j_tso

iTrader: (2)

I thought Kentetsu's motor would last forever.

Kentetsu

And join you in your class? Not a chance! I still have bruises on my *** from last year that haven't healed yet. I'm going to try to stay in CSP if at all possible.

Kentetsu

LOL, maybe I should have had more faith in her, like you did! I just ran to Autozone, and could not hear the noise at all. I just tried it in the driveway too, and she sounds fine once again....

I ain't gonna tell the wife though. I'm going to take this as a reality check, that my motor will not live forever. So I'm still going to search out an engine for when that day comes.

All I can think is that a seal was stuck, and the Seafoam just needed some time to work. Hopefully things are good again, and hopefully the noise won't come back. If it does come back, I'll let you guys know.

Thanks for all of the guesses, information, and support. 212,000 miles and STILL counting!

blwfly

iTrader: (4)

more of a high pitch whinning noise i think..
mates car had a bung water pump.

Kentetsu

While replacing the header gasket, I went ahead and took a look at the apex seals through the exhaust ports. One seal on the front rotor was stuck.

Before I left for a three day autocross event 200 miles away (I towed the car), I dumped a bunch of Seafoam and MMO down the carb while turning it over by hand. After the first day's event, the problem was gone and she was smooth as silk again.

The issue has come back a couple of times since then, but by repeating that procedure I have been able to correct it again each time. It seems to be the steady, long distance driving that leads to the issue. I haven't been using my 7 as a daily driver much lately (thanks to my new BMW), and I think that letting it sit for a few days between uses is also a cause. Either that or she's just jealous.

I'm beginning to believe that I may have a weak apex spring. So a replacement engine is still on my list of things to acquire. I really can't wait to pull this thing apart and see what she looks like internally after 213,000 miles...

Jeff20B

iTrader: (13)

It might not be just a weak apex spring, although with that many miles it is possible. I'd say it's a combination of very small apex seals and a weak spring. Probably 5.5mm or so in height (min spec is 7.0). Rebuild it before you break one.

Kentetsu

Jeff,

With this many miles, do you think a rebuild would even be feasible? Or should I look for another motor altogether? Thanks...

Rx-7Doctor

iTrader: (13)

As long as she has not been overheated You should have usable parts in there.

I agree with Jeff, the seals are probably at the end of her life. Better to tear down no before the seal goes and destroys the housings.

Kentetsu

You guys are probably correct. The only thing that makes me wonder is the fact that at times the issue is completely gone. It seems that the more I drive her, the better she behaves. This would seem to imply that the seals are still adequate, and I am dealing with a weak spring or carbon buildup. I'm going to try to finish this year with the current motor, then either rebuild or replace it before spring. Thanks for your input...

In this video, you can hear what it sounds like when its acting up. The problem is gone once again since I soaked it in Seafoam/MMO a couple of days ago.

http://youtube.com/watch?v=jB-JDdINMzU

Kentetsu

Well, after a couple of weeks of making noises off and on, she finally cleared up and started sounding great again for the last week. Power was back up and she felt really smooth again. Until....

R.I.P. She suddenly gave up an apex seal on the way home from work yesterday. I wasn't even getting on it, just idling at a stop light. She limped her way home on the remaining rotor, and crawled into the driveway just as the odometer rolled over to 213,100 miles exactly... Let's all shed a tear now.

So, I'll have to figure out what I want for the replacement. I'm hearing that some mild porting is allowable in CSP class, so now I've got that on my mind. Either way, she'll be back on the road soon enough.

Jeff20B

iTrader: (13)

I won't say I told you so, so you don't have to worry about that.

Get it apart soon and measure the height of the seals. I'd guess they're somewhere between 7mm and 5mm. Probably around 6.something. Check the slop in the rotor slots as well.

As for mild porting, you should go with '74 spec. It is considered a stock port for '74-'75, so you could technically use it where porting isn't allowed, if you're creative. Otherwise, it can be classed as a mild port because it is exactly that - a mild port.

You know PercentSevenC's white '83 GSL that I got running for him early last year? I ported that out to '74 spec and threw on an old RX-3-ish manifold (I'm not actually sure, but it outflows a '79 manifold and even has the ACV cover casting making it truely bolt on to any '81-'85 12A). It even had chanels. Anyway, that engine had plenty of midrange and tons from about 3500 to 7k. It only lost a little from idle to about 1500, and being a 12A, I wasn't really expecting much down there anyway. I have yet to upgrade the igniton to direct fire, which I'm sure will regain the loss in low end the '74 spec ports produced. Also the RB dual pipe exhaust probably was a little too big for such low RPM operation, and why it screams at high RPM.

Oh, and also thank the rotary gods if your rotor housings had missing chrome. Sounds like the only thing to feel bad about is a damaged rotor. So when you get a set of rotor housings and one more rotor, try mildly porting the exhaust ports too. Percent and I opened them 1mm sooner (slightly rounding the opening) and closed them 2mm later, since we all know US-spec exhaust ports are restrictive. We also went 2mm wider. Basically the bevel was used as a porting guide and a new bevel was created - make it 2mm @ 45°, just like Judge Ito recommends.

Jeff20B

iTrader: (13)

I found the thread. https://www.rx7club.com/forum/showthread.php?t=539579

Kentetsu

Thanks for the link Jeff, and for not saying you told me so. I never doubted you though, just didn't have any options for rebuilding or replacing yet...

Kentetsu

Well, thanks to Perfect_circle for hooking me up with a replacement motor! Also thanks to him and Man in Black for the installation assistance. This was really a case of rotorheads coming to the aid of one in need. Now it looks like my car will be ready for the race this weekend, which was totally unexpected!

Man in Black took the time to do a quick teardown on my original motor. This is how it looked after 213,000 miles of hard use, but regular seafoaming.

Cause of death: Broken apex seal on the rear rotor. You can see where it damaged the rotor, and the housing. Quite a bit of chrome flaking too, which was not due to the failed seal but simply age and mileage. We were pretty surprised to find that the apex seals appeared to be in pretty good shape overall. They haven't been measured yet, but it doesn't look like they're too far off spec if at all.

Now, on to the pics....

Kentetsu

Jeff-

I just measured the broken apex seal. 6.1 mm. Good call on your part.