can someone please identify?

[DerreckT]

I hope I did this right. What is this hole in the uppe rleft corner caused by? anyone know? I sure would appreciate some info. Thank you! (1971 gmc 454)

[a.c.ward]

the hole that you see there, above the hole for the pushrod, is the one that I think you are referring to, is an oil drain back hole. The reason that it looks funny in the pic, is that there is casting flash from the mold still there. The hole is normal. During the build of high performance motors, a machinist will take a carbide burr in a high speed grinder and remove the casting flash to promote oil drain back. You are probably asking yourself, why is the oil drain back hole so high in the head? Well, during upper RPM motoring, the oil level gets pretty high in the cylinder head. I have witnessed it my self with clear top valve covers in a drag boat, 632 big block running about 5000 RPM, almost fills the valve covers.

happy motoring.

[DerreckT]

wow, I guess that makes sense...I saw the same thing on my k5 blazer 6.2l. Well, thank you for clearing that up, it was driving me crazy for a while...well, looks like the heads are coming off anyway because there are manylittle pieces of aluminum and steel in the oil pan...damn. wasn't even racing it either....cant wait to find out what caused it...Many Thanks again.. -Derreck