Originally Posted by shane p
no 400ci i have a few 350, i was thinking about building a 400 until i was told they have heating issues, 2 cylinders firing side by side? i could be wrong. but for the $ i think i will stick with a 350 build. just want an everyday driver with good power, what do you think? im not a super mechanic either all advice is welcome thanx
In the Gen I small block family of motors, including the 350 and 400, there are not any two cylinders firing side by side.
The rumor of 400's overheating is an old wive's tale.
The cylinders are siamezed, with no space between the cylinders. This was necessary to arrive at the very large 4.125" cylinder bore, but created a stall point where the cylinders intersect. When the factory built the motor, they found that the coolant would just sit there in the corners of the cylinders with no way to escape. They would make such a hot spot in the motor that they would contribute to early ignition (detonation) and maybe even help create a weak spot where the motor could spit out the head gasket. The engineers found that if they added a series of holes between the block deck and the cylinder heads, that coolant could flow through and eliminate the hot spots. Many racers have found out that the holes are not necessary if the motor is operated only as a race motor, because at elevated revs, there is so much flow in the water jacket that it washes out the hot spots and everything works well.
Problems arise when a hobbyist builds a 400 for all or some street duty, because the revs are not always high enough to wash out the hot spots, so the motor spits out the head gaskets at worst, or overheats at best. So, rodders not knowing to drill the heads for steam holes is what has lead to the rumor of overheating on 400's. Like all rumors, this one has been exagerated so that most rodders think all 400's just naturally overheat.