The Stovebolt Site Forums The Shop Area Engine Shop What causes crud build up?

What is the cause of crud build up.
I would think high mileage.

Would like to share some thought and would love to get opinions.

I bought a 66 stepside with a 250. The motor blew blue smoke. Bad really bad, alot. Neighborhood mad.
I took the valve cover off and it is pretty darn clean. No "buildup" no crud.

I buy a used 250. No smoke at all. I take the valve cover off and can not believe the amount of "crud"... I must not omit the part that there was no oil getting up there either. But I believe the "crud" came first thus blocking the oil to the top. ANYWAY...

What is the cuase of "crud"

In the case of these two particular motors my thoughts are, and I am guessing...

The motor which smoked but had no crud was used very hard(I bought it from Virginia, maybe a farmer?)but was taken care of, oil changes,etc.
The rings gave out due to hard work?

The motor which does not smoke but is loaded with crud has high miles on it, was never worked hard(it came from a Nova) and rarely had the oil changed.

I wonder if anyone has any thoughts about this.

Its great to have a website like this one to help settle those thoughts running around my brain.
Thanks for any opinions

Freds,

I have seen that 'crud'. I think it has several contributing factors. Short trips without engine getting up to operating temp..infrequent oil changes, and possible use of a high ash or inferior motor oil. Together, these are real artery pluggers!

Stuart

Oils high in parafin will cause it, too. Especially with infrequent oil changes. Not to sound like I'm bashing any particular brand, but Quaker State used to be notorious for causing sludge buildup. I've torn down a 305 that had been run on Quaker.

I think it's mainly neglect, not doing the scheduled oil changes. Ditto on Quaker State.

What is the recommended time to change oil on a 235 is it still every 2000 miles under normal conditions

In the 60's, when you could use a 160 thermostat and combine that with a pariffin based oil and around town driving, you could almost guarantee that the valve train would have a thick layer of creamy crud build-up. Condensation build-up in the crankcase, never getting hot enough to burn off the moisture, the auto-choke dumping in fuel past the rings, which diluted the oil and the pariffin oil, turned to creamy butter! It didn't take much in-town driving to generate a real mess. Automatic transmission cars were worse than sticks.

Today's better oil blends, 195+ thermostats, EGR systems, and the accompanying higher operating temperatures has done much to eliminate this condition. Most high mileage modern engines, even with extended oil change schedules, rarely accumulate the type of crud we found in our older engines.

Oil and filter changes in a decent running 235, along with a 180 thermostat, at 2k should keep the ole girl running. Limited mileage, around town would have me changing both at 1K or twice a calender year. Oil and filters are cheap insurance! I also like Shell Rotella with a little higher zinc. Hope this helps answer your question.

Depends on what color the gunk is.

If it's black, it's from carbon. Usually blowing by worn or broken rings.

If it's creamy, white to tan, it's from water. This can be either from an internal coolant leak from a cracked head, headgasket or intake (on a V8). Or it can be water from condensation, where the operator hasn't changed the oil as often as necessary for the way the vehicle is driven.

The claims about certain oils causing sludge is one of the biggest myths in the industry. There are no unbiased, scientific studys that have proven that brand A causes sludge. It all goes back to engine maintenance. Either the oil hasn't been changed often enough for the driving conditions or the engine is in need of mechanical work.

Whatever the case, it is best not to attempt a chemical removal of the sludge. Leaks can occur, as can bearing damage when the dirt goes through them. If you wish, mechanical removal is best. Pull the valve cover(s) and pan and attack with a scraper. Removal all the loose gunk before putting things back together. And don't worry about the power loss claims. They aren't enough to measure the difference in terms of milage.