While this is a Jern Thunderbolt over head on Model A the info should be the same. What clearance are you setting the rocker arms at when using modern valves. The speck's for 28 Chevrolet say .006 intake and .008 exhaust when brought up to running temp. Too tight/loose? What do you set yours at cold? I would think the setting would work for RAJO etc over heads.
Mark - I have mine a bit wider, as was recommended my others on this forum. Cold settings: intakes are .012" and exhausts are .015". Seems to run great, no problems.
A old article from Vintage Ford regarding OVH valve clearances for RAJO heads suggested .009" for intakes and .012" for exhausts, cold. Hot settings suggested were .007" for intakes and .010" for exhausts.
Once I get my engine back together (replacing a rod), I may tighten them up a little and see how she runs.
Since Mr Jern is now deceased, are any of his family selling the kits to convert a chevy head to a T?
Yes. the web site is up and another fellow has taken over....
I think he was doing the machine work for Mr. Jern....