I was looking through the pics of another members engine teardown and someone said that certain seals and bearings looked good enough to reuse.

What seals MUST be replaced?
What seals SHOULD be replaced?
What seals CAN be reused?
What conditions show that seals should be replaced?

The build I'm planning on is far off, but I'm a bit of a geek and would like to know. I'm sure it'll save others some time and money too.

 

All the soft seals must be replaced. You can reuse any of the hard seals if they are within tolerances, but Id still replace the seal springs with new ones. When you tear down an engine, it is very important to label EVERY seal and spring so that if after cleaning and measuring, if the seal is within spec, you can put it back in its original place. I use ziploc sandwhich baggies and label the bag with masking tape. Then clean one seal at a time and put it in a new baggie. RB reccomends ( and so does Jim Downing IIRC) that rotor bearing replacement is on condition only. They last a long time and only if they are damaged or out of tolerances should they be changed. Only one Ive had go bad (seized from lack of oiling). Mains I'd say the same thing, but I'd be more apt to replace them since they are easy to change with a hydraulic press ( Ive only ruined 1 out of a dozen or so).

 

You need to put all hard seals back in their orignal place ? It's really not that important, as long the seals are within tolerance and the springs are in right it's fine. My engine build was very messy and unorganized. But it runs great.

 

Well it just makes it easier on the engine. Yes you can theoretically put them in any position that they fit in correctly. HOWEVER, in my experience building engines (that includes boingers), parts wear themselves in together and if you mix them up, you can cause accelerated wear cause they have to re-break in to one another. With a new part its not critical cause its never be worn on by another part. Just my $0.02

Oh and springs lose some of their springiness (tech term) after the many heat cycles and the hasrh environment they live in. And they are freakin dirt cheap. If I was assembling an engine out of all used parts that were good, I'd still replace ALL the apex, side and corner (use 3rd gen springs in the corner seals, they are much better) seal springs. Thats cheap insurance for the cost. Maybe $30?