katman

Okay, now we're getting somewhere. Take some front bar out. Is that the bias ply or the radial slick? The bias ply's run bigger slip angles and with power on it's not unusual for the rear to feel like its stepping out. I wouldn't expect any meaningful tire temps from an autox run. We're gonna need a skidpad or real track. Camber's sound about right, with that wide a tire. Also sounds like you need to confirm your alignment settings. I think the 1/4 in/outs mentioned by carusoracer is excessive- I don't like dragging tires around, rather make it handle properly with about 1/32 toe in out back and 1/8-3/16 tops toe out in front (road race I don't exceed 1/8, for autox slow corner turn in 3/16 should do it). Get back to us after you're rechecked your alignments. Got corner weights? How exactly did you check your tire temps, what kind of probe, what order, how deep? I'm not a big fan of big springs on an autox car. Parking lots tend to be bumpier than real tracks, plus in your case you have to drive it to and from. Plus, softer springs are easier to drive fast sooner, even though big springs may be slightly faster eventually. In other words, you get 4 minutes of race time, you need to be hooked into the car in the first 15 seconds. A softer car will be easier to figure out. Autox is 95% driver anyway, so there. Are you sure you have enough suspension travel everywhere? When you say "dances like its on ice", what you mean exactly? Just the snap oversteer, or is it chattering across the bumps, is it oscillating between oversteer and understeer, or what?

Well the obvious problem would be too much front roll stiffness. Less obvious possibilities: Not enough front bump on the shocks, not enough front bump travel, not enough front camber or toe out. Corner exit understeer caused by onset of throttle is usually standard corner entry understeer exacerbated by onset of throttle, so I suspect unless you don't have enough low speed front shiock rebound you've probably got plain ole slow corner understeer. Front roll stiffness has increased a lot by your own description, so that's proly it. What tires are you running, what camber, what toe, what shocks?

What racing class? There's several threads and some pics over at improvedtouring.com in the nissan forum. Air dam proly isn't a good location for NACA ducts. PM me and I can send you some pictures of what we used in ITS.

Oh, only 1100hp. Me thinks we just upped the ante to a lot more cage than you have shown. I'll check in for the revised pic.

Nice drawing. A few suggestions. For drag I don't see you needing T-bone protection like we do in road racing, therefore no elaborate door bars needed (although it looks like the rules require one on the driver side, I could be wrong). I think your main worry would be rollover (tire blows at speed for instance), and for that I'd really really want a diagonal in the main hoop. The two diagonals that go down to the tranny tunnel don't do squat, you're just adding weight with them (however, looks like the rules show them, more proof the NHRA has no structural engineers on staff). I generally don't like the X in the back, as it's weight up high that isn't necessary, UNLESS you have a tall driver and are taking advantage of the fact that the NHRA rules are stupid enough to let you get away without a diagonal in the plane of the main hoop. Which I gather is the case, so the X is the next best thing even though it's proly half as effective. An X for door bars on each side would give you some much needed torsional stiffness, as would a Top End Perf. type triangulated front strut bar. If it was a road race car I'd move the front horizontal down to about an inch off the tranny tunnel to help distribute the T-bone loads and help keep the floorboard from folding up, but since that proly isn't a big player in this app it's okay where it is (although again, it's weight up high that isn't really doing anything- the front half of the cage is just going to collapse in a rollover anyway, especially with no door bars). You don't say how fast this thing is going to be, but my guess is for drag racing your probability of crashing is very low, and the type and speed of crash you'll have will be much less severe than what we'd expect in road racing (concrete wall at 120 mph almost perpendicular, courtesy of Road Atlanta turn 12 for instance), so I'd go with minimum weight, maximum convenience (kinda like what you got), forget the additional rocker tubes, get it on the track and street asap and have fun sooner.

That's not a lot of tube. For ITS we use 1-3/4 x .095 wall. What's the design look like? Lot of NHRA legal cages I've seen don't even have a diagonal in the main hoop, that's the first thing I'd change. Are you limited in where/how you tie the cage to the unibody? Got a link to the rules?

Won't be in any NHRA sanctioned class then? Oh, you also say this: "Then I can mount the cage to this and still stay NHRA legal." Then it will need a cage meeting NHRA specs or not, and for what class? Is your seat going to be at the normal height or down on the floor? Let's figure out what the legal requirements are for where you're racing, then there may be some more important places to put that metal. Putting it in the rocker won't appreciably affect your torsional stiffness, nor is it usually a player in a T-bone or a rollover. Be glad to help but need more specifics.

If you're using aftermarket pistons then it isn't a bad idea. But as Dayz says, the factory did a great job in the beginning. Back in the Z heyday's of SCCA Showroom Stock the difference between a bone stock bottom end and a balanced and blueprinted bottom end was about....drum roll .... 1 hp.

This seems like a huge waste of time to me. Most of the real racing done with Z's these days is in ITS and EP. Old days was CP or GT2. None of these cars added a bar to the inside of the rocker. Now some people will run one of their door bars down on top of the rocker, which I almost agree with, but there's so much else to worry about. What kind of racing is this for?

I didn't say it wasn't weldable, just not as easy as a 5000 series, and I didn't say 7075 was. Point is the design needs to be vetted before we could answer his question. And yeah, I'd go billet with your machine shop too- and 7075 doesn't gum up the cutters like 6061.

Keep in mind 6061 isn't the most weldable (not like a 5000 series anyway) and it's strength is crap compared to REAL aircraft grade aluminum (like a 7075-T6) or most steels. Whether or not it's strong enough will depend a lot on the details of your design.

http://www.colemanracing.com/catalog/index.php?cPath=49_427 For the threaded collars anyway. Fits 240Z struts but not 280.

Ding! Ding! Ding! That could be 50hp right there. And before you start that how 'bout a leakdown check?

http://en.wikipedia.org/wiki/BOAC_Flight_911 Took the parents of a friend of mine. Also interesting because it was a Comet- famous for crashing for another reason, but that's an entirely different paper... By convective activity you mean low altitude microbursts for example? So the L-1011 crash in Ft. Worth would be ruled out.

225/50-14 Hoosier A6's on the Supra rims. Since that tire is about 1.9 inches smaller in diameter than stock you get almost an inch lower and get a better gear ratio, for free! Now you really need to save up for some Panasport race wheels, since, well, Z's love Panasports, but if you got the Supra mags already...

"God I'm an idiot." That's about how I felt watching one of my ITS cars at turn 12 at Road Atlanta lose the left rear wheel right in front of me. Uh, somebody forgot to tighten the lugs. I told the driver I used to have somebody on the team whose sole job was to manage wheels and tires and lugs, and if he wasn't so cheap that guy'd still be doing that- so it wasn't my fault! Shake it off ole buddy. Sorry it the lesson cost money.

Having built L6 headers myself all I can say is great job!

How much did you shave the head? We regularly removed up to .025 and slotted the curved guide on our ITS engines. I think the L28 part number for the curved guide has a smidge more meat on it for doing that.

Since TonyD mentioned ITS engines, here's another take. Don Potter, who is not only the most anal retentive engine builder on the planet but has also forgotten more about Datsun cams than most of us will ever know, always had us set up our ITS heads for exactly textbook centered on the rocker. By changing the wipe pattern to the pivot end in order to increase ratio you are also changing the shape of the valve event, which you cam grinder might not have intended and which might also affect spring harmonics. He thought in most applications you'd never see the difference anyway. That said, we set up our Sunbelt ITS engines halfway between your .150 and .160 pics. TonyD's proly right, go for it. Nice job on the photo's, BTW.

Take out your passenger seat and put it there. I've transported a Z motor in a Z that way. Much safer.

I bet that assembly is heavier than stock. And he's reduced the effective length. Nice bling but that's about it. Color me underwhelmed.

"Yep, that's one reason why I was so hesitant about the clevis link to the rear part of the arm. That could be a solid tube welded in and then the design would be a lot better in my opinion." Yup, Jon's right, won't work until something binds up. That rear piece is like a 4 bar link. It'll flop around.

Generally an S30 needs less camber in the back than the front, and generally we can never get enough camber in the front, which is proly where JohnC was going. Why don't you have your current cambers and toe's checked and let us know so we can make further suggestions. Previous poster was right, toe can tear up a tire as easily as camber. You could be limited in your inboard movement by the upper spring perch, assuming your coilovers are 2.5 ID and the spring is bigger in OD than the spring perch?

"However, if we are on the subject of cool physics stuff relating to ign. sys components; Anybody here ever gone into the garage on a moonless night and run their I-6 engine to see the spark corona? Very cool, I did it a couple of months ago, one night with nothing better to do." Oooh, yup, cool. Ever seen a clear distributor cap? Put one of those puppies from JC Whitney on a Mustang once and there's just a Johnny Cash "Burning Ring of Fire" in there, and that was with a 70's vintage points ignition. I've seen MSD arc 6 inches or more. Yikes!

Uh, yea, tie wrapping all the plug wires together. Now there's a recipe for crossfire. Pretty motor though. I made my own looms from phenolic blocks for our ITS motors and ran them around the front of the motor like the above picture since the valve cover was off all the time, only separated by 1/2 inch.