Considering these engines have been supercharged since 1999, I am fine running without them. Mercury marine, general motors, ran without them. Not saying it's wrong to run them, as if I wasn't so lazy I would be.

Yes big Al you hit it. My concern was thermal expansion as well as the rigidity of the bore itself say at 6000rpm boosted in a production non siamese bore block. Or should I say the bores ability to maintain its shape as it would be when fitting rings on the stand fresh out the machine shop. Is that a valid concern ?

dumping a small amount of water on a siamesed block prevents steam pockets in the rear of the block,if that happens the steam will not let the water flow through the block.i see no reason to dump from the back of the block on a standard 454 block.

When I tapped mine for dumps, I mainly did it to bleed off some excessive water pressure . I felt dumping it there was better than dumping it prior to the engine .

It's not the block that gets the steam pockets it's the head. I've tested back to back dumping water out the back of the intake/ blocked off. Absolutely no difference in temp either way. This was with a Dart block. After thinking about it I would have to say that if you pull water from the back of the intake (create a short circuit in the cooling system) it would be more prone to getting steam pockets in the head than if it was blocked off. I can tell you this from experimenting that introducing cold water to the back of the intake drastically reduces detonation. If you look at some of the high dollar cylinder heads out there now they have a manifold made into the back of the head...

We haven't seen any issues running this way on the 460/B&M 250 equipped engines in the Cigarette either. One engine with well over 100 hours, and the other with between 80 and 100 hours, though these are not wild engines by any means (575 HP give or take a few).

If I was only doing the top end and didn't have the engine out of the boat, I'd probably be going that direction myself. It just makes sense to me to do it since it's all apart. Just my take on it though.

Thanks Bob! I'm all set now.

STD 454 block isn't likely to steam pocket around the rear, however bleeding a small potion off still helps even out the overall temp front to rear just my opinion... and we all know what that means!! there's another azzhole on the board!! lmfao

While on the subject of engine cooling and hot spots.....How many engines have ever been built by GM, Mercuruiser or Mercury Racing without circulating pumps?