I purchased a 77 sr5 pickup for 300 bucks too commute to work. It needed a timing chain. While changing chain I milled head .005 to clean it up and ported exhaust to 1.5 removing smog tubes. I also lapped valves and reassembled motor. Didn't touch lower end as bore looked good and didn't want to put much money into it. Now that winter has hit I'm having some probs. When starting in morning it has too turn over a little while to start but always starts even when below zero. Here's the problem though, when turning over it builds pressure in coolant system enough where I get a geyser coming out of radiator cap and vent hole on lid of reservoir. This is from turning motor over with starter before it even fires up. once it starts it's fine. I'm not getting oil in coolant or coolant in oil. It runs great once started and not overheating. I've replaced all hoses, the thermostat, and the radiator cap. It's got me baffled.

Nickle Eye

 

Headgasket faliure or a blockage in the coolant system is my first guess, it shouldn't be coming out of the cap it would normally go into the overflow so it could be as simple as a bad rad cap or maybe you have it over filled, over "MAX" in the overflow tank.

 

yep .. you have blockage !

 

Yep Blockage. Same thing happened to my friends Ford Courier when he put the headgasket on upside down.

 

I'll try flushing the system this weekend. Pretty sure I didn't get the head gasket upside down as this just started lately. It was coming out of cap because I put old one on to relieve some pressure. With new one on it had actually blown a hose without even starting. Looks like I found a great resource for this old truck!

 

Well today was a beautiful day in the 40s and I tore into my truck. I flushed out the system and decided to check oil leak on valve cover while I was at it. I didn't notice much crud from flushing system but decided to retorque the head while cover was off. All the bolts were loose so I torqued all to 34 ft pounds and everything is cleared up back to normal. Must have been getting some blow by. Seems strange that no coolant or oil was getting blown through but it appears fixed now.l