heater core installation

[Chris L.]

Hi,
I have a '74 Omega which I recently changed the heads on (to '71 #7 heads). I also changed the stock EGR intake to an Edelbrock Performer. I noticed that the original intake has a valve of some sort on the water exit port going to the heater core. Ever since changing the heads & intake, first my original heater core let go (blew up, really), then I replaced it (man, that was a lot of work!), but it too is leaking. The only thing I can think is causing it is not reusing (or replacing) that valve coming off the head going into the core.
However, I've noticed that earlier years/ models of not only Olds, but other GMs didn't use that valve. Has anyone had an experience like mine with changing the intake and having their heater core blow up? Any suggestions?
Thanks,
Chris L. (Berkeley, CA)
you can respond to my e-mail at: chrisandcammi@yahoo.com

[Oldsguy]

That's your heater control valve, most of them are operated by a vacumm signal from your heater/ac controls. It allows water to circulate from your heater core back into the back of the block water jacket. This allows the heater core to really heat up since the water is circulating, if it doesn't circulate the heater core doesn't give off as much heat after a while with the air blowing over it. This is done to keep the heater core form radiating too much heat in the summer. I took mine off when I rebuilt my 455 and I don't notice that much heat (although it ain't August yet). I think they look to big and akward and just plain nasty on a nicely cleaned up engine so I left it off mine. I think in your case you just got unlucky on the second heater core, you have to be really careful when you install one that you don't break a neck when attaching the hoses, done that before myself.