3 5/8 bore shovelhead w/andrews "C" grind came BENT intake

I have a generator bottom with shovelhead top 3 5/8 bore with Andrews "C" grind cam, (ANDREWS part# 212600 (48-69) C 37/61 278 318 .525 .550 .234 Hi-lift)

Went for a ride, RPM was probably in the 6 grand, got off the freeway parked, and KAKAaaabooom, engine stole, and couldn't get it to start again

Later found out Push rods on rear were both bent, took the head off and found out the intake valve hit the piston and bent itself, rocker arms and shafts are fine not frozen...

shell I worry about the piston rods etc???? the hit mark on the piston isn't too bad but noticeable...

I'm thinking the guy before didn't use the high-lift springs for the valves, or still has the 80-81 guides which limit the lift to .430 or so?????? the bike ran fine till I pushed it hard to 6,000rpm ... any ideas?

here are some pics

From your description, I get the idea that the engine was still running OK until you were parking? If so, that would tend to eliminate a problem associated with valve float, such as valve to valve clearance, collar to seal clearance, low spring pressure, etc. My guess would be that the hard run added some extra heat, and pulling in to park took away some air cooling, resulting in a valve sticking due to almost, but not quite enough valve to guide clearance.

If my guess is right, you will find evidence of scoring on the valve stem and/or guide bore. You will likely find the exhaust valve bent also. I would still check the spring pressures while its apart, no matter what you find.

Thanks for the reply Lee, you are right heat had lots to do with it,

I haven't taking the valves out, but take a look at the exhaust valve seat, it was partially coming loose, whoever did the valve job stuck the seat in without the proper clearance, and didn't heat up the head...
causing the intake valve to hit the exhaust seat; which lead to the bent valve.


or it was way too hot and the seat came out because of it ...

will check spring clearance & guides etc and get back with results.



Cheers...

as a general comment on tuned iron engines, I have always believed the practice of running a lap on a trailing throttle at the end of a race is beneficial that way. It is actually done for marshalling reasons, to get people off the track safely without anyone turning against oncoming riders behind them, but it means your engine gets some cool-down time before shutting off.