Doing a tune up on my friends buick. Unknown miles but the motor looks well used. I was wondering if it was a safe idea to run some NAPA brand Mac's oil flush. Any potential dangers to be concerned about? Thanks guys.
I would not, repeat, would not run any type of an oil cleaner through an old engine. Sometimes that varnish you're trying to remove is the only thing holding that motor together. If the motor has 100K or more on it, then it'll be just about guaranteed to blow smoke and knock afterwards.
I have used motor flush products with no problems. On one SBC, I cleaned sludge out of the heads and valve covers. Oil barely was coming out of the pushrods. I dumped a quart of flush in along with some ATF. Left the valve covers off. Started and let idle. After about 15 minutes, the oil was shooting over the fenders. Shut it off and immediately drained the oil. Filled with 30W cheap stuff. Ran it. Drained and went to regular changes. No problems. On the car you are working on, if it's not really full of sludge, I'd just change oil and keep an eye on it.
Just keep changing the oil with a higher quality oil that has plenty of detergents in them & don't forget about the ZDDP additives that the old engine needs. I've come across plenty of slugged up engines in the past & as long as the oil in the pan wasn't gelled just keep changing the oil & filter EVERY 500 miles or so for the next couple of years & it will clean itself up.
If in doubt pull the pan and clean it and the screen. Most of those old engines that ran on leaded fuel and the "at the time" inferior oils will have massive sludge in the pans. No 'miracle in a can' can clean that. Also that old sludge has highly toxic lead...wear gloves and dispose of responsibly.
It can be a crap shoot! it can help with oil flow recduction from gummed up passage and it can also free up small enough items of crap off the bottom of the pan that then find there way into the oil pump check ball and hold it open making for low oil pressure! if that takes place your pulling the pan off no matter what! are you gonna roll the Dice?
In my experience, there has been more grief than good caused by using engine cleaners on old worn engines. Some guys were lucky and swore by it, others, well, they swore at it when they were yanking the motor out. The question is all about timing, how long to leave that in the block. I've seen more yanking than running. When I was 16 I ruined my first car by doing that; it had 100,000 miles on it, and it started to knock and smoke and go out of whack; - I had that crud in there for 5 minutes before my father came out and smacked me upside the head for being so stupid and told me to get that crud out of the car. That was 35 years ago. In that ensuing time, I've watched a lot of friends destroy engines doing the same thing. Only one guy I know of used it with no ill effects; turns out his car was running synthetic oil from day 1. When any machine wears and gets old, there is a certain amount of mechanical wear that occurs. Rings scuffing on block sides, bearings running on a light film or lousy grade mineral oil, and then of course the passages which were made narrower by crud which compensates for the increased clearances on the wear parts. You're also playing with a very old engine that probably spent the first 20-30 years of it's life on cheap oil and infrequent oil changes, particularly in the later part of that period as it was a used car. Remember that the metallurgy on a 60 year old engine is nothing like one built today; - it's a lot softer, the parts wear a lot faster, and the heat dissipation just wasn't there. Believe me, you will open up a Pandora's Box of issues if you attempt to clean that thing chemically, don't do it.
^^^agree 1000% I've seen thousands of engines. Flushing never seems to save the impending harm. You might get lucky, likely not. If it's worth the risk to you, go ahead and give it a shot.
I gave flushing a chance twice on used motors! both times to free up stuck lifters which it did in short order , then less then two weeks later what I posted about before took place on both motors , and each motor was down to 5 psi of oil pressure when fully warmed up! In retrospect I would have sooner pulled the manifold off both motors to free up the lifters, than to yank it out of the engine bay to drop the pan off!!!
Don't flush it, not worth doing and can cause way more harm than good. Pull the motor and pop the pan to clean and put a fresh oil pump in(or rebuild yours). I just sold a 401 core to a guy who got his family's Wildcat back on the road after sitting for 15+ years and he launched 2 rods and destroyed the entire bottom end because the oil had congealed at the bottom of the pan. Nalheads of all sizes are getting scarce, spend the $$$ and do it right. If you want another 264 to rebuild, I have a complete one for sale.
Do what Tom says. If the lifters aren't clattering there is oil getting to them. Check to see if oil is getting to the rockers. If all is well, just keep changing the oil and filters. Try not to start the engine unless you are going to run it long enough for it to reach normal operating temperature and stay there for a while; 20 miles or more would be ideal. It will clean itself out. BTW: a Nailhead with 100,000 miles on factory pistons will be needing a refresh that involves new pistons soon.
