12a Rebuild continued...

Cleaning and measuring the last of the internal parts.

On the Oil Control Rings, the Haynes book specifies .5mm or less on the lip width.

Just confirming the lip-width is the distance between the arrow pairs in the attached image. (If true, then only 1 of the 8 is within spec with some over 1.0mm.)

Thanks for your help as always.

True: This is will be much easier the second time around.

 

I know this is the 1979 model, but page 2-20 has what you're after plus lots more.

http://www.foxed.ca/rx7manual/manual...ria%201979.pdf

 

If you're cheap like some of us, you can reuse those. Be sure to get new Viton o-rings from Atkins (they're slightly thicker than OEM). Also get new competition outer springs. The stock inners can be reused. The engine shouldn't smoke on startup after the break in period. In fact it will probably stop smoking on startup after 50 miles like mine did. Just be sure to NOT resurface the irons. If you do, all bets are off.

 

You're measuring correctly.

Oil control rings are those kind of things that you tend to hoard if you've dealt with enough engines. If I buy a core engine and everything is trashed but it has good oil rings, I figure that I made out ahead on the deal. I have a small stack of them, and when I build an engine, the best four of each size go in. So far I haven't had to go over spec.

And the lesson is... clean oil and clean air, so you don't wear those expensive little buggers out! I had dirty air and oil cause some rings to get worn completely across the face. That hurt as they were almost as-new when installed.

 

yeah what PJ said... you're measuring the shiny bit, i'll go to like 1mm (its actually hard to measure)

oh and be careful, they look round and harmless, but are actually the sharpest things on the planet. the first engine i built i used blood instead of vaseline, because of one of those...

 

I previously downloaded all the ones I thought were applicable to the 84 12a, but the 1979 Overhaul Criteria has better illustrations and some more detailed info. Thanks for that.

 

My original projected budget was $1500. I did not fully comprehend the added tools necessary. With housing and stationary gears I'm 2/3rd spent. Cheap, but I want it working for awhile.

My springs have no paint indicators for front orientation. Still need to measure them.

Thanks for the Viton and competition outer springs recommendations.

(Irons left as found. I was warned some time ago if I lapped them someone would be making a house call.)

 

1mm saves some cash. Thanks.
Have not sliced a finger yet, but they are like playing with a straight razor.

 

Remeasured after cleaning.
Out of the 8 only 2 were either less than 1mm chrome edge, or without massive or multiple chipping. The 2 were both inner. Looks like a new set.