View Full Version : Smoking 390

07-14-2014, 08:22 PM
Have a 390 in a 65 T Bird that all a sudden started blowing blue smoke and actually blowing some oil out the exhaust. Just as quickly as it started it stopped. Engine never missed or run rough. Car was at highway speeds when this occurred. Possible oil control ring problem?

07-14-2014, 09:33 PM
Before I blamed it on the rings I would take the valve covers off and check to see if the oil returns are clogged. If they are ok check the valve seals. They can get brittle and break allowing oil to leak down into the cylinders.


07-15-2014, 12:15 AM
Blue smoke, eh?

Is your brake reservoir low or do you keep topping it off?

Is it possible that your PCV valve let a slug of oil through?

07-17-2014, 07:12 PM
brake reservoir was a little low so I topped it off Can brake fluid get into engine?

07-17-2014, 09:56 PM
The seal at the back of your Master Cylinder and the one on your power booster can suck brake fluid right into the intake manifold.

You said it happened in spurts. That's usually what happens when the booster is nearly full and the liquid line reaches the check valve. The fluid is 'sipped' and then it's not. - Dave

07-30-2014, 08:32 PM
Thanks I see a leak under the master cylinder maybe its getting into booster. Also I removed vale covers and wow is it dirty in there. Black residue. What would you suggest to run through engine to clean out engine. Marvel mystery oil? seafoam? May change engine oil several times?

07-31-2014, 12:21 AM
...I removed vale covers and wow is it dirty in there. Black residue. What would you suggest to run through engine to clean out engine...

Back in the day, non-detergent oil was commonly used which left sludge all over the internal parts of everyone's engine. Never attempt to clean the inside of your engine with one of those engine flush procedures that many shops try to sell.

We have had lots of discussion about oil pickups that clogged from folks who changed to detergent oil. If there is a lot of sludge then the last thing you want to do is to dislodge it all at once.

I suggest you cover your floor with lots of cardboard, pull your rocker covers off AND your oil pan. Stuff rags in the oil return holes and manually clean the sludge from the top of your heads, inside your covers and oil pan, and clean your oil pickup.

I use diesel oil or kerosene with brushes that won't shed bristles. This is a good time to remove your rocker shafts and clean them inside and out (http://www.squarebirds.org/penelope/390Build/RockerShafts.htm). Remove the cotter pins on the ends and the plugs, rocker arms and springs. Take lots of pictures as you go. Clear the oil holes in the rocker arms and inspect the shafts for galling or scoring. If everything looks good, reassemble. All of this costs no money but an investment of your time.

Modern detergent oil is designed to keep sludge in suspension and get dark. You want to change it before it saturates. If you are diligent about detergent-oil changes there will be no future sludge except for the small amount you couldn't reach when you cleaned your internal parts. Keep checking it and use ZDDP additive in your flat tappet engines. - Dave

07-31-2014, 08:38 PM
Thanks for the reply What weight engine oil do you recommend? is synthetic OK?

08-01-2014, 03:08 AM
Synthetic oil was developed to combat oil breakdown due to overheating in aircraft engines with turbochargers. Turbochargers operate from exhaust gasses so keeping them lubricated was a challenge.

If your engine is naturally aspirated and operates just fine without overheating, synthetic oil has no advantage over dinosaur oils. Synthetic oils never claimed to lubricate better or reduce flat tappet friction, they are meant for extreme heat service. If you put synthetic in your classic car it will perform the same as conventional oil only it costs a lot more money.

Some folks use synthetic oil because they extend time periods between changes. It still gets just as dirty with ash and acids from the combustion process. Synthetic oils tend to leak easier because it thins into very small areas.

I prefer to change my oil frequently (~ 3,000 miles or so) because that is the only way to truly filter the oil. Most of your oil gets bypassed in the filter until it warms up and thins out provided your filter is not saturated. In our Michigan winters, I don't think much of our oil gets filtered before the engine runs for more than five minutes. Race cars have two filters because one simply isn't enough to do the job.

If you have flat tappets you need ZDDP (Zinc & Phosphorous) or your cam will wear away. Oil with '40' or more in the numbers are allowed to carry enough ZDDP (at least 1,200 - 1,500 PPM) to prevent cam wear.

I use Shell Rotella-T 15W-40 in my classic engines. It is basically a diesel engine oil that produces very low ash and it has 1,500 PPM ZDDP. Ash is that black stuff that is produced when oil burns. Detergents keep it in suspension so sludge doesn't form.

Racing oils and synthetics with '40' or higher in their numbers should also satisfy our requirement for ZDDP but you need to check with the oil manufacturer. Many of them will not say (like STP) because ZDDP kills catalytic converters but they want the public to buy their oil.

Part of the problem is, they reformulate our oil frequently so you must pay attention to when the tests were done. You may be using oil that used to protect but now it destroys your cam. - Dave