Hot Rods Whats the pro and cons on flushing out old oil with engine flush

73RR.I am Really glad I asked on he before I did any thing wrong!!!!!Bruce.

 

THIS WORKS!! Drop the oil, put on a cheap filter. Put a gallon and a half of # 2 Diesel fuel in the engine, fire it up and let it idle, you don't have to rev it, just let it idle, after 15-20 minuets or so, pull the drain plug and filter. Take a good look at the fuel oil, it will be nasty, if your engine is really dirty, do it again, chances are you won't have to. The fuel oil will clean your pump, oil passages, rocker arms and push rods, flush all of the old gunk that's been building up in your engine over the years and it will even sound a lot different because now it's clean. You will NOT harm your bearings our anything else in your engine, Diesel Fuel is a Lubricant and one hell of a cleaner!! I've done this and it works!

 

Someone try this and report the results please

 

Lets start out with what makes motor oil inside a motor dirty in the first place. The process of the motor starting and running create metal, and nonmetal fragments to wear off the internal motor parts. As the motor runs it creates heat. The process of creating heat pulls moisture out of the air through condensation. This moisture mixes with the metallic and non metallic material that has worn off the internal motor parts and forms a sledge. It the old days, (before about the late 50s) most oil did not have detergents in them that was designed to collect this sledge and carry it to the pan, but the process of the oil moving through the motor did carry much of the sledge towards the corners of the motor where it would collect. It the old days motors tended to run pretty cool, so the moisture would build up pretty fast.
The process of burning gas under pressure creates carbon, unburned gas, and other contaminates to be forced past the rings. This creates a gaseous mixture known as blowby. In an enclosed motor (after about the mid 20s), this blowby would build up in the crankcase as the motor runs. It order to keep the pressure of the blowby from blowing out the gaskets, the blowby had to be expelled from the motor. The engineers of the day determined they could add an air intake breather to vent the crankcase of the blowby, and if they also added a hollow tube from the top of the motor, and ran it under the vehicle, the passing air when the vehicle was moving would pull the blowby out of the motor, and the breather would allow fresh air in. They could regulate the amount of air exiting the motor, by limiting how much air came into the motor. The hollow tube extending out under the car is called a road draft tube.
The road draft tube worked quite well, except it also allowed dust and dirt to be blown into the crankcase when the motor was not running. They discovered that changing the oil removed a lot of that dirt from the motor, and if the added a filter to the oil system, it could catch a lot more of the dirt. Another benefit of changing the oil was it also removed a lot of the moisture and sledge, but not all. Most auto manufacturers started adding filters for the oil system in the 30s, but sledge was still building up inside motors. During that time, 30,000 mile motor overhauls were pretty much expected.
Sometime in the late 50s, or early 60s some detergent began being added to the oil, but the "new" detergent oil was only to be put into the "modern" new cars, and the old cars still required non-detergent oil. Adding the detergent oil to the motors ran without oil containing detergent caused the oil systems to become clogged up and ruined the motors. Motors that had the detergent oil from when they were new, had extended the expected overhaul intervals to 60,000 miles or more!
The Road Draft Tube remained intact until the Government determined the blowby drifting out under all these cars was bad for our health, especially in places like southern California. Along with a Clean Air Act, and new emissions testing, the Road Draft Tube was mandated by the government to be replaced with a Positive Crankcase Ventilation system. That system retained the air breather, but routed the blowby through a check valve (pcv valve) and reintroduced it back into the combustion process through a port under the carb on the intake where most of it could be burned off. Eliminating the Road Draft Tube reduced the amount of contaminates in the oil by a large amount.

So, how does all this apply to us now?

We are finding all these 30s, 40s and 50s cars that all had Road Draft Tubes and never had detergent oil in them. Most have been sitting for 60+ years in some garage or barn someplace, and many have exceeded the expected overhaul range for the time they were built by 2 or 3 times. Most have large amounts of sledge build up sitting in them. Because most of us have been around moden cars that have always had detergent oil, PCV systems, and years of tech advances in motor development, where an overhaul isn't expected until the mileage nears 200,000 miles or more, we expect these old motors to be in great condition with only 75,000 miles on them. We fail to comprehend the differences between the old stuff and the more modern stuff. Most of us never knew the experiences of the people that were around in the 50s and early 60s that have understanding of the differences between detergent and non-detergent oil, and the effect it has on sledge build up. We simply can not comprehend the concept of a non-detergent oil, and probably have not even seen a quart of it for sale.

Lets not forget what makes up the sledge. How much do you really want to pick up and suspend in some super cleaner and run through your bearings?
There are 3 ways to remove the sledge from a motor.
1) Tear it down and clean it up.
2) Run a cleaner through the motor, loosen all the sledge up at one time, and wipe out the bearings and oil pump, and clog up the oil pickup as you run the motor. Then you can tear it down clean the sledge out of it and rebuild it.
3) Use a standard detergent oil, change it and the filter often, and slowly remove the sledge, as you plan to rebuild it someday.

The remaining option is to locate some non-detergent oil, change it and the filter often, and drive it until it needs an overhaul, in about 10,000-15,000 miles, or less.. Gene

 

Above post pretty much nails it all.

Detergent oils were just finding their way out here into the hills about the time I started driving. The transition to them came with much debate before all the real reasons for the issues that came with them got figured out.

FWIW I tried an "old timers flush" [using a kerosene mix IIRC] on a '57 Plymouth flathead 6 about '65. Wasn't worth the time and effort, wound up doing a teardown and rebuild. Haven't bothered to try one since.

Ed

 

Gene, I think you covered the subject pretty well there.Thanks Bruce.

 

Well I made it home with the old M. I will post a picture of the inside of the oil pan in a day or two.