Scottie-GNZ

Dale, you are correct. My approach was to work from the outside in as I was concerned about where the outside edge of the tire was. One approach is to take the published rear track of 53" and adjust for the stock wheel offset. I have no idea which wheel was used when this measurement was taken. The swastika wheel is 10mm and if you use that as the standard, then I would go with 53.75" hub-to-hub (mounting point, i.e.)

As you can see below, the rod is supported in the middle. I can understand a change in geometry causing binding, but tightening down the clamps should only effect a minor change. I have actually rotated the rack causing severe angles in the u-joint and without the rack bolted down tight, I get no binding. As soon as I tighten it down to "normal", it binds. Mike, when yours binds, does it retun to center like normal or do you have to turn the wheel back yourself?

John, one more time. Take a look at the pic below of a 71 hub and you will see that the 4.5" diameter of the lugs would actualy be on the edge of the 4 cutouts. Not possible to do the Chevy lugs on that hub. Remember, I am trying to to go from the Datsun 4x4.5 to a Chevy 5x4.75. I have no choice but to press the Chevy lugs in the adaptor. Mike, any luck getting those pics? SCCA, hope you do not mind me using one of your pics.

I did not see any mention of it, but in case no one is aware, Cartech Is Corky Bell.

I would not rule out the extra u-joint, but lets think about it for a second. What exactly is happening when we tighten down on the 2 clamps? The rack is being "lowered", but it can only go as far as the bottom portion of the bushing will compress and they are urethane bushing. Are we missing something else that happens when those clamps are tightened? I would be curious to know if your steering would loosen up if you also loosen those clamps. Gotta love these cars

Unless I misunderstand what John is trying to say, the problem is that the 71 hub diameter is not wide for the 5x4.75 bolt pattern and it is not even perfectly round. I do not see a choice but having the Chevy lugs in the new adaptor. In addition, the Vette uses 12x1.5 lugs and I already have ARPs on the rear and plan the same on the front. Minor, but a clarification nonetheless. Remember that the early hub is completely different from the later ones.

I used Illuminas, F & R, when I had the Datsun IRS and still use the Illuminas in the front with setting #3 for the street and #1 for the track.

OK, aluminum is out . I redid the calculations and went out to trial fit for confirmation. A 13/16" stack of spacers provided the perfect spacing with the fender when turning in. What that translates into is the wheel coming out 3.42" from the hub. To match that spacing with the 17s I would need a spacer .543" thick. Since aluminum is out, .5 steel sounds on the money. DAW, I like your idea of no threads and a nut inside the rotor in case I do something funky later with the rotor/hat. 1/2" steel should be enough thickness for the lugs. OK, it is time to reveal where I am going with as it relates to brakes. I want to do the C4 12" brakes to match the 11.4" rears. Below are 2 shots of the C4 brakes on a F-body. If my adaptor can accomodate the 5x4.75 and the 4 holes for the hub, so can the C4 rotor. So, I plan to drill the C4 rotor for the additional 4 holes and position it like the stock rotor. Note that the hat is deeper and that would require a caliper bracket and spacers to position the caliper correctly. Now I need to find a kind C4 owner who can loan me a caliper and rotor. Grumpy, you listening? Do not be shy about telling me I am MAD.

Lone, you hit it on the head. Seems the "every turbo car has lag" stigma will never go away. With a properly configured turbo setup, lag is a thing of the past and such complex setups are not needed.

This is going to sound nuts, because I still do not believe it but am living it. My steering tightens up the more I tighten the 2 u-clamps. I have tried everything even to the point of repositioning the rack so that the u-joint was totally out of whack. I have resigned myself to using longer bolts and tightening (no where close to "normal") to the point where I can feel it tightening up, then using a lock nut on the end of the bolts. Couple of weeks ago when I realigned the front-end, the shop did me a favor and tightened up the "loose" bolts on the rack for me . It is almost as if when I tighten the clamps that the rack is being crushed or bent, but of course it is not

10mm. Hmmm, that explains why the wheel/tire had less clearance with the perch than I thought it should. I will redo the calculations, but just looking for thoughts on the design. I suspected aluminum might not cut and that is why I asked. BTW, I have to use that wheel because that is what is already on the rear and chosen for its offset to fit the Vette IRS install. Here is a frontal view of the design to make it a little clearer. Do not have CAD so the crude PPT drawings will have to do for now.

Hot off the press from the Buick meet at Bowling Green this past week.

Mike, you are taxing my memory but if I recall we did not want the car lowered because we were going to be using 245/50-15 on 15x9s in NYC!!! 235/60s is a very tall tire!! 26.1" and so clearance will be tight especially if the wheels do not have the correct offset. You need to check that, regardless of which spring you plan on using.

My front wheels will be 17x8.5 with a 5.625" BS and a 5x4.75 bolt pattern. That means the wheels go out 2.875" from the hub mounting point. I mounted a Swastika 15x6 (which I assume has 0 offset), with 215/60-15 tires for trial fitting with various thickness of spacers. I maxed it out to 1.125" of spacers before I encountered interference with the fender where the valance/front dam bolts up and the problem is when the wheel/tire turns in. At this point, the wheel should be out 4.125" from the hub mount point. I figure I can overcome this interference since the tire I plan to use will have a slightly smaller diameter and if I limit the wheel to 3.75" out from the hub. Problem: This then requires a 4x4.5" to 5x4.75" adaptor/spacer only .825" thick. Far as I can tell, that is not possible after speaking with several manufacturers. Seems 1" is a stretch with 1.25 the minimum and some strongly recommend only a 2-piece design when changing the number of lugs. My Solution: Machine a 5.25" diameter, .825" thick, hub-centric disc with the 5x4.75" bolt pattern and lugs. It would also have 4 holes drilled an tapped to match the bolt pattern of the bolts that fixes the rotor to the hub. The original lugs would be removed from the hub and the hub trimmed enough to provide clearance for the 5x4.75" lugs in the disc. The threads for the 4 bolt holes in the hub would be cleaned out just enough to pass a longer bolt through it and be threaded into the disc which would be mounted over the hub. Where most adaptors are universal to fit a bolt pattern, this one is specific to a 240Z (or maybe 1st-gen) because it is hub-centric and bolts up over the hub. What do you think? Any reason why this could not be made out of aluminum? Please, no "why not go 5x4.5" suggestions. This is the first step in the front-end upgrade. I have not figured out how to solve the tire/perch clearance yet but will wait until I make the adaptor and see how much clearance I need. Also does not alter any plans for the brake upgrade. Here is a rough draft, repeat, rough .

That is Derek Grubb. Best to date that I know is 10.59 @ 130+ with a 1.49 60'. Do not know if those were all in the same run. Typically they are not. The tires are Phoenix and are about 6.5" wide but that is all I know. He occasionally posts here.

Grumpy, I believe that formula should say RWHP not @Flywheel. I wanted to see how much HP it said I needed to run 10.86 with a weight of 2,750lbs and it punched out 424 @ flywheel!! Using a 85% factor for RWHP with an automatic, that is 360RWHP. We could only dream about running hi-10s with only 360RWHP. The only formula I use is the one that factors in ET and MPH because it takes into consideration cars that launch quick but die on top-end and cars like SupraTTs that launch slow but have big MPH. (((MPH * MPH)/ET)*(weight with driver/1000))/9.1 = RWHP Plug that in a spreadsheet and you can play what-if. Like a dyno, every formula is going to spit out different numbers, so pick one and stick with it. I like this one because you can see who is BSing who when someone claims a ridiculous timeslip. BTW, with a weight of 2,750lbs, it spit out 430.3RWHP for 10.866 @ 124.39 and 435.3 for a follow-up 10.95 @ 125.59 after a minor tweak but a lousy 60'. I knew the car would have a little more HP on the 2nd pass but the ET was slower because of the launch and the formula showed that.

Start here - http://members.home.net/drax77/newpage.html then go here - http://zdriver.com/members/scottiegnz/scotties240zt.htm

Grumpy, how about adding a forum for Other Cars that have Vette components? A lot of hybrids (not just Zs) would love to chat specifics about Corvette components - drivetrain, suspension, brakes, etc, without Vette owners turning their noses up at us.

Damon did not say which Supra. I was looking at the Mk IV which has a 3.13:1 ratio with the manual trans, perfect for me but probably not desirable for a L6 or even a V-8. Do not have the dimension off the top of my head but it is definitely too wide for a stock-fendered Z. By my measurement I recall I would not have had to narrow it for the 3" flares if I used wheels with a deep backspace.

OK, hope we are back on track. I am curious to know how you are going to mount the 2 GN I/Cs. There is a guy with a really nice and quick El Camino with a GN drivetrain and 2.5 GN I/Cs!!!. Actually the 1.5 is the result of an I/C being extended with half of another I/C. He has that one in the stock location on the engine and another as a FMIC. Car makes phenominal power. If you are interested, I will see if I can get a photo. The one thing I agree with in this thread is the fact that you cannot think 700hp and low-budget. Do not forget that the mods to the chassis/suspension to support 700hp is going to hit deep into your pocket also.

Just as important as the head gasket is the clamping force, so I would look into ARP head bolts or studs, whichever the VG30 uses. Internally, I would also do ARP rod bolts. Cheap insurance.

Unfortunately, I also suspect the inner tie rods and that is not something I want to tackle right now. How difficult a job is that?

1fastz, 3.5 secs? I think you are way off and it is probably more like low-2.0s. Here is a spreadsheet developed by one of the Buicks guys that plots 0-60 using calculus with input from your timeslip. Download the spreadsheet and plug in your numbers. You will need the 60', 330', 1/8 and 1000' times and that is good because with my 1.57 60', my car would appear to be quicker than yours and it is no where close. That is why I do not like the one that uses only the 60' time as input, because the car is not going 60mph at that point. When you download it, use my numbers as an example. After you plug in the timeslips values in cells F11 - F14, get the 2 new values after "Y=" and plug them into B11 & B12. As the instructions say, do not change any cells in red. 0-60 Calculator PLEASE!!! for those that would like to play with this, I would appreciate if you downloaded it and not change the copy on the web. If someone tries it online and screws it up, it leaves a bad sample for others who would like to try it. Have Fun and cannot wait to see the numbers from you, Ron, Jap Tin, etc. We talk routinely about how fast our hybridz are but this will really hit home when you compare your time to the supercars.

I read Al's issue with great interest and now would like to throw mine out for dissection. I have always had a little shake in the front wheels at about 55-65mph only. It was so minor, I never paid much attention to it. Now it has gotten considerably worse and I need to do something about it. Keep in mind that the problem kicks in sharply at 55 and goes away just as sharply at 65 with no evidence of a problem outside that range. The wheels are Swastikas and the tires are 205/60-15, recently mounted and balanced. The previous tires had the very same minor shake, so I rule out the tire switch. Hi-po springs, Illuminas, recent (w/in 2 yrs) ball joints and outer tie-rod ends, alignment just a coule of weeks ago and that produce no change in the minor shake. Parked the car for 2 weeks to do bodywork and started getting the violent shake immediately after that. I also rule out the fenders . Obviously the minor and major shakes are the same problem but what brought on the sudden change? Checked and retightend wheel bearings but no effect.

If that works I am going to find you and give you a big smooch. OK, hug. OK, handshake