Quick Revving L28

[Ted.]

While this may seem like somewhat of an odd question, I figured you guys would be able to give me the most insight to see if I've actually found something that will work. To start off, I've been an avid Z car nut for close to 8 or so years now (8th grade to 23), and have owned 6 different Zs. Them being a '73 240z, a '74 260z, a '78 280z, an '86 300zx Turbo, and two '87 300zx Turbos. You could say I have a bit of a problem! I'm extremely familiar with the L series engine, having built a few for friends, but I would like to double check with you guys for your opinion on this engine concept.

I love the torque out of the L28, but what I really like is the rev happy L24. I figure why not try to mesh the two? There have been plenty of L series hybrids over the year, but I don't think I've ever seen one like what I'm proposing, which makes me think I may have found buried treasure. I want that perfect symmetry of displacement and throttle response that everyone loves. So, here is the build that I am proposing.

Block: L28 F54 (The N42 is good, but with the webbing in the coolant ports the F54 is more rigid)

Head: L24 E31 (Best for building a higher compression in my opinion)

Crank: L24 E31 (Simply for the fact that I could get a whole series 1 engine and have most of what I need)

Connecting Rods: FJ20DET (This is where it gets interesting)

Pistons: L28 P79 (Flat top from the F54 N/A engines)

Thats just the basics, but if my math is correct, it should give me roughly the same displacement (A little bit higher, but nothing significant), and a healthy but still street worthy 10.5:1 compression. The reason for the FJ20DET rods is pretty simple, actually. They come from the factory with the same big end diameter as the L series rods, and just under 1mm smaller on the small end with plenty of material to be spec'd. Not only that, but with the rods 140mm length, they make up for the smaller stroke of the L24 crank. Also, on top of being forged, they are just slightly wider then the L series, so there isn't a chance of hitting the journals. With the cranks smaller stroke, it should act like a destroked engine, but with the displacement for a good torque curve.

Induction and fuel would be an E88 intake manifold, because of the water inlets to keep the car usable in cooler weather. Pair this with early 3 bolt SU carbs with the SM needles, rotary vane fuel pump and adjustable fuel pressure regulator. Clean the casting flash in the intake and exhaust ports and crank area. Electronics is pretty simple, just the 8.5" F54 Distributor with the E12-80 ignition module and the F54 60 amp alternator.

Use this with a light weight flywheel and single row crank pulley (to eliminate the power steering and A/C), the 1st and 2nd gears from the 77-80 5 speeds and the 3rd, 4th, and 5th gears from the 81-83 5 speeds. Then its just a 3.70 R200 LSD and your done! This would give you a close ratio 5 speed with a tall 5th gear for highway cruising, and a torquey, high comp L28 with the happy rev characteristics of an L24, all for the cost of OEM Nissan components.

Once I get back from basic, I intend to see if this would work, but I would love to get some input from you guys to see if you have any thoughts or suggestions. Tell me what you think!

[Zed Head]

According to this calculator (which seems to be pretty accurate) your piston will protrude out of the bore by 7.1 mm.

http://www.ozdat.com/ozdatonline/enginedesign/

RB26DETT pistons look close but will give you an 11.25 CR.

[Ted.]

Wow, I guess my math was really off xD ah well, back to the drawing board. I still feel like there is a way to make this work

[Zed Head]

Didn't mean to be a downer. The topic comes up often and generates lots of discussion. Here's an interesting thread, in a similar vein, with lots of good insight - http://forums.hybridz.org/index.php/topic/102085-200-whp-na-build/

The short stroke of the L24 crank lowers your displacement also. The calculator shows 2.569 L.

From what I've read, the lightened flywheel alone will make it feel "revvier", and some moderate flow work on the head will actually make it more rev happy. My limited knowledge...

[LeonV]

The reason the L28 doesn't feel as "rev happy" as the L24 is simply because of the cam. People love to get into B/S and R/S ratio bench racing, but it's pointless for 99% of the engines out there.

Instead of spending time and money on all that, get a more aggressive cam and maybe triples. The lightweight flywheel is a good idea. Not sure why you want to mess with transmission gears since the late ZX 5-speed is already close ratio. Using 1st and 2nd from the early 5-speed completely defeats the entire purpose.

A 3.9 diff, late ZX 5-speed, lightweight flywheel and more aggressive cam will transform an L28 without much effort.

[cygnusx1]

What Leon said.

[Ted.]

Its not just the cam, its also the fact that the L24 crank is a shorter stroke. Shorter stroke means a shorter distance it has to travel for a full rotation, I.E. faster revolution, or 'rev happy' in comparison. The L24 cam has 8 degrees of duration over all of the L28s and the lift is virtually the same, so it doesn't have as much to do with the cam as you would think.

As far as the transmission goes, the entire reason for the gear swap is because I want the gear ratios from the earlier 1st and 2nd because they are taller to help deal with the wheel spin from a rev happy engine. They would be going into the later transmission, because of the earlier 5th/reverse fork issues. This gives me a stronger tranny with gearing I want.

The 3.9 is an open diff, which isn't really what I'm after since I want to have a car that would be effective when I take it to a track or autocross event. I do have a question though; would the 3.9 gear work in the 3.7 lsd? They both have the same pinion, right?

I figured something out now, actually using all L series parts, too! So, it is possible to get 2.8l with the L24 crank, though it requires a set of custom pistons and a bore, which isn't really necessary for my goal, so, I've decided a 2.6 is fine for me. Round 2, start!

Block: L28 F54

Head: L24 E31

Crank: L24 E31

Con Rods: L24 E31

Pistons: L28 P79

If everything is right, and I triple checked this time and the checked again in the engine calculator Zed Head posted, with a Nismo .6mm head gasket it would give me 2569cc (2.6l) and 10.6:1 compression. Run this with the L26 cam (256/256 and same lift) and I think I would be set!

[Oiluj]

The L24 doesn't have adjustible valve timing of modern engines. Maybe I'm wrong, but 10.6:1 compression sounds a bit high for running "pump" gas, which was part of the initial posting.

It's not my area of expertise, so perhaps others may be able to shed more light on this...

[Ted.]

10.6:1 with 93 octane and proper ignition and fuel should be fine. I'm still researching that aspect of it. If it ends up being an issue, Kameari makes a 1mm head gasket with the stock bore that would put it at almost 10:1 even (its actually like 9.983 technically), so I'm not to worried about it as of yet

[olzed]

Ted. I remember this same modification from a Z Car Magazine from 1997.

This guy wanted a engine that could make power from revs. I won't quote the article word for word, but the guts of it is---

280 Block

240 Crank

240z Rods

Non Turbo 280ZX Flat top pistons

240 E31 Head

Install larger 280Z valves, and unshroud the valves by removing small ammounts of metal in the combustion chamber close to the valves. This improves breathing as well as lowering compression to 10.1 1

He stated he regularly takes it to 7000 rpm, and it's a blast to drive, although it needs to be kept 'on the boil'

A stroke of under 3inches is desirable for keeping mean piston speed at a reasonable value at high RPM, and for ensuring an engine that lasts.

Same as what you are proposing only some valve and head work.

Edited December 9, 2011 by olzed

[Ted.]

Oh cool! You wouldn't happen to have a link to that article, would you? Or am I going to have to hunt for a back copy?

[olzed]

I doubt that you would get a back copy now Ted I think the magazine went out of print some time ago. I guess you can try.

The Magazine is called Z Car Magazine . Issue Nov/Dec 1997. The article is called One Mans 263Z. 280Z block 240Z crank= power and revs.

If you have no luck send me a PM with your email and I will copy it for you. It's rather lengthy but you would not need the whole thing. The same guy was experimenting with triple SUs on the same engine, but had not finished when the article went to print.

Brian.`