I thought it was pretty standard to have the irons machined. Where have you heard that machining them ruins them?

 

the FSM for the pre nitrided (pre Rx7) engines tells you to surface them, the later engines you are supposed to measure and replace as needed.

you CAN grind them, but it removes the nitride layer. you can have them renitrided, but then you're spending more than just buying new, and it takes longer.

 

^^ That sucks.


I like the idea about the JB weld and the puddy knife. Has that been tried?

 

The irons from the 80 engine I nabbed from the junkyard seem to be in much better shape! Was hoping to have that set in reserve in case I goofed up my first build which seems to be a common theme on the boards here so I anticipate my first build being less than stellar. I guess I'll be in the market for a whole new engine but I'll cross that bridge when I get to it.

I think the 80 had a water leak tho into the back of the rear housing judging by the rust trail from the intake manifold.





As you can see I still need to clean these up but they already look MUCH better than the 79 irons that came out of my car. As I was taking this engine apart it looked fairly fresh. Prolly should have tried to start it before I tore it down.





So I got to comparing the different plates. My 79 irons are all R5. The 80 front iron is R5, but the middle iron and rear iron are Y plates. The biggest difference I can see is that the Y plates use one less engine bolt to bolt it all together. There are also two less threaded ports for peripherals on the rear plate, and some machining differences in the oil passages along the bottom here and there.





I know there's a lot of discussion comparing and contrasting (wow, doesn't THAT take you back to high school??) the R5 and Y plates on Ray's thread, but can someone educate me on why there is one less engine bolt for those? I know that there is a bigger water jacket/port in place of the bolt, but is there any performance differences?

Thanks everyone for looking, and thanks for the advice - keep it coming!

 

Wow! Great info, thanks. I was thinking of machining mine, but I definitely won't now. I think they are fine, I'll just have to take a CLOSE look at them.

 

Sweet find! I just recently found a FD in a barn

 

Yep, it sucks. You can grind them down, but you lose the hard layer and then they wear down easily. Bummer. Luckily though it looks like the irons from the 80 engine are good. As a matter of fact, everything on that 80 engine looks good. It prolly would have ran!

Thanks! Welcome to the board.

 

Took the front bumper molding off because everytime I bumped into it more rust would fall onto the floor and I'd have to clean it up, so I decided to just take the thing off finally. It's seen better days...

 

... with these irons. I took a razorblade scraper to the 80 irons last weekend and thought I was in the clear. They looked perfect and just needed to be cleaned up. No signs of pitting at all - perfectly flat. Then I cleaned them up and was surprised to see underneath the baked on remnants of the o-rings (which were stretchy when I took them out) more pitting, although not as bad as the 79 engine I took out of the car. I even found some damage to the face of the front iron.

So I have a couple questions: 1) Would anyone use these to rebuild with? 2) Are any used irons NOT pitted to some degree?

 

herrow?? Anyone? Anyone? Beuller? Beuller?...

 

We'll find out. Picked up a > 1980 (1983 maybe??) 12A that the PO said was locked up. Got it home and adjusted it's stance on the wood crate it was sitting on and wallah! It rotates! PO said it hasn't been run in 8 years and I see that mice have made a home in the intake ports, but it would be nice to have a dyno setup where I could see if it runs...

I can only get it to rotate half way though. Anyone out there have any ideas why that would be the case? Dead mouse?

How can I test fire this thing? That's a real question so if anyone can and is inclined to do so feel free to enlighten me - THANKS!

 

There are three N/A FC's in a junkyard in Orangeburg... 13B's are 10 times eazyer to find.


But I like the JB weld idea. Its not like the pitted areas are of any structral importance.



As for a bench test you need a transmission to bolt to. If I was to do it I'd pull the engine up along side of the car and use the ignition coils as they sit in the car (The wires should be long enough from the front fender).

 

If it doesn't turn freely all 360 degrees of rotation, I would not be trying to force it by starting the thing. You could be doing more damage. Not all things can be fixed with a bigger hammer.

Adhesion would be my biggest concern with the JB weld idea. I'd hate to have a small chunk fall out and get in with the rotating bits.

 

The pits are where the housing sandwhiches to the iron. I don't think adhesion would be an issue its not like the goobers would be going anywhere except into the rubber of the coolent seals.

Now obiously you'd wanna keep the combustion area free and clear of any residuals but for just where the coolent groves are I don't see an issue.


But the more reacent iron pictures that have been posted look worse than the prior ones. I would put them past tolerance.

 

I've recently given more thought to the idea of dropping in a 13b if I found one running for a price I could afford. I found a CL ad for one that had just been rebuilt, painted and ready to go for 900. Couldn't believe it. It sounded like the deal of the decade. Wish I had that kind of money to throw around but sadly I do not.


You're absolutely right Banzai. I've only turned it by hand and gotten it to rotate half way. I think since the mice have made a home of the intake ports that I'll try vacuuming it out as much as possible. As I thought more about it last night I thought that maybe there's enough stuff in there that is preventing air intake and creating a vacuum that I cannot overcome by hand so I'll try to clean it up and see what happens.

My thought for lighting it off was only if I could get it to completely rotate freely first and if there was an easy way to do it. This motor is just the stripped down keg so I'd need to borrow parts like a running carb or rebuild mine in order to do that though so it's a "down the road" type plan. The PO said that it didn't smoke or run poorly at all. Just swapped out for a ported racing motor with a competition clutch, so when I discovered that it wasn't actually locked up, got me all excited. But the more I think about it I guess it's better to fail conservative with these motors and if I was going to swap in a motor that I should look for one that is known to be running rather than just try and see if one that has been sitting for years can be made to run.


Yeah Qingdao, I'd say that it's six of one, half a dozen of the other with those irons. I just really have my doubts that a motor that sits for a significant length of time without being run will not have corrosion on the seating surfaces. I did FINALLY find a thread where someone said you'd have to weld the irons with high nickel content filler and grind down, which is WAAAYYYYYYY out of my area of expertise.

I'm now leaning towards trying to find a machine shop here in SE VA that can lap the irons. Since I don't plan to race dad's baby but try to restore her to some semblance of former glory and toy around with it I don't think that too much hardness would be taken away if, say 0.002" is taken off. Assuming of course that 0.002" will solve my problem with these irons.

And then there's the used parts market, but again, I'm not sure that there are any 12A irons out there that when polished up will not reveal any pitting or corrosion.

Thanks guys for the feedback - I really truly appreciate it! Being new to this kind of thing and not wanting to screw it up makes me know that there's a lot I don't know! And with my search for useable irons, I don't want to spend over $1000 for a rebuild kit (I need all new seals, hard and soft) only to find out I should have used better parts.

 

Call Dave in Chesapeake. He has a ton of 12a stuff. Probably has some good irons or a complete motor.

 

I thought I had some Mazda information about the gas nitride process they used on their Irons but that's at home and I'm overseas until this fall. I don't remember if it even specified how deep their process penetrated. Bear in mind, this was 30 years ago and automakers have to balance quality vs. price all the time. To save money, it could literally be "tenths" thick, which would mean that even shaving .001 (one thousands) off would remove it. I googled it and found that typically it also could be .005-.030 thick. I'd guess on our Irons, its somewhere between .005 and .015 but some of your pits would go deeper than that. If its not too expensive, you could try and have someone lap say .010 off the worst one and you can see how much cleanup you have.

Gas Nitriding Surface Hardening Process at Metlab and Metlab Potero of Wyndmoor PA.

gas nitriding, altering metal surface properties, metal surface protection, gears, driveshaft, iron nitride layer

 

Thanks Banzai!! That one place is just up the road from me. Would be interesting to see if they take on research projects...

From my research I'd found that most ppl take up to 0.004 off, so I figured that it I only had 0.002 taken off then I'd still be ok (if it removed all the pitting). Reading your post seems like removing 0.004 still would be ok-ish if your guess is right (0.005 to 0.015).

Food for thought! Thanks again everyone for the PMs and the responses. I very much appreciate it. Nice to know I'm not alone out there in cyber-RX-7 world!

I'll be sure to keep eveyone up to date on what I decide to do.

 

HAHAHAHAHAAA!!

As I said, I noticed mouse poop on the engine and in the towels that it was wrapped in, and vacuumed out a bunch of cat food from the intake. These pictures explain why I could get this motor to only rotate about 2/3 or 3/4 of a revolution, then it wouldn't go any further. That's because catfood isn't compressible except with a high torque applied to the flywheel! I couldn't produce enough by hand.

THIS has got to be a first for the RX-7 Club!





At any rate, I may (MAY) have found some useable irons with this engine, but I'm gonna reach out and see if I can find any that are actually flat with absolutely no pitting or grooves. These have a bit, but it's definitely the best set I've gotten so far.

The oil pump looks like it's cracked and maybe seen better days. Not sure if this is useable or not:



Still have yet to sandblast anything. Spring sports are in full swing!

 

Wow!! I thought the birds best and bird seed I found in the intake carb and engine was bad. Lol

I tore apart 3 or 4 motors recently. I have a lot of stuff. I'll probably not use. All I wanted was good rotors and rotor housings. Get a list of what you need and I'll let you know if I have it.

Too bad you weren't local. You could come browse through.

 

That'd be awesome if we did live closer! Thanks for the offer. I'll definitely keep that in mind when I finally get my act together, thanks Mike-P!

 

great find, why these barn with cool stuff never existed in my place, lols
definitely this will be a good looking car.

 

Finally made some time and took off the fenders and inner fenders. Was hoping it wasn't all rotted under there and luckily it isn't. Not bad for a NY car. Now all I have to do is remove the suspension and I can get into the sandblasting.

 

This is where the worst of the rust is. A bad spot in the corner of the engine bay seems to have gotten almost all the way thru. Need some fabrication here...

 

Which has seen better days. I'm hoping the black dragon replacement really is cheap. My latest book says like $40 for the three pieces.