I have a 400 block that I want to put in my nova but I have heard lots of stories about them having heating problems...can anyone tell me what precautions I need to take to keep that from happening? like super bad headgaskets or high flow waterpump or what... I really want to build this block but don't want it to be something un-reliable. It will be in a street car but will be raced often.
any help would be appreciated!
thanks,
Jesse

Most important: 400 blocks and overheating is an old story with some, but not a lot, of basis in fact. It's nowhere near as bad as the rumor mill would have you believe. This is not to say that you can ignore ignition timing, have a radiator half plugged with scale, use coolant that is so old it looks like hot chocolate from rust, and then jet the carb lean and use a flex-fan to save gas. You absolutely need to insure that your cylinderheads are drilled for the six small "steam holes". All 400 heads are drilled, but no other OEM heads are, and not all aftermarket heads are drilled.

One thing I recommend is that you check your block for a coolant passage in the deck surfaces, on each side. You are looking for a 1/2 or so hole between the center cylinders. Some 400 blocks have this hole, others do not.

This hole supplies added coolant to the cylinder head, and since the head is hottest at the two siamesed exhaust ports, this is a good modification to make.

You of course want to use a head gasket that also has this extra hole. I'm thinking that all the heads have the hole, but verify it to be sure.

Complete details are in John Lingenfelters book on small block Chevies.

Jessie,
Answered your post in the Engine Section but here it is again ;)

Don't know who started this crap about 400 overheating & being unreliable.
They do sometimes tend to run a little warmer than a 350 but it is usually because you are making more power & no matter what you build the more power you make the more heat you need to get rid of.
If you have an adequate cooling system including a good radiator, pump, fan or fans etc as you should have especially with any hi performance engine they should not have a heating problem.
You must drill the steam holes if you are using a stock block & are going to run it on the street where it will see lower rpms but other than that there is nothing special about running a 400.
I would suggest you spend the money on a Stewart pump as I feel it is one of the best on the market.
They are all we use on circle track deals & also on almost all performance engines we do if there is one available ;)

I had a 408" sbc in my prostreet ss nova,making 600 hp,and had a PG trans w/5500 stall and 5.13 gears.It had an aluminum radiator with single electric fan,and it only ran hot at first till the rings were seated.Then it actually ran a little to cool.