LM 318 with one oily plug

Before I start my weekend - perhaps one of you guys can help me with my 1984 Chrysler Marine LM 318 reverse rotation (1 2 7 5 6 3 4 8) timed to 5° BTDC and a gap of 0.035. It has a pertronix distributor and fairly hot pertronix coil, and an edelbrock 1409 carb. It was all working fine, just like it does on the port side (but reversed).


The last few times out, white smoke has been puffing out of this motor. More smoke with higher RPM. I don't think it's steam. Additionally, the motor can't maintain power above 2200 RPM - it bogs and dies. At the marina, at idle, I pulled a plug wire from each cylinder to watch for rpm drop / stumbles. Cylinder 4 had no affect on rpm, and when I removed and looked at it - it was fully coated in fresh, clean oil. Replaced with new plug and checked wires - all should be good. subsequent runs are all the same - smoke and inability to get above 2200 RPM.


I pray it's a valve seat, but fear it may be a cylinder ring. Thus the question(s).

• What are the odds it's a valve seat and an easy pull of the head(s) and rebuild will cure everything.
• Looks more like a ring problem - which requires an engine pull and rebuild.
• What are the odds that it's a tired old engine and just needs to be pulled and replaced with a 360.
• Anything else I'm missing? I think timing is good, and I think the carb is doing what it needs to - the same (reversed) configuration on the port side hits a WOT of 3900 RPM.

Thanks for looking - you guys have helped out in all my boating (mis)adventures.
Brooks

Ayuh,.... A compression test, 'n a leak-down tests should tell ya exactly where the problem is,.....

bondo said:

Ayuh,.... A compression test, 'n a leak-down tests should tell ya exactly where the problem is,.....

Click to expand...

I was hoping to get a decent excuse to re-power... but I'll do the compression and leak down test... thanks for the reminder!
Brooks

Borrow a borescope and take a look inside of the cylinder

Is it puffing out the valve cover breather. Might just be a head gasket pulling oil in from the valley.

The compression and leak down tests revealed cyls 1 and 3 had 45 PSI, and lots of flow into the carb. No other sounds, smells, bubbles, etc noticed.

Pulling the heads this week. The (relative) good news is that the other cylinders were all 140 to 160 PSI. Better than I would have thought for a 1984 motor.

Thanks again everyone!
Brooks