Head Aches

After lapping the valves I was ready to assemble the heads. Unfortunately I realised that the intake valves would need 0.1 inches of shims. That's a lot and I wasn't sure if they would stay put. I took the heads and their parts to TuumaCID and found a solution. We measured a bunch of other valve springs and found a set that had the same pressures as my original Comp 942-16 but with 1.800 inch install height. With them I would not need to add any shims.

While we were checking the springs, I also decided to get new rocker arm studs. One was missing and the rest were quite worn anyway so I got a full set. Problems started when I installed them. I removed the old and screwed in the new. At that point I noticed that at least two flanges in the head had cracks in them. The new studs were wider at the top of the threads and opened them up. Great...

Luckily I found help from the same place where the valves and seats had been machined. I removed everything from the heads and drove over to see if they could be fixed. After waiting some hours one of them had been welded. Next we tested the studs again and realized, that the new ones were a lot longer that the old. This actually proved to be a good thing because we could machine the flanges 8 mm lower. By doing that, their walls at least doubled in thickness.

I left the heads to be finalized and after a couple of days they were done. There had been three cracks in both heads and all were welded. Luckily the cracks were in the flanges and not in the combustion chamber. The threads had also been pretty bad and heli-coils had been installed in two holes. The rest had just needed some re-threading. Finally all flanges had been lowered. The results looked really good.

Welded and machined head

Repaired threads

After investigating the new studs, we realized that they were meant to be used with guide plates. The flare in the threads situated the plate correctly. As I did not use them, I needed to place a thick washers on the heads. To make sure no water would leak from the studs, I added some thread sealer and thread locker on them. Hopefully they were finally ready to be used.

Lapping The Valves

Lapping the valves should not be absolutely necessary after a valve job but I did it anyway to see where the valves contacted the seats. The heads had been modified quite extensively so I did not want leave any doubts about the valves fitting them.

Lapping itself is really simple. I bought some lapping compound and a lapping tool that is just a stick with suction cups in each end. The grinding compound had coarse and fine paste and you start with the rough stuff. I spread it on the valve face, pushed the stem in the guide and attached the tool.

I rotated the lapping tool back and forth between my hands while pressing it lightly towards the head. After a few rotations I tapped the valve with its seat a few times to get more paste between them. After doing this I got a nice grey ring on both surfaces. Then I needed to clean the valve and seat and do the same thing with the fine paste. It took a few hours to lap all 16 valves.

All seats were fine but the contact area on the intake valves was quite near the edge. Should be fine but there is no room for any more machining.