Re: 400 sbc question about running hot?
Alright alright alright. The 400 running hot thing more often then not came from running non-400 heads on a GM 400 block. GM put the steam holes in the block because the way it was cast it could have a pocket develop in certain spots and under certain conditions. 400 heads and gaskets have corresponding holes that let any steam that may form and get trapped at continuous low RPM operation (which Lingenfelter called under 3500RPM) up into the head so it can get swept away. High speed operation without steam holes in the heads can sweep the pockets away on its own. If you know that and you know how your engine is used, it's up to you whether or not to drill the holes in the heads.
Now, I think the confusion comes about because 400's don't necessarily "run hot" by the normal definition which is going by the coolant temperature. The pockets that can form cause a localized hot spot in a place on the block which is subject to high heat which is also a relatively thin spot. Over time this can lead to a crack forming and when it has happened I'll bet the majority of the time it has happened with non-400 heads without steam holes corresponding to the block holes. GM most likely did the steam hole thing not because it was the best option but because it was the cheapest and easiest.
My question is this: If every reputable head manufacturer on the planet says to drill the steam holes in the heads if they are being used on a GM 400 block, why would anyone not do it when using a GM 400 block regardless of what anyone else says? It certainly can't hurt, doesn't cost much, and takes no time. It's like saying that no one in your immediate circle of friends has ever lost an eye while using a grinder therefore safety glasses are never necessary.
The aftermarket blocks do not require it. Why? Because they do not have steam holes in the block. Why? Because the water jackets have been redesigned so that pockets do not form like in a GM block and the area is thicker.
Owner of a Dart SHP 400 block with AFR heads and NO steam holes.
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
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