1275 Smoking Problem...

[Kurtis]

Here's an update on my smoking problem.

Recap - Blue smoke at idle and low speed. Disappears at higher throttle.

I ordered a leak down tester, which arrived today. I bought a cheapo unit from Harbor Freight, and leaned once again that you get what you pay for. The thing simply would not calibrate or give anything even remotely resembling consistent results. I'm sending it back tomorrow.

I did go ahead and pressurize each cylinder and listen for air leaks all the same. What I discovered was that all cylinders exhibit leakage through the rings. I assume some leakage would be normal, especially considering I performed all testing with the engine cold.

None of the cylinders exhibited leakage into the coolant (no sound at the radiator cap).

None of the cylinders exhibited leakage through the intake valves.

Cylinder 1 had significant leakage through the exhaust valve (listening at the tail pipe). All other cylinders exhibited no leakage through the exhaust valve.

I made sure each cylinder was at TDC with valves closed for each test.

Could this be my problem? I assume that for oil to actually get in there that it would have to be a problem with the valve guide and or seal, and not a burned valve. Is this correct?

 

[dklawson]

Since you found a leaky exhaust valve, I would consider that a red herring relative to the oil burning problem. It needs to be addressed, but it will not be the source of the blue smoke. On the other hand, tired rings will certainly allow for a lot of smoke.

I'm surprised that the HF leak-down tester wasn't any good. I know that a lot of their stuff is junk, but there isn't that much to a leak down tester. They are basically a pressure regulator with a 0.040" orifice in the discharge port and one or two pressure gauges. As for calibrating... how did they tell you to do that? Mine is homemade and all you have to do is set the regulator to deliver 100 PSI when the discharge port is plugged. After that, when you connect it to the spark plug hole, the pressure drop across the 0.040" orifice is "readable" as the percent leakage.

 

[Jim_Gruber]

Google Leak Down Tester and you will find info on making a homemade one with a compression gauge and a few fittings.

 

[nomad]

Before you tear down for the valve leak I would pull the valve cover, slide the rocker over and tap on the valve stem a few times. May just have carbon sticking in it. My .02.
KA.

 

[Hap Waldrop]

Here's the thing about a LD tester either you have the cylinder being tested at TDC compression stroke or the air pressure will rotate the engine, so either you get a reading or see 100% leakage if not on TDC compression stroke.

 

[bgbassplyr]

Before you tear down for the valve leak I would pull the valve cover, slide the rocker over and tap on the valve stem a few times. May just have carbon sticking in it. My .02.
KA.

And/or, with the engine running, squirt some water into the carbs (using a spray bottle). Rev the engine a little so that it won't choke on the h2o. A couple of applications of the water will usually blast the carbon deposits off of the valves and piston tops. There will be steam out of the tail pipe during this operation.

 

[athenssprite]

I am dealing with a similar issue. I'll give the water a try if it's a safe recommendation...

 

[Billm]

Fill a Coke bottle full and slowly pour it down the carb (one at a time) while trying to keep the revs around 3000 or so, takes a steady hand but works!
BillM