Oh, I forgot to answer the RPM question.  We run it to no more the 7,000 RPM in theory, though I have had four drivers in it for a total of 20 hours, so who knows what could have happened in that time.  Going forward, I will have a data acquisition system that will record all vital engine data.

The good news is that I have a garage full of spare engines, so if the crank is bent, it won't be a huge loss.  One engine has already donated a few parts.

I'm now fairly confident that you are correct and that I will find a bent crank.  As long as nothing inside is damaged, it will be a simple repair.  

I'm betting the loose bolt ended up bending the crank snout. Mine took a about 3 thirty minute races, and then the spindle gear sheared and the worm gear cracked . Engine stopped mighty quick.

If stock L28 bottom end and used for enduros's I'd drop rpm to about 6,500 if possible. Especially if still using factory balancing. 7,000 RPM on an L28 can give a lot of secondary vibrations. Old syaing that is very true : RPM's = $$$

And secure the Crank Bolt with High Strength Red Loctite or Stud Lock. Same with Flywheel bolts ( alternator bolts, driveshaft bolts, caliper mounting bolts and just about every danged thing on the car!! ) . Red loctite is a Racers best friend. Although Red- Green may argue....

Good advice.  Again, I have never had a crank bolt come loose, so I don't think it got retorqued between races.

When you bent your crank, did the bearings get damaged?  Just curious.  

No, I was lucky. Mine was more of an immediate failure. No misfires. From what I could tell the worm gear cracked at the keyway ( from vibrations ) spun on crank and engine stopped with 5 feet of flame shooting out of tailpipe. Spindle gear was damaged, but not nearly as bad as your's. Plus the bypass valve in oil filter block was removed and plugged, so all oil was filtered in one pass.

Edit: We did end up replacing crank though. Found no evidence of damage to bearings but I still pulled the entire engine apart and cleaned all oil passages.  Pissed me off though, because it was a $1,200 knife edged Tilton crank. That was $1,200 in 1980 dollars... 

With the amount of damage to that gear, I think I'd play it safe and pull EVERYTHING apart. Check and clean all oil galleries in block and head. Pull the oil pump apart. If you start finding any chips in oil galleries or bearings, throw out the oil cooler and oil cooler hoses. Oil coolers cannot be cleaned of all metal chips unless they are very carefully cleaned in an Ultrasonic blaster. Oil lines will get chips embedded in hose lining and cannot be completely removed by flushing with solvent or other means. You will always have some chips remaining, and they will come loose at the most inappropriate times.

Now aluminium gears eating themselves up is not too bad. It's relatively soft and may get ground to a fine particulate. But you still have to pull everything apart and check. 

Valve train parts like Tappets and are the absolute worst for engine damage. Those are very hard chips, and usually shatter into many, many small pieces. You blow up valve train parts and you have to do major forensics to engine. Usually takes out everything... and I mean everything. Including dry sump pumps.  Oil coolers and  all the oil cooler lines are trash  and even the Dry sump reservoir has  to come out for cleaning. 

Edited April 19, 20178 yr by Chickenman

Will do.  My next move will be to cut the oil filter apart just to see how much it caught.  I saw nothing in the head or in the oil I drained from the pan.  When I drained the oil, I put a clean shop paper towel in the drain pan as a filter.  I ran my fingers over every mm of it and found absolutely no specs.  Even with a light shining on the paper towel, there were no signs of debris.  With the number of teeth missing, it had to go somewhere.  The inside of the oil pump looked pretty darn good considering what had happened.  If it wasn't a race car, I wouldn't hesitate to reuse the pump.  It had micro scratches that I could feel with a fingernail, but very little visible damage.  Again, oil pressure was great right up until it stopped running.

Easy peasy on a lathe. Just make sure you have a catch pan under it.