I bought a gas cap from a local parts house from over the counter specifically for my 62. it was "vented" and fit very tight on my 62 flatbed which I installed at 7:30 am. The truck sat in the sun and at 1:30 I walked by the truck and smelled gas and observed gas dripping under the truck.

Short story is I investigated and found it was coming from the front oil seal on the crank and a little from the carb. The crank case was full of gasoline.

I opened the gas tank and it had a lot of pressure on it.

The sun had pressurized the tank, pushing gas through the fuel pump, flooded the carb, went into a cyclinder via an open intake valve, leaked past the rings into the crankcase.

I drained just under 3 1/2 gallons of oil and gas mixture from the crank case.

I checked the "Vented" cap I bought by blowing and sucking on the relief valve in it. It is a vacume release not a pressure release cap or the pressure relief part failed.

I removed the vacume relief valve from the cap and put it back on the truck. I checked the tank later and it was not pressurized.

I suggest you do the same before you find your crankcase or garage full of gasoline.

Dennis

In 40 years of owning old trucks, I have never seen this. Normally gas in the crank case is from a leaking fuel pump diaphram.

 

you'll need to replace your fuel pump. Gas in the crankcase means a potentially ruined pump diapham.

 

carras,

Normally yes but not this time. The gas was spilling through the carb into the intake. Very rare for the float valve to not take the pressure from the gas tank, that valve most likely needs replaced. I left the drain plug out overnight and no more gas came out, if the diaphram was busted the tank would have drained through that route as it is above the pump. I will keep an eye on it by checking the oil level every time I run it for a while.

Dennis

 

Dang, good info