sevenracer

I seriously overheated my 12A in my race car.



I ran it 3 laps overtemp - way off race pace trying to avoid a DNF. Water temps spiked to like 250 for a few seconds and then settled at about 210 at the slower pace. My oil temp gauge seemed to quit working - went to zero. Oil pressure remained good. Power dropped off considerably and the engine would not restart. Did not spin as freely as normal by hand aftewards. Oh and the radiator was leaking afterwards as well - I think this is what started the whole mess.



Anyway, after dis-assembling, here's what I see and here are my questions:



- All the bearings look ok, except one rotor bearing has some discolored stripes - it may be a problem.

- The eshaft looks ok to me as well.

- The side plates are darkened in the combustion area.

- The rotors look ok to me - all the seals still moved fine in their grooves.

- The housing surfaces basically look smooth, but with some spots on one, and some shiny sections on the other. See pics - This is after light scrubbing with scotchbrite and WD40.

- The biggest obvious issue is that the aluminum housing "gave" in one area of the combustion seal groove on both housings - the metal bowed out into the water jacket and the combustion groove got wider in that area. I think similar to a common failure on 13B's. Is there a way to repair this - assuming the rest of the housing measures out ok?



Also, there seemed to be some glitter in the oil - but the bearings looked ok. I have not looked inside the filter yet.



Any thoughts on what typically gets knackered from a major overheat? Is it crazy to re-use the rotors, bearings, etc? What about side seals and springs? I have another set of irons, but would need to find new rotors and housings if that's what it takes.



Thanks

phinsup

ouch.

Lynn E. Hanover

The high temps have cause the oil film to fail in several areas. The shiny rotor housings around the spark plugs for example.



The scored rotor bearings.



The rotors are usually unaffected by excess heat. Replace the springs under every seal. The seals and the "O" rings under the oil scrapers.



The rotor housings are toast and usually warp anyway.



The irons are probably OK. Just lap them against a known good iron with valve grinding compound and check for flat. If the overheated iron only touches in two places, it is scrap. You have to lap through the Nitride to get it flat again.



The crank is probably OK. oil the journals. Wind a long strip of 400 silicone carbide paper (wet or dry sand paper) around the journal. Wind a leather shoe lace around the paper and pull back and fourth like you are trying to start a fire. Journals should look like chrome when finished.



Pressure wash the crank to get all of the carbide swarf out.



Lynn E. Hanover

sevenracer

Thanks Lynn



Just to clarify: you think the rotor bearing is ruined or still ok? To me they don't look scored. Just discolored and not worn down to the copper.



Also, the rotor housings are trash because of the shiny spots or the other issues?



Thanks again, trying to learn more about what exactly happens to the parts when overheated.

Lynn E. Hanover

The housings appear to have started melting and the back side of the groove has started to move away under combustion pressure. Also check the area around the plugs for shrinkage. The housing gets too hot and trys to expand but is held flat by the irons. So it gets a bit fatter. Then when it cools down,

the housing does not touch the iron around the plug area. It will be too narrow and not seal at all.



The soft surface metal (Lead antimony and Tin) on the bearing has started to move under pressure. So some of the material is not as thick as it should be. And in some places (the shiny part)it is thicker than it should be.



Scrap the bearing.



I did spin up new puzzel lock bearings in the lathe and sand off (wet or dry silicone carbid paper and motor oil)the grey stuff to almost all copper. Other folks actually use the lathe to turn out the soft overly and run only on the copper. My lath is not that good.



This is for racing only and very low RPM oil pressure will be dismal. Also you must check rotor face to rotor housing clearance and be ready to sand of some rotor face as the loss of bearing material will allow a bit more rotor movement when screaming the engine. Always a 100 PSI minimum oil pressure.

Synthetic racing oil at least 40 weight.



Rotor bearings are not perfectly round until pressed into a rotor. You can grind off the indexing tab on the new bearing. It is not needed on rotor bearings. It is needed on main bearings to maintain alignment with the oil passage.



Water temperature gages read zero when there is no coolant near the bulb.



Front stationary gears fail first with a stock oiling system. Add a oil hose from the oil filter stand to the front latteral drilling to the front stationary gear. Do not plug the top dowl gallery, as your aim is to double the gallery cross section to the front bearing. Drill out the latteral gallery and tap for a AN boss by AN 10. Have this done by a machinist on a mill. Spot face the casting last and add a shamfer as the boss fitting seals with an "O" ring. Do not use a tapered pipe thread. You will split the boss and ruin the iron. You can save it by screwing in a steel AN by pipe thread and braze it in place. It works fine but shame on you.



Lynn E. Hanover