Are B heads all the Same?

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  1. #1

    Default Are B heads all the Same?

    Hi Everyone,
    I'm running B heads in my drag car, its a 4.6 liter modular motor with a vortech xi supercharger. Was originally running a teksid but decided to give the 5.0 boss block a try with more cu inch. The stamp on the heads is Rf-F6ZE-6CO64-AD. I run a custom Hogan intake manifold. Currently I have decided to have a new intake manifold built this winter. The fabricator has asked me to send my heads to him so he can build the new intake. I was thinking since I have so much money invested into my heads that it may be a wise to buy a set of used B heads for cheap and send them for him to build off and keep the modified ones on my motor. The problem I'm faced with is I cant seem to find a used set with the same stamp as I currently have. Do all B heads have the same perimeter dimensions, same port sizes, etc? I really don't want to have an expensive intake built to later find out they don't fit. If this is true what yrs and makes all have the same b heads?

    Thanks in advance,

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  3. #2


    From an external dimensions and fit point of view any '93 or later Mk VIII head should be the same, Peter. You might want to check the port dimensions on your FoxLake heads to see if they are larger than the as cast OEM head. If they are you would be better off sending the heads you will use on the motor to the fabricator so he can properly port match the manifold flange to the heads.

    With respect to the BOSS 5.0 block you might want to tread lightly over there. For n/a applications the block has performed better than it has for boosted applications. The issue is 100mm bore centers and 94mm bores. That only leaves a 6mm (0.236") web between bores. This is inadequate to seal up a supercharged engine. The upshot is a failed head gasket and a cutting torch like flame propagating through the gap between the block and the head from the now destroyed gasket. That cutting torch like flame can and will melt away both block and head material. You will be left with an unusable block and severely damaged high dollar heads.

    Copper gaskets and stainless o-rings can help to somewhat improve the block / head interface but the bottom line is the block is a great n/a block and not so great a supercharged block. Get a good standard bore Teksid or Aluminator block. You will be much happier.


  4. #3


    Thanks for the info. I have been thinking of going back to the safe all teksid but will give the boss a try with cation.

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