OldSkoolFool

I'm going to go check out a 1980 RX-7 track car and have a few questions, don't really know a whole lot about these cars. First of all, how do you check if the diff is LSD? Thought I remember hearing that if you jack the car up, spin one wheel, and the other spins the same direction it's LSD, if it spins the opposite direction it's not. Is that accurate?

Car has a fuel cell and owner says there's either an issue with the carb or fuel pump. Pretty sure he stated there isn't a fuel return line currently on the car, should there be one? Any good way to determine the condition of a rotary engine other than obvious ways such as making sure it revs smoothly, not smoking, etc...?

What other kinds of issues should I be checking for besides obvious ones such as rust?

Thanks for the help.

justint5387

iTrader: (1)

If it has rear disc brakes, it should have a LSD. To double confirm, you can jack up the rear of the car and spin the wheel. If both wheel spins the same direction, it has LSD.

Tanjo

Well, the limited slip diff on these cars came with rear disk brakes. So, 9 times out of 10, if it has rear disks, its got LSD. Unless someone did a brake swap on an open diff. But yes, your method usually works too.

Im pretty its the carb that decides whether or not you need a return line. It should be obvious, because the carb will either have a return port, or it wont. The coolant should be clean, oil as well. look in the FAQ for 'champagne bubbles'. And if you can get it compression checked before you buy it, that would be the real indication as to how much life is left on it.

OldSkoolFool

Thanks for the replies.

Did these cars have a fuel return line from the factory?

I'll check the FAQ after for some more answers but what PSI range should it be at for a 12a stock?

RX-7 Chris

iTrader: (19)

Yes they did.

3-4psi if it is a stock carb. A little higher if it is an aftermarket like a weber or holley but 6psi max.

OldSkoolFool

Did some searching around on how to do a compression check but have only been finding procedures for the 13B fuel injected engines. Not sure how to do it for a carb'd car.

Does unplug both top spark plugs, screw in the compression tester, disable fuel and ignition, and turn engine over sound about right? With button pressed down on tester, pressure readings should blip evenly, if not then either a apex or side seal is bad. Do it again but with button not pressed on the tester, should get about 100psi for a good engine?

Now the question is, what's the best way to disable fuel on a carb'd RX-7?

RX-7 Chris

iTrader: (19)

Pull the fuse for the fuel pump.

justint5387

iTrader: (1)

90+ psi should be good condition.