The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 400 sbc heads and steamholes? add them or?

B. W. · 03-23-2018, 03:09 PM

the theory is that without the steam holes the coolant doesn't flow in the pockets created by the siamese cylinders so it kinda sits it the pockets and creates hot spots. If I build a 400 I drill the holes but I have run a 400 with aluminum heads & no steam holes with no adverse effects. I'd still drill them though.

I don't know why you couldn't run drilled heads on a 350, the head gasket would seal them but, I haven't done it.

03-23-2018, 03:09 PM	#4
B. W. Registered User Join Date: Nov 2014 Location: Bigfork, Montana Posts: 1,137	Re: 400 sbc heads and steamholes? add them or? the theory is that without the steam holes the coolant doesn't flow in the pockets created by the siamese cylinders so it kinda sits it the pockets and creates hot spots. If I build a 400 I drill the holes but I have run a 400 with aluminum heads & no steam holes with no adverse effects. I'd still drill them though. I don't know why you couldn't run drilled heads on a 350, the head gasket would seal them but, I haven't done it.