Yes, another Pontiac 400 overheating question!
Yes, another Pontiac 400 overheating post. I know. Sorry. But, before i begin, a few facts:
I am old. I bought leaded gas.
Grew up in a Pontiac family (Star Chief- grandfather, Catalina wagon - dad, 68 GTO convert, brothers, and several Grand Prix's and Firebirds). Been a car guy pretty much since the beginning. i have managed to rebuild Porsche and Mercedes engines, so I am probably not a total handicap. That said...
So i am pretty sure i have addressed all of the known and possible gremlins...(water pump plate spacing, cast iron impeller, radiator, air flow, radiator fan, shroud spacing, timing cranked to max advance possible, thermostat working right, good top to bottom radiator temp delta T's, flow is excellent) and on and on. The only thing i can think of on this is that the vehicle might be running a bit lean, so i installed an AEM wide band sensor and ran the car across a broad range of conditions (freeway, hard acceleration, part throttle, up hills, over hill, over dale, you name it) and it's running at what appears to be excellent AFR's at all demand levels but perhaps just approaching 14.7 at cruise at highway speeds. One thing i have observed is that the car heats up amazingly fast. Like crazy fast. It can jump to 180 in just a minute or so. Might be exaggerating a but here but i will time it. The car will idle all day in the hottest weather at 180. Get it out on the highway and she gets hot. Question is, how lead does she need to be before she get hot because of a lean cruise mix? I am certainly not above 14.7 at cruise. Probably closer to 14.
Also, probably important to note that it's .40 over and the PO put a cam in it (i will check to see if it's possibly too rowdy when i yank it) but do these blocks start to run hot when they get bored out this far?
My car has a 73 400
4X heads with small valves
Stage 1 Quadrajet
HEI from mid 70's Yak but it was set curved by Majhor Murray in PDX (seem competent)
Pretty sure I am getting 32+ degrees of advance but it jumps around a lot
3:23 Rear end
Again, i am yanking the engine to address this mystery leak (car only has 2k on it since rebuild) but i can't deal with leaks. Any advice is welcome at this point. And no, i refuse to put a modern engine in it. Who would give up the sound of a 400 with a quadrajet for that ?