Head Rebuild info please. Oil consumption...

[Mattiee7]

Hi Guys,

I have a oil consumption issue and smoke.(Basically connected)

I have smoke on startup, on overun and when I rev it hard at high RPM's.

Compression is good so first port of call is head rebuild.

My old girl has only covered 10,000miles since 1985 so I am hoping and praying the rings are ok.

Any experiences and advice please....

Regards
Matt

 

[rsporsche]

do you get smoke when you are driving down the freeway and let off to slow down at an exit ramp? if so, that is typically valve guides. sometimes smoke, when you hit it hard, is just carbon from air / fuel mixture ... sometimes its from bad rings, etc. ... but one is gray and the other is blue. what color are you spark plugs?

 

[lloyd]

Hi Guys,

I have a oil consumption issue and smoke.(Basically connected)

I have smoke on startup, on overun and when I rev it hard at high RPM's.

Compression is good so first port of call is head rebuild.

My old girl has only covered 10,000miles since 1985 so I am hoping and praying the rings are ok.

Any experiences and advice please....

Regards
Matt

Before pulling a cylinder head - a few preliminary considerations.

Details regarding engine condition might prove helpful for shade tree diagnosticians. You mention 10,000 miles traveled, but is this after a rebuild, a rehone, valve job, oil change or just plain low miles since 1985? How many miles on the lower end? You never described the color and/or severity of the exhaust smoke, nor your compression readings. Obviously different compression gauges can produce different readings for the same engine. But if the compression is acceptable, e.g., ≥140 lb/in2 for all cylinders, your rings are likely in good shape. That also includes the oil rings. How certain are you that the engine is burning oil rather than too much fuel? Have you examined the spark plugs?

What kind of blow-by is your engine producing? If you remove the oil filler cap with the engine running, how significant is the positive pressure? Too much can be a problem if you are using the stock crankcase ventilation system. Rerouting the valve cover vent to a catch can might minimize some of the smoke and could be easier/less costly than pulling the head and performing a typical valve job.

Even assuming you are burning oil that is being drawn past valve seals and/or guides, the issue may still be mitigable. You did not describe the type oil you are currently using, including viscosity and oil change intervals. If, for example, your engine has significant mileage (and wear) your engine oil may be too thin. Similarly, oil that is used too long or in a poorly tuned engine may become contaminated and thin enough to pass through guides, seals or worn valve stems. A fresh oil change to a slightly heavier viscosity might work wonders.

Naturally, if you have significantly worn valve stems, valve guides and/or seals, the general fix is to R&R.

HTH

 

[teahead]

Leak down test too

 

[Mattiee7]

Before pulling a cylinder head - a few preliminary considerations.

Details regarding engine condition might prove helpful for shade tree diagnosticians. You mention 10,000 miles traveled, but is this after a rebuild, a rehone, valve job, oil change or just plain low miles since 1985? How many miles on the lower end? You never described the color and/or severity of the exhaust smoke, nor your compression readings. Obviously different compression gauges can produce different readings for the same engine. But if the compression is acceptable, e.g., ≥140 lb/in2 for all cylinders, your rings are likely in good shape. That also includes the oil rings. How certain are you that the engine is burning oil rather than too much fuel? Have you examined the spark plugs?

What kind of blow-by is your engine producing? If you remove the oil filler cap with the engine running, how significant is the positive pressure? Too much can be a problem if you are using the stock crankcase ventilation system. Rerouting the valve cover vent to a catch can might minimize some of the smoke and could be easier/less costly than pulling the head and performing a typical valve job.

Even assuming you are burning oil that is being drawn past valve seals and/or guides, the issue may still be mitigable. You did not describe the type oil you are currently using, including viscosity and oil change intervals. If, for example, your engine has significant mileage (and wear) your engine oil may be too thin. Similarly, oil that is used too long or in a poorly tuned engine may become contaminated and thin enough to pass through guides, seals or worn valve stems. A fresh oil change to a slightly heavier viscosity might work wonders.

Naturally, if you have significantly worn valve stems, valve guides and/or seals, the general fix is to R&R.

HTH

The Car has all the MOT's from 1979 so it has 86,000miles genuine.

The pressure form the filler cap is normal not splashing your face.

Oil is as recommended 20/50

Compression was tested by garage as good. Dont have the exact figures.

The car also made 148bhp on a rolling road at the wheels. (would indicate good Rings ??)

Many thanks for everybodys help.

 

[lloyd]

The Car has all the MOT's from 1979 so it has 86,000miles genuine.

The pressure form the filler cap is normal not splashing your face.

Oil is as recommended 20/50

Compression was tested by garage as good. Dont have the exact figures.

The car also made 148bhp on a rolling road at the wheels. (would indicate good Rings ??)

Many thanks for everybodys help.

An M30 engine's lower end is ordinarily quite stout, and unless your example is an exception to the norm, you probably have rings capable of many 1000s more miles. That said, any engine can suffer from neglect or abuse, but yours does not seem to fit that bill, especially given your dynamometer results. Since you mentioned MOT, is the "puffery" enough to prevent certification, or something that only a discerning critic (or tailgater) might find objectionable? I have had fairly good experiences with low oil consumption and M30 engines - I have owned/maintained. To be sure, I have worked on a few M30 engines that were not in the best condition, but these were engines with questionable-undocumented histories, including maintenance. Higher-than-normal oil consumption seems more prevalent with similar M10 engines, although I have no empirical data to support this conclusion. And in those very few instances, changing oil, even to a different brand, could make a marked difference in "visible" oil consumption.

The problem with this potential recommendation is that oil formulations and classifications change over time and those changes are hard to track. So what may have proven true ten+ years ago may not be valid today. But in the same vein, an off-the-shelf oil additive, might provide some marginal benefit worth trying. If for example, your problem was dried up valve stem seals, some of these products, including so-called "high mileage" oils, might prove beneficial by causing the seals to soften and swell. Mind you, I have no personal experience with these products, but I rather doubt they would do any harm, other than to nick your wallet. Nevertheless, if it buys some noticeable smoke reduction, it may be worth a try. Again, not knowing the extent of your problem, this may be one of the few times that an oil additive or high mileage-oil may be a fair idea.

Since it takes only a little oil to create a lot of smoke, I suppose it is possible that some of your oil burning problem is related to a stuck oil ring. However, this explanation is attenuated since moderate driving and a change of oil should easily free things up. As mentioned before, excessive blowby directed into the intake could be a problem with smoke production yet your response indicates that is a non-issue.


???

Another alternative?

Or this

"Mobil 1 High Mileage oils are designed to help extend engine life in high mileage engines. These advanced full synthetic motor oils feature:

• A proprietary blend of high-performance synthetic base oils that deliver up to 500,000 miles of proven protection
• Higher base oil viscosity to help reduce leaks and provide better high-temperature protection†
• A boosted level of seal conditioner to protect engine seals because, over time, rubber seals can harden or shrink, resulting in oil leaks

If your engine contains excessive sludge deposits due to less-than-adequate maintenance practices, Mobil 1 High Mileage synthetic motor oil can help reduce this sludge. For severe cases of engine sludge, short oil change intervals (3,000-5,000 miles) are recommended for the first two or three oil changes as the sludge reduction takes place. (In cases of engine damage that may have resulted from poor maintenance, even Mobil 1™ motor oil cannot remedy years of neglect.)

Still have additional questions, such as, "Should I use high mileage oil?" or, "Is high mileage oil worth it?" Visit "The 500,000-Mile Challenge" to learn more about the benefits of high mileage oils."

 

[Mattiee7]

Quick update.
Head off and being rebuilt. Cylinders in good shape. Head very coked up.

Should be a good result.

 

[rsporsche]

hope you are soon on your way back to driving and enjoying the coupe. keep us posted

 

[Mattiee7]

Rebuilt head back on new stem seals and fully rebuilt and cleaned skimmed etc. Still a bit smokey changed oil and the filter is in this state. Would this explain some extra smoke crank pressure?

Regards Matt

 

[aearch]

CRANK SMOKE IS THE RINGS

 

[gazzol]

Rebuilt head back on new stem seals and fully rebuilt and cleaned skimmed etc. Still a bit smokey changed oil and the filter is in this state. Would this explain some extra smoke crank pressure?

Regards Matt

That was a blocked oil filter nothing to do with crank case pressure, the suction from the pump collapsed it! You really need to change your oil more often. Oil (once used) breaks down over time irrespective of the mileage. Due to contamination from combustion the oil ends up with acidic compounds in it which break it down and ruin it. |For what it costs I would change the oil every year. Also to stop the valve stem oil seals from going hard due to lack of use I would put a seal conditioner in the new oil.

Regards

Gary

 

[Mattiee7]

I've paid for an oil change less than 1k ago. Whether it was done who knows?

The engine has done less than 10k since 1986.

I need to drive it some distance let everything free up. Compression all checks out.

 

[lloyd]

I've paid for an oil change less than 1k ago. Whether it was done who knows?

The engine has done less than 10k since 1986.

I need to drive it some distance let everything free up. Compression all checks out.

Did you ever confirm exactly what needed to be replaced on the cylinder head - that would have caused the smoke? Or was it merely presumed that your engine had worn valve guides, valve stems and/or valve seals? Any of those things could contribute to a smokey tail pipe, but so could many other things, including an engine that is severely out of tune, the wrong oil, too much oil - or bottom end issues. Of course a valve job is never a bad thing, if the engine could benefit from it.

The idea of driving to "let everything free up" probably has more application to an engine with recently machined surfaces, including freshly honed cylinders, new rings and new bearings. I'm guessing - and this is just a guess with little factual information - that your engine has already been run for 1-2 hours, including idling, since you first noticed the smoke. This should have (probably) been ample time to free things - unless you are using extra-slippery oil or only running the engine in 5 minute increments and not under load. If you have a new camshaft or rockers or rocker shafts, then all of those things should have time to bed in, but it is unlikely they have any connection with tail pipe-oil consumption. BTW, if the camshaft or rockers were changed or even if the latter were moved to another location, you should consider using an oil designed for flat tappets i.e., an oil with a higher-than-normal zinc concentration.

With the head removed, it would have been an appropriate time to examine the cylinder walls and test each piston's ring set for any obvious problems. Glazed cylinder walls or gouging would speak for themselves. Cylinder wall taper or loose fitting pistons may not be that obvious.

Black oil, as represented by your filter photo, could indicate excessive contamination due to poor combustion or poor maintenance. Black oil could also be normal if using a molybdenum or graphite additive. If it wasn't the latter, perhaps an increase in routine maintenance was in order. If an oil change or two doesn't make much of a difference in oil color, I would consider removing the oil sump and examining it and the pump pickup for solids, aka sludge. If the sump has significant sludge buildup, left unremoved, it will quickly contaminate any fresh oil, requiring much more frequent changes than normal. There are many products advertised as engine flushes that typically contain light viscosity oil and serious solvents and detergents. These might be worth a try as an alternative to cleaning out the sump, but I have my doubts.

 

[Mattiee7]

Did you ever confirm exactly what needed to be replaced on the cylinder head - that would have caused the smoke? Or was it merely presumed that your engine had worn valve guides, valve stems and/or valve seals? Any of those things could contribute to a smokey tail pipe, but so could many other things, including an engine that is severely out of tune, the wrong oil, too much oil - or bottom end issues. Of course a valve job is never a bad thing, if the engine could benefit from it.

The idea of driving to "let everything free up" probably has more application to an engine with recently machined surfaces, including freshly honed cylinders, new rings and new bearings. I'm guessing - and this is just a guess with little factual information - that your engine has already been run for 1-2 hours, including idling, since you first noticed the smoke. This should have (probably) been ample time to free things - unless you are using extra-slippery oil or only running the engine in 5 minute increments and not under load. If you have a new camshaft or rockers or rocker shafts, then all of those things should have time to bed in, but it is unlikely they have any connection with tail pipe-oil consumption. BTW, if the camshaft or rockers were changed or even if the latter were moved to another location, you should consider using an oil designed for flat tappets i.e., an oil with a higher-than-normal zinc concentration.

With the head removed, it would have been an appropriate time to examine the cylinder walls and test each piston's ring set for any obvious problems. Glazed cylinder walls or gouging would speak for themselves. Cylinder wall taper or loose fitting pistons may not be that obvious.

Black oil, as represented by your filter photo, could indicate excessive contamination due to poor combustion or poor maintenance. Black oil could also be normal if using a molybdenum or graphite additive. If it wasn't the latter, perhaps an increase in routine maintenance was in order. If an oil change or two doesn't make much of a difference in oil color, I would consider removing the oil sump and examining it and the pump pickup for solids, aka sludge. If the sump has significant sludge buildup, left unremoved, it will quickly contaminate any fresh oil, requiring much more frequent changes than normal. There are many products advertised as engine flushes that typically contain light viscosity oil and serious solvents and detergents. These might be worth a try as an alternative to cleaning out the sump, but I have my doubts.

Thanks for your comments.

I have driven it about 200miles and its cleared a good bit.

I have 20/50 classic oil and new filter...

 

[Mattiee7]

Out and about

 

[lloyd]

Very very pretty.