Dan Baldwin

The previous post compared an L24 stroke w/ an LD28. L28 crank at same piston acceleration would be redlined at ~7215rpm. 7.2% greater torque and ~2.7% greater peak power potential than the L24 crank motor. Whoops, with 130.35mm rods that'd be 7200 rpm, and only ~2.5% greater peak power potential. Anyway, I know which crank I'd rather have in my engine. Displacement being unlimited, of course.

It is true that a longer stroke will reduce redline rpm. However, the loads in an engine vary with the square of rpm, and only linearly with stroke, so the increased rpm of the short-stroke motor is (pretty much) never enough to compensate for the additional torque of the longer-stroke motor. A 73.7mm-stroke L28 will have the same piston acceleration at 7530 rpm as an 83mm-stroke L28 at 7000, giving the short-stroke a ~7.6% higher redline (these numbers also account for the better rod/stroke ratio of the short-stroke motor). But the stroker has 12.6% greater torque from idle to 7000, and has about 4.6% greater peak power potential. If you're in a displacement-limited class, it does make sense to go with the shorter-stroke/larger bore combo. If not, big bore AND stroke is best:) And of course the stroker WILL rev up more quickly under load (say, when accelerating out of the tightest corner on your favorite road course, or from a stop through 1/4 mile).

This comes up all the time. It assumes that all that added crank throw from a longer-throw crank is gonna reduce the engine's acceleration. It is bullshit. For one thing, the added polar moment of the crank is minimal, and for another, the real load is not the crank, but the mass of the car. The increased leverage at the crank will only INCREASE engine acceleration under load. The only quick-revving contest a short-stroke engine will win is the one where the engines are turned over by hand! Stick with the L28 crank. Or get an LD28 crank!

I've got a set of 45mm 3X2 OER Racing (formerly SK) carburetors, and need to get gaskets and maybe jets for them. Anybody got a source? Anybody wanna compose an email to OER in Japanese for me to get parts from there? Anybody near Providence, RI or New Bedford, MA that has Mikuni or Weber carbs so I can see if the jets interchange with the OER jets? Thanks

I've been looking to buy a '94-'97 Z28 M6, and all I have to say is they feel SLOW compared to my '71 3.1. It's a track/street compromise car, but does have a few $$ in it. I'd say your best bet is to find a 280ZX turbo and transplant the motor, or rebuild an L28 as a 3.1 liter with 10+:1 compression. Both routes could be pretty reasonable $$ to start out, would have excellent low-end torque, and have a lot of potential for good horsepower and better power/weight than a V8 F-body given some further mods. I would NOT go with a road-race suspension on a street Z. Will cost you for coil-overs, and you'll hate the ride and never get to fully utilize the full handling potential. I just went with stiffer springs, sway bars, and adjustable shocks, and the handling is still a lot better than quite a few track-only cars at the race track. And is somewhat tolerable on the street, too. 4.38 gearing sounds like a lot more than you'll need, particularly with a 280Z 5-speed. I've got more than enough torque to boil the tires with a 280ZX 5-speed (much taller 1st gear) with a 3.70 (come to think of it, I did with the old 3.36 diff, too). In future, I might go to 3.90, but I doubt I'd ever go to 4:10s, even strictly for roadrace. As far as parts sources, Nissan is the source for 90% of what you'll need for a hot N/A motor. No Dart, Feulling, Edelbrock, Weiand, yadda yadda yadda stuff available for an L6 anyway. Don't let your V8 mechanic buddies work on your motor, go to someone w/ extensive L6 experience. Have fun!

John, Looks pretty kick-ass! Your motor is at the right place, but of course you knew that. My cylinder head is gonna be with those guys for some relatively minor tweaking. Let us know how it develops!

Just got a set of OER Racing (formerly SK, I'm told) carbs, 3X2bbl, 45mm. Came off of an L31 in Japan. Anyway, I'd like to get a good first guess at jetting for the beast. My engine is a 3.1, 11:1 CR, with a 290/.503" (@zero lash) cam. Jets in the carbs now: 60 pilot air, 220 main air, 165 main fuel. The main air jets look similar to Mikuni jets, main fuel look similar to Mikuni and Weber, pilot air similar to Weber, but one piece, not two (judging from drawings in the "How to Modify..." book). I know this differs from your info, Ruben, any ideas? Anybody know for sure what will directly fit, or do I have to try to source OER jets from Japan? Also, the jet holders don't appear to have emulsion tubes in them. Emulsion function appears to be handled by the jet holders(?) themselves. TIA,

Thanks, Ruben. I have a feeling this is going to be a challenge getting the 3X2 dialed in.

Hey all, I might be buying a set of 45mm SK carbs, bought in Japan. Seems they were only available in the states for a few years. Just wondered if anyone had any direct knowledge as to whether or not Weber pilot, main, air jets, emulsion tubes, etc. drop in, as I don't think SK parts are readily available. Thanks,

You'll need stubs from an R200-equipped 280Z, as well as input flange. IF your diff is a viscous unit from an SS model (all pearl white), then you've got some more work to do to make the stubs fit. I've heard that snap-ring grooves must be machined into one or both output flanges to fit. Also, you're going to need to either modify your existing moustache bar, or get one from an R200 280Z. The R200 has larger studs mounting the back cover to the car, and they are spaced further apart. What I did was slot the holes in my existing moustache bar. I found I also had to slot the holes in the front diff mount. Some say R200 280Z halfshafts are required, but I've used my old 240Z halfshafts with my LSD R200 for over 5 years now. Rotsa Ruck!

Hey all, I might be buying a set of 45mm SK carbs, bought in Japan. Seems they were only available in the states for a few years. Just wondered if anyone had any direct knowledge as to whether or not Weber pilot, main, and air jets drop in, as I don't think SK parts would be readily available. Thanks,

I made 189 lb-ft at 3500 at the rear wheels on the dyno last year. Power was on its way to at least 190rw, looking at the curve, but the engine developed a miss above 4800 rpm. After I invested in an MSD6AL, I discovered that the problem had been a busted spark plug. Will dyno again this spring, possibly w/ higher compression and some minor port-matching done. The motor: L28, LD28 crank, L24 rods, KA24E pistons, 2mm head gasket, N42 head, 10.14:1 CR, 290/.503" cam, 2" SU carbs w/ N36 intake manifolds hogged out to match, TWM air horns w/ ITG filters. It's got about 20,000 street miles and upwards of 30 track days on it. Was built in '94-'95

There were FOUR different E88s: '71 had E31 combustion chambers (42.4cc), and small valves, 10.2:1 unshaved w/ flat-tops '72 had 44.7cc combustion chambers, small valves, 9.8:1 unshaved w/ flat-tops '73 had 47.8cc combustion chambers, small valves, 9.3:1 '74 had 47.8cc combustion chambers, bigger exhaust valve, 9.3:1 The '73s and '74s are avoided, BTW. Shaving off .040" should get you more than 1 on compression (9.8:1 => 10.8+:1). Wish I had that head dimension handy for you... Dished pistons reduce comp. by ~1.5. BTW, an F54 N/A is a flat-top piston L28, F54 turbos had dished. I'm assuming yours is a non-turbo, right? DAW's right on about it not being an easy task to install larger intake valves. (My info coming from D.L. Potter's reply to a letter in an old ZCar Magazine) Should work fine, though you'll likely be running out of breath above ~5200-5400 with a stock cam and carbs. You shouldn't have any valve clearance issues. I've got KA24E pistons that stick up about .025", and a 290/.503" cam and have not interference probs. Then again my head isn't shaved. Yet. Theoretical hp gain is about the same as the ratio you go up (9.5/8.5 would be ~12%). Consider that the most you could ever get in your wildest dreams with no other changes. Real world maybe 8%?

Performance cars on dry and damp pavement definitely want to be rwd, not fwd. NO amount of "tuning" can change the facts that: a) the driven wheels are UNloaded during acceleration, leading to absurd weight distribution designed-in just to ensure acceptable drive traction is maintained (like 65/35 F/R) c) for neutral handling this requires the heavy front end be less stiff in roll than the lightweight rear, which must be much more stiff in roll, ensuring that d) in a given turn the outside rear is overworked and the inside rear isn't doing anything, meaning e) total lateral tire grip suffers Yes, there are successful fwd race cars, and yes a well-prepared fwd car beats a less well-prepared rwd car of equal lb/hp. RWD is still the clearly superior architecture compared to fwd for a race car on dry and even damp tarmac. "All things being equal" Yeah, I know they never are, but why start out with such an inherent disadvantage? Ever seen a fwd FSAE car? That's because with a clean sheet of paper design the ENGINEERS-to-be that design and build them KNOW better! Without a clean sheet of paper, the unfortunate fact is that there aren't many lightweight rwd platforms (then again, there are fewer and fewer lightweight fwd platforms every year, too!), so sometimes the INHERENTLY EVIL fwd compromise is accepted in order to have a lighter race car. Long live the Z!

I maintain this design should be analyzed. If someone can show me the analysis done to prove it, I'd be glad to review it. As far as AP and Brembo making aluminum brackets, that does nothing to validate THIS particular bracket design. It's not a question of whether aluminum is an appropriate material for caliper brackets in general. Regarding the properties of 6061-T6 vs. 1023 cold finished steel, Bruhn's Analysis and Design of Flight Vehicle Structures (OLD aero bible) has: 6061-T6: 42 ksi Ftu, 35 ksi Fcy 1023: 55 ksi Ftu, 36 ksi Fcy MatWeb gives 45 and 40 for the Al, 62 and 52 for the 1023 steel. Not that you'd use 1023, you'd likely use 4140 or 4340. What these numbers DON'T tell you, however, is that the aluminum has no fatigue limit (stress below which cracks will never develop). This *might* not be much of an issue, since there is little to no reversal, and it seems the lifetime number of cycles should be relatively low. Still, aluminum CRACKS. Also, Al properties drop off far more precipitously with temperature. Comparing 6061-T6 with 90ksi 4000-series steel (usig Bruhn), 6061-T6 only has about 59% of its room-temp strength at 450F, while steel has 80% of its RT strength at 500F. Yes, aluminum is a great material for building lightweight structures. That's why the AEROSPACE ENGINEERS (the smartest and best-looking folks on the planet) at Boeing (not BOING!), Lockheed Martin, etc. use it extensively in the design of aircraft and spacecraft. This does NOT mean that a suspension or brake part on a Z can be reliably and safely made from aluminum when the original Nissan part (designed by smart and diligent AUTOMOTIVE ENGINEERS) was steel! Maybe it can be, but some good ENGINEERING design and analysis must be done to ensure safety and reliability. I maintain that I wouldn't put it on my car until I'd done some analysis. There's not a lot of space in that tight radius for adding material, which you generally need to do when going from a steel to an aluminum design. Dan Baldwin M.S., B.S. Aerospace Engineering

Sounds like the adjustment mechanism. You use your parking brake? That should keep you in adjustment. You might need to take the drums off and clean and lube the adj. mechanism.

Man, I dunno about this. This part wants to be STEEL. Even the mildest steel is stronger than 6061-T6, and would have much greater fatigue strength and life. I believe some of the HybridZers have made a bracket out of 4340 steel, which I would feel a LOT better about. I managed to get the Maxima bracket for my Z. No worries! Dan Baldwin B.S., M.S. Aerospace Engineering (structures emphasis)

Dome-top SUs are fine for performance, probably better than any 4bbl setup (lotsa 90 degree bends, lotsa fuel dropped outta suspension). EASY to balance with a Unisyn tool. Jetting changes done by turning the adjustment wheel at the bottom of the carb, raising or lowering the metering needle.

Bubafett and all interested, Despite the current big-wheel trend, I believe fantastic street and track handling can be had with available 16, 15, and 14" tires. I run 225/50-15 Bridgestone S-03 Pole Positions for street and wet track usage, and use 225/50-14 Hoosier R3S03 DOT competition tires for dry to damp track conditions. Don't have any problems outhandling 16, 17, and 18" wheeled cars. 225/50-15s fit without rubbing anywhere on 7" wide zero offset (4" backspace) wheels on my car, which is lowered an inch or so. If you want wider street tires, you have to go to 16" wheels at least. 245/50-15 Hoosiers are available for track work, but no 245 14"ers are available. All else being equal, taller wheels are slightly heavier, and have greater polar moment than shorter wheels of the same width. Greater unsprung and rotational mass. Also, despite lower aspect ratio tires for taller wheels, they usually wind up taller overall. This means the c.g. is higher, overall gearing is taller (reduced acceleration), and braking response is reduced (less braking gs per pound effort at the pedal). If that weren't enough, taller wheels and tires are more expensive, and the tires are recurring costs. Less money for motor stuff! Lastly, it's my personal belief that the current trend in super-tall tires is in an effort to make todays tremendously oversized cars look O.K. Smaller cars (Zs, Miatas, etc.) look like they're on stilts with 17"+ wheels. (note: This is my OPINION only.) Street tire nominal ODs for available sizes: 225/50-15 23.9" 225/45-16 24.0" 225/45-17 25.0" 245/45-16 24.7" 245/40-17 24.7" DOT competition tires: 225/50-14 22.9" 225/45-15 23.0" 225/50-16 24.9" 245/50-15 24.7" 245/45-16 24.7" 245/45-17 25.7" 245/40-17 24.7" An inch increase in tire OD is roughly equivalent to a gear change from 3.70 to 3.54, or 3.90 to 3.70. Worth thinkin' about.

I run 160 lb/in front, 200 rear on my street/track 3.1 liter 240Z. VERY good compromise in my opinion. A bit stiff for the street and somewhat soft for the track (I guess). I still outhandle a lot of track-only vehicles at the track. Dan Baldwin '71 240Z 3.1 COMSCC #7 SPB

Broken record man here. I've had NO problems with the stock setup on plenty of road courses (WAY more heat than ANY street or quarter stuff). The Toyo 4-pots do look cooler, but they also WEIGH more. As long as there's enough braking power to lock the tires, more gets you zero. I did the rear disc swap to avoid having to adjust at the track, and to get (presumably) more rear bias (drums are more lockup-prone). Going to Lime Rock on Tuesday, with my all stock front/'82-'83 ZX rear setup. Just bled the brakes w/ DOT4, ready fer action! A well maintained stock system with decent pads/shoes and fresh fluid is a lot better than most people realize, IMO.

Got it. One tenacious bastard it was.

The going is slow, and my chisels are dulling. I'm not going all the way through the shell for fear of marring the control arm pin. Am I doing this right? I've gone about .5" out of ~2". When done I'll force the split open. Wish me luck.

Thanks a ton, Mike. I'll give it a shot. If you hear about a Mill building in New Bedford Mass going up in flames, you'll know what happened!

I'm replacing the rear inner control arm bushings on my '71. 3 of the old ones slid right off, but the last one won't budge. I've gotten all the rubber off of it and tried to twist it with vise grips, no good. Tried to split it apart with a chisel, very little progress. Ideas?