howracer

i found cracks in my rotor housings radiating from my sparkplug holes. has anyone else had this problem? one housing has 2 cracks approx 1/4 inch in length (thru the chrome and aluminum). the other has 3 that are only visable with a magnifying glass. detonation?

howard coleman

mazda_racer

Its common and accepted that there will be some small cracks around the spark plug hole.





I just checked the Factory Manual but could not find the acceptable length for such cracks. Maybe its in the video or someone else here might have it handy



Later,

Peter

mazda_racer

OK. Here's the information from Mazdaspeed. You make up your own mind ~



"You should replace the housing if any of the following are found:



1. Cracks around the trailing spark plug hole on the trochoid inner surface that exceed 8mm in length.

2. Any flaking, dents, scratches or deformation of the surface.

3. Galling or small scratches on the side of the rotor housing between the O-ring and the inner trochoid surface."



Hope this helps

Peter

j9fd3s

it might be signs of detonation/too much heat

93BlackFD

imagine how big those cracks get when that metal is up to operating temps...

howracer

the cracked housings aren't going back in my motor. i was just wondering how common the problem is and the cause...

howard coleman

Badog

Had cracks in my stock housings. Both around the trailing plugs...so I heard, I never saw. Rob said it was fairly normal. Gives new meaning to not over-torquing the spark plugs for me.



Tony

howracer

hi tony, thanks for the response.. we have a company nearby that may be the pre-eminent motorcyle/snowmobile engine bore replater. i am going to take my rotor housings to them next week for evaluation. the housings are excellent except for spark plug radial cracks. maybe there is a fix since new housings are around 550-600. (and mayber there isn't, but it is worthwhile to check and this company wrote the book on plating). judge ito is doing a new shortblock for me and my project in the meantime. OBTW, after wrenching for lots of decades i would be one of the last people to overtorque a sparkplug. i hope yr project is tracking well and i will give you a call one of these days.

howard coleman

howracer

peter, thanks for the info from mazdaspeed. i noticed they mentioned cracks at the trailing plug hole... mine are located at the leading plug.

howard coleman