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lexx077

32/36 weber on an l20b running rich with white smoke...

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My son and I have a 73' 620 that i picked up for $400, which had been sitting for roughly 4 yrs. The motor was swapped for an l20b with a dogleg 5 speed and may have lead to the reason for it getting parked. The engine appears to have been cleaned up and possibly gone thru ( I can see some red gasket sealer on some parts). We installed a brand new Weber 32/36 dgev, and had the timing set. We drove it for about 40 miles and it smoked the whole way ( all-be it not excessive unless accelerating and smelling more rich as well). Despite the the rule that black smoke is rich, blue smoke is oil, and white smoke is coolant, this pukes white smoke!? not sweet like antifreeze or like burnt oil ( i have had those experiences when I was young with my own 510's and 620's). Here's what i know:

engine idles and runs strong,

*has decent compression, 1-140, 2-130, 3-125, 4-135...( there is a variance in the compression results that suggest an issue in # 2-3 cylinders, but that wouldn't lead to the overly rich smell)

*original plugs where black and wet smelled like fuel

*new plugs are wet and somewhat black( although they have approx 1 hr on them in the garage not driven, but throttle cycled for tuning)

*I removed the carb and adapter plates then resealed them with * cough* gasket sealer... o.0 to try and see if that was the issue

*Spraying starter fluid around the base and under the intake makes the engine stumble ( like it has a vacuum leak, double checked all bolts and gaskets. everything is tight)

*There are no bubbles in the radiator, or coolant level changes,( although engine seems to warm up very quickly... thermos stat, or lean condition? contradictory)

*there is no water in the oil or a reduction in the oil level ( again the smoke has no burnt oil smell)

*I was beginning to think that it may be a PCV valve issue, but it doesn't appear to be ( i removed the crank case hose and plugged the PCV still has same issue)

I am trying to trouble shoot as mucha s possible before i resort to removing the intake and head... any suggestions?

 

Here's a video of the issue:

 

 

 

 

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I'll guess a bad intake manifold gasket. That can cause both a vacuum leak (which seems to show up when you spray starting fluid below the manifold), and coolant being sucked into the intake ports and on into the cylinders. Does this intake manifold have coolant hoses hooked to it? Even if it doesn't, some heads have coolant holes for use with manifolds that run coolant. I would imagine coolant could be sucked out through these holes if the intake gasket is bad even if the manifold itself is a dry one.

 

It seems like you should see a drop in coolant level, but I don't know how much or little coolant it takes to result in lots of smoke.

 

I have seen Weber adapters crack from being over tightened which can cause a vacuum leak, but it doesn't look on your vid like you have a leak at the carb base.

 

Len

 

 

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Looks like blue oil smoke to me.

 

*has decent compression, 1-140, 2-130, 3-125, 4-135...( there is a variance in the compression results that suggest an issue in # 2-3 cylinders, but that wouldn't lead to the overly rich smell)

 

OK compression I would call decent 150 and above

 

*original plugs where black and wet smelled like fuel

*new plugs are wet and somewhat black( although they have approx 1 hr on them in the garage not driven, but throttle cycled for tuning)

 

Vacuum leak or water wouldn't cause blackness. Could be fuel but likely oil.

 

*I removed the carb and adapter plates then resealed them with * cough* gasket sealer... o.0 to try and see if that was the issue

*Spraying starter fluid around the base and under the intake makes the engine stumble ( like it has a vacuum leak, double checked all bolts and gaskets. everything is tight)

 

Can't explain he stumble unless there is a small vacuum leak AND burning oil.

 

*There are no bubbles in the radiator, or coolant level changes,( although engine seems to warm up very quickly... thermos stat, or lean condition? contradictory)

*there is no water in the oil or a reduction in the oil level ( again the smoke has no burnt oil smell)

 

No water loss then not steam we're seeing. Doesn't take much oil to make a lot of smoke. At one drop of oil per cylinder per firing stroke, a 4 cylinder will go less than 4 miles on a US quart.

 

 

 

Every time I look at this I see blue smoke.

 

 

 



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I had to take lexx077's word for it on the color of the smoke being white. I have a pretty mediocre eye for color. Looking at the vid again, pretty much everything looks blueish to me, except the 620 (it is yellow isn't it?) and there is something red parked in the driveway. :D Come to think of it, I don't know why I think I hear the engine note change when starting fluid is spray below the manifold. My hearing is about as bad as my vision.

 

It does occur to me that by the time you drain the coolant and remove the manifolds, you are well on the way to having the head off. If this is an unknown engine, replacing the head gasket would give you peace of mind. But with the head off, it is the logical time to do rings and bearings. I guess you will need to decide how much time and money you want to put into it.

 

Len

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