Spiney-lock is a method of casting the iron cylinder liner to the aluminum cylinder block so that there is a bond between the aluminum and iron sufficient to seal the interface and not allow differential movement between the two parts. This method has been used successfully for years in auto engines (read 'water-cooled'). Generally, the difference in thermal expansion of aluminum to iron is 2:1. The more the parts heat/cool from their solid cast temperature, the higher the stress at the interface. This can be
The interesting thing about the AIM article is that while the 110 engine casting sample was noted to have a different spiney-lock-cast distance from the head gasket than the 96 engine, in no way was there separation along the length of the cylinder body. So how could the top surface of the cylinder not be even with the top surface of the block? Don't know, but Donny stated he did find a diff on the rear cylinder of the 110 in his article.
Someone on this thread remarked they knew only 2 folks who has >5K miles without the upgrade. Don't know if they are including me, but, if not, make me #3. I have a FLHTCUSE3 (08) with 10,300 miles and no symptoms/leaks yet. I'm waiting for a symptom b4 I use my letter from the MOCO (received it in Aug 08, with the fancy book). Not sure if I should be proactive or not - hate to open up a tight, good running motor.
T-man in TN