400 or 350 chevy engine?

Got them off, dad's friend said to use a stiff putty knife. We hit the gasket away at the top enough to get a screwdriver in between to pry it up. Thanks- Caleb  

The only reason people will tell you to choose the 350 over the 400 is the simple fact that it is a much more well known engine and performance parts are easier to find. The 400 is larger by almost 1 liter (.9 L) then the 350 and can produce more HP and torque. I own a 400 and I love it, its the best engine ive ever had in a car. So its basically a matter of personal opinion, but I would choose the 400 10 out of 10 times over the 350.  

Nothing wrong with the 400, overheating issues almost ALWAYs are the result of poor cooling system maintenance. If you compare your 400 Cyl. heads to a 350 or smaller Cyl. head, you'll see there's an extra set of holes in the deck surfaces of the block and heads (between the cylinders). These holes prevent the formation of steam bubbles between the cylinders, and are only found on 400's because they are a siamised cylinder block (the cylinder bores connect inside the coolant passages inside the block) to allow for the bigger 400 cylinder bores. Any small block Chevy cylinder head can be used on a 400 block, as long as it has the extra holes drilled in it to match the block. The easiest way to do this is use the 400 head gasket as a teplate to mark the holes. When proper cooling system maintenance isn't performed (Personally, I flush and change coolant twice a year in all my cars, early summer and late fall), the rust and sludge builds up in these steam relief holes and plugs them up (Their only about 1/8 inch). Was your 400 running before you got it? Later 400's are known for thinner castings, that are more susceptable to cracking. I would use one of the casting number decoders to find out what year block it is, and if it's after about 1975, it would be money well spent to have it checked for cracks before spending any money on rebuilding / assembling it.  

just bought a '77 K-20 today. truck is all original and in really excellent shape for it's age. am trying to decide whether to rebuild the 400 or, drop a 454 in it. 400 has 128k miles on it and runs great. doing research has turned up probs with heads/blocks cracking,(which was addressed above)& spinning crank bearings. have also read that 400's can only be bored .030 over. any more makes the bores too thin and creates a cooling issue. any truth to this? 1 more??, why the 106 deg cam and avoid the 110? are the motors that picky??  

Since you won't be investing in a stroker kit, the best you could do w/ a 350 is to offset grind the crank to pre-1968 connecting rod size, for 360cid...and a .060 overbore would get you out to 370cid.  Hence, the 400 is a better choice.

BUT--that 400 has siamesed bore walls, so there are steam holes in those 400 heads, not found in 350 heads, nor in 350 gaskets.  So, try not to ruin the gaskets, you'll want those as templates to make certain your new head gaskets indeed have those steam holes...or you're gonna overheat, as others have in the past.

Joe Sherman was pulling an affordable 600hp out of these things...back in the 80's.  so, the potential is there, if you like the 3 C's--cam, carb, and compression.  But, money spent making that Nova even lighter (fiberglass, etc) can replace money spent making the engine make more power, and you'll get money back with gas mileage, and you'll have less handling and brake needs, which also might just offset money needing to be spent.  

my 408sbc had some cooling problems, i had the steem holes drilled,i started with a single electric fan from a 5.0 with a factory radiator, then tried no thermostat, and then 180*stat,then dual pass dual 1" core aluminume northern radiator, with perma cool fans,1-12" 1- 14" still overheated sitting still,
finally i got my hands on a factory set of dual electic fans ( with fan shrouds ) and tried another factory radiator that kept it at 190-200* at a stop light.
don't underestimate the power of a proper fan shroud...  

Yes a fan shroud helps direct the air thru the radiator...but don't underestimate the power of a working thermostat, either     Usually its considered a barrier, but typically the problem gets found elsewhere....