A waste of time, money and effort. The sludge stays on the bottom of the sump unless you upset it, i would not even use a high detergent oil either, just make sure the oil has enough ZDDP in it.

When it needs a rebuild, you strip it down and clean it and send it to the hot tank. Don't fix it if it ain't broke + Let sleeping dogs lie!

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69 142S Overdrive + 69 164S Manual

I have used solvent flushes three times on old, dirty engines.

Each time, I have had lifter problems some time later.

I think that this is because the top of the engine drains down through the lifter area.

Once, I used an old shop vac, a crevice tool, and a scraper to clean the top of the engine. This actually worked well.

The next time I try to clean up an old engine, I will clean under the rocker cover, than install a new filter and detergent oil.

When you change the oil, try to drive the car up on blocks or ramps to tip the car so that the sump drain is low and make sure the oil is hot, you will get more gunk out that way.

Best method...d not do it. Worried about sludge, run good quality oil with a high detergent quality (honestly, any major brand oil these days) and change at short intervals. Two reasons:

Where is that sludge going to go before it become liquid again? Likely the pump pick-up screen. This can easily lead to oil starvation and premature engine rebuild.

What do you think is keeping that engine from leaking out all the seals until you have spent some time making sure the pcv system work and works well. This include cleaning the flame trap and replacing all the vac lines that are dry rotted.

There so, so many better places to spend your time and money. If you absolutely, positively feel you have to do this, just add a /2 quart o ATf at the oil change and let the engine gett up to operating them for about 15 minutes. Then change the oil and filter.