i recently had a 406 sbc built for my truck and when i had the valve covers off to adjust the valves it was spitting coolant from the front outer bolt hole for the valve cover on the driver side. Is this common in a bored out 400? Or can anyone tell me what it might be from? thanks
406
- Thread starter rhino1980
- Start date
I think it would be interesting to see how deep that bolthole goes.Sounds like it may go into the water jacket in the head. Maybe you could run a bottoming tap in that hole and get a set screw from the hardware store coat it with permatex and run it down the hole and plug it up. Just an idea. 
Firepower354
Well Known Member
It's got nothing to do with the shortblock, someone drilled the valve cover hold down hole too deep 
. There was likely a broken bolt or stripped top threads and the repairer got carried away with the drill. No biggie, just clean the holes(better check them all) out and Loctite some studs in. Just tube-a-gasket-ing the bolt would probably work, but I wouldn't want to risk watering down the oil. Watch the water temp on that 406, especially during break-in.
. There was likely a broken bolt or stripped top threads and the repairer got carried away with the drill. No biggie, just clean the holes(better check them all) out and Loctite some studs in. Just tube-a-gasket-ing the bolt would probably work, but I wouldn't want to risk watering down the oil. Watch the water temp on that 406, especially during break-in.
Firepower354
Well Known Member
Wrapping uncoated headers is an invitation for moisture to collect and rust them faster. I don't know what truck you have and how you use it, but for a driver, wrap creates trouble. There's some decent priced coated one now. Try adding a second snorkle to a truck air cleaner and getting all your air from out front too. Verify TDC and your total running timing curve. Rich caburetion and retarded timing both can cause extra exhaust heat. Iron center dump vette manifolds are within a few horsepower of headers, almost never leak, and keep the heat in the pipes and out the back too.