AS41 Engine – Day 4 – Valve lapping day is here!

There seemed to be a lot of people in agreement on a lot of different forums that regardless of if an head is new that the valves should all be lapped.

I tried to do it manually with the lapping tool I bought (below) but for whatever reason, that thing just would not work well on the valve. I don’t know if it is the incorrect size or what but it was a slow barely going nightmare.

Now many of the videos I watched didn’t use these old school tools at all. They all used drills attached to the stem to do the lapping. So I cut some fuel line to clamp on to a screw bit and then inserted the other end into the stem. I would quickly do it in one direction, then the other, then the other, never getting all that fast in revolutions. I was really trying to mimic the speed you could get rolling the suction tool in your hands. I think they turned out ok and are seated fairly well.

I took everything into the kitchen and cleaned the heads, valves, SCAT springs, and other assorted items with a Simply Green bath, being careful to keep the valves associated with their correct lapped port. I dried everything, and then re-cleaned the springs with carb cleaner.

Now reassembly proved far more difficult. Basically, the valve spring compressor really needs to be permanently mounted to a table. The action needed to compress the heads tends to cause the whole thing to slip, and you really need to simultaneously push down on the valve retainer to get the valve stem up through it to get the keepers on. I ended up using some c-clamps I had to more or less make the thing stationary and it made assembly a hell of a lot easier.

So all of the SCAT products are on the EMPI heads.

The next thing I need to do is decide on the rocker arms.

Now if I go with the stock 1:1 ratio ones, I can use the existing push rods I cleaned up. However, there’s almost no point in going to that new C20 cam with stock ratio.

Now I haven’t even started really looking into which way to go. The 1.25 ratio SCAT forged rockers with solid shafts (above) are what the SCAT rep recommended on the phone to go with the C20.

However, several other guides I read on cams said the 1.4 ratio arms were best for the C20. I also have a set of these (above) and they are very different than the SCAT and stock ones. You actually adjust the valve at the pushrod end… not the valve. Very different.

I’ll have to invest a bit more in the engine if I go with the ratio ones. I can decide later of course, but I’ll need to pick up one of those adjustable rod tools and a set of aftermarket pushrods that can be cut to fit whatever the rocker arm geometry comes out to with the specific ratio chosen.

Perhaps I’ll just go with the stock arm and stock pushrod setup for break-in on the stand and then determine afterwards if I want to swap the rockers and do all that custom geometry.