Conclusion of this article. CVO 110 Cylinder Studs
Steve and I began to measure the distance between cylinder studs on the various Twin Cam engines. The TC 88 studs are 3.720" apart from side to side and 3.120" apart from front to rear. We then did the same measurements on a TC 96 engine and found them to be the same as the TC 88, which is not a great surprise. Obviously, the cylinder stud distances will be the same for big-bore TC 95 and TC 103 engines as their smaller-bore TC 88 and TC 96 counterparts. The CVO 110 measurements are 3.720" apart from side to side and 3.120" apart from front to rear.
Wow! That means the factory is using the same cylinder stud dimensions across a 0.250" larger bore differential! With that being the case, how can the cylinder studs on both engines be in the middle of the gasket surface to apply equal pressure? This is one more redesign that needs to occur.
Although, in all fairness, I must say that the S&S 116", 4"-bore cylinders and 124" with even bigger 4-1/8"-bore cylinders use the stock Twin Cam cylinders’ stud dimensions when these engines are built with stock Twin Cam engine crankcases. I think the differences in success ratios exist in the better construction of the S&S big-bore cylinders, and the fact that its engines run cooler than the CVO 110 because of its use of an IST ignition system. The IST has an antiknock component, which means it senses combustion chamber detonation (spark knock) and changes ignition timing to eliminate the knock. Detonation occurs from heat, so the IST ignition allows sufficient fuel and altered timing to combat the effects of excess heat.
Cross Section Of Cylinders
As you can see in the accompanying photo, we cut a TC 88 cylinder and a CVO 110 problematic cylinder in half. The difference in bore sizes is evident, since the TC 88 has a bore diameter of 3-3/4", while the massive bore of the CVO 110 is 4", which is a full 1/4" (0.250") bigger in diameter.
The cylinder liner is not a press fit into the cast portions of the cylinder. In fact, on both the TC 88 and CVO 110 cylinders, the cast-iron liners are spiny-lock-cast into the aluminum cylinder bodies. Therefore, we cannot remove the liner nor can it move up or down. The question becomes, if the liner cannot move then why does there appear to be separation of the liner from the cylinder body at the top gasket deck?
The 45-degree crosshatching in the cylinder bores indicates that neither cylinder has much mileage on it. Rings would not break in correctly if the fine abrasions in the crosshatching were on the same horizontal plane. The crosshatch also serves for oil retention in the cylinder wall to assist in piston-to-wall lubrication. From top to bottom on both cylinders, there is a narrow circumference band of carbon buildup. Combustion byproduct carbon burns on in this area, located above the farthest distance travelled by the piston’s top compression ring. The next area is wider and is worn. This is where the rings stop in the cylinder at the Top Dead Center (TDC) point of their stroke and change direction. The crosshatched section is next. It’s the largest area of the cylinder, and it’s where the pistons and rings travel. The next narrow circumferential band is the area where the rings once again stop and change direction at Bottom Dead Center (BDC).
Finally, the last portion is the liner flange, which extends down into the motor case spigot hole. The flange has a dual function. First, the external outside portion receives and gives symbiotic support with and to the engine cases. Second, it gives support to the piston near and at the bottom of its stroke. Remember, the piston extends farther down after the lowest oil ring set.
Oil Return Dowel
As stated earlier, the dowels in the cylinder’s head gasket surface do double duty as a cylinder-to-head locating pin and a return oil router. Evo engines suffered from weeping head gaskets because the oil return hole on the head gasket surface between the cylinder and head didn’t have an O-ring or a dowel to help keep the return oil where it belongs. For the last two decades the Heavy Duty Cycles crew has been machining the problematic Evo head gasket surface return holes to a larger diameter in both the head and cylinder to accommodate a hollow oil-routing dowel pin. We then use a Viton rubber O-ring around the dowel as an extra sealing measure.
The Twin Cam instituted this sealing system to its credit in the 1999-2003 TC 88. However, H-D then discontinued the dowel’s O-ring, thus eliminating this sealing design. As you can see in the photo on the previous page, these dowel pins are located just outside the cylinder liner.
The cast-iron liner and the aluminum alloy cylinder expand and contract at different rates. On a damaged CVO 110 cylinder, I can run my fingernail along the alloy cylinder gasket surface towards the cylinder bore and it will hook onto the edge of the cylinder liner. The multilayer system (MLS) gasket design depends on a flat surface to seal in compression and seal out oil. This cylinder liner lip, in conjunction with a warped head gasket surface, wreaks havoc with a MLS gasket’s sealing capability.
Compounding this problem is the fact that there is not enough space between the dowel and cylinder liner. It is my belief that the 110 cylinder needs a redesign for a variety of undeniable reasons. The cylinder and head fins are inadequate, since they are less than a TC 88’s fin area. The CVO 110 needs an increase in fin surface area for heat dissipation. Both the dowels and the cylinder studs need relocation to the center of the gasket surface, so one metal type will adequately surround the dowels.
Replacing the four cylinder studs with five equidistant ones will ably assist in combating the exceptional rear cylinder heat, since the cylinder studs will be able to apply more even pressure to seal the head gasket. The alloy composition of the heads also needs changing to resist high temperature-induced warping. Finally, the spiny-lock methodology found in the TC 88 cylinder needs reintroduction into the CVO 110 spiny-lock design.
However, not all the above solutions would be necessary if there were a reduction in combustion chamber temperatures. These are some of the reasons we are using aftermarket cylinders on the CVO 110s we repair, in conjunction with oil coolers, a cylinder head fan, and lowering the air/fuel mixture ratios.
Conclusion
Next month I’m going to continue investigating the controversial head gasket and other cylinder liner issues.
Donny Petersen
Tattoo Tony’s Heavy Duty Cycles
Toronto, Canada
www.HeavyDutyCycles.com 
Techline-March09-H-D 110" CVO - Part III: The cylinders and other issues (concludes) 
Linear Mode
