tom13
Part of things
Posts: 571
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Mar 13, 2018 23:49:56 GMT
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Hi guys,
Hopefully looking at an fb rx7 tomorrow. Hasnt been on the road since 2007. Couple of rust spots but not that bad runs well by all accounts. Super original. What do i need to be looking at and what value would you guys roughly put on it.
Cheers
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ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
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Looking at buying an fb rx7.ChasR
@chasr
Club Retro Rides Member 170
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FBs seem to be on the way up in terms of value I am no real Rotard but all I remember are the following: -Rust; Check everywhere! Japaense stuff rusts terribly! -Engine; Ideally, getting a compression test with the correct equipment would be one way to save potentially alot of hassle! A normal compression tester won't give a valid result since rotaries do the Otto (combustion) cycle within one revolution, unlike your normal piston engines which do it in two revolutions. In Layman's terms: As Side 1 of the rotor is sucking in air/fuel, side 2 will be compressing it. At the same time side 3 have the 'bang' (combustion) occur! Eventually as the Side 3 goes around a little more it will then throw the gasses out. It's because of the rotors doing all of the cycles in that revolution for why if the rotor housings or even one of the tips are worn the engine will run terribly with a rebuild being your only option. But in this instance, looking for signs of regular maintenance and seeing that the engine runs well will go a very long way, both in terms of avoid financial expense and heartache! Even things like regular coolant changes can go quite a way to prolong the rotary's engine life ; if the water jackets go it really can be terrible news! I don't mean to make it sound like doom and gloom but it seems rotaries don't take neglect too well! -Spares; If they are like anything from the 80s these are quickly becoming like gold dust! No-one makes this stuff anymore, so having trim missing etc. may seem benign but be tempted to hunt around for it! There is probably much more but luckyseven will be your man to speak to here. If you are looking specifically for an RX-7 it may be worth checking out adam73bgt 's FC RX-7 Turbo, which does run very well! |
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Last Edit: Mar 15, 2018 9:53:10 GMT by ChasR
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goldnrust
West Midlands
Minimalist
Posts: 1,872
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Mar 15, 2018 10:28:03 GMT
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www.rx7fb.com is where you want to look. What those guys don't know about early Rx7s isn't worth knowing. If you're in the market for one, they also have a handy thread which tracks any FB that they can find that comes up for sale. Like any 80s car they can rust anywhere, but the big point to watch for is the upper rear suspension arm mount area. See Tepper's thread for pictures. Engine wise, whilst a compression test is the primary way to test a rotary engine, it's not quite as simple a procedure as a normal engine, and the results can vary a lot depending on cranking speed, engine temperature etc. Sorry to contradict you ChasR, but you can use a normal compression tester to get a rough idea of engine health, you wont get a super accurate result but it will give you a ball park of whether its knackered or not, you're looking for preferably greater than 5 bar on each rotor, and most importantly not too great a difference between the two. If using a piston compression tester you must make sure compression tester you use doesn't have a longer reach that the spark plugs, otherwise the rotor can catch the tester as it sweeps by and potentially damage the rotor seal and housing. Given that it's an old 12a engine in a car that's stood for 10+ years, I wouldn't necessarily worry if you can't do a compression test. There are some more basic signs to engine health you can follow, first I would suggest removing the leading (lower) spark plugs, put your hand over the spark plug hole and have someone crank the engine, you're looking for feel for even pulse of air as each of the 3 chambers of the rotor pass. Seals can get stuck when the engines sit, and that would be indicated by an uneven pattern to the air, so if your repeating pattern of 3 is more like 'pulse - pulse - nothing' then you've got problems. If that test is all good, then I would be looking for clean starting from both hot and cold. If it struggles to start from hot thats a sign of poor compression.
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luckyseven
Posted a lot
Owning sneering dismissive pedantry since 1970
Posts: 3,839
Club RR Member Number: 45
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Looking at buying an fb rx7.luckyseven
@luckyseven
Club Retro Rides Member 45
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Mar 15, 2018 10:56:38 GMT
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Wow, eleven years standing? Depending on whether it's been out in all weathers, I'd expect rust pretty much anywhere. And everywhere. Plus everything goldnrust said about engines, consider water seal failure. 12As are less prone to it than later 13Bs due to the water seal groove being different, but after 11 years I'd expect some corrosion of the metal around the seal if it's been left with coolant in it (or worse still, coolant that isn't alloy-compatible). Not unusual for derelict RX-7s to prove relatively easy to get started but find the water seals prolapse like a baboon's backside after a week or so of use. If that happens, you're taking the engine apart. Only way you can really check without a sniffer is to see if the colant's being pressurised madly... a litre plastic bottle with the base cut off... neck-down into the filler neck... tape around neck to seal it... run engine ...let coolant expand up into the bottle and check whether you get millions of manic bubbles in the coolant. It's called the champagne test for that reason. Bit involved though so a seller may not want you faffing about like that. Most running spares can still be found from Atkins Rotary, Racing Beat or Rock Auto in the states. Mazda UK dealers are about as much use as nipples on the Pope, don't even bother. As ChasR said, it's bodywork, trim and suchlike that's unobtanium now. If big bits are missing on it, they're likely to stay missing Be sure and post some pics, lol |
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ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
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Looking at buying an fb rx7.ChasR
@chasr
Club Retro Rides Member 170
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Mar 15, 2018 11:01:45 GMT
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You learn something new everyday! I figured a normal compression tester would be useless due to them having a 1 way valve to store the compressed air; i.e one side of the rotor/tips could be fine but one of the tips could be shot. But I can see how it could give a very rough guide to the state of the engine; i.e if the engine is still serviceable/cost effective to rebuild.
I take it if the water was drained out of the car that may be a saving grace for the engine; i.e no water to make the housings/seals go iffy.
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