Strange 620 issues today

[reelmagic]

So its a been about 2 months since I ran the 620 (its a 77 with l20b).  Today I had lots of issues and I can't exactly pinpoint what it could be.  First it was VERY difficult to get started.  Finally got it to start, it ran very rough and smoked out the exhaust pipe and in the engine compartment.  I noticed the header was wet with what looked like oil.  There was no leak from the carb that I could find.  But if I touched under the intake manifold I could wipe some oil.  Anyway got distracted for about a half hour and then came back, truck started in one try and ran perfect - no smoke, no wetness on header nothing.  A friend was with me so I had him run the truck up and down the road to see how it ran, as I helped my brother with his boat.  After about 20 minutes, he came back with the 620 and I noticed something dripping from the truck.  I opened the hood and the truck had spewed what appears to be oil all over the left side of the engine compartment. The exact opposite side than I was having issues with earlier!!  I could not find where this came from.  It again was hard to start but we got it running again and still no leak to be found?  To makes things more interesting I took the fuel cap off at that time and sucked a bunch of air into the tank like a vacuum.  As another bit of information the truck was having a very tough time running with the air cleaner in place and ran MUCH better with it off (it is a webber not the original hitachi).  Any ideas as to what is causing all of these issues?  Im thinking its all tied together but Im just not really sure.  Thanks.

[datzenmike]

OK first the right side is if you are sitting in the vehicle not standing in the front or to one side. Right side is the spark plug side. Left side is the manifolds or driver's side.

 

 

So header was wet with oil and as it warmed up, it smoked as it was burned off. This explains the smoke. How the oil got there can be several things.

 

Valve cover gasket is leaking and running down all over the header.*

The valve cover vent hose is dripping oil. You have a weber so it should be connected to the air filter. 

The block vent pipe or the hose from it to the PCV valve is off or missing and oil spewing out onto the header.

 

*most likely

 

  I opened the hood and the truck had spewed what appears to be oil all over the left side of the engine compartment. The exact opposite side than I was having issues with earlier!! .

 

As the earlier oil problem was on the header side and this is the opposite or RIGHT side this can be also the...

 

Valve cover loose or it's gasket leaking.*

Oil pressure sender loose or leaking

Dip stick loose or missing

Oil filter loose or leaking.

 

* most likely

[ddrum]

My 620 used to get full of oil  all over the passenger side engine bay, and after many headaches and degreaser cans later. I found out that my mechanical fuel pump was seeping oil through one of the holes that it has (towards the firewall side). Turns out that as it was seeping oil, the direction of the radiator fan would blow and disperse the oil all over the passenger side of the engine bay.

[distributorguy]

I'd guess your engine venting is plugged, so its trying to vent anywhere it can, and oil is blowing out at the same time.  A plugged charcoal canister (plugged engine venting) will also not allow the gas tank to be properly vented, which explains your fuel tank vacuum.  There are 2 vent lines on your tank and both are plugged?  Not good.  The engine won't run well with the tank pulling a vacuum, as its starving the engine of fuel.  You're also making the fuel pump work harder, causing the oil leak issue listed above?

[datzenmike]

Yes, good point about the fuel pump. The stock one has a plastic spacer between it and the head and needs two gaskets. They tend to seep oil from the hinge pin... sometimes. After market pumps? are usually crap.

 

 

Have you or was the truck de-smogged? This is a common an ill advised thing to do as it often introduces problems because people do not understand how the emission systems work.

 

Last... is the oil over filled? Happens if a wrong dip stick is used from another engine.

[banzai510(hainz)]

left side would be like PCV valve. Seen dumbasses block the crank vent tube when they dont run a hose to the lower intake PCV valve.

 

I heard of oil filter gaskets double stacked. which blows out.. Oil sender switch or oil line cracked

 

Hot water line loose above intake causing drips and smoke.