DAW

Part II. So the LD28 bottom-half/P90 top-half is the "budget" stage II project and both of these engines (stage I and II) have decent rod/stroke improvements over the L28, and far better than the 83mm stroke/133mm rod formula. The next stage is to optimize the performance capabilities through increasing displacement (bore) of the LD28 and selecting piston/rod combos to get the best rod/stroke that the taller LD6 block affords. Stage III is still budget-minded as it uses stock Nissan L4, L6 and LD6 components rather than custom pistons, rods, etc. It is an overbore from stock 84.5mm to 86mm (unlikely that this is the max overbore, discuss later), use L28ET pistons (38.1mm c.ht.), L20B rods (145.9mm, same pin size, 21mm), and the P90 top-half. The 10.9cc dished turbo pistons keep the c.r. reasonable when the displacement is increased by the overbore, and the rod/stroke is now 145.9/83mm = 1.76. I've heard a lot of hearesay about the hybrid engine I'm talking about (like it can't be done, the LDblock which is built for 22:1ish c.r. can't be overbored [right! makes sense to me]), but haven't compared notes to many fellow builder/users of this engine hybrid. I'd like to compare notes to others out there who have actually built and driven cars so equipped with LD28 bottom-half/L6 top-half. I discussed my plan with a NISMO tech-rep (Ron) over the phone back in '96 or so and he was helpful but told me it couldn't be done. I wouldn't have pursued it if I had unlimited access to custom forged pistons and rods in order to have a decent rod/stroke performance engine but since I don't, poverty is the mother of invention. You have to crunch all the numbers, measure and search for a part to fit what you need (BMW headbolts, L20B timing cover, etc.) to make this work. Hey, what about marketing a kit requiring a customer's good bare L6 head core to exchange for a bolt-on conversion bare head and Stage package of choice? Not difficult, but I don't have the time to do it. Better do it yourself before the LD28 blocks become valuable. Most are discarded when the crank is taken out. DAW

I've yet to transfer the LD28 bottom-end/N42 topped hybrid I put together in '96 or so from my '82 Maxima into the '72 240Z waiting for it but one of these days I'll get around to it. The front sump/oil pickup vs rear is not a big deal, but it is an issue in the transfer between cars. Meanwhile, I use the car as one of my family cars, running my kids around to school, soccer, getting groceries, etc. It's very reliable, starts instantly every time. This is my "mule" for setting up the LD6/L6 engine and it's the "budget" prototype with stock bore (84.5mm), rods (140mm, large floating pins), and pistons (46.5mm c.ht.) which yields just over 10.0:1 c.r. with the N42 head. Cranking pressures are 210-220 p.s.i. with the stock N42 cam. I've never heard it ping. I've just done some crude tweeking of the stock N42 e.f.i. by changing sensor resistance values, thermostat, AFM door spring tension, etc. I'm using 280ZX headers with long secondaries into a 280ZXT rear pipe & muffler. BTW, the chassis components have been substituted on the Maxima with 280ZXT components and I cut the diesel springs down all around (the nose was pointing up without the LD28 upper end on the LD28 bottom end). I'm using the LD28 torque convertor (the Maxima trans has a hydraulically-activated lock-up convertor that the 280Z/ZXs didn't get). The stall speed is lower than the gas engine convertor but with the stock cam it works fine. With the high compression ratio the throttle response is excellent and the power goes right to the ground. The car is just a daily driver and looks like a stock Maxima except it has Infinity 15x6.5" wheels with 205/55-15s, an Audi 4000S front air dam and later year Maxima trunk-lid spoiler, and it has a lower-than-stock stance. Basically, it makes a good "sleeper". The plan was to swap it straight across to the early Z which is an A/T car and substitute an '84 300ZXT 4LN71B trans for the L3N71B, sort it out, then put a mild cam in it and select the best final drive ratio with that combination. I guess that's still the plan for the first stage hybrid, but the Maxima makes a very practical vehicle as-is and too useful to take off the road right now. What I may do instead, is to remove the N42 top portion and modify and install a P90 L28ET top onto the stock LD28 bottom-end. I'm confident that the bottom-end, built for 22:1 or so c.r. can handle a significant static c.r. increase and boost increase vs L28ET. Since the LD28 pistons have a tiny dish vs the 10.9cc dish of the stock L28ET, with equivilant 2.8L displacements the P90 head yields an increased but manageable c.r. on the LD bottom-end. I don't foresee getting by with the LD28 torque convertor, but I may choose a n.a.-range convertor rather than a turbo-range since the static c.r. will be higher and throttle response good; turbo lag lower. Intermission. I'm not going to risk losing this book to some computer glich or crash, so I'll post part II separately. DAW

Mine's the car with the "virtual 454" badge on the fender. Drax, if you're looking for something unique in your Nissan L6 build, forget the F54 block. "Short block" takes on a whole new meaning with the L18, L24/26/28 engines as they are vertically challenged if any significant amount of stroke is used because you end up with a lousy rod/stroke or impossibly low compression ht. piston requirements. So what's the unique approach? Explore the LD28 block. Look at the history and evolution of the L18. Nissan stroked the L18 from a "L28" stroke to 86mm (just a bit more than the LD28 stroke of 83mm). In order to do this, they were forced to increase the L20B block ht by something like 19.7mm more than the L18. That is exactly what they did to the L28 block in order to preserve some reasonable rod/stroke for the 83mm stroke LD28 engine, they increased the ht of the block by the same amount. You have all the room in the world with the LD28 block to build some great rod/stroke combinations. Adaptation of the block has some challenges but they are really fairly minor. I've written about this hybridization of the LD28 engine to high performance gasoline-fueled use several times on this site over the past 3 years or so. Search it out. If that doesn't pan out, then I'll lay it out again if you're interested. There are many approaches for a wide range of budgets. In my opinion, this is the most undersung, least-explored territory of L6 engine building and the most logical Nissan-engineered solution of going from a 79mm stroke to an 83mm stroke in the L6, DAW

20R pistons in +0.5mm oversize are 89mm but the pin is 22mm (L24 rods are 21mm) and the c.ht. is high, 38mm at the outer edge with the center even higher at 41mm c.ht. You have to study listings by Weisco, TopLine, Sterling, and Silvolite to come up with potential possibilities. You may have more luck finding a piston that is just smaller than 89mm, but otherwise meets the c.ht. & pin criteria, and order oversize (+0.5, 1.0, 1.5mm etc.) to get the 89mm piston that meets all the parameters. DAW

That's twice now. I don't know if it's my computer, the ISP, or the site, but there's an interruption and deletion of my response each time. The first time I'd invested a huge amount of time into a detailed technical response..oh well. To simplify, LD28 and FJ20 rods are 140mm. The LD rods use large floating wrist pins, while the FJ20 are 21 or 22mm. Both would requie 28.5mm compression ht. (c.ht.) 89mm pistons. Chevy S-10 are close but the pins are tiny. Forged would have to be ordered, but the rod/stroke is nice. So, L24 (133mm, 9mm bolt) rods are more practical and give a ho-hum rod/stroke of 1.68; better than a stock L28, worse than a stock L24, much better than an an 89mm/83mm hybrid with L24 rods. KA24 and Z24 pistons leave you with negative deck ht., and dished-piston compression ratios, BMW 3.0L 89mm and Toyota 20R 89mm pistons leave you with far too positive deck ht., requiring shorted rod lengths or shorter stroke (L24 crank) in order to use them, and both have pin-fit problems. I'm in the same situation as as you, as I set out to build an 89mm/83mm stroke L28 with L24 rods. But the abysmally low rod/stroke dissuaded me and I'm building instead a LD28 block/crank (1.5mm-over to 86mm), L28ET piston, L20B rod, adapted P90 head, L28ET turbo system engine with a 1.76 rod/stroke; and not a L28 block/LD28 crank hybrid with its 1.60 rod/stroke. Huge difference. Stock L24 was 1.8. Anyway, looking at 87-88.5mm pistons with the appropriate pin size and c.ht., ordered in the appropriate oversize, seems like the reasonable way to go to keep it on a sane budget. I'm going to check out some options and I'll post when I have some candidates. DAW

Rick, so obviously I have some mental block, but the fun-factor has an undeniable appeal in this formula. I have some surplus Z-cars, and I suppose if the right conversion kit and sbc came along at the right price, I'd have to go for it. At some level, it doesn't matter what makes your head snap backwards. DAW

Very well done, Rick. Makes a lot of sense, but I have a tough time rekindling some sort of relationship with pushrods. 5.7 liters should be accountable for a lot of horsepower since it's twice the displacement of the L6's. I've built a lot of really fine Chevy engines and had a lot of fun with them but there's some aesthetic re powerplants wherein garden variety Chevys (Fords, Pontiacs, Mopars, etc., etc.) don't make the grade. GN V6 turbos are far more progressive, in spite of the pushrods, but SOHC/DOHC engines have a simplicity/horsepower ratio that is far more satisfying. Wankels make a lot of power for their weight and deserve a look...the c.i./hp ratio as compared to a Chevy engine, stock or modified, makes the Chevy look antiquatede, anemic, and pathetic. I can't believe I'm actually writing this...I just drove from the Florida Keys to Seattle with what seems to be a herniated thoracic disk and a numb arm...must be the pain meds talking and I disclaim this text...DAW

I think that when using a MAS or AFM you want to use/acount for all of the metered air. Blowing it out of the system makes it more difficult for consistant overall fuel metering. This is my guess, plus it seems that during a blow-off condition, rerouting blow-off it is the most efficient way to equilibrate the pressure differential across the intake turbine, thus optimize spooling and preserving the momentum so that it's there for the next throttle opening. Why throw out your turbocharging energy instead of using it? DAW

CarTech offered a triple Weber (Solex, Delloroto, TWM-fit) plenum many years ago for the Zcar. I bought a new one from Corky Bell about 8 years ago and had to wait for them to drag out the old casting molds and cast a few. I sold it to a member here a couple of years ago, so there are a few of these out there to make the job easier. I wouldn't do a blow-through though, I'd use the triples strictly as throttle bodies (plug all unused carb ports) and mount injector bungs on the intake manifold, or use $TWM-type throttle body/injector assys in place of the Webers. It would be a unique setup but a lot of effort vs a conventional turbo/e.f.i. setup. DAW

It sounds like a Mitsubishi BOV, is the vacuum unit a dull olive-green grey with a small MItsubishi logo om it? DAW

Nice study, thanks. This type of issue is about bang-for-the-buck modifications. Yes there are concerns ultimately with airflow through the intercooler, etc., etc. But given the hp/price ratio vs no intercooler at all, and combined with a 1st gen eclipse BOV, we're talking a night-and-day benefit in performance at the grassroots level. When you're rich, but a Spearco and do it right. In the meantime, go for the hp/$ route. DAW

The '82-'83s do use a distributor-type crank angle sensor but the '81s have a crank-type sensor. I don't know how many teeth, but a lot. I'm not using this set-up, I've just seen it. I need a CAS to use on my road race PL510 and this may be what I need. DAW

The dampner has a toothed wheel and the timing cover mounts a crank angle sensor pickup. The later L28ETs used a distributor CAS.

Have you looked at the '81 L28ET set-up?

The fuse can corrode inside (from condensation) at the connections from the filament to the bases. It's difficult to see and otherwise the fuse is unblown. You could check with an ohmmeter but I would replace the fuse first before looking elsewhere. DAW

I know there are people at this site that have extensive knowledge on oil viscocity effects, and my input here is purely anecdotal based on my own experiences only. My impression is that thicker oil increases pressure and takes up space but that higher weight synthetic oils aren't necessarily thicker yet they meet the load ratings of the equivilant non-synthetic weight. I've begun using semi-synthetic Castrol 20W-50 in most of my higher mileage or higher clearances engines and if there is a specific high clearances issue I would run 30 weight in the summer in that engine. DAW

All things considered, with the oil film/spacer effect at the thrust bearing and role of oil pressure as key factors here, I'd make a change from the Mobil 1 10W-30 you're using, to 20W- 50. DAW

You probably want this in the "body" forum... DAW

Maybe I missed something, but is that straight 6 of yours an L24 or an L28 bore? Sterling pistons make an L28 oversize piston with a compression ht. compatible with the longer L24 rod (133mm). These are cast pistons. DAW

Bastaad- I think complete access to the articles costs $55, which buys some 250 back issues. From what I've seen in the previews, there's a wealth of knowledge there. I'll probably go ahead and purchase the archives, but passing on articles may violate copyright law. DAW

oops!...http://www.autospeed.com/cms/S_3/start_10/section.html...DAW

Check it out, they archive too...DAW

I stumbled upon this info and I'm passing it on...

I did a front bumper adaptation on a 280Z by gutting the bumper shocks (deflate pressure and remove piston), leaving just the shock housing bolted to the frame. I took the stock 240Z bumper with brackets attached and fit the bracket ends (flat steel, about 1/4"x1 1/2") by sliding them into the shock tubes. I took a "J hook" of 3/8" threaded rod, inserted through the hole in the bracket, fed it out the back of the shock housing (through the 3/8"ish hole there), and pulled it tight. I adjusted the bumper straight and level using the shock housing adjustments, tightened them, and then welded where the steel 240Z bracket goes into the 280Z shock housing. Looks good and no problems. DAW

Definitely worth a try. The L28ET exhaust manifold can be made to work on the LD28 head. The modifications will be re the mounting holes especially for the 3 center bolts, but minor mods will make it work. Intercool it somehow, even with a Saab, Volvo, Audi, etc., intercooler. This seems like a natural evolution of the LD28 had Nissan kept it. DAW