Had a major breakdown tonight- got off the freeway and jumped on it after the first stoplight and motor started clanging loudly... immediately pulled over- called AAA and after a 2 hour wait, finnaly got it towed home.

I was thinking maybe a bent pushrod or something in the valve train (It still ran okay & had good Oil pressure when the sound hit for the half block i drove it getting it pulled over off the road- so not I'm thinking bearings or bottom end. No shiny stuff in the oil on the dipstick)

Anyway- I got home a little while ago, pulled the valve covers- On both heads, i see a large rough shaped opening into the valve train at one end, and another large rough opening about halfway down the head- both open into the lifter valley. You can easily see the lifters through these holes.

Is this normal, or are these heads seriously toasted? I have never looked at BBC heads up close so no idea if it is expected. Both heads have the same holes (except on opposite ends) but the rough openings look slightly different.

Any thoughts?
Guess i will be digging into this engine sooner than later. Had hoped it would make it till the aug 18th Aces nw show... Oh well. Guess i was right to not try and drive it to oregon last weekend!

BTW: these are 3964290 Oval port Closed chamber heads... they are original on this motor.

THanks-
Ben

Both my 781's and 820's have those rough cast holes.
Seems to be a normal thing for BBC heads.

When you take it to the shop, have them deburred. Helps oil flow. Do the valley also. Wait till you pull the intake. You are going to think your block split in half.

If your using a stock flywheel/ flexplate, you could have cracked it, It makes a sound like a rod rap!

Sounds like your describing the typical holes that allow oil to flow back down to the pan, via the intake valley after it was sent upwards through the oiling system. I dont have a picture of the top of a set of heads but perhaps someone may have a pic to post and you can point it out.

If its what im thinking of I have seen them on every set of BBC heads I have ever seen. Including my pair of 781's and the set on my 66 (cant remember the numbers).

Any news Ben? During the half block you drove it, was it still clanging? or just under load?

Yeah... not good. Looks like its a rod bearing. So its coming out of the car this weekend for teardown to see what the real damage is. Hopefully the block & Crank are ok and can be reused.

I created a new post over in Chevelle Tech...
http://www.chevelles.com/forums/showthread.php?t=139129