Hi guys, I'm glad to have found this forum. On my very first post, unfortunately I'm needing some help. I have a 1969 Firebird with a 455 bored .030" over. It has probably 75 miles on the engine since the rebuild, where it received a new crank and forged rods and pistons. It has an Edelbrock 750 carb, Performer RPM intake, a mild cam (214/224 at .050 I believe), headers, 400 hood. I have a stock water pump, 4 core stock-type radiator, and 7-blade, 19" clutch fan. The car came with AC, which is not currently hooked up. It runs 190-210 all day around town, but as soon as you're on the highway for 10-15 minutes at cruising speed (65 mph), it creeps up to around 230F. When you shut it off, it hits 245. Start driving around again, it goes back to 230. I have several questions, concerns, issues, etc:
1) I have no idea what my compression ratio is. It's anywhere from 9.0 to 10.0 I think. I have 6X heads from a 350...could that be part of the problem (too much compression?) I only have available 87 octane in the town where I live, but I add a can of octane booster to every can. I found a compression ratio calculator online, (http://www.rbracing-rsr.com/compstaticcalc.html) but I'm not sure what the volume of the pistons should be (I have stock-type pistons with the dual valve reliefs)?
2) My overflow can/tank has a hole purposely put in the top by whomever I bought it from so they could put a bolt through to secure it down. Does this overflow tank need to be airtight? Would the radiator suck in a bunch of air if it wasn't, causing over heating?
3) Could the carb be a problem? I've recently heard that the Edelbrocks tend to overheat the fuel to the point of boiling. Anyone else use Edelbrock carbs? I should probably get a Holley.
4) Could the clutch fan not be working? How can I tell? I've been told to go with a direct-drive fan with no clutch. Any idea how much horsepower this might use? I'm think 10-15 hp maybe? I can afford that if it'll keep the engine cool.
5) The harmonic balancer may not be correct. I can't get it to line up with a timing light at all. The machine shop that did the rebuild told me they balanced the engine with the balancer on, so I'm not really too worried about it, I just can't use it to set the timing at all.
6) Could a vacuum leak cause this? It's very possible that I may have one or more leaks around the car. You can hear a hissing sound inside that sounds like it's coming from the heater controls.
It does seem to run fine, it just gets too hot! And it does ping when it gets hot, but not until then. I did find a leaky stopcock on the radiator, which I'm replacing tonight, and I'm also going to try Water Wetter with around a 25% mix of antifreeze/water (25% antifreeze/75% water). If this doesn't help, I may try a clutchless fan.
Thanks for reading all! Any suggestions please let me know! I am by no means a mechanic, I just love my car. I'll let you know if the Water Wetter helps.
