Just working on a 5 litre V8. Removed valve covers and saw hard, brittle black carbon looking deposits around the middle of the cylinder head around the valves on cylinders 3 and 5. This stuff removes easily but crumbles in my hand. How exactly do these crystal like deposits occur? The engine has been serviced regularly (oil changes), or so the service book says!!

Thanks for any reply.
Andy.

PS Big picture!

 

not to take over the tread but i had that happen to me as well. from what i know its carbon deposits, but how they actually get there, i dont know. i do know that you do not want to get that stuff down into your motor. i used a vacuum cleaner. that was lke 4 years ago. man was my mom pissed

 

It's a combination of broken-down "viscosity improvers" from multi-grade oil; disintegrated molecules of the base stock of parafin-based oil; and combustion products that leaked past the rings.

Leave it alone while you have the engine apart. Then when it's back together, run one quart of ATF in place of one quart of oil. ATF is extremely high detergent, and will eat that stuff off, and dissolve it in the oil. Change the oil soon, like 1000 miles; it WILL need it. You won't believe how black and gooey it comes out. Run the quart of ATF in the oil for the next couple of oil changes, until the oil starts to look more normal.

In the future, use oil with less "viscosity improvers" in it; i.e., where the "W" number and the other one are more nearly the same. For instance, 10W-30 instead of 10W-40. The way those work, is it's really 10 weight oil, with molecules in it that make it act like 30 or 40 weight when hot. The farther the spread between the numbers, the more of that stuff is required; and at the same time, the less actual lubricant there is in your crankcase fill.

Synthetic oil is also far better at retaining its stability, since all the molecules are the same, and can be tailored for their exact properties; unlike dinosaur juice, which is more of a situation where what comes out of the ground is what you get.

 

sounds like a good enough answer to me!! thanx:hail:

 

The two major contributors to this condition are, not enough oil changes and also a bad pvc system.

 

Wow! That's that explained then!!
Thanks a lot you guys!

I'm glad it's not my engine. Although I've still got to fix it.

Andy.

 

i can see you doing something like that!

 

The former, maybe. The latter - nah. RB said it.

Note that they are concentrated in the center of the head, the location of that lovely feature called the "exhaust cross-over". It's the heat that gets the oil, and it'll get it no matter how often you change it. The fresh oil will tend to desolve a little of it at first, but it'll also be forming it's own new coal at the same time.

Now, remove the intake manifold, remove the splash pan from the bottom of it, and you'll find even more of that stuff.

The VI improver additives are the primary culprits. A "real" synthetic will have less or none of these. Synthetics also tend to be better detergents. Instead of RB's ATF, substitute a quart of "real" synthetic for a quart of "regular" oil first, increasing the amount of synthetic with each change until it's all synthetic, will also help clean it out - that way you're also using a product in the engine that is intended for the engine, unlike ATF.

Personally, I'm an advocate of cleaning as much of it out manually as you can. It'll contaminate the oil for thousands and thousands of miles and decades of ATF or synthetic oil changes unless removed first.

 

five7kid you are correct I should of added heat as another major contributor to the break down plus many other "minor" combination of conditions that promote accelerated (or normal if the oil is never changed) break down of the oil.
I also agree that manual clean up is the best to the point of pulling the engine and doing a rebuild because at the looks of the picture (not knowing the mileage and history of care) there is probably pretty good wear on this engine.

 

I don't really think so.... that looks to me like a typical non-enthusiast type of motor. Like you'd see if the same motor had been wrapped in a Caprice instead of a Camaro. Just real normal stuff, nothing the least bit unusual or severe.

 

You might consider giving this stuff a try. It's not snake oil, it actually works. I have it in my car now, and can actually see the difference it's making.


http://www.auto-rx.com/

 

Ya just hard to tell without more info just thinking "if" it was high milage poor care history it would be a good time for a rebuild

Edit: just saw the part about the oil change record ha! I must be going blind sorry

 

Sorry if its kinda off topic here, but what kind of exhaust manifolds are those? They kinda look like the ones on the '79 Z28 my 350 came out of!

Anyway, I think your problem's been pretty well covered, so I got nothing useful to add. Good luck!

 

Hi Air_Adam
The engine is in a 1983 Chevy G20 Dayvan here in the UK that I am trying to restore for a friend. I have removed the AIR pipes and welded them up! Hope this clears it up for you!

Andy.