Bore-through
A through-hole is not automatically a design
Some heads left the factory with a barrel open at the sole. Some met a drill press in a two-car garage and have been called “bore-through” ever since. Mal Vickers will tell you which one you set on the clapboard bench.
Factory
Chatter that was meant to be there
A true through-bore has a consistent wall, a planned ferrule stack, and a sole exit that was finished, not torn. Those heads can take a recut and a new film. They still hate chloride under the collar, same as a tip-in. The difference is how the stem is captured — through, not stopped.
Garage
A ragged exit and an oval mouth
A converted tip-in often shows torn sole metal, a bellied mouth, and epoxy where a designer never put a sleeve. Sometimes there is enough wall to recut. Sometimes the honest sentence is scrap. Full Bore at $320 is the consult plus the recut — it is not a resurrection guarantee.
Ferrule stack
Through-bores wear a different collar
A through-barrel usually wants a longer collar and a different seat. Catalog ferrules sold for tip-in heads hover or split on a through-bore after one Gulf summer. We measure the OD and the seat depth; we do not grab the bag that “looks close.”
Hold a full bore