Carbon deposits in my engine oil?

[z3skybolt]

Always something,

I just changed the oil in my 1940 Cadillac 346 engine.  Other than the initial breakin oil changes this is the fourth oil change since the engine received a complete and very expensive overhaul.  When overhauled it was bored 40 over and had new ROSS forged pistons, wrist pins, HASTING rings, lifters, stainless valves, valve guides, bearings, timing gear, chain, NOS distributor drive gear, two new rods, rebuilt oil pump, etc.  It was "hot tanked" thoroughly cleaned, magnifluxed, sonic tested for cyl. wall thickness. Everything except the cam and crank, which only had 4,000 miles on them and were in perfect condition was replaced.

I drive the car frequently, 20 to 50 mile trips including a couple of 120 mile trips.  Typically I cruise around 45/ 50 mph. Once in a while I kick it up to 60/65 mph for a couple of miles.  The engine starts easily, runs smoothly,powerfully and nearly silently. I have driven the overhauled engine a bit over 4,200 miles within the past year and change the oil every 1,000 miles. My engine does not have an oil filter. I am using highly recommended Valvoline VR-1 10W30, high zinc racing oil.  During previous oil changes I didn't inspect the old oil  carefully but didn't notice anything unusual.

After reading of another forum member's discovery of "junk" in his oil.... I carefully inspected my old oil upon changing it today.  Much to my surprise I found numerous tiny deposits of carbon in the bottom of the pan into which I drained the oil. They were very small specks, like tiny grains of sand and crumbled easily between my fingers.  However there was one chunk the size of the tip of my little finger. It also crunched up easily when pinched between my fingers.  There were no particles of metal whatsoever.

So...is this to be expected?  Or does it indicate an issue of concern?  The engine "uses" about one quart every 800 miles.  Not perfect but perhaps not unusual given the 79 year old engine technology. I don't know.  However there is one minor issue.  The number 2 spark plug shows signs of oil or carbon build up on it . It isn't significant enough to foul the plug and I clean and then rotate it among the other cylinders.  The other seven plugs burn cleanly.  I suspect that the #2 piston rings are allowing a bit of oil to bypass and causing the buildup. It should not happen with a "quality" rebuild but the fact remains. If it doesn't worsen over time I can live with it.

My questions are....Why would I see the carbon in my oil? Except for the one larger chunk would this be normal? Would a different oil perhaps behave differently?  Could the possible oil bypass in the number 2 cyl. contribute to the carbon build up in my oil?

I use a  Hi Tier, non ethanol, 91 oct, unleaded fuel in the car.  It is the only non-ethanol fuel legal in Missouri. Could the gasoline add to my carbon issue.

I am open to all opinions and expert advice from those of you who have experience with this engine and may be aware of such issues.  Perhaps this is not uncommon.  I can only hope so.

Thanks in advance.

Bob

[Bobby B]

Bob,
  As an Experienced Pilot, I'm sure you're familiar with the word "Coking".....Coke is the solid residue created when oil undergoes severe oxidative and thermal breakdown at extreme engine temperatures. The higher the temperature, the harder, blacker and more brittle the coke/deposit residue. Coking performance of oils varies based on formulation and the engine environmental conditions. Hot Running, Low idle, Lean Burning engines will experience this, plus add the Flathead bonus factor of NO oil filter  , and there's a good chance coking might occur. I know you probably have over 500 miles on that baby now, so maybe try switching to a synthetic oil with a High Zinc content, OR a different brand like Brad Penn, Joe Gibbs, etc. I run the Valvoline VR-1 in all my old cars with no problems, but they all have oil filters, and aren't hot running lean burn engines. I have 0 miles on my own Flathead yet, so I can't say from experience. As far as the spark plug issue, do a quick compression check NOW. Call me if you want......
            Bobby

[z3skybolt]

Thanks Bobby,

I understood the chemistry....basically.  Just didn't know it this was to be expected with a non-filtered flathead and/or the oil I am using. Would not have expected it with only1,000 miles on the oil.  I will consider adding a filter to keep the crap out of circulation.  Had also given thought to using Amzoil synthetic,  They make an oil with high zinc content.

Will run his oil change a few hundred miles, drain it, see what it looks like and then make a change. Unless you think I should not continue at all with the Valvoline.  Will get a compression check on the #2 cyl.

To further demonstrate my lack of knowledge....are you saying that the flatheads are by nature hot running, lean burning engines?  My engine runs cool as far as the water temp is concerned. Thanks as always for you expert thoughts.

Bob

[V63]

My understanding:

The reason synthetic oil stays so clean and translucent is that it does not ‘burn’ at temperatures experienced in a typical internal combustion engine. The burning (conversion to carbon by heat) of the lubricant is what causes the oil (and parts) to turn black as it loads with abrasive carbon. The down side of synthetics is the sealing technology (in old cars) keeping it from seeping and/or leaking.

[Bobby B]

Bob,
It's not easy to put a full flow remote filter on a Flathead. It's been done, but it's a little bit of a project. The filtering canisters that you see mounted on the block/ heads, etc., really only offer partial filtering because of the physical take off on the block, the way the oil is piped to the top end, and the way the internal oil passageways in the block are cast. There are some really good posts on this subject on the forum and on the net if you search it. I have a set-up here, but I never bothered to install it because I figured that frequent oil changes would take care of it. Since your engine has been rebuilt with new seals and all, I think you could give a synthetic oil a shot and see what happens. Oils based from crude will Coke under the right circumstances. Keep us posted.......
                                                             Bobby

[z3skybolt]

Bobby,

Sounds logical.  You often illuminate that which are dim "thoughts" within my own mind, including the engineering associated with adding a filter to a flathead.  I fell asleep last night trying to imagine how a filter would be fitted to my engine.

I ordered a case of AMZOIL Z-ROD 10W30 before turning in last night. We will see how that goes.

As always...thank you.

Bob

[Cape Cod Fleetwood]

Bobby,

Sounds logical.  You often illuminate that which are dim "thoughts" within my own mind, including the engineering associated with adding a filter to a flathead.  I fell asleep last night trying to imagine how a filter would be fitted to my engine.

I ordered a case of AMZOIL Z-ROD 10W30 before turning in last night. We will see how that goes.

As always...thank you.

Bob

FWIW, Lucas Hot Rod oil is a similar product, available from Summit Racing. Its what I use in The Ark.

\m/
Laurie

[fishnjim]

If you have one cylinder by-passing oil that's burning, unless you fix that, no kind of oil will solve it.   It's probably not bad enough for blue smoke.
In the old days, we'd throw a can of STP in and pray for a divine miracle.   
The rings are supposed to wipe the cylinder down in the intake stroke so there's no more than a thin film, and if that's not efficient and leaves too much oil behind, it'll burn (rich) because there's plenty of gas burning around to ignite it.   Could be a problem with the ring installation, improper sizing or installation or that cylinder is cracked, out of round, has boring/honing issues, etc..   That residue gets wiped down by the next stroke and into the oil.   With no oil filter, it has little recourse but to settle out as sludge in the pan.   These cars were simply designed on very cheap oil and frequent changes/pan cleanings, which presents an economy and reliability issue and not what we're used to today.   Otherwise, they'd still build them that way.
As far as synthetic, that's only the base oil used as opposed to "naturally" occurring crude derived stock.   They make the base from chemistry rather than just take what comes out in a distillation cut.   It's a "cleaner" material, per se, and then additives selected to improve wear, etc.   No magic, it's lubrication science and marketing to raise prices.
If you're not willing to fix the cylinder, aka "ring job" then increase the frequency of the oil changes.

[z3skybolt]

fishnjim

Thanks for the response. As I have thought more about this issue: engaged in a couple of discussions and refreshed my limited mechanical knowledge .....I am coming to realize that there may be more than one contributing factor with my engine.  Makes a lot of sense to me.  One would not have expected that the Valvoline V-1 would "coke" in only 1,100 miles. But given that it is designed as racing oil....I could imagine that it might not hold up well over many miles.

Having spent a fortune on the overhaul I hate to tear into the engine again.  But if that is what is necessary to solve the issue then it will have to be done.  The difficulty will be as in the beginning....finding someone willing and competent to do the work. My extended effort to do so originally: at great cost and time did not end so successfully.  I have little confidence in future prospects either.

I will get a compression check on the #2 cyl and see how it compares.  An "old time" mechanic told me that he has seen engines take up to 8,000 miles before the rings fully seated. My engine has 4,200 miles on it and only the #2  seems to be an issue. The engine does not smoke at all. I'll keep searching for the cure and in the meantime change the oil even more frequently. Ultimately I will get it fixed.

Bob

[V63]

Certainly do not want to use synthetic until you are convinced it’s all broke in. Maybe 8,000 miles

[z3skybolt]

V63,

I am asking for advice here so I accept your comment with appreciation.  But 8,000 miles to fully break in before using synthetic?  Perhaps that is so but I've not heard that before. May I ask if this comes from personal experience or some other source?

If it is important to wait....I can always monitor the situation and change the Valvoline VR-1 more frequently. I intend to have a compression check done on #2 before making any lubrication changes.

One thing I was hoping to learn here is the experience of others with Flathead engines concerning the carbon content of their oil upon changing it. Guess there are few Flatheads being driven any more. At least not very many miles. Some forum members have been around these old engines for ages. Hope to hear from them as well.

Thanks,
Bob

[James Landi]

Bob indicated that surprisingly, there was a "chunk" of carbon in the oil along with much smaller particulate.   Could these deposits be coming from highly heated valve stems...in a flat head engine, carbon heating up on the underside of the cylinder heads where the valve stems pass through?  Typically, there would be a hot spots on those stems, and lubricant might burn and "coke" and drop off into the pan, especially on the area where exhaust valves pass through.  Carbon deposits from weak compression would not, in my experience, create harden chunks of carbon, so that the one spark plug with deposits might well be unrelated to the Bob's initial concern.  Just trying to help,  James

[Bobby B]

Certainly do not want to use synthetic until you are convinced it’s all broke in. Maybe 8,000 miles

Cast rings correctly sized, fitted, and installed with the correct cylinder wall bore/hone finish, seat rather quickly. An old racer trick is to use some MMO on the cylinder walls when installing to help the seating process. The issue here was concerning the particles in the pan. Most break-in oil gets dumped after 500 or so miles, so if your rings aren't seated by then, I think you have some underlying problems. In the 30+ engines that I've rebuilt, I've NEVER had a smoking or oil burning issue other than the first few minutes of run-in which pretty much boils down to all the lubes and excess oil burning. Usually more smoke coming from the damn manifolds and engine paint than out the tailpipe. Again....There's rebuilds, and there's rebuilds.
                                     Bobby

[z3skybolt]

Finally enough snow melted that I could get my LaSalle out for a compression check.  The idea is to try to track down the cause of "carbon" in my oil and a consumption rate of around 1 quart every 500 miles or so. Also an effort to determine why the #2 cyl is pumping a bit of oil....leading to a mild build up on the spark plug.

The engine was overhauled 4,000 miles ago and should not be using any oil but it does. The question about ring seating has arisen..... causing oil consumption and the possibility of "blow by" in #2 cyl. contributing to the carbon issue. I fully expected to find low compression on the oil burning #2 cyl.

Anyhow this is what we found today.  Cyl # 1, 3, 4 are 100 psi.  Cyl #5, 7,2 and 6 are 90 psi. Cyl #8 was 75 psi. The cyl that has been pumping a bit of oil #2 had 90 psi!  That would lead one to believe that the rings are seated and not the cause of consumption or blowby.  The only other culprit we could think of, causing the #2 to pump oil is the valve guides.

Leaving that aside we were surprised that compression was low on #8.  The spark plug was clean and no evidence of oil residue what so ever. So we compressed air into the cyl and listened for it to escape.    Nothing from the exhaust, nothing from the carb.  When I pulled the oil dipstick out....I could hear air hissing.  That would indicated air bypassing the rings.  For one reason or another.....that cyl. seems not to be sealing properly.

I reported the findings to a helpful friend who has rebuilt dozens of flatheads.  First he said that he had always considered 75/80 of compression to be "normal" on a flathead and of little concern.  He acknowledged that air must be bypassing the rings.  He further stated that the old "iron" rings, which he still uses, seat rather quickly and last for more miles that most collector owners would ever drive.  Marc continued to say that if my engine builder put new types of rings of modern materials....they would often take far longer to seal. My rings were built by Hasting. But I have no idea of the metal composition.

Anyhow....I am no closer to determining how the carbon ended up in my oil after a change of 1,000 miles.  But I have only about 150 miles on the latest change. Plan to change again after about 500 miles and see what it looks like.  As for the 75 lb. compression and mild oil usage.....my intention is to keep driving and see if anything changes.

What say you?

Bob

[Bobby B]

Bob,
Hi...Those compression ratios are fine. Try and find out what style/type of rings were used. Top compression rings vary in style, as do oil wiper rings. I did tell you that cast rings set rather quickly if installed properly. NOW.....They ARE easy to break when installing and not know it. With your compression readings the way they are, I doubt that's the case. With a 3-piece oil ring, It's ALSO just as easy to accidentally OVERLAP your wiper ring or have it hang up within itself when installing. It's a critical process that takes some practice and focus, along with the correct filing, gapping, chamfering of sharp edges, orientation of the rings themselves, and loading into your band compressor for install. Just before loading into the clamp, I always dip my piston assemblies head first into some MMO and let them "drip-dry' for a few seconds.
                    Bobby

[Bobby B]

Bob,
This might help you get started....Click on "America's Master Catalog" on the right hand side and go to page 175. It has the kits for our Flatheads Listed.
                                                                             Bobby

www.hastingspistonrings.com

[V63]

V63,

I am asking for advice here so I accept your comment with appreciation.  But 8,000 miles to fully break in before using synthetic?  Perhaps that is so but I've not heard that before. May I ask if this comes from personal experience or some other source?

If it is important to wait....I can always monitor the situation and change the Valvoline VR-1 more frequently. I intend to have a compression check done on #2 before making any lubrication changes.

One thing I was hoping to learn here is the experience of others with Flathead engines concerning the carbon content of their oil upon changing it. Guess there are few Flatheads being driven any more. At least not very many miles. Some forum members have been around these old engines for ages. Hope to hear from them as well.

Thanks,
Bob

I remember reading in an owners manual (probably a new ford truck) advised not using synthetic oils until after break in of 7,500 miles. More over, it Makes good sense to me...there are numerous moving parts to fully seat.