Thanks for the input, guys. Yep, I know (and knew) that it's almost assuredly a radiator problem. So here's my radiator story: When I bought the car 15 years ago (this July) it had a small radiator leak. I had just bought the car, was getting married in a few weeks, and was pretty much broke. It was the original one then so I had a shop look at it but they said it was too far gone. So in went an Autozone rad and all was well until 3-4 years ago when I had another leak. Somehow, I found my receipt from 11 years prior and since it was a lifetime warranty AZ honored it and replaced it for free. Sounds like their quality control has gone down since this one only lasted 3 or 4 years and the first one lasted 11 or 12. So trying to decide what to do - Barr's stop leak, new AZ rad (maybe they'll give me another new one, who knows) or get the current AZ rad fixed. I'd like to get a good aluminum rad, but not sure a new DeWitt is in the cards right now. Both AZ rads have cooled the car well, even after I rebuilt and bumped up compression I've never once had any concerns with overheating.
I'm considering trying some stop leak, but that kind of thing always makes me a little nervous. I don't care if it messes up the rad, but don't want any problems somewhere else, like in a water jacket or the heater core. Thoughts?
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1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.