what is the space between the apex seal plug thing?

 

Ok little hard to understand your question, but here goes...

The spacing between the cornerseal and sideseal is supposed to be withtin 0.0040" - 0.0060"
and a MAX tolerance of 0.0080"

 

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anybody?

 

its for a rubber plug if u are using the factory corner seals.theyre supposed to help on cold starts i believe.but ive heard of people running without the plug.

 

Side-seal clearance?

B

 

yes

 

srry about dumb post I was a little drunk

 

It wasnt a dumb question. Side seal clearance is important... on the unsuccessful (never able to start) rebuild motor that I bought from some stoner kid... I found that his side seal clearances were HUGE! The SMALLEST clearance that he had on any one side seal was .06, which is roughly four times the "allowable" limit, and ten times more than the max reccomended clearance if you are trimming down new ones. WTF was this kid thinking? That was also one of the more minor things that I found wrong with the engine.

 

so .01? what s the best space?

 

Absolutely not. That is too much. Haynes says between .002 and .006. I've trimmed all of mine down to zero clearance so far. I think I am going to finalize them at about .003. The low side of the spectrum scares me a little bit in terms of heat expansion. I do not want them to bind up.

 

where would I find a gaper like that or spacer ?

 

Go to sears and buy a feeler gauge that can read those gaps.

 

how much do they run?

 

NM I found it

 

so is that rubber plug in the corner seal not neccesary?

 

The plug is designed to help with compression.

 

.003"

 

The clearance is so tight its tough to measure especially with feeler guages. The best practice is to hand file the side seals until it fits and does not hang up or drag against the corner seal. This takes time and patience. My clearance is around 2 thousnadths of a inch. Good luck

 

thats a good thing to know, i though it was to help stop vibration or something

 

How it works is that during the compression stroke, the compressed fuel/air mixture will leak in between the apex seal itself and it's rotor groove. The compressed mixture will then travel under the seal to the apex seal springs then to each corner of the apex seals and exit out the circular hole of the corner seals. The plug prevents this from hapening as much. Without the plug you will loose a little more compression and more carbon build-up will form under the apex seals because of the air/fuel mixture flowing in the area. The 1st gens were really bad about this carbon under the springs because they didn't have the plugs.

 

Uhm...

So there are 2 corner seals (and thus 2 open holes, if you do not use plugs in them) under each apex seal. So given what you just said, compression leaks into one of the 2 holes and travels under the seal and exits out the other hole...back to...where it came from. But wait...an equivalent pressure was always present at the 2nd hole...so that pressure would have went...out the first hole...back to where it came from? By definition your statement makes no sense.

You are right in the aspect that carbon will form under the seals, but keep in mind that the travel of the seal and springs only allows buildup in dormant areas anyway, so it is a moot point. I have never seen a groove with more carbon than the seal/spring would allow during it's full range of movement. Obviously since the engine must first be running to form carbon, and the seals and springs are travelling in and out to make the engine run, carbon cannot form in any place that the seals and springs need to travel to, it would be pushed out of the way quicily and would not form there.

IF you've ever taken apart an engine with the plugs installed you know they are ROCK hard and are often rotated so that the "slot" side is not even in alignment with the apex seal. They usually fall out when you remove the corner seal, because they have hardened and shrunk. I've taken apart 10k mile rebuilds in this condition. Obviously they cannot seal properly this way, and that 10k miles of proper sealing doesnt do any good when they fail and let carbon build up for the next 40k or however long the engine lasts (thinking FD engines right now).

I havent built an engine with butt plugs since 2001. Compression has not suffered in any way shape or form as measured with a mazda digital tester, neither hot nor cold compression. Bottom line it's 25 bucks not well spent. It's not something to lose sleep over.

 

At first I couldn't understand how you could get my explanation confused so I had to read it over and over again. Above when I said seal, I meant the compressed mixture will then travel under the "apex" seal to the apex seal springs. I just never said "apex" seals and never thought someone would get that confused. By the way I did say corner seals ("s" as in plural meaning more than one)

I really need to show you pics of the springs in my 12a that were completely deformed because of all the carbon build-up under them. I'll take pics tomorrow.

 

I understood perfectly. I never said anything about side seals. There is equal pressure on each "corner" of the apex seal where it meets the corner seal. SO how can you say that pressure will travel under the seal and out the other side, when there is equal pressure on BOTH sides? True, the pressure and some of the a/f mix will travel under the seal from both sides...but the way you put it was incorrect, more like you were describing airflow from a high pressure side to a low pressure side...when pressure is the same throughout.

I have seen deformed springs from overheating, and springs with carbon on/under them. But unless the engine was assembled with the carbon already there, you can't say that a spring was being inhibited by the carbon buildup.

IF you run windshield wipers during a snow, the snow builds up to the side of the wipers, but not on the area being constantly wiped...right? So long as those wipers are moving, snow cannot build up where they are sweeping...only in areas where they cannot reach anyway. Same with carbon under seals/springs. IF they are moving, carbon cannot form there.

You cannot say that carbon forms there while they are not moving...because the engine has to be running to form carbon to begin with.

 

I never did either.

How are you still getting the impression that I'm saying that the pressure will travel out one side when I clearly said "corner seals" which means both?

Again my quote: "during the compression stroke, the compressed fuel/air mixture will leak in between the apex seal itself and it's rotor groove. The compressed mixture will then travel under the seal to the apex seal springs then to "each" corner of the apex seals and exit out the circular hole of the corner "seals". I'm not trying to imply that the pressure will enter under the seal and then travel out only "ONE" side. That is not what I'm saying.

Well your probably right on that one because my 84 12A engine lasted 10k with the OMP not functioning fully. The cotter pin that held the throttle linkage in place broke not allowing the pump to meter the correct amounts of oil to the rotors during higher rpm operation. Both housings show signs of overheating because of a lack of lubrication. Also my granny driving and me not replacing the spark plugs regularly caused the excessive carbon build-up. To add my 12A in my 81 rx7 over heated 3 times because of a radiator leak. When that engine locked, I tore it down and the springs where perfectly fine. Below are pics of all the carbon build-up inside the 84 engine.



You just said that you've seen the build up here:
But yet above with the springs moving they cannot form there?

On a higher mileage engine, the apex seal springs aren't compressed as much because the apex seal itself isn't as tall due to being worn from the mileage. This makes the spring more "U" shaped giving more area under it for more carbon deposits to build-up. You already know this because you have to scrape the apex seal groove of carbon deposits every time when cleaning the rotors. The build-up is always towards each end of the apex seals groove under the part were the spring isn't compressed enough.


When did I say that something wasn't moving?