katman

A friend and I got pulled over for speeding (50 in a 35) on the way to a movie once. Now, late for the movie, decide to head to my house. Get pulled over for speeding again (45 in a 35, hey, we're getting slower!) by a different cop. 5 minutes after receiving the first ticket. In response to "but we just got a ticket a few minutes ago" the cop says "we'll you're really racking them up tonight, eh?" No profiling, just good policing! Dang speeders.

Don Potter has been hot boring and honing Z engines for 30+ years. He also uses a torque plate that exactly mimics the distortion that a real head on a gasket causes, which isn't exactly what a constant thickness block of steel (typical torque plate) does. Of course what could ruin all that is cheap aftermarket pistons. Since pistons aren't round when they're cold, you have to trust that the piston engineers have done a good job to make them round when they're at operating temperature. Important? Tuning will kill more power than hot honing will ever make, but we did put an amazing number of races on D.L.Potter engines without any degradation in leakdowns.

The letters stamped on the back of Nissan cams mean nothing, other than A's are generally found in L24's and L28's and C's are sometimes found in L26's. Along with about every other letter of the alphabet. And there's about 12 variations on the "A" grind and C's were sometimes on late L24's. You have to "Cam Doctor" it to know for sure.

And they will break a stud. On #6. It's a given. Oooh, Columbia SC, I could pick me up some Maurice's BBQ at Piggy Park....

That'd be about right for a shop that doesn't do it every day. You have to remove the intake also to replace the gasket. A Z person could do it in an hour.

As far as headers go the Monza is junk- mass market at a low price. Almost all of the performance increase you get over stock will be due to a bigger exhaust pipe, not the header. But, a free header is cheaper than a used stock manifold (unless it is also free). Better? More engine compartment heat, more noise, more likely to leak at the gasket, more likely to rust out, not likely to make any more than a horsepower or two over stock. Your call. Stick with a single exhaust in the stock location exiting out the back. I believe the Dynomax Super Turbo part number for a 2.5 diameter that will fit a Z is 17723 or 17223. Been awhile.

I would endeavor to one day be able to run near zero toe in the back. No sense in dragging the tires around all the time if you don't have to. On the front, unfortunately, 1/8 toe out is about what we found was required to get good low speed turn in, even after exhaustive changes to springs and bars and shocks.

Don't do it! Unless, of course, you enjoy taking the tranny out every few weeks to relube the bearing. That's a race only part and frankly not even needed for that. Everybody I know that's tried one on a street car has reverted back to the stock bushing.

The zhome results were just a piece of the initial results we collected over a 3 year period. The real work was done on an engine dyno and not shown. Out of morbid curiosity I also made note of other header testing done by car mags over the last few years from the import tuners to the big block Chebbies. For the ITS motor it's easy to blame the lack of response on the stock cam and carburetion, although when we quit the ITS 240Z program we were making 208 real SAE east coast hp, which is proly more than most people get with triples and a cam that don't have the resources to really tune. Still, about 4-6hp could blanket the results between most aftermarket headers and a good N42 manifold on a 200 hp Z motor utilizing the tuning tools most people would have available. At best you might get 4% or 8 hp. The real eye opener for me was a test I ran across in Super Chevy or something like that where they had a 454 with your typical mods: aftermarket cam, aluminum aftermarket heads, decent compression, proper Holley, Edelbrock manifold, etc. The difference between the stock 454 exhaust manifold and the best header they tested was about 20 horsepower, or 4% of the 500 the motor was putting out. Basically, and amazingly, about the same as a Z. So I'll give you 4-6% for headers over a stock manifold IF you can tune to it (which means lambda sensors and dyno runs), and 1-3% difference between any header and any other header. That would be for an engine in the mild category. Wouldn't be fair to test an N42 manifold against headers on a 3.1 liter with trips and a cam since the N42 wasn't designed for that much flow. But if Nissan had put out 3.1 liter motors with hot cams and triple Mikuni's, I bet the difference between the stock manifold for that and all the aftermarket headers would only be 4%. Hey, I put them on our street Z's because they look and sound cool, but I don't kid myself about how much horsepower I'm making with them. Definitely a requirement for bigger and hotter motors since there is no stock manifold equivalent. Am I making sense?

Hey, but the good news is a square port will work as good on a round port head as 99% of the round port headers work on a round port head. Which is to say they look just as cool, which is good for a 15% power increase easy.

Degree+ less. Less camber on the rear, by a degree or more.

Degree+ less. Less camber on the rear, by a degree or more.

I wouldn't use an IR gun. Surface temps change too quickly. A Z will need up to a degree+ less camber on the back and the temp bias will be the same. Long term keep track of tire wear. For us that bias produced best handling and even tire wear. Counterintuitive- you'd think the hotter insides would wear faster. One last thing- when in comes to engine or chassis, never assume the basics are still right just because so and so hasn't been changed and hasn't been a problem before. When diagnosing either I always start back at square one to verify everything is still where I think it should be. For chassis, the progression would be hardware (is everything tight and uncracked?), corner weights, toe, tires (as in throw on another set and see if the problem is still there). Only then do I start looking at springs/bars/adjustments. Oh, and 20 degrees for 150 degree tires is proly a lot worse at the 190-210 you should be at on a normal day....

I wouldn't use an IR gun. Surface temps change too quickly. A Z will need up to a degree+ less camber on the back and the temp bias will be the same. Long term keep track of tire wear. For us that bias produced best handling and even tire wear. Counterintuitive- you'd think the hotter insides would wear faster. One last thing- when in comes to engine or chassis, never assume the basics are still right just because so and so hasn't been changed and hasn't been a problem before. When diagnosing either I always start back at square one to verify everything is still where I think it should be. For chassis, the progression would be hardware (is everything tight and uncracked?), corner weights, toe, tires (as in throw on another set and see if the problem is still there). Only then do I start looking at springs/bars/adjustments. Oh, and 20 degrees for 150 degree tires is proly a lot worse at the 190-210 you should be at on a normal day....

Well here's some hints. 1. I never change anything based on temps from one session. I need repeatable data before I make an adjustment. 2. I check in this order- LF LR RR RF 3. I go inner-middle-outer on each tire in that order and use a needle probe that I can get a good 1/16th below the tread. 4. We try to get a 20-25 degree bias toward the inside. Hoosiers respond well to camber thrust so the inside should run hotter. In the old bias ply days we were even to 10 degrees bias. 5. If your setup is right, especially the shocks, all 4 tires should be close to the same- like there shouldn't be more than 20 degrees difference between the average temps of each tire. On an ITS 240Z at Road Atlanta your highest temp will be the left rear, followed by the left front, right rear, and then right front. I dare say most setups proly have a 40+ degrees spread between the left rear and right front. 6. If you're not getting 160+ minimum it's too cold outside or you're too slow to make any worthwhile adjustments. 7. Follow the Hoosier rep around your ties and compare your temps to his. They round things off but generally trend propely, so if you're not seeing the same trends as the numbers they give you there's something wrong with your technique. 8. There's generally a big gradient around the corners of the tread, especially with big camber, so be consistent with where you measure. YMMV.

Well here's some hints. 1. I never change anything based on temps from one session. I need repeatable data before I make an adjustment. 2. I check in this order- LF LR RR RF 3. I go inner-middle-outer on each tire in that order and use a needle probe that I can get a good 1/16th below the tread. 4. We try to get a 20-25 degree bias toward the inside. Hoosiers respond well to camber thrust so the inside should run hotter. In the old bias ply days we were even to 10 degrees bias. 5. If your setup is right, especially the shocks, all 4 tires should be close to the same- like there shouldn't be more than 20 degrees difference between the average temps of each tire. On an ITS 240Z at Road Atlanta your highest temp will be the left rear, followed by the left front, right rear, and then right front. I dare say most setups proly have a 40+ degrees spread between the left rear and right front. 6. If you're not getting 160+ minimum it's too cold outside or you're too slow to make any worthwhile adjustments. 7. Follow the Hoosier rep around your ties and compare your temps to his. They round things off but generally trend propely, so if you're not seeing the same trends as the numbers they give you there's something wrong with your technique. 8. There's generally a big gradient around the corners of the tread, especially with big camber, so be consistent with where you measure. YMMV.

For road racing we do use spring rates to balance the car, but the initial rates are based on how much spring we think we can get away with before the car skips over bumps or won't put power down, or slides without warning, or locks up tires easily. The goal is to preserve contact patch geometry- which for a Mcpherson strut means try not to let it move much. Then try to find shocks to control those rates. Hoosiers are a lot more sensitive to lockup under braking than most street tires, and that was probably the limit (and chassis stiffness) that kept us from going over 400/350 on the ITS car. I'd do what JohnC says, or a little softer. His is a good plan. I mentioned 115F/145R as something I've had a blast with, but I did have a daily driver at 185/185 that was also equal fun and still streetable (albeit with Recaro's to cushion my derierre). Couple data points on Tociko's: Some people seem to get away with it, and maybe the newer ones are better, but we destroyed Illumina's at 240 lb/in rates. For ITS we used to also use a Tociko BZ3099 I think (not an Illumina) that was a strut originally designed for the Dodge Colt Rallye team or some such other nonsense, that Tokico told us would be good for 200 lb/in rates and marginal at the 240 we were running at the time. They held up well, but we were running bias ply Hoosiers back then.

For road racing we do use spring rates to balance the car, but the initial rates are based on how much spring we think we can get away with before the car skips over bumps or won't put power down, or slides without warning, or locks up tires easily. The goal is to preserve contact patch geometry- which for a Mcpherson strut means try not to let it move much. Then try to find shocks to control those rates. Hoosiers are a lot more sensitive to lockup under braking than most street tires, and that was probably the limit (and chassis stiffness) that kept us from going over 400/350 on the ITS car. I'd do what JohnC says, or a little softer. His is a good plan. I mentioned 115F/145R as something I've had a blast with, but I did have a daily driver at 185/185 that was also equal fun and still streetable (albeit with Recaro's to cushion my derierre). Couple data points on Tociko's: Some people seem to get away with it, and maybe the newer ones are better, but we destroyed Illumina's at 240 lb/in rates. For ITS we used to also use a Tociko BZ3099 I think (not an Illumina) that was a strut originally designed for the Dodge Colt Rallye team or some such other nonsense, that Tokico told us would be good for 200 lb/in rates and marginal at the 240 we were running at the time. They held up well, but we were running bias ply Hoosiers back then.

I don't recommend 300/250 either, so you're on your own. But the Bilsteins should work with that too.

I don't recommend 300/250 either, so you're on your own. But the Bilsteins should work with that too.

To do the Bilstein converesion with the P30-0032 struts you need 4 P/N 450424 (M48x1.5) gland nuts. Then you need to cut your strut housings 2.0 inches front and rear. The fronts require a 9/16 thick spacer under the Bilstein, and the rears require a 2-1/16 spacer under them. However, for anything resembling a street car, I wouldn't run anything near those spring rates. You can have 99% of the fun with something on the order of 115 lb/in front and 145 lb/in rear springs, Suspension Techniques bars, the appropriate bushings all around, and a real tire (Khumo or Hoosier for example) for track days. These rates would allow you to get away with a Koni or Tokico Illumina shock and a streetable ride height. At the ITS level spring rates you pound the chassis and will be foreverer chasing around cracks in your dual purpose street car. Whether your kidneys are good for it or not, its not worth it IMHO. I have driven our ITS race car and a street car set up like the above paragraph on the same road course and been within a second of my ITS time with a negligible difference in fun quotient. And could play the radio and hear it.

To do the Bilstein converesion with the P30-0032 struts you need 4 P/N 450424 (M48x1.5) gland nuts. Then you need to cut your strut housings 2.0 inches front and rear. The fronts require a 9/16 thick spacer under the Bilstein, and the rears require a 2-1/16 spacer under them. However, for anything resembling a street car, I wouldn't run anything near those spring rates. You can have 99% of the fun with something on the order of 115 lb/in front and 145 lb/in rear springs, Suspension Techniques bars, the appropriate bushings all around, and a real tire (Khumo or Hoosier for example) for track days. These rates would allow you to get away with a Koni or Tokico Illumina shock and a streetable ride height. At the ITS level spring rates you pound the chassis and will be foreverer chasing around cracks in your dual purpose street car. Whether your kidneys are good for it or not, its not worth it IMHO. I have driven our ITS race car and a street car set up like the above paragraph on the same road course and been within a second of my ITS time with a negligible difference in fun quotient. And could play the radio and hear it.

The horizontals in the main hoop should be at the kinks in the main hoop, not above them, but otherwise not too shabby.