Okay, I got all the springs out of the head and was cleaning it today. I notice where the valve broke (1/4" off the top of one on the end) the spring seat only is in the main body of the head. Like on the edge it isnt there. But on the other end, it is fully intact going around the spring seat. They are both exhaust valves. It makes sense to me that if the seat was broken off at that part, then the spring may have lifted and it caused the valve to break when it came down.

Any help is appreciated, I think I need new heads, but am probably looking for a reason to get them knowing me.

 

it's common for the springs seats to not be machined fully around the valve guide. the spring will not lift, there's too much preasure on it.

 

Thanks again, I assumed since it was in one part that it should be there. Now I can go ahead and assemble the head and get it ready to bolt on.

 

84TA,

I think I can envision what you are describing. Correct me if I misunderstand, but it sounds like you are saying that the valve spring seat machined into the head is larger in diameter than the casting, so that part of the stationary end (bottom) of the spring has no support. I've had some early '70s heads that appeared to have too little material for the exhaust valve springs at the outer ends, right where the head bolt is installed. The spring almost hangs off the "ledge" created where the #1 and #7 exhaust spring seats are machined.

This isn't usually a problem on stock diameter springs, but can be an issue with larger springs, since machining the seat only makes the problem worse. If these areas are machined deep enough you can use spring centering cups as additional support. However, this makes installing the head bolts a bit of a challenge. Also, the heads themselves aren't that great a design, and unless you weld in extra metal and do some serious port work, the flows are nothing compared to some of the later SBC head castings.

If I'm off-base with my assessment, let me know where I misunderstood you statement.

 

EXACTLY! There looks to be very little material. these heads are to tie me over until I get the cash to rebuild the motor right with new heads, but they needed springs and its good experience. It looks deep enough to take the spring no problem. I have a set of valve springs my uncle gave me that were on his nova for a season or two. Raced it in stock series, but these are heavy single springs and are much stiffer than what Ive got, They arent doubles though, and they were in my budget. I worry about using used springs, but they look new. They fit in just fine. I just havent done that last valve yet, I need to take a die grinder as the valve has mushroomed over and gotten stuck as the top broke off.

The spring isnt hanging over at all, I just put it in there. I looked at my spare set of heads (624's) and noticed they are the same way. I just figured Id check with you guys to make sure I didnt go through the trouble of doing springs only to break something.

I know these heads arent the greatest, but compared to the 624's they look 10X better. Hopefully an 8.5:1 forged 383 with topline iron lightnings on top running 8lbs of boost will be sitting under the hood in a year or so.

I really appreciate the help, 6 months ago I would be afraid to change an air cleaner, now Im ripping heads apart. Im learning slowly I guess.

 

Sounds like you've got it hap'nin'...