I bought a 1981 f100 and the engine runs good, but there is sooo much buildup in the engine. I am looking for something to "clean" the inside. I do not what to take the engine apart. I have heard everything from off the shelf cleaners to adding diesel to the oil. I have some time to get this done because the transmission is be overhauled (not in the truck - it is at a shop).
Change the oil and substitute one quart of oil for diesel fuel. Dont run it long, cause you know diesel is combustible.. LOL But you can run the engine for about 10min and it wont hurt it. DONT rev it up either, that can harm it due to the low viscosity of the oil/diesel mix.
If it aint clean enough after the first time, "rinse and repeat".. LMAO... All kidding aside it should get the job done for you. Just done use regular gasoline.
On a side note. If you can see tons of build up in the valve cover or where ever you see it. Imagine what your oil gallery looks like, those drilled passages in the crank, and the oil passages in your push rods... HMMM, makes ya wonder how clean the engine really is huh? Makes ya wanna tear it down and clean it up right don't it.... Just some food for thought...
Ford Tech
ATF makes a good cleaner and you can leave that in there and drive it. (one quart, not six)
You do not want to use anything that cleans it too quickly. That may cause problems by plugging oil passages, the pickup screen and filter. Put it on short oil change intervals like 1K miles for a while using 1 qt of ATF with the oil. Also, make sure the engine is running hot enough to activate the "detergent" action of the oil. This generally requires the temperature of the oil to be above 140 deg/f. Keep in mind that you will probably never get all of the gunk out short of rebuilding the engine so don't be too concerned about it if all is well otherwise. If you get it too clean at this point, you may be rushing overhaul time. Every mile you drive before overhaul is cheaper.
Lugnut
I had a '69 Bronco, added a quart of kerosene (basically the same as that Gunk additive), ran it for 10 minutes and you wouldn't believe the crap that drained out. If you can get it, biodiesel will really clean that sucker out being a better solvent then petro based fuels.
I suspect you are looking through the breather on the valve cover and seeing heavy deposits of gunk...right? Signs of bad maintenance and short trips. This is one of those; "if it ain't broke, don't fix it" deals. You can add (whatever) to the oil and it may help, but I wouldn't. Use a good detergent oil and a good filter, I use only Wix, and change with religious regularity. Check/change the PVC valve. Clean the breather and make sure the hose between them is good. I've got the same truck/engine. The valve train on mine is pretty darn clean for the 26yrs it's been my daily-driver. The 300cid is near bullet proof and maintenance is everything.
Dave S(Texas)
Thanks for all the good suggestions. I will let you know that come out. HAHAHA
Marvel Mystery Oil, one quart added day before oil change, drive easy. Or Sea Foam if you can find it. Both work well. Gunk is rough on seals, both those that keep oil in the block, and in places like lifters. Big problem to worry about if it is really sludged up is the pick up screen on the oil pump getting plugged up if large pieces start breaking loose and migrating to the pan which is a very good (bad?) possibility.
Whitelightning
I'd go with this suggestion also. It's not broken. Try not to drive it on short trips where it doesn't get to regular operating temps.
While the trans. is out , put in a NEW rear main seal.
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