Engine Runs Warm, Need Help with Cooling System

[dgheinen]

My 68 C10 was originally a straight six. One of the previous owners put in a 350 sbc from a 72 K10 (I checked the block code) and I believe he must have used the straight six frame mounting locations. The engine sits pretty close to the firewall, much tighter than my 78 Corvette does. Also, the front of the fan is about 3 inches away from the rad shroud. It usually runs about 190-195 degrees when driving down the road and has reached about 210 once or twice when sitting in traffic.

Last Friday it was really warm here in Seattle, and the temp rose to about 230 before I could pull over. I shut it off and waited for everything to cool to about 160 degrees and pulled the rad cap. The radiator was about half full. I checked the dip stick and it looked perfect, no frothy, milky substance in the oil at all. I topped it back off and drove the rest of the way home (about 15 mintues) and the temp was hovering around 190-200 the whole time without ever really coming down or going up from there. When I got home and let it sit, the radiator is lower by about 1/3 again. Somewhere, I'm losing coolant. When I popped the hood originally on the side of the freeway, there was some small pockets of coolant on top of the intake at the front next to the heater hose. I'm thinking I may have a couple of issues here.

1) Fan needs to be ~1/2 in the shroud. I think the best solution is to extend the shroud, rather than moving the drivetrain forward and needing a new driveshaft.

2) Thermostat may be a higher temp (not a 180) or may not be opening all the way, which may explain why the motor likes to hover around 190.

3) Coolant leak somewhere. I'm thinking not a head gasket as the oil looks very clean. Could it be an intake gasket? Or possibly a crack in the heater hose.

What do yall think is the best approach to figuring this problem out? Thanks in advance.

Damon