Dan Baldwin

I've been running the HKS 2mm gasket (2x 0.5mm layers and 3x 0.33mm layers) with one thick and one thin layer removed for years now, no problemo. So I'm at 1.17mm. This gasket is a relative bargain considering it allows you to tailor h.g. thickness to your needs. You could use two thin layers to make a 0.67mm gasket.

NA 3133cc (89.5 x 83mm) Sunbelt ported, minor chamber work and cam (.550"/310deg/106 lobe centers) 3x2 45mm/39mm OER Racing carbs Nismo 1 3/4" 6=>2 header, 3" exhaust 255rwhp/221rwtq at New England Dyno in Worcester, MA. Run turned ugly due to points bounce above 6200rpm, but I stubbornly persisted to 7200. The 280Z distributor I had been using crapped out the day before the dyno:(. With a magnetic pickup she runs clean to redline:)

There are little mesh filters in the banjo fittings where the fuel lines go into the carbs. Check them.

FWIW, I lost a lobe on my Schneider cam a few years back. They replaced it without a hassle, though it was over a year old. I inspected the new cam they gave me and lo and behold, one of the oil dribble holes wasn't *quite* drilled all the way through! Just a pinhole where the hole met the rifle drilling down the middle of the camshaft. That lobe woulda been toast for SURE. So if you get one, CHECK THE DRIBBLE HOLES!

Going from DGV's to 3x2's definitely shouldn't cause it to start detonating. Sounds like something else. Silent, Dunno who said "110% v.e.", but even higher v.e.'s are possible, but not over any tremendous rpm range. "Volumetric efficiency" isn't REALLY an efficiency, no physical laws are violated.

Are you running vac advance? It sounds like it might be adding too much advance at part-throttle. You might try running it with the vac advance disconnected. Increased load when going to WOT should normally make it detonate more. GM's and Harley's used to detonate under light-throttle cruise conditions and it was considered "normal"! Trying to maximize economy and minimize HC emissions, they ran as close to (just over?) the limit as possible with vacuum ignition advance and lean A/F mixtures.

2315 lb. on the NHIS scales, with ~1/8 of a tank. Figure right at 2300 empty.

After mods to get decent camber up front, and reduced toe-in at the rear, I removed the rear bar after fellow drivers commented that I was at about a 7-degree drift angle all the way around the south oval at NHIS! It felt slower after removing it, no more "servo-steer" effect, but was in fact WAY quicker around every track I go to. Better drive out of slower corners, too. BTW, unless there are serious unibody stiffness issues, the amount of body roll at both ends of the car is always the same! The difference is the way the rolling moment reacted front/rear. Long/short, you may or may not need or want a rear bar depending on your setup and your usage.

I should clarify that I was running the stock N42 head (shaved ~.010") with *stock cam* on the original 3.1 build for a number of years. ~10.35:1, running full advance, on 93 pump. Now I'm running 11:1 with the big cam. I had wanted to go ~11.5, but it just wasn't happening due to piston/valve clearance issues. I'd have to go with custom pistons vs. KA's with machined valve reliefs (which I probably shoulda done with the last rebuild). The reason cammed engines can run more compression ratio is that they're have very low V.E. at lower lugging engine rpms, so chamber pressures are lower. They only start to get good V.E. at higher rpms, and at higher rpms detonation doesn't have as much time to take place. So you can run higher compression ratios before detonation is a problem, DESPITE any additional pressure from slight supercharging effect you can get with reflected wave action at higher rpms with more valve overlap.

FWIW, I ran a stock N42 head on my 3.1 at 10.35:1 on pump gas with full (35 total) advance for years. Currently running 11:1 with a pretty big cam (310/.550"). No probs on pump gas. However, the ZCCNE club car with N47 stock cam on flat tops had to run with timing retarded by ~8deg. Go figure...

Even temps across the tread does not *necessarily* imply the quickest setup. No direct experience meself (not nearly consistent enough to make a judgment, and besides, I'm lazy. I just run conservatively high pressures) but at least one successful 240Z race effort found they had quicker lap times with higher temps on the inside of the tread. Tire sizes were somewhat skinnier than 275, though. Just playin' devil's advocate! (plus, who am I to resist an opportunity to stir the pot?)

In the immortal words of Homer J. Simpson: "Sweet, merciful CRAP!" Now I remember why I come to this site. Rock. On.

Version 5.0, not 2005 or 2006? I'm running Cosmos 2005 with Solidworks 2006FWIW, so perhaps earlier versions of Cosmos can work with later versions of SW to some point. Do you have a "dongle" (security device attached to printer port or USB port)? If you get to the point that you're going to get something made, I could do a quick sanity check on it. It's always better to do the anyalysis BEFORE the parts get made!

Ah, college... The rim is inherently pretty strong due to it's being a relatively small-radius cylinder with an outer lip and a drop-center section. Depending on how much curb impact and tire-mounting-goon-induced localized load you want to take, you can make the rim portion pretty skinny. Spun or forged rims can be quite thin and lightweight. But of course you then have to transfer the load from the rim to the hub! Are you talking about the CosmosExpress demo software (really too limited to be of more than illustrative use), or do you have one of the CosmosWorks add-on packages? Either way, you should also study up on stress analysis, statics and dynamics, etc. as you get into using the FEA package. It is VERY easy to make stress contour plots that look real but are off by HUGE amounts! Pay attention to sensitivity to mesh size in critical areas. You will have to refine the mesh in critical areas of interest. Here's a useful reference: http://www.weibull.com/mil_std/mil_hdbk_5j.pdf Also, http://www.matweb.com is good for reference only (mostly shows typical rather than minimum properties) If you are casting the centers, you'll most likely end up with 356, which will have to be heat-treated to T6 for strength. If you would be machining from billet, 6061-T6 would be your most likely choice. If you can find a foundry to cast magnesium for you, and a machine shop to machine it, AZ91E (-T4 or -T6). Nah, aluminum/aluminum.

I know SolidWorks has an optional analysis package, CosmosWorks, I use it all the time. But it's only as good as the human telling it what to do,how to do it, and then interpreting the results! Only commenting because I *KNOW* that the vast majority of enthusiasts will simply bolt on criticial structural components without any analysis backing up the design. I've seen a wrecked cars at the track due to underengineered aftermarket lightweight suspension components. They look great, are well put-together, but are in reality structurally inadequate. This is totally stupid and unnecessary. Just putting it out there, since nobody else had.

It is AMAZING to me that people would be willing to just bolt on anything in place of ENGINEERED STRUCTURE, for CRITICAL structural components on their cars/bikes/boats/etc! This "mumbo jumbo" isnt' for NOTHING! It'd be easy enough (for one practised in the art) to take a basic "styling" design and sculpt it into something stronger and lighter, without modifying the basic intent of the "artiste". Actually, this process almost always vastly INCREASES aesthetic appeal. The underlying laws of physics and nature we are designing/engineering to have an inherent beauty of their own, optimization brings this out. The question is whether you want to ensure structural integrity and at the same time minimize weight. This is the HEART of engineering for performance. Nothing uglier to me than those CAD machined from billet centers, "styled" but not ENGINEERED. Hideous. You can BET that if those custom billet wheels are strong enough, they're WAY heavier than necessary. Leave that crap for the custom chopper lame-brains. Performance vehicles deserve opmtimized components. FWIW, I use SolidWorks and CosmosWorks (the FEA package). For more detailed and/or advanced analyses I use MSC/NASTRAN, but for most basic analysis it's a lot easier and quicker to go with the native Solidworks package.

Cool-lookin' stuff! But, you know, the part between the rim and the hub is PRIMARY VEHICLE STRUCTURE! I don't think I'd just design something up and use it without analysis. This would also allow you to minimize weight while ensuring (hopefully) structural integrity. Want me to do an FEA? Send tequila (Don Julia anejo)... I did the wheels for this: Original design of the front wheel from the styling studio was 17 lb. (!). My version of that design is 8.6 lb. I made a less stylin' design of my own at 5 lb. in magnesium (of which we're having a limited run made). 17' version will not clear Z wheel arches I don't think. But at least it won't be in danger of being trod-upon by a dwarf!

Short stroke/oversquare is a fine idea (my Aprilia is 97mm/67.5mm), but if you're giving up displacement for it you are giving up power. Throwing away stroke just to get a "better" bore/stroke ratio (or rod length/stroke ratio) is barking up the wrong tree imo. Fuel economy differences between the destroker 2.75 and stroker 3.1 would be minuscule. Consider that for a given weight and aerodynamic characteristics, it takes the same hp to the ground to drive the car at a given speed, whatever the displacement is. The larger displacement will have greater internal losses, but not by much. Gear the smaller-displacement motor appropriately as recommended and any fuel economy benefit disappears! Closer-ratio gearbox is desirable anyway if the engine has a relatively narrow powerband. Which is why I have an '84 truck 5-speed. No doubt a 302 Z28 is a blast to drive (never had the opportunity)! But a similarly-tuned 383 would be, too! It'd be much faster, and wouldn't give up as much revs up top as you might think. Nothing's more fun than pressing the accelerator down and getting THRUST. More thrust = more fun (to me!). Even if the bore/stroke looks more like a tractor's than an F1 engine's. To each his own! But don't deceive yourself...

Either way, really. Which has less shaft play? If you stick with the 240 dist, you either have to run ~10deg idle advance or partially fill in the advance slots. I filled mine in on the low-rpm side, so if the JBWeld ever wore away or dropped out it would only reduce my idle advance, not increase max advance. Either way, it's not the end of the world to lose the vac advance.

Oh yeah, I *did* have a problem with the Pertronix once! It was at least fixable. I did recurve the 240 distributor to give more advance at idle. Stock curve limits you to around 10deg idle advance.

Never had problems with the Pertronix. Did have a 280Z module fail on me once, though (it was 25 yrs old!). Instead of "you need at least 34 degrees", I'd say you need no more than 36deg total spark advance. I get max power between 34 and 38, so I keep it set to 35. Doesn't cost me any hp, and gives some margin for lower-octane fuel.

Hmmm, so is power GOOD, or BAD?! If you're SERIOUS about maximizing power, you may as well know that destroking is not the way to do it, as cool and novel an idea as it may seem. When Mark Donohue (race driver/engineer extraordinaire) was asked how much power was TOO much (he drove 1000hp turbo Porsche CanAm cars), he said when he could spin the tires at the end of the straight, that was enough. Cirrusly, just because you've as good as bought the destroker crank doesn't mean you have to use it! I still encourage you to make the MOST of your build and not bother with destroking it. But, in the words of Aleister Crowley, "Do as thou wilt"!

Which, relative to the lost displacement, will amount to somewhere between diddley and squat in terms of power/torque (i.e., you'll still be making way less with this "superior" r/s of 2:1). Absolutely NOTHING wrong with gaining power through revs. BUT, giving away 7% displacement to gain ~3.5% more theoretical rpm (not even that on the L6!) is not the way to improved performance! Actually, the way to make power is big cubes AND high rpm! But displacement IS more important. Maximize displacement, THEN maximize rpm!

Read above. Power is a function of torque and rpm, as you say. But while torque is a LINEAR function of stroke, theoretical rpm potential is only a function of the SQUARE ROOT of stroke. Reduce stroke by 5%, and AT BEST gain 2.5% in revs (or possibly gain closer to NOTHING on the L6), but LOSE 5% torque everywhere for SURE! ~2.5% lost power potential. A losing proposition. Also, there may indeed be benefits to increasing R/S ratio, but not enough to make up for the lost displacement. I'll stick with 3.1 liters and "inferior" R/S and B/S! *IF* (big if) the highest hp na Lseries ever is an L24, it is only because nobody's ever built up an L28 to the same extent.

The additional mass and polar moment of inertia of the L28 or LD28 crank vs. L24 crank is pretty much negligible relative to other loads on the engine. As for "smoother-running", if the L28 or LD28 is balanced to the same tolerance as the L24, they should run just as smoothly, no?