Engine smoke?

L

larryfish

New member
When I start my truck it runs fine. Then, in about 5 minutes it starts to blow white/blue smoke from exhaust. Pretty bad. All of my plugs are covered in oil, oil is clear, compression test read 125 psi in all cylinders except one read 150. Engine is a 304. I did have some valve taping and read that if you added an extra quart of oil it would help, so I did add an extra quart of oil and a couple of days later the smoking started. Oil level now back to normal but still smoking? Head gasket? Valve guides? Any clue? Thanks.
 
White smoke tends to be steam. Blue smoke tends to be motor oil. Black smoke in conjunction with strong fuel odor and rough engine idle indicates an over Rich air to fuel ratio. Based on the description given, its pretty tough from my vantage point to isolate what's causing your billow. Being one quart of oil over the full Mark on the dipstick should have no ill effect on a healthy sv8. I've run both my engines above the full Mark for years with no issues. The five minutes of run time before you start seeing smoke would jive with heat possibly reacting to a casting crack or failed head gasket and allowing coolant to go where it shouldn't go. But again, steam from coolant burning isn't blue. When you did you compression test, did you have all the plugs removed and the throttle blocked open? That's the correct way. Not doing it that way will throw off your numbers.
 
If you have pcv hooked up like you should, you might want to make sure you are not sucking oil into the intake through it. More likely to happen after the oil thins a little when it gets warmed up. I just put an oil trap between the pcv valve and intake on mine, because I suspect thats where my expensive purple swepco oil is going.
 
The smoke looks white to me it does have a blueish tint to it though. When I put my hand by the exhaust my hand doesn't get wet as I think it would if it was steam. My comperession test was not done with all the plugs out and throttle open. I'll have to retest it. The pvc ill have to check also. Thanks for the input. Any suggestions help.
 
I don't think valve guides are the root cause. Most would only cause a slight smoke at idle under normal conditions and heavy smoke after deceleration..

The biggest symptom is the smoking after 5 minutes of running.

My suspicion is either a blockage of the head oil drain back holes
or as mentioned already, a passage of oil by the pcv plumbing.. The pcv valve is going to be connected to manifold vacuum via a hose. Disconnect the hose at the manifold and plug the manifold port.
Remove the valve from its grommet or threaded port at the valve cover.. Leave the grommet or port open.. Start the engine and see it the smoking starts back up after the 5 minutes.

If it does, remove the valve covers and inspect the drain back holes for crap. This is common on these IH engines from usage with the old oils and lack of proper oil change intervals. The buildup of oil under the valve covers will flood the valve train under oil. The oil has a clear shot to get by the guides then or
getting sucked by the pcv system plumbed to the valve cover..

If you can offer any history on the 304 that could help point us in a more accurate dirrection
 
You must log in or register to reply here.
Back
Top