pparaska

I is a engineer . At least I play one at work. B.S. (Bull S__t) and M.S. (More S__t) in Mechanical engineering. Now I play with missiles at work, kind of like a rocket scientist w/o a license and other neat stuff. What are you studying? But I'll tell you what. I was "this close" to being an auto mechanic. My dad talked me out of it and I just spent my money on college instead. Even without those engineering degrees, I'd be tinkering on everything in sight anyway. Lone and me are very much alike like that! Degrees don't seem to make much difference when I'm in the garage making stuff. It's mostly gut feel for me when I'm working on stuff.

John, raising or lowering the CA pickup point has no effect on the ride height, suspension travel, etc. Only the strut located stuff (C/C plates, springs, coilovers) do that. The bumpsteer spacers don't lower it either. I took your statement that raising the CA pivot lowered the car - is that what you meant? I think you have to balance the amount you lower the car with the CA pickup point location change, and the "bumpsteer" spacer thickness. This is really all a juggling act to get the CA to a near stock angle relative to the horizontal when the car is at ride height. Maybe a bit more or less of an angle is advantageous, I don't know. But if you lower the car, the CA starts to become horizontal (maybe goes up from the pivot points if you lower enough?) and you need to reverse that by either the spacers of moving the pivot point. The deal is that raising the pivot point not only changes the CA angle (and the roll center and camber curve as well - as do the "bumpsteer spacers"), but it also changes the bumpsteer curve, for the better.

A bit of high tech aero stuff that a bud (Christian LeHew) sent me the URL for: Check out the Tech section and the "Guest Articles" stuff. http://www.mulsannescorner.com/

JohnC, thanks for digging that up! Terry, everything I've points to two conditions for elimination of bump steer: 1) Parallel lines connecting the pivots of: a) the tie rods, and the inner pivot and ball joint 2) The lines connecting the pivots must be of the same length. (Same effective length of the tie rod and control arm.) So if you keep the CA pivots in the same lateral location, and use the same steering knuckles, yeah, a wider or shorter rack will force the effective length of the tie rod to be shorter or longer than stock, respectively - causing a change in the bumpsteer curve. BTW, Al (alsil), what is the difference between the inner tie rod end pivots on the 240Z and the Mustang rack you used?

Psyched - yeah, I never thought I'd ever be this close! I am positively itching to drive it. I'm trying to get the correct mind set. Yes, it will be faster than 99% of the cars I meet, but that other 1% means quite a few cars that can take it. I have to keep reminding myself I didn't build a barn burner but a nice GT. That said, I'm STOKED !!

I'd talk to a few shops that build race cars. I think that you need to consider that .125 tubing is not a ton more weight. If I were to do it again, I'd probably do .125" wall. However, the place I bought the tubing from does circle and drag car fabrication and they thought that for what I was doing, 0.083 was enough.

Yes, the camel hump (double hump, fuelie, Corvette, Z/28 (early) ) heads are the high performance heads. They were the ones everyone in the SBC world looked for in the yards for many years (70s and 80s). BTW, I hear these are now becoming worth more to the restorers. I'd love to sell mine for a nice pile to be able to upgrade to some nice AL heads. Problem is I'd have a hell of a time deciding which to buy!

I tend to call the people that play with the looks of the car the "stylist" to separate them from those that do "design" work, the engineers. Design to me means actually working stuff out, not just drawing pretty (or not so pretty) pictures of cars. Sorry, that's the engineer in me making that distinction. I can't "style" anything, but I can design.

John, TimZ posted that each Z car is different, as far as the correct height to get (near) zero bump steer, and I agree, to some extent. My caveat to that is that this is a production tolerance stack up and there is a distribution of errors that make it such that some number like 7/8" for raising the CA pickup point is probably right. I'd shoot for 3/4" of 7/8" and then convert the tie rods to heim joints and do the fine tuning there, I guess.

I hate to sound negative, but that was exactly the tact I took years ago, before I could start the V8 conversion. I played with lighter springs in the distributor, changed the valve lash around, and tweaked the SUs. But I never felt it was worth putting the little money I had into the L6, because I knew I'd need a bunch to make it have the power I wanted. No biggie, I had fun with the car anyway!

I made my own floors and put in subframe connectors to replace the sorry excuse for "frame rails" that Datsun had in the 240Z. You can see some of this at: http://members.home.net/pparaska/structuralmods.htm The front frame rail replacement is there as well. All the stuff was from scratch using thin walled tubing and flat sheet stock. That's the way I did it anyway.

Terry, I remember doing that as well! Thanks for the memory jog.

You might need to grind/file down the closed end of the wrench to let it slip on.

Yeah, that's a list for GM manuals. Ford and Mopar are to follow in other catalogs.

quote: Originally posted by JAMIE T: ...My question now is, do you guys think this would be worth the trouble? And, does a greater PMOI add to improved handling? To weigh the pros and cons, on one side the car will look more like the originals, then again, I will have to re-work a nice piece of fiberglass with difficult curves. If the handling is not to be affected in a bad way, it seems like it would be a good modification. Jamie That's a tough one. I tihnk it's a really cool idea to try to imitate the true proportions of the GTO250. Bute whether it's worth it, I dunno. Looking a SpeedRacers GTO 250 replica makes me think I'd just do it that way. Personal decision I can't help with.

You'd be hard pressed to hurt a good 283 or 327 small journal crank with a 300-350hp goal. Bill "Grumpy" Jenkins won alot of races with just stock 327 small journal cranks - they're forged and "herky" by his account. The 283 would be really cool. One minor drawback to building power with this engine is that the smaller bore size is not compatible with alot of the heads out these days. But since the 305 is close to (the same) bore, some of the aftermarket heads for the 305 would work well. Anyway, the 302 (3" stroke, 4" bore) would be awesome! Sounds like a great plan for building a Z with a healthy amount of horsepower, without all the upgrades being needed as you say. [ April 28, 2001: Message edited by: pparaska ]

Jay, welcome to HybridZ! I'll take a shot at a few of your questions: RamJet - that puppie does look tall, but don't know. We could get measurements for some of the intake/carb/aircleaner setups people have and you could get in touch with GM Performance Parts and ask what the height off the front of the block at the intake is and we could start there. Exhaust manifolds. JTR manual has good info on that. But most people just get blcokhugger headers (I recommend getting them ceramic/metallic coated).

The Avenger is just a Holley (3310?) that has a few upgrades done to it (out of the Holley parts bin, BTW) to make it a little more fool proof and easier to tune.

The Tremec 5spd is right around 100 lbs. The Lakewood blow sheild is about 25-30 lbs. My UPS driver has a bad back, thanks to me .

Davy, thanks again for the Kudos, but ain't no way I'd stop the project for that mod - it's one of those "once the car's on the road things". I was thinking about some kind of custom setup for the 14" air cleaner though. Some kind of fabbed up stuff to sandwich in between the edges of the top and bottom of the cleaner lids with 3" outlets pointed downward just below the strut tower bar, and silicon hose to the holes on either side of the radiator. Then again, maybe steel 3" tubing running to the openings, and have them stainless ceramic coated? Back into the high dollar stuff again . There are alot of those "it'll have to wait" projects on my car these days. The car's in paint jail for at least another 3 weeks. If that's all, I can throw a few interior parts in, put the glass and lights in, and start driving and debugging the thing. Hopefully still make the Kingston Convention! BTW, took the Roll bar to the the body/street rod shop tonight and the guys are going to put it in for me BEFORE they paint it. And I do have a bracket made up to mount the Corrola Mirrors in the front corner of the windows - very simple, with no fasteners, just high performance epoxy. [ April 27, 2001: Message edited by: pparaska ]

Mike, looking good. I really like the looks of your CA and T/C rods that are there now!

TimZ, I believe you when you say that the bumpsteer is very sensitive to the inner pivot placement - exactly why I made mine adjustable. I had an "incident" where the horn bracket that holds the rack and pinion was tweaked (upward) an imperceptible (to the naked eye) amount. The bumpsteer change was very dramatic. As for it falling out of adjustment, there's little chance that the height adjustment I have could move (I need to take pictures of this setup, I imagine), but the "camber" adjustment direction of the hole might move. I'd planned to do exactly as you suggest - weld the puppy together once I get it where I want it. The problem will be me getting "happy" enough with that setting to allow my self to weld it down. I really like the idea of uncoupling the camber gain adjustment (height of the inner pivot) from the bumpsteer by making at the outer tie rod end (heim joint). I may go that way some day.

Mike (Kelly), I agree totally with Dan on the steel vs AL thing. That's sprung weight anyway, and AL and fatigue issues always gives me the willies (no fatigue limit). I'd say go with the steel one and powder coat or POR-15 the steel body black. As for the bending loads on the threaded rod, that is a concern. I'd like to see an analysis of the bending and shear loads on that rod. Since it starts near the sway bar mount point an the arm, the bending moment will be high at the root of the threaded rod where it comes out of the tapped welded in block. I really like Mike (scca)'s idea of a piece of hex threaded where the threads only need to be - this gets the threads away from the root of the clamped end near the sway bar mount - a good thing. Shear loads will be present, and I'd like to see an analysis of that also. Dan, do you have any ballpark for the vertical load that a hefty sway bar imparts to the CA, for turning a Z at 1g? I'd imagine the dynamic load would be of little consquence in this case, unless you hit a big sharp bump during a turn. Pete

Ross, on the Z, that area (cowl) is for pass compartment fresh air intak only - although I've had thoughts of cutting a hole to provide engine intake air. I'm now leaning toward a ram air box, but $100+ for a piece of plastic and some metal stampings really doesn't sit well. Plus I don't want to have to mod my strut tower bar mounts for it.

There are urethane and ABS (solid connection) couplers available to replace the stock rubber one. Check MSA, etc. I've used an old nylon coupler for years, and it does transmit lots of road noise into the wheel, horn button area and really transmits every little pebble to the hands on the wheel. But the entire Z is an intense vehicle to drive, always requiring attention. Especially with wide tires, short steering knuckles, bumpsteer, etc.