Cleaning out a cast iron block

turbojimmy wrote:
This is my second season with my '84 Allegro. Bought it with a blown engine. Put a Craigslist-found 454 in it (truck spec GM Performance crate engine). When I got the engine home, put it on a stand and turned it upside down a bunch of rusty water came out of it. An alarming amount actually.

With the water pump off of it I ran water through it until it came out clean. Last year was the first camping season with it. It ran great, though on the warm side.

This year, on my last trip out, it overheated pretty bad. I could not get it to cool down.

Yanked the radiator and brought it to a local shop to be rebuilt. For a significant sum of money, I'm getting an all-new radiator custom built. The rad shop called me today and said my problem was that there was a baseball-sized chunk of rust clogging the inlet side of the radiator. The radiator was toast anyway, but they advised me to figure out why this happened otherwise the new radiator will meet the same fate.

So - I need to clean the block out some how. On the one hand I'd like to think the many heat cycles have dislodged most of the rust in there. Upon removing the radiator the lower hose drained clean. I took the thermostat housing off and hosed out the engine - came out clean too. But how can I be sure?

The radiator guy suggested yanking out the drain plugs and seeing whats in there. He suggested pulling out the freeze plugs too.

So....does anyone have any advice that's different than this? Ideas would be appreciated.

TurboJimmy,
Long, long ago in a far away place, (Star Wars stuff, remember?) I used to rebuild engines for side job. When I pulled them and put them on stand to perform surgery on them, I'd take them all the way down to a gain as much access to any portion of the block I could get my little hands on.

Every single time, I'd pull every freeze plug and drain plug. You'd be surprised on how much SAND I'd find in there, big chunks of black carbon, solid chunks of pure rust etc. I'd have to pry much of it out and or, use a chisel and break much of it up to be able to remove it through the freeze plug holes. Once all the debris, sand and other big stuff was removed, then I'd hit with special, long nosed nozzle that I had for my garden hose. You'd still be surprised at what came out as a result of using that nozzle.

That was then, (from about '65 to, oh around '90 is when I quit that non-sense) and this is now. Unless it's an old hot rod, i.e. '60s Chevy etc., I won't even think about pulling an engine in a motor home. But, back to your issue. Yep, pulling the freeze plugs is the least you can do to get the closest inspection at the cheapest cost. Freeze plugs are cheap.

If you have one or, have access to one, you can use an "Inspection camera" to get into many tight places, inside the water jackets of that block. You know, the kind that Home Depot, Lowes, and other tool places sell. I got mine from Costco quite a while back and, it's not the best but, it sure works for getting into very tight places and seeing what's in there. Good luck.
Scott