Dan Baldwin
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Posts posted by Dan Baldwin
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My caster is about 2.5 degrees, and I like the way the car handles for the most part. Effort at the helm is very light, there's an almost servo-steer effect. However, it does seem way more "oversteery" at fast tracks like Mosport and Watkins Glen, while at NHIS it seems about neutral. More caster should give relatively more negative camber in slower turns (more steering wheel angle). So I'm thinking of dialing in additional caster.
I *thought* increased camber change with steering angle was the big effect of increased caster, along with increased self-centering of the steering wheel. I don't think I quite understand the increased camber change with bump John mentions. Comments?
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I have Al/delrin bushings at the rear. I wrapped a layer of sanding screen around the aluminum before clamping down, and they haven't moved a bit after 5 track events and maybe 5000 miles on the street. The stuff looks like screen door material, but it's (der) abrasive. I also lubricated both sides of the delrin flanged sleeves with never-sieze. Haven't inspected for wear yet.
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First off, what's your displacement? At 2.8 or more, you'll want bigger carbs than 40mm. And for a mild cam and moderate power, you're likely better off with the stock FI or SU carbs, or 2" Jaguar SUs. Triple carbs are the LAST thing on my list of engine mods ('bout to install 44mm 3X2 OER Racing carbs in place of 2" SUs).
Now, lemme defend the N42. It is the only stock head that has smallish combustion chambers (only the E31 has smaller), big valves, and square exhaust ports (no liner). No one has ever demonstrated to me that there are any performance disadvantages to the chamber design other than vague references to increased likelihood of detonation. I've run over 10:1 on street gas with the stock cam and was able to run 36 degrees and (inadvertently) even more full advance at rpm with no problems. Now I'm at 10.8:1 compression, with some chamber reshaping, porting, and a 302/.550" cam (all done at Sunbelt), running 93 pump still. The N42 has MUCH smaller combustion chambers than the P-series heads, not nearly as much (if any) milling required to get a decent compression ratio. More milling means you either have to take up a lot more slack in the chain and advance the cam timing, or use cam tower shims and live with slightly screwed-up cam/rocker/valve geometry. In any case, you'll likely want to have professional headwork done before going triple webers.
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I'm convinced that the "iron drums are stiffer and give better pedal feel" effort is a myth invented by 510 drivers who want our aluminum drums. I can't imagine there's any benefit, and there's definitely increased unsprung mass and reduced heat dissipation. Plus, the finned aluminum looks cool (for drums). When I swapped in ZX disks at the rear, a 510 racer snapped up my drums in a heartbeat. No complaints from him:) I never had any pedal feel/firmness issues at the track with the aluminum drums myself, either.
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I just let mine flop around with the car in the air, and then make sure they seat properly when I let the car back down. No biggie, been doing this for 7 years, 50+ track events. I've heard of folks using safety wire, and some coilover setups offer "helper" springs, but I don't see the need for either.
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Cycling the parking brake a number of times after messing with the rears, before you apply
brake pressure, is a good idea. This *should* turn the adjustment wheel out for you, and
you don't even get your hands dirty (depending on the state of your parking brake handle).
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I have the stock 240Z calipers on my track/street 240Z, and THEY work great.
Otaku, what will you be using this car for, and how much hp will you be making?
The answers to these questions will determine what, if ANYthing, you need to modify from
stock. Fact is, the Toyo brake calipers have ~4% greater piston area than stock. This means
more front bias, which means you'd theoretically increase your stopping distance (stock setup
is already appropriately overbiased to the fronts). Unless you're making a TON more hp than
stock AND are doing roadrace track work, the stock setup with good pads/shoes and fresh
fluid (trackworthy on both counts if that's what you'll be doing) will suffice.
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Motorsport Auto in Orange California has brake rotors for ~$40/ea. You don't need anything special here (drilled/slotted/cryo treated, etc.) for your application. I've used plain solid cast iron rotors at the track for years, no problemo.
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How to Modify book says 3 - 3.5 psi, but the crew chief behind the fastest ITS car in the country told me 4+. Mine are at 4.
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Have you already bought the seats? I almost bought a Forza seat, but luckily was able to try out a floor model, and found the seat bottom to be way too short for adequate thigh support, and I'm only 5'11". Maybe you're talking about the Forza II? Multiple dimensions for most racing seats can be found on the internet, so I estimated what I wanted relative to the Forza I tried out, and ordered a Momo Rookie. Fits me very well. More money, but I definitely like the feel of a form-fitting fiberglass seat to tubular steel with webbing and padding. Regarding mounting brackets, I didn't use any. Just bolted the seat to the Momo dual ratchet sliders, and bolted those to the stock seat mounts. I did have to drill new holes in the mounts. Seems like most racing seats should bolt in like this, without using brackets, though I only have experience with mine. My seat is quite a bit lower than stock, even using one spacer (~.5"). Everyone I've ever heard of using brackets has wound up with a really high seat.
The rockers should provide ample stiffness for handling the car with the floorpans out, the stiffeners in the floorpans appear to be more for local stiffening of the floor, they can't do much for overall chassis stiffness.
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As has been mentioned, F=u*N doesn't begin to describe the interaction between tire and pavement, particularly a drag slick. The reason greater contact area (more a function of tire pressure than width) improves grip is that there is an adhesive effect between a hot drag slick and a grippy launch pad. There would be some tractive grip between the two even with ZERO normal force. Try and try again 'til you find which tire works best for YOUR car. No need for you to understand all the intricacies of what's going on. Probably only a handful of people in the world who really have a grasp on it anyway.
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1. I know of a stroker motor with the P90A that runs to 7300 rpm, so it can do highish rpm. I still think I'd go with the non-hydraulic head.
2. I've seen some REALLY clean FI manifolds, some with the extraneous bosses/holes filled with weld and worked to match the casting. Lotta work, good luck!
3. FI fuel pumpage/management *required*
DAW, my info says there are FOUR E88 heads:
'71, which has the E31 combustion chambers, and supposedly the best-flowing L6 runners
'72, 44.7cc chambers, still good for decent compression (9.8:1 on a flat-top L28)
'73, bigger chambers (47.8?), avoided
'74, same as '73 but with bigger L28-sized exhaust valves, also avoided
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240Z's were rated at 150 GROSS hp. More like 121 SAE net. 280Z was ~136 SAE net. Stock vs. stock, the 280Z has more hp. Structurally, the front sway bar mount issue is easily addressed. I ran long bolts through the frame rails, with a plate on top. Used nylock nuts, otherwise you just squish the rails. Additional weight: maybe 1 lb. Haven't seen the dreaded C-pillar cracks. I did about 15 track days before I installed a roll bar in '99, maybe 21 track days since. Roll bar weight: 50 lb., probably well worth it.
Myself, if I'd bought a 280Z instead of a 240Z, I KNOW the additional weight would be absolutely bugging the hell out of me every time I went to the track. For a high performance street car, I'd agree that cost/condition/availability are relatively important. For a street/track or track-only car, I'd only consider a '70-'72 240Z. Again, that's ME.
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Check your hot pressures. Hoosier recommends 41 - 43 psi hot, IIRC. This can give you a clue
to your setup as well. I normally run 35 cold, but noticed at WGI that the fronts were only
getting to 40-41 psi, while the rears were getting to 44-45. I adjusted pressures accordingly,
but the message is I'm working the rears harder than the fronts.
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Absolutely no way increased chassis stiffness will increase steady state cornering grip from
1.2 to 1.5g. Conceivable that it could increase transient from 1.7 to 1.9, though. If that
chassis stiffness increase comes by way of an additional 400 lb. weight, you can expect
some loss of cornering gs due to that, more loss than the gain would offset I'd bet.
240Zs corner better than 280Zs on the same tires, chassis stiffness be damned (not that I
believe a 280Z's chassis is much, if any, stiffer).
As far as "all things being equal", they pretty much are as far as 240Z vs. 280Z suspension
and tire size potential. No question 240Zs are faster on the track, despite having less hp.
Adding chassis stiffness to a 240Z doesn't require a 400 lb. weight gain. It HAS to be a
much better starting point for building a performance car. Fiberglass hood and plexiglass
"glass" gives similar weight reduction to 240Z as 280Z. Easy choice, 400 lb. lighter is faster.
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Absolutely no question about it, start with a 240Z. Ask anybody who's tried to race a 280Z in ITS. More weight on the same tires => slower cornering speeds. Longer braking distances, too. It's a hell of a lot easier to start with a lightweight car than to try to remove it from an overweight car. My 240Z (not stripped, BTW) without the spare but with a roll bar weighs less than 2300 lb. empty. 280Z is more like 2700 lb. AFAIK, '73 was the year things started going to hell.
Don't settle for anything other than a '69 - '72 240Z.
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If by "early E88" you mean the '71 E88, it might be better. In a letters reply by DL Potter in an old ZCarMag, he identified this head as the best-flowing stock head. It had the peanut-shaped combustion chamber like the E31. '72 E88 has a combustion chamber similar to the N42, but with smaller valves. '73 and '74 E88 heads had lower compression and are generally avoided.
Real answer: I don't know, I'm relying on second-hand info. I would assume the N42 is a good choice, there may be better ones.
What did your E88 combustion chambers look like, and what exactly is "much more success"? Had either head been shaved at all?
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Figures, John's STREET tires are a 1.5x wider version of my TRACK tires.
335s?! Your car tubbed or somethin?
With stock springs and bodywork, 225/50-15s or 225/45-16s fit up front, and 245s should fit in back given the proper offset. At least on a 240Z, 280 should be similar. Seems like more 15" seriously high performance street tires are being made available these days, lucky us. Go to www.tirerack.com and check out what's available. Greater selection in 16" sizes.
Only sickos like John would run Hoosiers on the street (though I did last night, in two different cars!). Kumhos, Yok A032Rs, or Toyo RA1s make better street tires, I know folks who drive 400+ miles on them to do track days.
John, what are those Michelins? DOT-legal or slicks? When/where are you going to be racing your car? Is it ready?
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Here's what I did for one of my front struts (removed from car):
4' steel pipe on the stub axle
channel-locks on the gland nut
2' steel pipe on channel lock handle
5' steel rod inserted in 2' steel pipe
Then I put my foot on the pipe on the stub axle, and with my body fully stretched out pulled on
the ~6' compound extension on the channel locks. Musta looked pretty hilarious, but it worked! On about the 4th try. Not the best method, thougt I'd include it for yuks.
Oh yeah, on the car gland nuts have been known to back off on their own, no effort at all required.
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A 600cfm carb is more than you need/want. 4-bbl manifold is widely criticized for poor flow path, you can get a LOT out of twin SU carbs (ask Norm, in the 12s with N/A 2.9 liter). What's your compression ratio? You should go at least 10:1. This will require flat-top pistons, so if it's a ZX 2.8 N/A, you're in business there, you just need to get the right cylinder head. An N42 (280Z) head on an F54 (280ZX) flat-top piston block will get you to 9.8:1. N42 exhaust manifold is pretty good, too, but you could get a few more ponies with a header (Nismo 1 5/8" probably best bet). Dynomax super turbo muffler on a 2 1/2" exhaust and you're in business, exhaust-wise. Intake should be low restriction (ITG, K&N, etc), with air horns. Again, I believe side-draft carburetion (or FI) is your best bet here.
Have fun!
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If your drum ID is within spec, new Nissan shoes and you're OK. I used Nissan shoes for dozens of track events, and never had any problems, though I did have to adjust the shoes once per track day. If you need new drums, they are about $115/each (whew). Once the drums get to their maximum allowable ID, the liners will crack under severe (race track) usage. Disc swap ain't exactly cheap, either. I did the Maxima bracket/280ZX caliper and rotor swap. Be aware that you need to maintain good front/rear brake balance, or you'll only reduce braking performance. I removed the Z prop valve and installed a ZX one, balance seems pretty good. An adjustable prop valve isn't a bad idea, or you can try different cf pads front and rear to get the desired balance (fronts should lock just before the rears). I also used a 15/16 ZX master cylinder, which increases pedal effort ~15%. Now I'm using Carbotech Panther XP pads, which have a noticeably higher cf, bringing pedal effort back to normal and giving very good, reliable performance on the street and at the track. A fair amount of dust, though.
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'81-'83 5 speed has a taller 5th (.745:1 vs. .864:1 for the 280Z 5-speed). Also has a much better 2-3 shift. Go here: http://www.geocities.com/z_design_studio/
Pretty cool resource for figuring your desired gearing.
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The Al/delrin bushings haven't moved at the rear of my Z, after ~5000 miles of street usage and three two-day track events at Lime Rock, Summit Point, and Mosport. Again, I used sanding screen to hold them in place. Don't know about wear yet, but I've got high hopes for the never-sieze as lubricant solution. The shock towers can be slotted without using plates, that's what I did back in '94 and I've had no problems despite very hard usage. This costs zero, but then you have butchered your shock towers, ugly. Having the tires look like this: | | is probably OK for 1/4-mile usage, but for the street I'd want at around 1 degree negative camber, if you want any corner-carving capability at all. My more extreme (still mild for serious track usage, though) camber has provided me with even wear at all four corners, under street/track usage.
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Perhaps most important, you should figure out what your compression ratio is now, and increase it to ~10:1, more if you've got a cam. Will probably require shaving the head, unless you swap in a 280ZX NA bottom end w/ flat-tops. This gives you torque and power EVERYwhere. '70 - '72 heads are good for CR, as are the N42 and N47 280Z heads, which also have bigger valves. N42 is the only square-port, big valve head that offers good CR. A 5-speed would be good to go with a shorter-geared diff. The 4-speeds have big gaps between the ratios. Z 5-speed has a better 4-5 shift (.864:1 5th), while the ZX box has a much better 2-3 shift but a tallish .745:1 5th.
Ideal Compression Ratio for N/A L6?
in 6 Cylinder Z Forums
Posted
10:1 shouldn't be a problem for a mild street car.