John Coffey

I apologize for the technobabble. I was trying to give you more then a yes or no answer to a question that cannot be answered yes or no. The answers to your original post are "no" and "no." No you cannot use any offset (a meaningless term by itself but you seem to like it) with any spacer and no there's no such thing as a best "offset" for a Z because you need to know more things then just offset. For example: A zero offset 18" wide wheel will not fit a 240Z because you're looking at 9" of backspace which will not fit but an 18" wide wheel with 14" of positive offset will fit if you flare the car. Hopefully this isn't too technical.

Offset is a meaningless term unless you know wheel width and backspacing. Some of the basics: Wheel Width The horizontal distance between the inner tire bead mounting surfaces. Backspacing The distance from the wheel mounting surface (where the wheel contacts the hub) to the inner tire bead mounting surface. Offset The distance the centerline of the wheel width is offset from the wheel mounting surface. Positive is an offset to out outside and negative is an offset to the inside (or I might have that backwards). ------ The confusion surrounding a Z "requiring" zero offset has more to do with backspacing on wider wheels. Most Z specific wheels are made with zero offset which means a 7" wide wheel will have 3.5" of backspace. A stock Z suspension can accomodate a wheel with 4" of backspace before things start rubbing on the spring and strut. Again, assuming you're using a 7" wide wheel that means the wheel will have 1/2" of negative offset if you can find one with 4" of backspace.

The R series of diffs are made by Hitachi for a number of OEMs. They range from an R100 through an R500 the last I heard. They are available from Hitachi with different pinion shaft lengths and housing designs. What's found in Nissan products (from old 510s through the latest Infinity products) are R160s through R230s. The 240/260/280Zs sold in the US were available with the Hitachi R180 and the R200. None came from the factory with a LSD. Hitachi offered a clutch pack LSD for the R180 and the R200 and a viscous LSD for the R230. NISMO and Nissan Competition sell the Hitachi clutch pack LSD for the R180 and the R200. Quaife sells an ATB (automatic torque biasing) differential for the R180 and the R200.

Style 2 are Dura-Lites. They are about the lightest you can buy but at the 240Z ITS legal weight of 2425 they tend to be a bit flexible.

You can run an IT 240/260/280Z in BSP. Rules section 13.0 states: "Cars listed as eligible and preparred to the current national Improved Touring rules are premittied to compete in their respective Street Prepared classes. Neither Street Prepared nor Touring cars are permitted to interchange preparation rules..." So, a Z built to the SCCA GCR for IT can compete in BSP but it cannot use any of the preparation allowances for Street Prepared. For example: you have to run 14" x 7" wheels (IT rules).

If you are building a legal BSP 280Z: 1. You cannot remove the sound deadening material. 2. You cannot remove the factory undercoating - but can remove any dealer applied stuff. 3. You must run with the 280Z bumpers. 280Zs are competitive in regional events, but not at National level competition. A "to the limit" BSP prepared 240 and 280 will have the same horsepower, brakes, and suspension but the 280 will weight at least 250 lbs more. FYI... ITS prepared 240Zs must weight a minimum of 2435 lbs at the end of the race with driver aboard. An ITS 280Z must wieght around 2700 lbs.

Or maybe it has something to do with the shorter tire sidewalls giving better response...

In the context of the original post (basically stock springs, no radical suspension changes) the stock front anti-roll bar and a small (or maybe no) rear anti-roll bar will work best. You really want to control weight transfer with springs more than with bars. Because an autocross is mostly transitions, stiff bars and soft springs tend to overload the tires so that you get an initial push on corner entry and then snap oversteer as the car falls over on the springs, just when the driver starts turning the other way. If a person gets serious about building a dedicated BSP car, then there are a number of things that have to be done to get a Z to turn in well and stay planted. And, no, I'm not going to list those things until I think someone is serious... ;-)

I wish this urban myth would die, but I'll try to explain again... A lot of time racers will find something that gives a little more power for a particular engine configuration that's limited by the sanctioning body rules. Racers will spend thousands of dollars and/or hundreds of hours trying to find 10 more legal horsepower. They exploit that something and word travels around the racing community. Soon, street racers hear about this modification and think its some magic bullet so they apply the magic to their modified engines and feel faster. But, if they spent the same time and effort on other mods (not restricted by any rules) they will see much much greater horsepower gians. The N36/33 manifold giving 10/20/30 more horsepower is one of those myths. Yes, it does give slightly more horsepower on a basically stock motor than the other UNMODIFIED intake manifolds if the motor is in perfect shape. ITS engine builders discovered this years ago. But, any L6 intake manifold that's had some mild porting, polishing, and/or extrude honing done will flow equal to or better than a stock or modified N36/33. I know, I've seen the hours and hours of dyno tests. So, if you already have a pair of N36 manifolds (I wouldn't spend the time and money to source a pair of these "trick" parts) then bolt them on after you're made sure engine compression is perfect, the carbs are tuned perfect, the ignition system is perfect, etc. A poor running motor with N36 manifolds will always get smoked by a good running motor with E88 manifolds.

Sounds like a linkage problem. I'm not a transmission guy so I guess you'll have to find someone local who can pull the tailshaft and see if there are any obvious problems.

A stock 240Z with a perfect stock suspension is generally horsepower limited on a racetrack. Get the basic platform solid before doing any modifications. Putting better springs/shocks on a car with worn suspension bushings, structural rust, worn mounts (engine, trans, diff), worn bearings, or a bad steering rack is asking for trouble. If the basic platform is marginal and then you increase the loads via bigger tire and rims, high rate springs, etc. you are increasing the chances of failure. My "order of mods" suggestion: 1. Structural rust 2. Bushings 3. Bearings 4. Mounts 5. Steering 6. Shocks 7. Springs 8. Anti-roll bars

If I'm not mistaken, I don't think you can buy any "real" lead (tetrahydrol?) additives anymore. Most of the octane boosters sold just create deposits on your valves. You car should be fine on premium unleaded. If you're really worried about it, you can buy a barrel of racing fuel from VP Racing and add 5 gallons of it to each tank of pump gas.

A 250+ hp Nissan L6 is very possible and it can be easy to drive on the street and very reliable. The sophisticated engine managment systems now on the market (SDS, Electromotive, DTA, Motec) ranging in price from $800 on up can make lots of power with smooth driveability.

I ran a modified Tilton 8 lb. aluminum flywheel on my BSP 240 for years. For a daily driven street car I would not run something that light but for a track car its well worth the money. I would also run a Nissan Motorsports clutch and pressure plate. And yes, the car will idle just fine - engine don't need a flywheel to idle. My new engine has a Quartermaster 5.5" multi-disk clutch and no flywheel and it idles fine.

Transmission mount. Typing problem on my part. The diff mount is the rubber mount at the front of the differential and you'll be working around it when you're unbolting the driveshaft.

Most likely the driveshaft u-joints are bad. Pull the driveshaft and have them replaced. While you are under the car, replace the transmission and the front diff mounts.

Boy, that's an old post Mike. New e-mail address below:

Check the back of the head gasket and the coolant tube that runs in that area.

What's the serial number? If it is indeed an early Z, you would be better off financially restoring it stock. Look for the serial number on the driver's door jamb, next to the master cylinder on the firewall, or on the plate attached to the right front strut tower in the engine compantment. The number should start with an "H".

Dave Rebello wants $600 to rebuild an R180 and install the Quaiffe!? Call these guys: http://www.gearedbyunitrax.com/main.html - Ask for Jerry. They've built me three R180s - one with the Nissan Comp LSD and two with Quaifes. $300 including all new bearings and seals.

I think both carbs flow a combined 290cfm. But, I question your basic premise. Many folks have tried the 2/4 barrel conversions on Nissan L6s and are extremely lucky to get them to perform as well as the stock SUs. Familiarity with certain carburator designs may make this a more comfortable choice, but why pass up the chance to learn something new? SU carbs are as reliable as any Holley, Autolite, Carter, or Rochester when setup correctly and are as unreliable as the same carbs when setup incorrectly.

You don't really need a complete box around the carb intakes. What I suggest you do is two things: 1. Build a heat shield between the headers and the carbs that routs the heat rearward and up. 2. Add an opening in the hood (probably use a 280Z hood) that lets that heat escape. At low speeds you have to use convection to get the heat out of the engine compartment.