if you are...have you been having any problems? what are some pros and cons?

I'm running a 406, and its been awesome. If steam holes aren't drilled in the heads you will have overheating issues. Motor is pretty mild and still makes massive torque. No replacement for displacement.

where do you drill steam holes?
speed costs - how fast can you afford to go? there is no substitute for cubic inches! sign in the local speed shop back in late 50's/early 60's. some truths never change.

For fun on the street, without boost or nitrous, a 400 is an excellent choice. 400s really NEED good aftermarket heads, such as the Dart Pro 1 Platinum 200s or the AFR 195s, even for a mild build. Then have a machine shop drill the steam holes in the heads if you choose heads that can't be ordered with them. You'll be best off with a "reverse-dome" piston design.

I have run a 400, and I will have to say they are kind of a pita. It is not overheating issues, but the big bore thins the block out so much. I have run into virgin blocks that have to go .040 over. Which is really a liitle more than you want to overbore without a sonic check on a 400. The main webbing is also really thin, probably not to much of an issue with a street motor, but if you want to make some real power, than you are asking for trouble. The bore spacing is also a little tight, which can lead to cracks developing between bores. And about every 400 I have seen is extremely thin at the bottom of the bore. Which makes that area extremely vulnerable to cracks.

I guess my advice is, for a street motor with about 400hp, than a 400 is a decent motor. But after that, the high price of the core, cost of machine work, and chance that even after having the block built right having something go wrong. I would just buy an SHP block, or build a 383.

I have a .030 /400 with Dart heads . They are not drilled and I live in Florida. I run a 4 core radiator and have had zero problems overheating. We run in open road racing and I have never had a heating problem. Run a good engine oil cooler and a trans cooler. I have 6 inch rods and .05 flat top pistons. You can change the static compression ratio with head gaskets. Don't put cheap stuff in the engine and it like anything else will work fine. Stay away from claimer pistons and cheap rods. I like the 400 internally balanced and will run it over 5500 RPM for 118 miles. They are just good old truck motors that can be built.

The lack of the steam holes doesn't cause overheating. What happens is steam pockets can develop between the cylinders where the cylinder walls are siamesed - the "original" SBC's had a gap between the cylinder walls in the coolant passage so there was always a way for any steam that developed to get carried out with the coolant flow.

The problem with steam pockets is vapor doesn't carry away heat from the cylinder wall. So, you can develop a hot spot, which among other things can warp the block/head sealing surface and/or cylinder wall - not a good thing.

im considering running a 400 in my camaro...dont know where to start..dont know what to look for... i can get ahold of a complete 400...ran when pulled out..for 200 bucks..what would be a good cheap build on this for some decent power??

True. Dart and World blocks do not have steam holes. Best is to plug the holds weld and remill. solves the problem of weak area between steam holes and head studs