BR-Z Posted June 29, 2008 Share Posted June 29, 2008 I've found a P90 head which I would like to rebuild for a mild l28. The problem is, the cam and cam towers (plus rockers etc.) are gone! No problem (other than core) on the cam as I was planning on a custom cam anyway, and I believe new rockers are a good idea as well, but... WHAT can I do for cam towers? Can I pull towers from any L28? I would imagine that internally oiled cams (like the p90) would have unique oil passages, is this true? Do I need to find towers specifically from a P90 and nothing else? Finally, I understand it would be a good idea to maintain the cam tower positions from the donor head, but is there enough variance in the machining from the factory that I'm "doomed" such that cam towers from one head will never "line up" on a different head and give a true line-bored center? If not, the aluminum towers are themselves the bearing surface, so I'm not sure if there would be any options to re-machine... Please help, ye who are much smarter than me! Quote Link to comment Share on other sites More sharing options...
Zmanco Posted July 5, 2008 Share Posted July 5, 2008 I'm in the middle of switching to a P90 for my L28 NA and have a similar situation in that one of the towers on the head is cracked. My plan is to swap all the towers from a donor N42 head. I looked at the towers from the P90 and my donor N42 and the only difference I can see is that the there is only 1 oil hole on the bearing surface on the P90 at 6 oclock while there is a second at 9 oclock (facing the front of the head) on the N42. Also, given the N42 is externally oiled, there are the machined surfaces and holes for the oiling tube to be attached. I did notice that on the side of each tower near the base there is a two digit number. Does anyone know what it represents? If you search here you will find two sets of opinions on the importance (or lack thereof) in keeping the towers in place. Some claim it's no big deal to remove them as long as you are careful to ensure the cam doesn't bind when reinstalling. Others say the towers were line bored and should never be touched. I haven't seen anything definitive posted. In about two weeks I'll have mine together and will know more. Quote Link to comment Share on other sites More sharing options...
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