Hi Everyone,

A little back story. Last Fall I picked up my '77 F150. The good, when I bought it the PO had the papers from when he replaced the original 351 with a crate 400, and according to the odometer it had around 1500 miles on the new engine. The bad, it had sat for around 15 years with occasional startups to move it around the property. I did all the necessary work and then some; changed all rubber lines, all fluids, new fuel pump, thermostat, pcv valve, carb rebuild, cleaned both tanks out, rear disc brake swap. Once done it started right up and I took it for a drive around the block, then I parked it for the winter as it wasn't quite highway worthy yet. This spring I went out and trickle charged the battery and it fired right up as I did some work on the interior and added a tach. and some temp gauges.

The last thing I did was to add a coolant temp guage in the port on the passenger side of the water pump. Since I lost a bit of coolant and allowed air into the system I wanted to burp the system and replace coolant. Yesterday I went out and started the truck with the radiator cap off and proceeded to let it idle with the heater on. As it idled, there was a mess of small bubbles in the coolant (like soapy water) and then coolant started boiling out of the filler hole. Then white smoke started to appear around the driver side valve cover, so I shut it off. Once it shutdown there was a coolant geyser out of the filler hole, two fairly loud knocks and the temp guage was hovering around 190-200 degrees. There was never any white smoke out of the exhaust pipes (true duals), and I haven't drained the oil to see if there's coolant there yet. Just wanted to know if you all think this is definitely a head gasket or if there's potential that it's just a valve cover gasket or something else. I'm planning on draining the oil today and pulling the plugs to check for coolant.

This engine only has around 1500 miles on, is it possible that sitting so long could have caused enough damage that 15-20 starts and one cruise around the block would cause a head gasket to blow?

 

Howdy.

First off...are you sure you have the right thermostat? And its operation is verified? After settin' for 6 or so months it could be froze up. If you go to the parts store for a new one, tell those pencil necked geeks you have a 400 - not a 351M/400 cause what they'll hear is '351' and give you a Windsor T stat. Not good.

Second, and , again after settin' fer so long, I would drain the coolant and flush, flush, flush that puppy 'till the cows come home. Who knows what goober stuff has built up in there with tap water and anti freeze? Refill with 50% distilled water and 50% antifreeze.

Oil/filter change is a must after settin so long. Check the dipstick for "milkyness" in color....means water/coolant is in the oil. I understand this is on today's menu.....as well as the plug change. What do the plugs tell you?

Ok, with all that...there's more but I'll focus on yer basic querie - the white smoke around the valve cover could be just condensation heating up and burning off. The tiny bubbles in the radiator has me a bit concerned....could be a head gasket, could be the flow "burping" or the water pump cavitating....

Run her for a spell after the all the new stuff you're doing...and, as you already know, watch fer white (or any other color) in the exhaust.

I'd check the T stat though, fer sho....