1969 Dodge Dart Custom Sedan Slant Six, Father-Son Project
Thank you, eBay, for helping me find a remanufactured cylinder head for cheaper than what it wouldve cost to have the stock one machined! It came with new bronze liners, hardened valve seats, and a single-angle valve job.
After many, many careful measurements, I concluded that the remanufactured head was milled somewhere between 0.021 and 0.026. This was consistent with the shop I bought it from saying that it was the second time this head had been worked.
It has the same casting number as the original head, which I was glad for, since 1969 heads had a more efficient combustion chamber shape compared to earlier heads.
The rotary tool got a workout doing clean up to the valve bowls and passageways leading to them (yes, a respirator was worn). Mostly this consisted of blending out machining marks, matching the valve seat insert diameters to the bowls below them (they were quite a bit different, leaving a ledge), and contouring the valve stem casting bump-out. Some of the runners had really horrible casting blemishes resembling mini-stalactites!
On the exhaust side, I did an extra step of smoothing everything. On the intake side I didnt bother; a little bit of roughness can help keep fuel atomized a bit better, especially at low RPM / low throttle settings (when intake port velocities are low enough to not care how clean and big the port sizes are).
I also removed casting roughness from the combustion chambers, as well as blended a bit off of the sides of combustion chambers along the outboard edges of the valve seat areas.
No hogging-out, just simple, conservative machining work.
My poor-mans flow bench (think shop vac and kill-a-watt meter) resulted in a small but noticeable amount of flow increase, which was good enough for me!
With all that done, the head was cleaned and painted, and the stiffer valve springs that match the Erson camshaft were installed. Assembly lube on the valve stems and rocker arm shaft. Lookin good.