I have 91 rx7 convertable hibernating 4 years... Doing nothing.. Now want to restore to a driving condion but everything is siezed.... It did start once but can't get it going again...engine all coroded. I need a 1 ton of wd 40 can to get it started again... Any ideas??? Would it be cheaper just to buy another one??

 

I have an 88 that was sitting for 10 years with throttle body off, no belt driven ancillaries attached (as car was parked due to blown water pump).
What I did was pour an oz MMO down the spark holes and crank it by hand with a socket on e-shaft pulley every three days for two weeks while I waited for all new hoses, belts, plugs, plug wires to arrive.
After cleaning grounds, replacing battery to starter cable, and diagnosing poor contacts at CAS, car fired up.
MMO is wonderful stuff.
I also have a street ported engine that was sitting in the back of an old junker that I put MMO in, and when I tore it down last weekend I found the mmo had softened the carbon/rust on the rotors and motor looks essentially brand new inside (aside from water jacket being caked with gunk)
Give it a try

 

Change your oil and filter.
Drain the gas. There is a plug in the bottom of the gas tank which is pretty convenient. Put some fresh gas in 'er.
Make sure your battery is fully charged. If it's been sitting there for 4 years I would definitely charge the battery. It should be reading 12.6 volts.

 

Removing An RX-7 From Storage, Dealing With Improper Storage