Well first off I finally got it all the way up to temp and it exploded the heater core (which I should have expected) and now it has a new heater core. I had to take out the glove box to get it in and those clips suck asshole and I stabbed my finger but whatever. I finally got tired of trying to tune around a huge exhaust leak and found… a real weird one.
I had snugged down everything as best I could and still had what sounded like a massive exhaust leak on the drivers side. The passenger side sounded fine and looked like it was nice and sealed. No amount of evening out the manifold flange bolts would seal it up, in fact the leak sounded just as big as ever. I finally pulled the driver side manifold to investigate and found one “soft” feeling exhaust bolt on that side and a nasty exhaust leak. The last exhaust bolt in the back had pulled out about 1/4″ of threads. I replaced the bolt (and the frontmost bolt which was also too short and not engaging enough threads) with an LA style short stud which was able to get plenty of thread further down in the hole. Everything looked fine, and I was taking the manifold in to clean it up when I noticed it has SHATTERED. The source of my exhaust leak was now obvious.
I have no idea what could have caused the breakage other than a somewhat angular block lug about halfway between the exhaust port and the starter. It’s possible that was hitting the manifold in some way and tightening down the exhaust bolts levered it until it shattered (I didn’t see any contact when I put them in or took them out but who knows) or maybe I just dropped them and it cracked and the thermal stress broke em’ but they are fuckin’ trashed. I busted out Mr Visa again and bought some cheapo headers and a dual exhaust kit, hopefully they will show up sooner rather than later. Hopefully she sounds like a muscley grumble car and not like a sharting two stroke.
I definitely want this bitch to stop givin’ me hassle.
Update: I have found the origin of the crack and I now believe this to be an incompatibility between the late Magnum block and the 73 smog manifolds. The kink in toward the block before the manifold hits the Y pipe interferes with a square lug on the back of the block. Some dressing with a grinder would probably fix it, and it might not happen with any headers other than the late smoggers, but it sucks balls and I broke my manifolds. Oh well, I have headers and duallies coming UPS, I didn’t want to do that this year but fuck it whatever.