johnc

Per the latest issue of Circle Track magazine... Shoulder belts should be mounted so that the angle from the top of the driver's shoulder to the mounting point is no lower than 5 degrees or higher than 30 degrees. Lap belts should be mounted so, when fastened and tightened down along the driver's pelvic bones, they have an angle from 45 to 55 degrees up from the mounting points.

There are two schools of thought regarding ITS Z car suspension setup: East Coast 325 to 375 lb. in. front springs 250 to 300 lb. in. rear springs Big front anti-roll bar No rear anti-roll bar West Coast 250 to 275 lb. in. front springs 275 to 325 lb. in. rear springs Small front anti-roll bar Medium rear anti-roll bar Both seem to work. You do need a rate difference between the front and rear springs of at least 25 lb. in. Since I'm a west coast guy, I suggest you run 225 front and 250 rear to start with. And spend as much money as you can on shocks.

You're confused because you're hanging on to 1960s thinking... Trans Am race cars use a single exhaust but the exhaust piping has a 8" x 24" cone shaped expansion chamber after the 2 into 1 merge. The expansion chamber and exhaust run throught the passenger compartment. A lot of the tricks that apply to two-stroke engines also apply to our four-stroke engines. Its all about flow and velocity and there has been a lot of research in the past 15 years into intake and exhaust flow. What was trick on race cars in the 1960s is now only suitable for old pickup trucks.

You might also want to weld a fitting in the exhaust pipe halfway between the header collector(s) and the mufflers. Connect a pressure guage to the fitting and measure the backpressure at various rpms during your testing. L6 engines like about 3psi of pressure in the exhaust system. I don't know what Chebbies want.

You need a solid front diff mount.

Pete, The metal thingys I was referring to are the clips that the belt gets wrapped through when looping the belts around the harness/roll bar. They cannot butt up against the back of the seat. In an impact they will probably damage the seat and punch through giving the driver a couple inches of slack before the belts tighten up again. That can't be good. If you're going to weld an eye bolt on the roll bar somehwere, make sure you can shorten your shoulder harnesses enough. Also, try to mount the eye bolt so it works in tension instead of shear and spread the load out across the bar. Remember, the should harness spreads the load over 2 to 3" of the bar.

Jeromio, Seat back #2 will still allow the shoulder straps to pop off your shoulders and the seatback. There's nothing to keep the shoulder straps from moving outward. In a frontal collision your collar bone and rib cage flex allowing your shoulders to move back. That allows the shoulder harnesses to slide off your collar bone. You need some kind of physical restraint to keep the shoulder harnesses in place. In the past, Sternum (in front of the chest) and H (behind the shoulders) straps were used to keep the shoulder straps on the shoulders. In the 1990s when F1, CART, SCCA, and other sanctioning bodies started taking safety research seriously they found problems with both straps. Sternum straps wouldn't let the rib cage flew thus causing heart bruising in hard hits. H straps didn't let the collar bone flex causing broken collar bones (both sides) and scapulas. Racing harnesses have to work in conjunction with a racing seat. Installation is critical (as we learned from Dale's wreck) and the seat and harness manufacturer's instructions must be followed to the letter. Unless you're willing to install a racing seat you're better off (from a safety standpoint) using the stock 3 point harness. BTW... the Scroth DOT approved belts are different than most others because they have a special part added in the right shoulder harness. It is designed to "give" a couple inches in an impact allowing your right shoulder to move forward more than your left. I don't know all the reasons why this works, but it keeps you from submarining under the lap belt and, I THINK, it also allows you to run these belts without a racing seat. I could be very mistaken about that last part so check with Schroth.

Most vintage racing associations specifically disallow current competitive vehicles. I think VARA is the only one that allows a 240Z to run.

Coast Fab

This is probably about the best you can do with a normally aspirated L6: Defcon 1

If you are going to a test only station most of the techs receive training to spot "funny" fuel. Whether they will or not is another story.

Yes, that should be enough room. You'll have to run the metal clip in front of the seat back holes so the wrap will be critical to keep the clip from hitting or laying on your shoulders (a comfort issue).

Keith, Maybe not as much weight up high if they were smart with their tubing selection. The horizontal X over the passenger area seems excessive, unless they are doing something special in the center of the engine compartment. I'ma ssuming this is an EP car.

Jeromio, The number 2 seatback in the diagram is a no-no also. Clip ins (where you bolt an eyebolt to the floor) are better from a strength and maintenance standpoint. Regarding price, Schroth is more expensive because of the little thingy on the right shoulder harness. It keeps you from submarining in a 4 point harness and I think they have a patent on it. You right shoulder will move forward a bit more than your left in an impact thus keeping you from flying under the lap belt and jamming your knees into your hips.

Funny. Jim Thompson at Sunbelt only recommends two oils for all his engines (including the World Challenge Mazda engines): Mobil 1 15w-50 and Redline 50 (15w-50). Mobil 1 if your running in a high humidity or dirty environment and Redline everywhere else. A cam change is not to be taken lightly. You need to match a lot of different things (port flow, intake and exhaust flow, springs, engine managment, etc.) to make an engine work well. Most folks overcam an engine.

Unfortunately, the bars going through the passenger area are critical. If you are going to eliminate those bars you need to design a competely different roll cage.

An eye bolt with a big washer works fine. Make sure its bolted through the end of the frame rail extension under the floor pan.

This is what you want: Schroth Profi III

I forgot if you are running the standard SUs or the 50mm ones. The standard SUs tend to lean out over 6,000 rpm on a 3L engine. Be careful during your testing. Maybe that's why Dave suggested a richer setting.

They work great up to about 250hp.

Burn's Stainless Used to, but I think they now just produce all the parts you need to make the exhaust yourself.

Autocross tends to be harder on differentials than track events. The hard acceleration out of tight, low speed corners quickly wears out clutch pack LSDs. An R160 will work but you'll have to inspect it frequently, change the fluid often, and rebuilt the clutch packs at least once per year.

Instead of washing the car a couple times a week, try using one of those duster thingys and some type of spray and wipe shine like Mother's Showtime. Water will promote rust over time so if you can keep the car clean without constantly getting it wet you'll be better off.

Be afraid! Be very, very afraid! Damn!

Cool! Its great when a 30 year old car can run with the yung uns!