Reply to "COBRA JET: Unleashing The Performance Capabilities Of 351 Cleveland Engines With Open Chamber 4V Heads (Q Code)"

Yes I've heard of this. I've also heard of D3ZE heads with the larger 4V sized valves. There was obviously a transition period during construction that occurred in this order:

D1ZE heads were cast with larger chambers
The casting number changed from D1ZE to D3ZE
The valve sizes were reduced from 2.19/1.71 to 2.04/1.65
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