QUOTE(Toast @ Jul 20 2004, 01:03 PM)
I had push rod tubes in my 1776 VW engine.
Different animals. The Type I pushrod tubes get sandwiched between the head and the case, which means you have to remove the cylinder head to replace the pushrod tube seals. (Or use one of the collapsible tubes, like they do on 911s.) The ends of the Type I tubes are "accordioned" to provide some pressure to keep the tube ends against the head and case when the engine expands.
The Type IV engine has tubes that simply slide through the head and into the case bores. They do not have any "accordion" section, and don't need to expand with heat. That's why we have O-rings that slide along their bores, to allow for that expansion.