. I'd then take a small amount of the surplus money I saved from not pouring it into a megaswap money hole, and buy a JY front LSD as used on the GXE models (if you don't already have one) and a strong clutch. The rest of the money I'd saved I would put aside as a down payment on a used 300ZX, WRX, etc., i.e. an AWD or RWD car built to take a lot of horsepower as-is. My hindsight visual acuity being as good it is, maybe I can steer others away from the types of mistakes I've made with my time and money. DAW

The MAF signal is voltage and the AFM is resistance, but with the MAF being less restrictive, maybe the whole system from a 300ZXT ECCS could be transfered over. V6 or inline 6; the cylinders fire at the same interval and both the L28ET and VG30ET use a crank angle sensor and thermistor sensors (in general, Bosch thermistors share the same ohms change per temp regardless of the type of car they're used in). You may have to modify the injector harness lengths to get the connectors to reach their injector, but that's easy. The ECCS doesn't know if it's hooked up to a V6, L6, or flat 6. DAW

A vibration tool?

You could put the MAF in front of the AFM and hook it up separately, with the voltmeter in the car, in order to see the signal at various rpm/flows, then put a stock AFM there and do the same (both tests would be upsteam of the working AFM system). DAW

Don't exclude other sources for MAF (BMW, Volvo, Saab, Mitsubishi, etc.), many of these use Bosch circuitry like the Nissan systems and may be adaptable. DAW

Tony, I'm thinking leaner at idle and off-load and richer at higher rpm (and boost) could be accomplished with a rising-rate fuel pressure regulator. The best piggy-back computer I can envision for need-based enrichenning would be in circuit with a G-meter...(I'm serious, I think it could be a useful parameter for performance tuning). DAW

The most unique "other hybrid" I've seen locally was a drag racing electric motor 1st gen RX-7. I don't remember exactly how fast it was, but surprisingly quick (for one run). DAW

er..AFMs on the L28s

I don't think I understand about the duty cycle portion..I was thinking if a stock injector sprayed a certain volume of fuel for a given pulse signal, that a larger injector just delivers more fuel for the same pulse. If it's too rich then you can shorten the pulse, lower the pressure, or go to a smaller injector. I agree re a bypass and a MAF system because both lumens are a fixed value rather than one constant and one varying all the time. I've wondered if there is a donor for MAFs with a similar range of output values as the MAFs on the L28s that could be adapted easily. DAW

I agree with the others above that for an entry-level of experience the L28ET with all the factory harnesses, ECU, fuel pump, etc from a wrecked 280ZXT would definitely be the way to go. This might not be the recommendation for someone of a higher experience level with easier access to parts and machining who wants to build a purpose-specific car, like autocross, or some classification re turbo vs na. DAW

How about a larger capacity AFM (BMW?) to increase airflow, coupled with another leaning approach for lower rpm with the big injectors: you could install a resistor in parallel (NOT series) across the cyl head temp wires in order to make the ECU think the engine is warmer than it actually is and the ECU will shorten the duration of the injector pulse accordingly (and accross the full rpm range). The problem with the bypass approach is that you are letting in unmetered air that doesn't stay at a constant relationship or proportion in flow to the flow of the changing lumen size of the AFM/flap door opening. Unmetered air has no ECU-regulated fuel flow to match up to it and you could end up with an overly lean spot under a condition that could destroy the engine. If you could get a large displacement-source AFM and map/compare then calibrate its sensor/voltage specs to a stock AFM then you could set the big AFM's door spring tension to approximate the stock unit's signal and start tuning with spring tension/mixture control from there. DAW

The diesel is in the Maxima, which was called the 810 also in '81 or so, then just called Maxima after that. It had an LD28 available until '84 as far as I know. The manifold will bolt-on and doesn't have any air pump tubes (which also have a restrictive "bump" inside the manifold port for the tubes). The outlet ports/flange are in the same location and angle as the other L6 na manifolds but I don't know if they are absolutely identical. Another possible choice is the '81-'83 280ZX L28 manifold. The P79 head has hexagonal/"round" ports and the manifold ports have the same shapes but it looks like it would work on an early square port head in a pinch. One reason I say this is the observation that the P90 L28ET head is square port but the turbo manifold ports are the hexagonal shape and look like it would work on either "round" or "square" port heads (read: you may be able to use a factory turbo setup on a stock '75-'78 block/head, 8.3 c.r., if you keep boost down). The feature on the '81-'83 L28E manifold that's nice is the exhaust gas sensor between the outlets which can be used for A/F tuning. Stay away from the L28 manifolds of '75-'78 as they are strictly emissions-control design and not performance-oriented. Regardless of which factory manifold you choose, if it has separate runners for 1-2-3; 4-5-6; paired into separate outlets, street power can be gained by running longer down tubes than stock. The stock 240Z pipes are great except they're too small dia. There are (or were) down pipes available that run down as two large pipes, make the turn to run rearward, and merge into a 2.5" collector about a foot long. I don't know the current mfg, I bought mine from Impact in N.Y. Happy hunting! DAW

LD28 has a smooth-flow square port exhaust manifold with separate 1-2-3; 4-5-6 chambers and strong downtude studs. DAW