tappet types

grahamdelooze · Post by **grahamdelooze** » Thu Apr 28, 2005 4:23 pm

I have two types of tappet in my engine plain end ferrari ones and ball end motorcycle ones.anyone know which motorcycle they are from.

Post by **tyang** » Thu Apr 28, 2005 9:27 pm

I've seen this modification done on some Ferrari engines, and seems like a worthwile mod. It gives the adjusting screw a larger contact area for the top of the valve, and I'm sure cuts down friction, heat, and wear. Porsche 911s have this type of adjusting screw, and may even be the same thread. Anyone know if these will work?

Tom

TOMKIZER · Post by **TOMKIZER** » Tue May 03, 2005 5:10 pm

Tom, if you are talking about the lash adjusting screw with a flattened ball in a socket in one end, I have them in my 365 GT 2+2. I've been running them since my engine restoration (completed 1997), which is about 3,000 km (2,000 mi). I have mixed feelings about them. First, I believe that they reduce the stress at the valve stem tip, where the adjusting screw contacts the valve. The flat on the ball is truly flat and is slightly over 3 mm diameter. Because the original adjusting screw has a rounded tip, its contact stress is necessarily higher in my opinion. That ball/socket feature, however, gives me two other concerns - lubrication and screw breakage. The ball/socket gets lubricated from the top through a hole drilled the length of the screw (based on the principle of "wishful thinking"). The drilled hole reduces the cross-sectional area of the screw, making it higher stressed in bending - possibly leading to a tendancy to break. Proof: One of mine broke after only 1,500 miles - possibly due to the aforementioned bending overstress or perhaps due to overheating due to lack of lubrication. Who Knows??? I replaced it with another identical screw and have had no further problems. I did, however, soak all the screws in oil for several hours before installing them the first time, to make sure that the ball socket was at least initially lubed. Now that I have frightened myself, I think I will verify that they are all free in their sockets before I put it back on the road.

I'm sorry for the novel but anything that can destroy a Ferrari engine is important to me.

Tom Kizer

Stephanm · Post by **Stephanm** » Tue May 03, 2005 8:04 pm

The "ball and socket" style is from an Alfa Romeo. I have seen them break on a 365 2+2 as well and think they are not a good idea. People use them as a "stop gap" to allow a tired engine to keep going but the gometry isn't right for the follower. In fact, the follower assembly for any Ferrari V-12 is incorrect because the wheel is too large causing the adjuster to slide on the valve stem too much.

grahamdelooze · Post by **grahamdelooze** » Sat May 07, 2005 4:38 pm

do you know if the folowers are hardened through so they will take a grind, mine have some surface marks.