I have 340 engine I rebuilt several years ago. It runs great but the frame on the car rusted out so the car has sat mostly outside for the last 5+ years. The engine has started to rust in spots. I want to clean it up and put in another body I bought. I don't want to blast the engine block and risk getting anything inside. Whats the best way to clean up the assembled engine and prevent (at least slow down) the rust from coming back? The body its going into will be kept inside. Thanks.

I'd block all the passages and wire brush it. Put a wire wheel on a drill and go to town.

.....and if you have access to a neddle scaler,they work well in tight corners and such.

A needle scaler will work but it will also scar up the cast iron surface while it's removing rust, use them with caution on cast iron if final cosmetics are important to you.

I scrub them down with oven cleaner soak,rinse,dry with air hose,spary it down good with brake clean,air dry,paunt it with duplicoler hemi orange

You can use wire end brushes and metal prep with gloves, after using above, spray down with brake clean and use self etching primer before spraying any paint.

logan426

you can buy SEM etching primer in cans at most paint jobbers.