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Discussion Starter #1
it doesn't take much thinking to look at a 400 head gasket laying on a head to understand how the bigger bore would help with airflow. Sooo,, thinking of how the 4.060 bore block i'm looking at , could you blend the top of the bore of the block to the 4.125 bore diameter and do the same to the heads to match the advantage of the bigger bore ???
 

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Many big blocks had this from the factory. I wouldn't go all the way to a 400 gasket because of the dead space everywhere else (most 400 gaskets are 4.165 bore). Stay away from the rings and remember you'll lose some compression. Unshrouding the heads to a 350 gasket will help a lot with less hassle.
 

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Un-shrouding the chambers can both help and hurt. By opening up the chamber around the valve you might see a flow improvement with the aid of a flowbench (or it could get worse if you do it by eyeball guess). One thing is for sure is you will add volume to your chamber which will lower your Static Compression Ratio. If the flow gains don't gain more HP than the HP lost from the reduction in CR then the end result is a net loss in performance.

I wouldn't even consider grinding the top of the 4.060" bore out to 4.125" unless you really need a spare boat anchor.
 

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Discussion Starter #4
reading ,,

i was reading about some guys that used to build datsun engines and did this ,,, just trying to gain as much information about any possible advantage before we start putting this thing together ,, once its in the car , its too late
 
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