I replaced the tubes through which the pushrods travel with stainless steel. Sounds easy enough but it turned into a labour of love: I ended up getting 1/16" wall tubing and having it turned down on a lathe to 1/32", which also made it the right outside diameter, 11/16" I think. It was then necessary to flare the top and bottom while the ends were coated with non-hardening Permatex. My friendly local machinist also made up a tool for flaring both ends at once, but it was challenging keeping the tubes in just the right spot, neither too high nor too low. (Remember that the oil from the top flows down these tubes to the lifters, so they can't be above the surface.)
In this picture you can also see that the intake guides are tapered at the top. After they were pressed in and reamed I brought home the head and a while later began staring at this feature and wondering about it. I think they may be upside down, but the originals were squared off like the exhausts anyway, and maybe less oil will sit around on the ledge this way, right?. Anyway, since they're a press-fit, it's not like they can be taken out and reversed now. |
