Yeah ernie that's why! You got me! I never said "Ray" wasn't any good....I just don't hang on his nuts like some people.

-J

 

Wasn't swinging by anyone's nuts. You didn't see me say he was the "BEST", did ya?

 

bump.. what is the diferance in the 2 rotors pictured? Anyone??

 

I can't honestly tell a difference unless I get a better picture of it. I don't think I took any of the engine when I first built it way back. I don't recall changing the rotors out, either. Unless by some chance they're of wildly different series and weight (and you'd know it; the assembly would vibrate to death), it won't be the cause of what's going on with the way the car's running when it's missing up high.

B

 

If one rotor is running at a different (higher or lower) compression ratio than the other, why would it not cause problems?

 

If they're two different compression ratios, sure it would. I don't think they are, however. A problem of that nature, if I didn't catch it when I put the engine together, would've been evidenced lots earlier than last week.

B

 

Who built the engine? Just curious.

 

Mike, did you notice the dark carbon spot on both sides of the spark plug hole? Also the cracks?

This indicates the lifting of that surface. My theory is that this wll break apex seals, chipped ends of the stock Mazda seals or in your case broken off centers.

This would call for better water cooling in the area of the spark plugs.

Barry

 

BDC Motorsports

 

Could it be possible since the housings were used they could have been that way when assembled?

 

We might ask when the spark plug area was rising first, but more importantly we should ask why are we seeing this problem?

What happens to the adjourning rotor phase when the seal is lifted and burning gasses escape into its fresh charge? Preignition?

Barry

 

I don't think I have ever seen a used housing that DIDN'T have carbon deposits like that around the spark plugs, NA or turbo.

 

Just about every one I've torn down here is like that. I've never quite figured out why it happens but it does come clean after blasting.

B

 

Yeah - My recent tear down/rebuild had those marks. The other J-spec's Iv'e torn down as cores had those also.

 

And why were we taking it apart?

My disassemblies were for broken apex seals. Imagine the seals snapping across that sparkplug high spot and jamming the wedge end against the point of the apex seal. I believe this is one failure mode for stock Mazda seals that I use.

The reason I came to this conclusion was that I found one unbroken but cracked apex seal. It was cracking from the bottom! I visualized them breaking from the top. Why would it break on the non-dynamic supported side?

I haven’t seen the centers burning out like this one of Mike’s or Ernie’s. This may be the failure mode for Atkins apex seals.

Barry

 

I've got an engine I'm building today, Barry. I'm going to have a peek at this a bit more closely and see if I can get a better idea as to what you're talking about. Give me a ring this afternoon if you're not too busy.

B

 

Barry, I did not go that deap into looking over the housing as well I should have. Once I saw the guage in the housing and the tearable wear marks plus broken apex seal I just sourced another housing. I was surprised on how it wore the surface of the housing. Maybe it was due to the seal chipping a little at a time??


So how do I get better cooling in that area?

 

Ignition misfire chipped a seal.

Perhaps there may be more to it though - but I'm curious as to why these marks are found so frequently (can't recall an engine I've torn down that didn't have these) since I'd rather avoid tear down's if at all possible, and if these marks are a sign of a preventable issue - I'd like to be on top of it.

Sorry to minorly thread jack (although somewhat related)

 

What heat range plugs you using ? you may want to run cooler plugs.
Are they fc housings or fd?


rgds
Brian

 

FD and 9's on low boost pump gas, NGK 10.5s on 114 gas...

 

Kenichi Yamamoto's book shows the temps around the plug area.



I think we need better cooling in this area. Some possibilities are:
1- Internal cooling fins.
2- Better water pump.
3- Tighter water pump impeller clearances.
4- Larger water passages next to the leading plug especially.
5- Supplemental cooling water per Afgmoto’s drawings.

Barry

 

check on the stamps of the rotors that should give you some idea on balance. also weight them,the hi comp rotors are lighter. i am almos 100% sure that you were running 2 different compressions in that motor. post more pics of the rotors or pm me and i will find out for you.
Tony Martinez

 

for example what stamps am I looking at/? I see some "S', "6", 4??

 

When I opened my j-spec 13B-T for the first time, it had rotors with differently shaped combustion pockets as well, so I don't think that has anything to do with it. The machining marks were the same though. Both were of the same code.

 

Your looking for letters for one, A,B,C,D,E also check for markings near the bearing on the non gear side on older rotors. Weigh them. Having one that is grooved and one that is not is not a big deal slight change in manufacturing. I'm guessing your rotor pair is not a issue for you at this point.