katman

Carrerra's- junk. Koni's- junk after a few races, upper bushings don't seem to last. GC Advanced Design- really junk, not enough volume on the rebound side of the Z strut, couldn't ever make them work. Ditto the BMW application we tried for ITS racing. Total crap. The people I find that love them are also lose when they race me. Bilstein P30-0032 revalved 300/100 in a shortened strut housing with some P/N 450424 gland nuts to adapt them to a Z strut thread. That's the non adjustable we went to in ITS after the SCCA outlawed our remote reservior double adjustables for that class, and also the shock that was used on the ERatadz Motorsports EP 240Z that finished second in the RunOffs 2 times before converting to the ShockTek remote reservior shock banned from ITS. Now I happen to have a set of the ShockTek struts for sale (only 4 sets ever built and the other 3 sets are in EP cars) if anybody has $2k burning a hole in their pocket for a great road racing shock. They're baseed on Penske and Bilstein parts, easily rebuildable and revalveable but ShockTek got bought and is defunct. Your best "still supported" alternative would be JohnC's remote reservior setup based on the Penske. Ain't much, but that's what I think about shocks.

That T/C spherical scares me. Coupla tack welds holding it in? Wrong load direction for a spherical IMHO. Now I've had spherical everything on my race cars but a good poly bushing is all I use on my street/dual purpose cars. Maybe I'm getting old...er.

KATMAN say: If you want to learn to be a good road race driver learn to beat the 300hp car with a 150hp car. Been there, done that, LMFAO the whole time. 300hp in a Z will teach you how to brake, maybe, and nothing else. A worn out stock engine in an ITS car will teach you how to corner and conserve momentum, i.e. how to be fast. Everybody that says suspension and brakes first is right, then HP.

I refuse to pay any attention to posts with no punctuation.

Improper metallurgy, improper geometry, internally oiled versus externally oiled cam, all good possibilities. IMHO this is usually a combo of all of these in conjunction with way too high seat pressures. And way too high seat pressures is usually a crutch for cam designers that can't get rid of valve train harmonics caused by their lack of R&D on specific applications. How many cam designers are really spending any time on L series Datsuns??? 99% of the "performance" cams out there for Z's are copies of copies of very early 70's profiles. It's been estimated that it takes 75hp to drive a stock L24 cam at 5000 rpm. Imagine how much hp it takes to drive a Schneider with big ole springs! I don't remember what the lift was on Mr. Coffey's Sunbelt cam but the spring seat pressure was LESS than stock. 306+ N/A East Coast hp. Now THAT's a cam!

We didn't try that- but if I end up in that situation again we'll look into it. Thanks for the tip. We were convinced it was the LSD and didn't really come to grips with the gears possibility until the season postmortem. By then we fixed it.

Diff and tranny guy for Sharp. John Caldwell was their engine builder if I'm not mistaken. Close enough, you win a beer next time I see you. Of course you know that Caldwell once roomed with Mark Womack's brother, and Mark of course founded Sunbelt Performance Engines, now owned by jim Thompson, builder of your last motor.

R180's came in the 280Z's with automatic transmissions only so me thinks you are stuck with the R200. However, as other astute Hybridz'ers have pointed out, you'll proly need the extra weight anyway and I can't think of a better place for it to be. I quit using welded diff's many years ago after breaking lots of stub axles, and I was never a big fan of dragging the rear wheels around anyway, especially in the rain (turn pig, turn! *%$#*). I have driven a "Quaiffe like" R200 (actually it was an original Gleason Torsen) on the track in an ITS 280Z and liked it. We always ran the factory clutch type LSD's in the R180's in the ITS 240Z's. With the R180 we had serious bad heat problems but only when we got above 3.70 ratios. Spent a whole season changing clutches, shims, preloads, lubes, etc. puking fluids the whole time. Even had Jasen Jasensky set up a couple diffs for us (quick trivia- who knows who this is?) to no avail. One time had a tranny temp gauge on the diff and after 8 laps at Road A the needle wrapped itself completely around and then broke off (325 degree gauge). Finally settled on a combination of Redline diff lube and BG additive before we could go a full race. We decided it was the gear ratio and not the diffs that tipped the heat generated minus head shed scale to the positive. An R200 would give you more cooling surface area for the same work input, so that might be another reason to go R200. You could swap the Quaiffe or factory LSD between ring and pinions once you get them set up, we had a couple LSD's we swapped around amongst several case/ring/pinion sets. Your real problem is going to be brakes. Lemme know when you get to that part of the build.

http://www.izzyscustomcages.com/ZCageArticle.html for a discussion of load paths and some basics on putting any cage in a Z. Around Atlanta there's Robinson Racing Enterprises in Cumming GA, and if you took it there a beer or two would get me up there for a face to face with Harry Robinson and Barry Trivette to make sure you got the perfect ITS or whatever cage.

Read the rules for the sanctioning body you are going to race with before you spend any money. Then read them again.

1-5/8 should take you comfortably to 300 hp, which you are nowhere near with SU's. That's of course a recommendation based on no information other than displacement- we really need to know head work, cam, intended application, rpm range, blah blah blah.

I've done some really nice handling 240Z street cars using cut 280Z springs, so nothing wrong there. 'Tis a bear to get ride heights where you want them exactly without coilovers, and every time you hack the springs to adjust the height you're changing the rates. Seems like using the 280Z rear spring cut about 3.5 coils is around 185 lb/in rate which is still streetable and enough for occasional track. I've heard of the Chevette spring mod but still don't have enough info to guess your current rate setup. Bottom line, loosening up the front bar seems to be working, and it's the cheapest route to go. Unfortunately, IMHO, balancing understeer/oversteer on a first gen Z is tough because roll center changes a lot with ride height (which affects what rates you need front to back), as does the requirements of the application- low speed corners like autox and Mid Ohio require significantly different spring setup than high speed corners like Road America and Road Atlanta. With your setup I see Trail and Error in your future...sorry. Good looking car, BTW.

What are the current spring rates and what is the application? I'm with JohnC, never been a big fan of big bars- I prefer my wheels to remain somewhat independent. "The car handles very well..." At 8/10ths everything handles very well At 10.5/10ths, well that's when the race engineer gets an earful, and real tuning begins.

Drill straight up through the existing mount nuts all the way out the upper surface of the frame rail. Make a 1/8 plate for the top and run some long bolts throught to capture the frame rail on both sides. Use nylon lock nuts or something similar so you don't have to squash the frame rail to keep the nuts tight.

I'd wait until your racing and the rules force you into a cage, otherwise you're just dragging along another 100# of high CG weight around on a street car.

I crashed several with roll cages, does that count?

Robinson Racing Enterprises, OPM Motorsports, any circle track shop, any machine shop with a welder...

What you do also depends on when and where it pushes. Turn in, mid corner, high speed versus low speed corners, after power application, etc.? JohnC is right though, if you have even wear for street driving then you're probably about 2+ degrees short on negative camber (and a smidge of toe out) to get the front to bite for real racing.

Did this to make one of our ITS cars one time. I drilled out the spotwelds that attached the front clip to the firewall- frame rails, inner fender, and hood ledges (old microfiche calls these the "food ledge" LOL). Worked great. Well up until the carbon lump in the driver's seat T-boned an RX-7 at the old Road Atlanta bridge anyway. That split the tranny tunnel and floor pans, but my clip held up great.

Ahmen.

Give that man a bucket of propwash and some brushes for his vortex generators- he's hit the nail on the head, aerodynamically speaking.

Yeah, 50 hp variation from operator/dyno to operator/dyno or day to day not unusual. They're really pretty worthless. You could see a 10hp variation or bigger in drivetrain losses depending on fluid temps. You could be seeing 30 hp easily in a bad tune. Get it on an engine dyno with the proper instrumentation and be amazed at the power of knowing your A/F ratio. Meanwhile, do a leakdown check just to be sure....

Just a reference point- using 1-3/4 .095 wall for an ITS cage, about 60 feet worth of tubing weighs 106 lbs. Using 1-1/2 .120 wall weighs about 126 lbs. The 1-3/4 .095 is lighter but also about 36% stiffer in bending (critical for door bars). Downside is it's bigger around so it encroaches on your cockpit more.

Yours looks good. Fortunately you had enough sense to redesign it. I'd rather use 1-3/4 .095 wall and be a lot lighter. Isn't the S&W something like .134 wall? [QOUTE=240hoke]...katman its no 200mph roll cage Nor would it have to be.....