Originally Posted by clevo400
I thought (4 dot) 4V heads were off a GT Phase 2,3 or 4 and were machined for solid cams !!!
I was wrong !!!
Anyone know about 4V (4 dot) heads ???
There is nothing special about the 4. heads in the US. The major difference between them and the plain 4 heads is that the chambers are slightly larger. The 4. heads are about a nominal 68cc and the 4 (no dot) heads are smaller at a nominal 64cc.
There isn't anything else that is really different about them. The 4. heads are a revision that slightly increased chamber size to help prevent detonation in "late" model engines where pinging was an issue with then-available regular fuel. A couple of CCs, combined with the retarded camshaft, reduced compression enough that the engines were more stable with regular fuel. Ford recommended premium fuel for 4V equiped engines, but people often didn't follow the recommendations and used regular fuel with warranty-related problems as the result. Ford's remedy for this was increasing the chamber size enough to help prevent pinging.
Neither was particularly likely to have mechanical valve train, as most were installed on M-code, hydraulic cammed engines with non-adjustable valve train.