khrizby

Hello! I'm a new member here, starting my first rotary rebuild for my rotary bug. It's a 13B from an '85 RX-7. It ran (kinda) when I bought it but since I know nothing about it's history I figured a rebuild, or at least a thorough disassembly/cleaning/inspection couldn't hurt and would help me get familiar with the rotary. I'd rather get started knowing I at least attempted to find any potential problems!

My first question comes before I even get into the engine. I took the intake manifold off and found the bottom center port (the rectangular one before the ovals, forgive my ignorance to it's actual name) stuffed completely with small rolls of aluminum foil.. I've searched and found absolutely nothing mentioning why somebody would put aluminum foil in their engine, is there a purpose for this, or is my OCD okay to remove the chunks?

If it's relevant the engine is no longer fuel injected, it's got a Weber carb, and the corresponding port on the
manifold is plugged off.

I apologize for the novel, but if anybody has heard of this any advice would be appreciated! I'm sure I'll have other questions at some point as well..

Aaron Cake

iTrader: (1)

Some idiot probably stuffed it full of foil to plug the EGR port.

diabolical1

iTrader: (3)

welcome to the board.

i will leave it up to you on whether or not you should rebuild the engine. you said it "kinda" ran when you bought it. do you know exactly what is wrong with it? what is it doing/not doing? perhaps you should address and/or repair that (assuming it's not because you NEED a rebuild ) before you consider rebuilding the engine.

the aluminum foil you found was probably the previous owner's attempt to block the EGR passage in an attempt to run a "cooler" manifold.

speaking only for myself, i'd rather read a novel (as long as it has relevant info) than have someone post some cryptic word like "rotor" or "radio" and then expect everyone to know that they wanted to know what muffler to buy.

Cldamman

I too am making a rotary bug have you dove into the cooling lines and exhaust yet? I'm at the motor rebuilding part myself as well

khrizby

Thank you

Yeah, I figured a detailed question might help get answers haha. So is there anything to this method, would it actually run a cooler manifold or should I keep them empty? Seems to me like it wouldn't deflect that much, especially with the manifold completely blocked, but I've heard of weirder things.

It started right up when I hooked it up, but wouldn't idle, I had to keep it above 3k rpm. I don't think the carb is jetted exactly right for a rotary, but I'd think it would still at least idle so I suspected a vacuum leak. Before I got to fixing that I got a couple of backfires at one point, and after that the engine started a sporadic kinda light screeching. I feared for my apex seals (I probably jumped to conclusions here, as I've only heard horror stories about broken apex seals), so that's when I started tearing it down to check everything. Upon taking external parts off I think the state of the gaskets confirmed that a leak was at least part of the problem, and made me think it hadn't been serviced in awhile, and I wondered more about the internal conditions.

At any rate, I've already got it completely disassembled.. So I guess too late for second thoughts. Typical me. Upon inspection this is what I found.

Apex seals:

Firstly, I dunno what happened to the other apex seal tips, I was sure I got them all.. Everything else seems normal to my unprofessional eyes (maybe?), except the plastic corner seal plug parts which vary widely in condition. Some seem very chewed up.

Front rotor housing:

Rear rotor housing:

These are the only signs of wear in the housings but are at least 3mm wide and down to the base metal. I read that anything over 2mm into the housing made it unusable; so I guess I'm gonna have to look around for a source for new ones before I reassemble the engine if I want it to last.

I actually have everything else pretty much in place. I didn't mount the radiator in front, it's mounted at a 45 degree angle under the rear cooling vents. I fabricated intake fins behind the quarter windows and piped them through the rear wall for air flow. My exhaust is just a bend straight into a stinger muffler. I can post some pics later if you're interested.

khrizby

It's proving difficult to locate used 84-85 housings in decent condition. So this may be stupid question, but theoretically, what happens if you run housings like that with 3mm of missing chrome? Will it just reduce compression and further wear the housing, or lead to something catastrophic? It did run previously..

diabolical1

iTrader: (3)

if the worn areas are limited to that part of the housing (the bottom), then it's leading into the exhaust stroke - meaning the compression/ignition has already taken place. so the engine should run okay. will it continue to wear? probably. i mean, it's what happens - especially with the 3 mm seals. i've seen engines (12As) run with even more missing chrome than that. it's kinda where we're at right now. as you have found, finding housings for those older 13Bs is getting harder and when you do come across them, they will command a premium.

all i can think of is look for an apex seal that is easy on the housings and premix.

Aaron Cake

iTrader: (1)

Another option is to buy a good used (or new) set of later housings and have the o-ring grooves machined into them. Several vendors perform that service and it's not too horrible. If you are friends with a machine shop, then they can do the job.

khrizby

Yes it's limited to the bottom on both housings, that's a good point, thank you! I'll probably do this at least for now. I'm assuming this wouldn't be a good long term plan though, is there any way to estimate how much life is left in them?

I searched and gather that stock seals are best for housing wear. I didn't find anything on maximum wear rates on them but they looked good to me, is a good idea to replace them while it's apart or would I be safe re-using the ones I posted above?

That's a good idea, I hadn't thought of that. I am friends with the local shop so when I look to replace them I'll probably go that way. Am I correct that I can use any of the later ones as long as they match each other, but the later the more durable they are? Thanks!

diabolical1

iTrader: (3)

the simple answer is no.

in a best case scenario, you can have several years of good use out of them. you might be able to "stack the cards" in your favor a bit by switching to Gen II rotors (based on the less friction premise), but that's both arguable and not a guarantee.

of course, you could have no luck at all, and put the thing together only to have it lose the ability to make compression in 2,000 miles for whatever reason.

that's totally going to come down if the seals are still comfortably within spec and if re-using them is your desire. what i will say is that if you do re-use them, hopefully you kept some kind of record of where they originally came from. also, keep in mind, new seals will require some break-in period in which they will have to wear on the housings.

that's definitely one avenue to explore and if you can make it happen, i would say go for it. i don't know how much the machine work would cost, but my guess is it can't be more than buying a new set of used SE housings. i hope my supposition is not ignorant. again, it would be your choice but if you got some Gen II housings, it might not hurt to look into getting rotors, too. maybe sell your SE housings to defray some of outright cost? just tossing ideas out there.

khrizby

Thanks for the info diabolical. I ended up reusing the housings and apex seals and I'll try my luck with how many miles I can get out of it, and when the time comes see about machining some . Unfortunately no records on the apex seals, they just came in the engine when I purchased it.

And thanks everybody, I got the engine rebuild and it started up and idled great. Still some tuning to do but already much better than before. I think the idle problem before was indeed simply a vacuum leak, but I'm glad I tore it apart, both to replace all the seals and I now understand my engine much better.

diabolical1

iTrader: (3)

hey man, great job on the engine. i'm glad everything worked out. i'm glad you're on the road to getting the car sorted out and that you're more in tune with how the engine works.

for the ... um ... record (really, no pun intended) ... my comment about recording where the seals came from was where they were oriented on the rotors and inside which housings. i was just suggesting that you try to put them back in the slots and housings they came out of. however, the engine is together and running now, so it's just something to think about for the next time.

also, i'm sure you noticed that i deleted a part of your post. my suggestion would be post that particular question in the Gen I section. (A) you still need a few post to be able to post an ad, (B) you'll probably get quicker answers there and (C) while you didn't actually post them for sale, it's a fine line and it's best not to get in trouble because (per the rules of the board) you can't post ads in this forum.

khrizby

Thank you, I'm glad it worked out also, first rotary rebuild under the belt!

Ohh that would make sense haha, I realized after I disassembled the rotors that I should have kept track. I tried to put them in so they all had about the same amount of spacing, figured that's about the best I could do at that point. But yeah next time, thanks for the tips I read that if they're tight they should wear to specs if I take it easy for awhile, so I should be okay?
Edit: Oops I was thinking of side seal clearance, that's what I get for reading distracted Although I suppose the apex seals would have the same concept.

And gotcha, I wasn't sure if this would be the best place for that, thanks for the info.