Just bought a 73 240Z, original for the most part.

During the first valve adjustment, we noticed much sludge and varnish when removing the valve cover.

It suppposedly has 113k original miles.

I'm sure it could use a rebuild, but in the mean time would and internal engine cleaner and or carbon flush help? Or hurt?

Which brands are good?

TY

uhoh7

Charlie, You've heard the old saying...."If it aint broken don't fix it!" If its running satisfactory, just maintain it until you do a rebuild. Sometimes issues can arrise from trying to flush out the old gunk.....leaking seals, semi-plugged passages, etc. Maybe someone else will jump in and share thier experiences with a similar issue.

Thank you sir...

I can see that with the internal engine cleaner, but what about the "carbon flush'" which deals with the combustion chambers only?

TY

Charlie

Leave the carbon alone too. It's abrasive.

It's probably not doing anything but raising the compression slightly in the cylinders.

JMO

My compression right now is 80 80 80 80 100 100

I concur! The sludge won't hurt a thing if you leave it alone. If you disturb it the sludge will plug up every oil passage in the engine. Carbon is no problem either. Every engine with high mileage has some.

OK I will take your guys advice and just change oil and filter.

What oil and filter should I use in this old Z?

TY

Charlie

Agreed. Depending on how much sludge accumulation you have it's better to leave it alone. I made the mistake once (emphasis on the once) of trying to clean some of the sludge on an old Dodge I had. It was atleast 1/16" thick in some places of the valve cover. I scraped as much as I could. I even thought about using those "engine flush" products. I was carefull not to leave any pieces laying around but it was all for not. A couple of weeks later while taking my girls to the Zoo the engine oil pressure light came on. Then the valves started to chatter. To make a long messy story a little shorter, a little piece of sludge the size of a pencil eraser had made it's way into the oil pump and siezed it. The oil pump drive shaft snapped. When I was able to reach into the oil pan I pulled handfulls of sludge, in solid and semi solid form out of there. A true pain in the A$$!

If the sludge is just a bit of discoloration on the engine components you can try using a high detergent oil.

Start saving and buying parts for a rebuild is probably the best thing you can do besides leaving it alone.

Suggestions on a "high detergent" oil?

TY sirs

...If the sludge is just a bit of discoloration on the engine components you can try using a high detergent oil.

Learned this from an old school mechanic when I was a teen...

When he got an older high mileage car that may not have had the motor oil changed as much as it should, he would get some motor oil designed for DIESEL engines. Cant give you a modern brand, this was 25 years ago but Exxon had some so finding it shouldn't be a problem. Put in a new oil filter, diesel oil and run the car. I saw this first hand on an Olds 88 he picked up. Ran it with the new diesel oil and filter for only about an hour and when it drained it was BLACK black! Filled it back up with new oil, new filter and ran it again, only this time for about a week. Oil was very dark, but not black as before. Third time used regular motor oil. Checked it after a week or two and it looked clean as a whistle.

Makes sense, diesels are by thier nature a lot "dirtier" than gas engines, so thier oils are higher in detergents. Cleaning the motor slowly is the key, instead of taking the chance of flushing it and not getting it all out as others have said.

JMHO

That sounds like a good idea...

I will look for diesel motor oil....

What about Chevron Delo® 400 Multigrade Heavy Duty Motor Oil?

Thanks, Great forum

Charlie

Probably any of them that are advertised as high detergent oils will work, but I know that (at least "back in the day") the diesel oil was not only higher in detergent, but cost only half the price of the name brand "high detergent" gasoline oils