Engine Diagnosis - Burning Oil

Commodore_254

I need some advice... My engine is burning about a quart of oil in about 200 miles. I used Valvoline 30wt oil. The oil consumption is not always visually noticeable in the exhaust pipe but friends following me at times can smell burnt oil. I have been told by an attentive follower that when I stop accelerating (shifting) there is a wisp of smoke. The only noticeable smoke I see is when I back it out of the driveway and accelerate down the road for the first time and a little belch of smoke occurs.

Last fall I replaced a blown head gasket because of a stuck exhaust dampner and then decided to clean and lap all 16 valves for good measure. After I lapped the valves I reset the valve backlash as follows:

Intake Valve Gap (cold) 0.011"
Exhaust Valve Gap (cold) 0.013"

I did notice with the head gasket off there is some scoring in the cylinder walls from a previous engine rebuild without deburring the ring grooves? I know at some point a rebuild will be required but prior to the blown head gasket oil consumption was not an issue.

The other day I did a compression check and the results dry are as follows: 80, 100, 95, 80, 50, 115, 65, and 110. Being low I rechecked compression in number 5 (50) and 7 (65) again with about a cap of oil. Wet cylinder 5 and 7 compression increased 5 psi 55 and 70 respectively.

Anyone have any ideas?

Ol racer

FYI
Ideally compression should be close to identical in all cyl's so eventually as you mentioned it will need a rebuild.. In the meantime if your in warm climate you could try 40wt oil. Additionally, Some people buy time by using a qt of Lucas Oil Stabilizer or a pint of'High Milage' STP. If use an additive suggest pour in with engine idling then take a drive to mix with the oil.

KTRON

When you lapped the valves, did you take note if you had full valve to seat contact around the circumference of the valve head? You shouldn't have more than a 10% difference in compression between cylinders. Forty to fifty psi of difference is more likely caused by a chipped valve or eroded seat than a scorn cylinder. 

Chris

53jetman

If that is a Hudson Eight, I certainly would not recommend using a SAE 40 wt motor oil.  That engine is internally lubricated by the dippers on the connecting rods, so the thinner oil would give better internal lubrication.

Uncle Josh

Use 10W40 for splashers.  Thin when it needs to be and thick when it has to be.  See Geoff's article in the last WTN.  Works for me.

Your problem is not with the valves.  There is oil getting up past the rings, probably on the ones with low compression.

It's worth a can of 'Sea Foam' which will free the rings if anything will.  I saw it start a 54 that we couldn't get any life out of. 

Howsomeever, if that ridge is keeping the rings from seating, you know what you have to do.

Per

     My understanding is that the cap full of oil will cause a large increase in compression reading if the problem is with the rings, but little or no change if the leakage is past the valves.  This makes me agree with KYTRON, since your readings didn't change much.

     Before the blown head gasket, did the engine idle on all its cylinders?

     Do all your spark plugs look about the same, or are some cleaner than others?

     For oil, I agree with Uncle Josh.  Recently I was told that using 15W-40 is a good idea.  Apparently it has additives that are not good for catalytic converters, but are good for old engines.   It is marketed as being made for diesel trucks.  I have started to use it.  

     In the old days, I was happy to get 100 miles per quart, and often got only 50.  My first ring job was on a car that got 30 miles per quart.

                                  Per

Commodore_254

Thanks for all the advice. I live in the Midwest so I prefer using 30 wt oil. I have added oil additives such as STP without improvement.

When the valves were lapped cylinder 7 exhaust was not making full seat. I would estimate about 75% contact. I didn't know how to resolve it so it just went back together.

Prior to the head gasket the car ran great, the month prior I went on a 600 mile road trip without issue.

This winter I plan on pulling the engine, boring the cylinders, new rings and Pistons, valve job, etc.

Any advice on rings? Are custom Pistons my long option?

Thanks everyone for your input.

Uncle Josh

If you're gonna bore it you'll need new pistons anyway.  Might as well get both pistons and rings from Dale Cooper.