I wouldn't use any of the store-bought engine cleaners. As a class, they are better than they used to be but if you use one with too much solvent in it, you might get a bunch of wear and/or a bad seal/leaking problem.
I'd use a 15W-40 gas/diesel motor oil to clean up an older or well-used motor. These dual rated, fleet-type "Heavy Duty Engine Oils" have a very stout detergent/dispersant additive package to keep diesel oil crankcases clean after many thousands of miles. They also have more anti-foamants and more barrier wear additives which make them suitable for high-RPM applications. This weight is also a pretty good one for most high-performance engines.
Months ago, I would have strongly urged you to use Pennzoil Long Life 15W-40 as it had nearly 200PPM of moly in it (more than any other mass-market brand) but very recently, they took the moly out. I'm not sure why.
Chevron Delo400 or pretty much any of them would work fine, I'm sure.
Oh, and not all straight 30 weight oils are non-detergent and ATFs don't necessarily have the high detergency many people think they do. Just wanted to mention that.
Edit - typos & minor changes.