NEW to the site. Glad to be in such good company. I have an ohc engine that I have just taken apart the bores look great bored .040 over. I am thinking of just haven it " cooked" checked for cracks then honing it out. My real question is with the cam housing and the head. Being that IM not real familar in taking these engines apart any input would be helpful.How does the cam come out of the housing? What precautions do you have to take as far as the valves are conserned? I was thinking about just sending it out to primetech. Will I get my best bang for the buck there? I actually have two ZH engines and one ZL. Im sure there is a member here with experience with them personlly but I forget your name ? Thanks Chris
the shop will do the repairs and replace the bearings just ask them usually they replace them if the are installed and cannot be removed without a tool to clean and prep. put bronze guides and stainless valves for the gas used today.
The cam comes out with careful application of a BFH. You have to drive the cam retaining plug out through the back of the cam housing using the cam as a battering ram. There are some advocates who claim you can also drop it nose-first onto a slab of wood, but I don't think that's the best way.
The valves are super critical. The tip of each valve must be 0.850" +/- 0.020" above the upper deck of the head. The ONLY exception to this is if you run a re-ground cam and you want to correct the valve-train geometry. There are no cam bearings in the cam housing. The cast Iron cam rides diectly on the Aluminum housing with oil pressure.
Contact me at Primatech and I will put you in touch with our cam replacement instructions. They describe removing the old cam and breaking in the new one.
We believe we do a better job on OHC heads than virtually anyone. We've done more OHC heads in the last 3 years than most machinists will do in their career. For an example of a head we've done, see:
