How to check your Rotor Housings

Written by Wesley Mahler

30.11.2005

Here is an article that will help you decide whether or not to use your rotor housings. If you have any questions please post them on the forum, in the rebuilding section. This will be helpful for you if you have some older rotor housings. Make sure you have the right tools when you do the measurements, if you're not sure contact your local rotary engine builder.

How to check your Rotor Housings

Here are some items to examine before you reuse your rotor housings.

Chrome Flaking on inner housing sides.
Inner surface ‘washbanding’
Spark plug damage ‘cracks’
Shrinkage
Check threads

Start by examining the inner rotor housing’s chrome flaking. This is the portion where the ends of the apex touch sides of the surface. It is normal to them to have worn edges. Although large amounts of chrome flaking will make your housings unusable. See the picture to the left for an example. Make sure, if you’re going to reuse it, you check the flaking with the factory rebuilding specs. Despite being more expensive, new rotor housings are generally the best way to go. Some engine builders like Pineapple Racing replace all of their rotary housings with brand new ones.

Next check the inner surface near the spark plug holes. You are looking for cracks on either side of the spark plugs. Although you can get away with reusing housings with small cracks by the spark plugs, check to make sure they are within factory rebuilding spec. The picture is an example of bad spark plug damage.

Then examine the entire inner chrome surface. You are looking for a ‘wash banding,’ effect on the housings. Feel the surface, if it is very bumpy it would be considered chatter, or washbanding. You want to avoid this on rebuilds, and if there’s chatter, the housing is probably not good. In general, the shiner the surface, the more worn down the surface is as well. The picture below shows color difference, and chatter between a good housing, and a bad one.

Finally check the housing for flatness, and shrinkage. In order to check the shrinkage, you’ll need a micrometer. Measure the width of the flat surfaces (plate sides), specifically measuring the hot spots and the cold spots. You’re looking for a large difference in width, check with the factory manual to see if your housing is within specs.
Finally, check all of the threads throughout the housing, and any other damage. Other spots to look, water jackets, water jacket seals, exhaust ports, spark plugs threads, etc.