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burnt apex seals?

Old 02-11-12, 08:01 PM
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burnt apex seals?

Today i was at my shop and decided to feed my curiosity. last year i swapped an S4 13b into my 82 rx7 to replace/upgrade my old worn out 12A. The 12A had ~100k on it but i could feel it was getting weak and took some encouragement to start, either way i had no intention of doin anything with the motor.

Upon tear down, I found the irons to be in great shape with minimal side/corner seal wear, and as expected the housings are junk with 1/4-1/2"of flaking in multiple areas though out the perimeter. There were also carbon/burnt streaks across the chrome around the leading spark plug holes as well as large burnt areas above the exhaust ports. Both rotors covered in black sooty carbon on the combustion faces (except the 1st 2 inches of the leading edges, which were clean). Further inspection showed that almost all of my corner seal springs were dead (corner seals moved freely, but sat flush with the surface of the rotor..springs werent doin a damn thing) as well as 3 or 4 apex seal springs that were virtually flat, while 1 still had an almost "new" shaped arch to it

lastly, ive torn down 4 other motors (3x 12A's and 1x 13B) before this one and i dont recall seeing this in any of them... all but 1 apex seal looks like theyve been heated to hell and back, definate discoloration and bluing





is this "normal" to have apex seals showing this kind of coloring? if not what would be the cause? I never overheated the motor, it never ate coolant, motor had a shimmed OPR @80-90psi
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Old 02-12-12, 04:02 PM
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were the corner seals the same way?
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Old 02-12-12, 04:07 PM
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bluing on the seals normal? no. it's a symptom of the seals running directly on the steel sleeve creating friction and excessive heat.
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Old 02-12-12, 05:44 PM
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ii seen that in engines with apex groove being to open
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Old 02-12-12, 05:47 PM
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So probably from the large bits of chrome flake letting the seals work against bare steel as apposed to the smooth chrome?

As for carzy driver's question. All other seals looked normal, no signs of heat discoloration, just the 5 out of 6 apex seals
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Old 02-12-12, 06:21 PM
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how the rotor groove?
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Old 02-12-12, 06:46 PM
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Ill have to check the slots tomorrow, I don't have the rotors with me right now. I do remember reading the the 3mm seals are more susceptible to wearing out the grooves than the later 2mm. I hope the rotors are still useable, as I was hoping to use them in my next build
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Old 02-12-12, 08:59 PM
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well, just got back from my shop and im guessing the heating was caused by both missing chrome and worn seal slots. i didnt look too closely at the housings and rotors yesterday, and now that i looked closer the rotors are junk too. one of the slots has a very pronounced lip developing from the apex seal spreading the slot ...so much for using that rotating assembly

just for fun i grabbed some pics of the housings, remember...12A with 103k

Front rotor housing




Rear rotor housing...the really bad one






why does it seem that rear rotor housings seem to get torn up worse than the fronts? ive seen heavier housing wear usually in the rear housings in the few motors ive pulled apart...weird
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Old 02-14-12, 01:18 PM
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for a 12A those housings look great. i've had engines come apart with way more chrome flaking, IE there almost was no chrome, and the apex seals wear heavily, but not burned
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