1972 Dodge Colt

what is the problem with the small bore that they cannot do?
The top plate that he seals the chamber to is larger than 4.0.
So to position the smaller slant chamber he could not find any plate to do it.
As he explained to me, it has to seal with no leaks to start the test.
Between the 4 head bolt holes on the small chamber it was no Bueno.