Wrote a post on facebook about building a 280zx race car. Figured I can post it here as well. Plenty of good discussions on Facebook but they get lost.
First, why 280zx and Chump? Because it's 150 pts, 21 gallon fuel tank and not to heavy. These are some of my learnings (in arbitrary order) from starting with a 280zx and knowing nothing about building race cars (or racing): 1. Rear hatch glass From a fire safety point of view you should add lexan on the rear hatch, it doesn't cost any points. We also noticed a big improvement in aero, it's terrible from an aero perspective to run without a rear glass. Buy a lexan sheet at homedepot and rivet it, you can make a template from cardboard first. Cut 2 metal bars to hold it down. Look at the chumpcar rules, there is a minimum thickness allowed. Everyone does this mod. 2. Fuel starvation Even with stock power we had fuel starvation at around half tank and way before 2h stint limit. If you don't care about placement then this is not a problem, but it's going to hold you back more than lack of power or suspension. We would be faster than many other car but we had to stop for fuel even we had plenty of fuel in the tank! Solution is either hydramat or surgetank, or both. Alternative do a fuel cell (but install it correct!) 3. Wheels Big drawback with he 280zx platform is the lack of wide wheel options, it's a unusal bolt pattern and offset. We found that 15x10 works best (we tried 16x6 Miata, 14" stock, 15"x8 Miata) these are the one we use: https://www.speedwaymotors.com/Bassett-50ST4B-15X10-D... ROTA and XXR makes some 15x8 and 15x9. There are some really nice tire options as well, Ventus RS-4 is the best one (245s). Some racing people say that wide wheels doesn't matter, but all the top teams run wide wheels (I think they can cope with the heat better). There are several seconds per lap difference between a 15x10 and the stock 14". 4. Suspension The stock 280zx 40 year old suspension is terrible for racing. Way to soft. This is obviously a very complex subject that I am not an expert in.
Poly bushings is an absolute must, for a budget build get some KYB and cut the springs.
But I would get GC (or T3) coil overs, camber adjusters and maybe swaybar. We are running MSA camber bolt, cut eibach springs and biggets front swaybar. Car handles pretty ok. If you want to spend money, get everything fromhttps://technotoytuning.com/nissan/s130
5. Suspension - safety The flimsy stock tierod ends are known to break, this is a disaster. From a safety perspective I would get https://technotoytuning.com/.../tension-control-rods... It's $240 so it sucks but loosing steering is not fun. If you get T3 control arms you don't need it. 6. Power We had megasquirt and headers on a stock 1980 engine. We could hang with E46 323 and smoke most NA miatas, but there are plenty of cars that has more power as well. With 21 gallons it's tempting to get some more power, you have the points for it as well. Going turbo might seem interesting on paper but it's rare to see successful chump teams with turbo engines.
So many options, it really comes down to budget, skill and the chumpcar rules.
Megasquirt, homeported head, cam, headers and hogged out intake is a good low point low cost solution.
There are also swaps, I think a 200hp crank swap is about what the rules allows for this car.
7. Brakes The 280zx stock calipers has decent stopping power, however I found them to struggle with the abuse (at COTA). The pre 81 rear brakes are TERRIBLE. Luckily they resdesinged the rear brakes after 81. For stock calipers we found that Carbotech RP2 in front and XP8 in back worked well. Motul 600 has worked well for us. However there are a few Wilwood conversions you can do, Arionza Z Car, Silvermine motors and T3 has some kits. I did the Silvermine in front and custom in the rear. Besides greater stopping power you get more pad options (cheaper). 8. Transmission The 4spd is made of glass, the pre 81 5spd is a little better. The post 81 5spd seems to be the best. There is a turbo transmission but this is rare and expensive. There is a very attractive modification you can do to a 240sx transmission, these are strong, plentiful and cheap. We have broken a 4spd and have 2 5spds that are a bit rough after a few races. I have a modified 240sx tranmsission, haven't installed it yet. Also get a lighter flywheel and a ACL-NX1-HDG6 clutch, works great. 9. Weight Remove as much as you can. There is a weight thread on this this forum. 10. Chassis We had a 4 points racetep strut brace that snapped. I think this means that it was needed!
Also make sure the roll cage attaches to everything, you can play the rules a little here. I would pull out bars to the strut towwers, just make sure you are within the rules