converting to modern type valves for Model t's

‘54-’56 Ford V-8’s exhaust valves may be substituted for both exhaust and intake valves with the following modifications. Valve guides must be reamed out to 11/32”. Drill 7/64” hold in stem of valves about 3/16” above half lock groove. This hole for the spring seat pin. Drill out spring seat washers to 11/32”. Overall stem length generally alright, but individual stem grinding must be done to bring tapper clearance to recommended .015-.030” range.

It is possible to install modern half locks and spring seats, but you must get longer springs having same rebound characteristics as a T spring. 

December 1958 - Antique Automobile