first autox complete - where to go from here?

[heavy85]

Well this past Sunday was the maden voyage for me and the Z. I used to autox a GTI followed by wheel to wheel go-karts now back to full size cars. Anyway I'm looking for some advice on where I take it from here. Car will be driven on nice days 1-2K miles per year with maybe a half dozen autoxes thrown in. Couple things I noticed imediately 1) it snap oversteers really bad if you lift - especially turning left, 2) it plows on slow speed corners which there were several at this event - especially turning right, 3) need more midrange power, 4) need real tires, & 5) need brakes that are a little more confidence inspiring. I know 2) can be fixed by a large part by driver not entering too hot .

 

Here's my stats:

 

'72 240Z w/out wipers, heater, spare, & battery relocated behind pass seat

15" generic wheels w/ Dunlap 'Sport' 225/60R15's (not high performance)

ZG flares (so I could fit big rubber if I had it)

225 / 250 springs on coilovers - front arms set level, rears with ~1/2" of rake

Tokico Illuminas (but I'm concerned they are about dead?)

EMI camber plates all around

2.5 deg neg camber on lefts, 1.5 deg neg on rights but garage not level

Offset aluminum bushings front and rear, rest poly

G-machine TC rod bushing

ST swaybars front and rear

Front and rear stut bars

L28 w/ headers, mild cam, tripple 44 Mikunis, MSD, & shaved P79

3.7 R200 LSD

Stock brakes with new rotors, pads, & shoes (brand unknown) well bled

3 out of 4 SS brake lines (??)

Early 'comp' 5 speed

 

So if I had a couple g's laying around to play with where should I go from here? I'm thinking I should start by getting real rubber but debating high performance street vs R compound. Also debating on new wheels. Next I'm thinking of properly shortening the struts so it doesn't hit the bump stops and adding single adjustable Koni's (although I thought I read they are NLA?). I just got but yet to install a wideband to hopefully tune carb to help the midrange unless I need cam and or cam timing change (timing chain sprocket set on 2 but not degree'ed in)? Any suggestions?

 

Seperately I also want to put in a rollbar but that's mostly for safetys sake - my wife currently wont even let the kids ride in it.

 

Thanks

Cameron

[zlalomz]

I would start with r compound tires on a seperate set of wheels. You will be amazed at the difference. Then start sorting out the handling after driving with sticky tires. I could fit my cantelevered 9 inch wide slicks, tool box, air tank, jack, wheel ramps(wood), folding chair inside the car for the drive to and from events. You have good spring rates for a dual purpose car.

[zguitar71]

With the coilovers and flares you should be able to run 275/45/16 Hoosiers (or other brand) in Street Mod on 16x10's. Get a good alligment. I run 1/8" toe out in the front and 1/8" toe in the back. I have about 3.5% caster in the front and 1.75% -camber all around, try to get around -2.5 in the back and -3 in the front if you can. (1.75 is all I could get out of the adj. bushings). It will eat tires on the street and be prepared to have the car follow ruts in the road, but at 2K a year your tires will still last years. With the rest of the mods you have allready your car should be pretty good. Get the other ss brake line missing too. The stock brakes work fine for autox. The stickier R tires will cure most of the handeling woes and braking distance. For the mid range power get a 3.9 or 4.11 rear end (lsd of course), move the gearing instead of changing the cam. The lower gearing will keep you in ther power band at lower speeds.

 

The roll bar is a good idea, but be careful if you get a roll cage. When you are on the street and you do not have a helmet on, if you hit your head (or your kid) on the bar in a wreck you could be hurt worse. If you go with a cage make sure you have anough clearence for your heads.

[JMortensen]

You have pretty close to the same setup I had a few years back.

 

Tires is going to be the most important thing.

 

If you're looking at suspension upgrades, the biggee for me was CASTER. Up the caster and you'll get rid of the plow. Also seems like you might be a little light on the camber. As zguitar says, toe in the back and that will help you stabilize that rear end. Also my MSA rear swaybar was binding really badly and I didn't realize it. You might want to check yours for bind and if you find any switch to a ST rear bar. If you decide to do this get it done before you change the alignment because you have to pull the uprights that locate the rear control arm bushings which will probably throw your alignment off a bit. Sectioning the struts is a good idea.

 

I don't remember which Nissan Comp trans you have. Do you know the ratios? Some of them wouldn't be very good at all for autox because first gear is like 2:1. You'd need a 4.44 or shorter gears to make that work I think.

[260DET]

What about the function of dampers in autox? Never done it myself but transitional handling would be significantly important?

 

Doing some relatively slow industrial estate testing with mine we found that more bump on the rear dampers cured a snappy 'lose the arse end' problem.

[johnc]

1. Get a good alignment!

2. Get a good alignment!

3. Get a good alignment!

4. Replace any defective shocks.

5. Replace the tires.

[heavy85]

Well I'm working on the alignment. Already adjusted for a little more camber and caster on the front but still haven't figured out why there is more camber on the left side both front and rear when both sides are set equally. I guess 30+ years of sagging and tolerances? I'll say I dont care much for the EMI set-up. Next will be to set toe. I'm also going to section my struts and upgrade to Konis. Does anyone know the story on the new single adjustable Konis since the old ones are NLA - like what part # to use and if they are any good? Lastly I'm going to get some race wheels/rubber. Question, though, what size wheels to get and how big of rubber should I be looking at for SM2? Main considerations are performance and cost. In reading over the last two issues of Grassroots Motorsports I have a good idea on the brand of tire just wonder how big to get in both diameter and width.

 

[edit] one last thing - can I easily swap the LSD from my 3.7 diff into my 3.9 diff because I really need lower gearing (or higher depending on how you look at it). Currently I can push high 60s MPH in second.

 

Thanks

Cameron

[johnc]

The Koni 8610-1437RACE is the same dimensions as the 1149 but compression damping had been doubled. For most applications that's OK but in a 240Z its probably too much. If you race on smooth tracks they might work out. For SM2 you'll need at least 265 width tire to run at the national level. I'm currently working with a customer to build a to-the-limit SM2 240Z and we are trying to decide between 295 and 315s.

[zguitar71]

I would get a lower diff than a 3:9. I run a 3:9 with a 83 5 sp and 22.5" diameter tires, on long faster courses it is fine but on the shorter slower course I think a 4:11 would work better for me. You will have a tire over 25" in diameter so your gearing will be pretty high plus the trans you have too. Mabey a 4:38 or lower ratio would be better for your set up. Or you could keep the 3:7 and go to a 4 sp trans, they are lighter and have a lower 1&2 but the 2-3 shift is a big jump but you will not need 3rd in an autox very often.

[heavy85]

JohnC - what rim diameter should I be looking at? Also since the new Koni's dont appear to work what do you recommend - this will be street driven some so I want a good strut that's not too expensive (in the ballpark of the old single adj Koni) so I know it wont be nationally or probably even regionally competitive. I have Illumina's now but am looking to upgrade some when I section the strut housings.

 

Thanks

Cameron

[MikeK280z]

I'll say I dont care much for the EMI set-up.

 

Out of curiosity, What exactly don't you care much for?

[johnc]

Rim diameter depends a lot of shock choice. The more sophisticated your shocks, the shorter sidewall you can run. With Tokicos or single adjustables you're probably limited to a 45 series sidewall at best. That would mean 15 or 16" rim diameters.

 

For single rebound adjustable shocks your choices are very limited. Carrera probably offers something but I don't know any specifics. The Koni 8610-1149RACE can have the compression revalved fro about $100 per shock and, according to Keith Thomas, there's a Bilstien applicattion P30-0032 that needs to also be revalved to work correctly in a 240Z applicaiton.

[heavy85]

Out of curiosity, What exactly don't you care much for?

 

Well it's got four holes on each side so there are discrete points which is a minor issue. The first real issue is that you have to remove the bolts to adjust then hold the wheel up to realign it and hope you dont crossthread into the aluminum. Also not all the possible positions are even achievable because it hits the strut towers near the outer (or inner - dont remember) holes. Lastly to adjust caster also changes camber and when you use diagonal holes to adjust caster the spacing obviously gets bigger so you have to wallow out the mounting holes at an angle to maintain the same camber. With all that said I've never had any others to compare to I just think these are sort of a backwards way of doing it. I know johnc used them and I assume liked them so maybe it's just me.

 

The Koni 8610-1149RACE can have the compression revalved fro about $100 per shock

 

That sucks - so $600 struts now just turned into $1,000 struts. Wonder how much double adjustable ones are??? Have to start researching other options.

 

Thanks

Cameron

[johnc]

Doubles are $1,200 for 4.