Quadrajet Carberator

[74 C-10 Shorty]

Yes, clean the tab off and you'll see numbers stamped on it.

[Steve341]

What number do I need to be on?

[Steve341]

The oil on the dipstick smells like gasoline

[Irish_Alley]

no no you look into the light. lol yes, but if its working right you will see a mark on the balancer. mark it with chalk will also help it stand out 0° will be on center. the smell is prob from blow by. i just change mine more often

[bd]

The oil on the dipstick smells like gasoline

Pull the oil dipstick and put one drop of oil on the pad of your finger.  Does the oil form a smooth-edged drop that holds its shape, or does it track quickly out along your fingerprint?  If the oil drop quickly wicks and tracks your fingerprint, the oil is saturated with fuel and needs to be replaced along with a new oil filter.  For the fuel to be that saturated, replace the mechanical fuel pump, as well, because it has a perforated diaphragm. 

Simple blowby will not cause that degree of oil saturation over a short period of time as long as the PCV system is functioning; neither will a flooding carburetor.

[Irish_Alley]

bd didnt know that maybe that could be one of my problems lol. but if the fuels not over flowing out the carb vents then how else would it make it to the engine?

[bd]

Irish, clarify your comm.

[Irish_Alley]

the diaphragm on the fuel pump hows that affect the oil?

[bd]

You're correct in that excessively rich fuel delivery can wash the cylinder walls so clean of oil that the rings won't seal and some of the fuel, as blowby, will collect in the crankcase.  But this scenario generally describes a "gradual" contamination of the oil over many hundred to a few thousand miles.  In this scenario exhaust often smells intolerably rich.  The problem exacerbates if the engine runs only short distances and is never allowed to warm up, so that fuel collecting in the oil doesn't vaporize and burn via the PCV system.  Excessive maintenance intervals will also exacerbate fuel accumulation in the oil over the service life of the oil.  But, I don't think that's the case here.  It seemed the OP was describing a situation that developed fairly quickly.

A common cause of fuel saturation of crankcase oil is a ruptured rubber diaphragm in the mechanical fuel pump.  The diaphragm is the primary barrier between liquid fuel in the pump and the crankcase.  If the diaphragm tears, fuel is pumped directly into the crankcase.  Contamination occurs fairly rapidly.  This is where I think the problem lies in this particular case.  It's not an unusual circumstance.

[Irish_Alley]

see thats where you lost me about the diaphragm tearing. i always thought if it torn you would get fuel since there was no vacuum being created. never really looked at fuel pump never had to change one, like i said this could be my problem then. mine is the same one i had when i first got my 86 and that was prob close to ten years ago

[bd]

LOL - The diaphragm essentially is a flexible 'piston' that's pushed in one direction by the pushrod off the cam eccentric, then pushed in the opposite direction by the pressure spring.  As it moves back-and-forth it flexes.  A small tear may not stop the pump from working, but when the diaphragm is in the right position, it can open and bleed some of the fuel into the oil.  If the tear is bad enough, fuel will also leak through the vent onto the ground.  The fuel pump also has an oil seal.  If the oil seal fails, engine oil will leak through the vent holes.  It's a cruel world!

[Irish_Alley]

lol and let me guess another sypthom of this would be fuel draining back from the fuel filter when the engine sits for a bit of time

[bd]

That's always possible, but I'm more inclined to think it drains when the needle valve opens in the carburetor and breaks the seal against the seat.  It's kind of like drawing soda into a straw and sealing the end with your tongue.  What happens when you pull your tongue from the straw?  The straw empties to the level in the cup.  Using a fuel filter with an integral check valve may well solve that symptom if it's a concern.

[Irish_Alley]

not really a concern just dont know what causes it. dont have no other visible fuel leaks. and from what i remember it did it before and after the carb rebuild

[Steve341]

So after reading these posts I think my pump is bad. I changed engine oil and filter on my truck late summer early fall of 2012. I barely drove it since because its a pig on fuel. I maybe put 5-600 miles on it. I didn't pull the dipstick and take a drop of oil. I did get a new pump it bolts right on fine and what not. I removed the inline fuel filter that someone had installed. In guessing the only filter from the factory is the fuel filter located just past the fuel inlet on the carb. According to my Haynes manual anyway. Long story short I ended up reinstalling the old mechanical pump as the inlets are on the opposite side on the new pump and my hoses would not reach. Also I fiddled with the line that goes straight up to the carb and for the life of me I could not get the threads to start into the pump. If I extend the rubber line and connect to the new fuel pump with the inlets on the opposite side the old pump will that work? Also can I reuse gaskets ? I put the gaskets from my new pump on to reuse my old one as I had to scrape away the previous gaskets. Also Haynes manual talks about some kind of spacer  meaning the pump a gasket a spacer a gasket then connect to engine. Can you tell me what that is about? I do not have the spacer.