Hi all - first post here! I've been a lurker for some years and finally stepped into RX-7 ownership a couple weeks ago. Also - I've used the search function quite a bit to try and find the answer to this question but most of what I found had broken pictures, so it wasn't much help. Sorry if this is a common question!

So I tore down two 12a's and am trying to pick the best batch of parts out of the two to build one solid engine, and have a question for you guys about the usability of this rotor. I'm guessing its a bookend, but who knows.



I also am curious about the usability of one of the rotor housings, ill post that one in a bit once you guys shoot me down here.

Thanks!

 

Here are pics of the likely destroyed rotor housing. (It ate an apex seal)

Thanks again for the input guys.

 

personally, i would not use either of those for a rebuild.

 

Would not use.

 

Nope on those two. Got pics of the rest?

 

I figured as much on these parts. I am finishing up getting the 3rd engine broken down, but it was my least favored based on its outside condition. I'll post pics of these rotors/housings and get your opinions. Hopefully one of them is good!

Thanks again guys.

 

Sometimes the nasty looking engines have the best parts, right Ray?

 

that rotor might be ok, the pitting isn't desirable, but we are more concerned with the seal groove. if the seal groove is nice then its a runner

 

My concern would be little bits coming off where it is pitted and scouring the housing.

 

Thanks for the responses all!

Looks like I am 0 for 6 on rotor housing off these 3 motors. The last one looks like it spent the last 5 years as a boat anchor. One housing is perfect except for some minor wear through the chrome that extends 3mm from the edge. I read earlier that 2mm was the maximum, is that correct?

I also found 2 rotors that are in much better shape then the one in my first post, I can get some pictures up once I get them cleaned up tonight.

I think I can get a set of decent irons out of the bunch here, but Ill post them too once I get them cleaned up in case you guys might see anything I don't.

Anyone got a set of usable housing for sale?

 

So I've been doing a lot of searching on resurfacing rotor housings, anyone have any experience with this? Looks like there are a few vendors that offer this kind of service, and I'm thinking a couple of these housings might be good candidates.

Thoughts?

 

Looks like the rotor tip was in the down position inside a housing flooded with coolant for years. Rust... Clean them up and sell them as displays. Otherwise they are junk.

 

it was when you could buy new ones, actually we used to double that spec when you could buy new ones, so 4mm, and hey since new ones are NLA and used ones are all bad (as you've noticed), maybe even go to 6mm.

i have had engines that ran ok but when taken apart had 60mm of chrome peeling...

 

I've had success with Atkins apex seals in old worn 12A rotor housings.

 

This gives me hope!

I still have 1 motor left that I have to take out of an 83 spare parts car, maybe ill find some 12A gold in there. I should be able to dig into it this afternoon.

I've heard good things about the Atkins seals. I've also heard good things about goopy seals. Any takes on cryo treated or carbon seals in not so perfect housings?

Also - anyone have input on 13b housings ground to 12A specs? Sounds like a decent option as far as I can tell if you want to start with a great rotor housing surface for less than a fortune.

 

A quick update!

I pulled the last (4th) motor from my parts car and discovered everything was in great condition!

With a brass wire wheel, a lot of degreaser and a lot of hours, here is the current result!



I'm pretty sure I stuck the engine mount on backwards, needed more sleep, haha.

Unfortunately my project will be on hold a few months, I'm headed overseas for a work assignment.

Thanks for all the help guys, couldn't have done it without this fantastic resource. Can't wait to get home and get it started!

 

Yep, engine mount is on backwards. The motor looks great!

As you have found out, you don't very often find usable parts in old 12a's anymore

 

Thanks!

Yes, it is really hard to find good 12A parts, particularly the rotor housings!

 

Its been a while, but wanted to throw some updates out there!

I installed the engine, ran like crap with the modified nikki on there. After a few weeks of dinking around with it, i swapped it out with a RB Holley 4bbl setup that I had laying around. The difference was astounding! It idles perfectly, and runs great with 1 issue, when I step on the gas from idle it wants to die before it catches back up, and I think its because the accelerator pump is dumping too much fuel into the venturis. Anyone know a possible solution? I still have a few unmolested but very dingy nikkis in a box somewhere, maybe one day ill give it another try with a freshly stripped one.

I also stripped off all the SCCA/Spec 7 stickers off and repainted the old blue with gloss black in my home made garage paint booth!

I could not have done it without you guys and the infinite knowledge in this forum, thanks again guys.

 

Looks nice. You should give the nikki another try. A Fat Nikki on a stockport 12A will work better
than any holley you can put together.

 

It might work better but what about hp?
I had a rb holley on my stockport and it ran good with nice power, last week I swapped it out for my yaw nikki and feels like less power but it does run smooth.
Venturies in a holley are larger than the nikki, maybe thats why

Sent from my samsung gs4 using RX7Club app

 

zip ties on the radiator hoses?

 

Guys, I have a 74 ported 4 port R5 13B and tried an RB Holley 600 and an even fatter Nikki (bigger venturis at 24.9mm or .98" as RB recommend). While the Holley did wow, the Nikki impressed me way more. Especially the mechanical secondaries which would zing the engine to 8 grand effortlessly while the Holley struggled with even the basics like glitches when you slow down, a lazy accel pump etc. Don't get me wrong, I'll test the Holley again, but not on anything that could get a Nikki.

There's two testimonials that a hogged out Nikki is better than an RB Holley.

 

Busted, thanks for pointing this out, almost forgot to swap clamps back in!

I'll give a fresh Nikki a try again, but the one I was using has ghosts in it.

 

car looks really nice!