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Hi all,

I have a 116GTV 2.0L that is running the same engine that I bought the car with in 2001 (unknown age and generally mistreated with supercharger add ons and irregular maintenance ). It's a seldom used hobby car that has probably done less than 40,000km in the last 14yrs and I have a question.

Compression test shows 185psi in #1 & 190psi in #4 and 200psi in #2 & #3. Oil in the cylinders brings #1 & #4 up to 190-192psi. I would consider the engine in pretty good health(I could be wrong and will accept guidance here) however the thing is a smoker(even for an alfa it's a bit embarrassing). I foul the plugs with lumpy build-up and it breathes very heavily. I am constantly chasing cam cover and oil cap sealing issues (valley and spark plug dents filled with oil) and my catch can outlet filter drips oil from the paper element.

My understanding of failing valve guide seals is excessive smoke after overrun situations which it doesn't seem to do. The only other conclusion for the smoke is the piston oil rings are failing.

The question..

Is it possible to show good compression tests while having poor piston oil rings?


As a side note, when the car was supercharged, crankcase pressure and oil contamination was a big issue indicating significant blow by and therefore poor ring sealing.. comp testing shows pretty decent numbers though and to be honest, the thing goes like a cut cat.

Please impart your wisdom
 

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Richard Jemison
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8,325 Posts
oil burning

Two significant clues, oil use and leaks caused from significant blow by indicates piston/liner clearance issues and ring sealing problems.
(regardless of CR at cranking speed)

On the running engine hold a piece of paper over the oil fill hole right on the surface of the cam cover. On engines with blowby the paper will be blown up away from the hole.
On engines properly sealed the paper will flap against the opening as the local air moved by #1 piston is pushed away and sucked back by the pistons up & down movement..

If as well oil spray comes out of the hole when running that indicates a blow by problem.

In such cases typically liner wear will preclude just changing rings.

To see if oil is comming down the valves look at the intake side of the valve while fully opened through the spark plug hole. If it`s nasty the that is a problem as well.

Check for leakage.
You don`t have to have a leak down tester.
Most compression testers have the gauge attached with a common air line type quick disconnect. There will be a "schrader valve"(same small spring loaded valve seal that screws into a tire valve)
Remove it and when the unit is screwed into a cyl and a air line from a compressor is attached, that pressure is blown into the cylinder.
You can tell by where the air escapes where the leak is. Either past the rings, or if CR is low in one cyl possibly out the intake or exhaust. If the air leak is past rings a ear around the oil openung will give you a idea of volumn passing the rings. light leaks are hardle audible. Significant leaks obvious.

I`ve found it best to do this with both cams off so you don`t have to worry with turning the engine to TDC with valves closed and clocking the car in gear to hold the engine in position.
As a matter of interest checking leaks with the cam off will typically take the piston to BDC. It`s there as often as TDC so leakage will be the same.
However if you check leakage with all four pistons at mid stroke, where wear is 2x that of either BDC or TDC you will find more accurately how much leakage is really happening in the motor, however keeping the engine locked it that position requires using 4th gear, the E-brake and serious chocks to keep it from turning .
 
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