I have used the search button but could not find the specific answer to my question, which is: What type of valve seals are recommended for a 1958 Chevy 235 cu. in. inline six? Mine has an 848 head on which a previous owner had installed umbrella type seals. The valve guides are worn pretty badly and will be replaced, but I don't know if it's better to stay with factory-type O ring seals or positive seals. Also I don't know if valve seals are recommended for both exhaust and intake valves. I would greatly appreciate advice from someone more familiar with these engines than I am. Thank you in advance!
Have your machinist machine the tops of the guide bosses to either .500" or .530" and install one of the many seals offered in the Summit, Jegs, Perfomance Parts, Speedway, etc catalogs. All my GMC's have them. I started with PC's but moved to the full metal side ones. Some say you don't need them on exhausts. All engines without roller tips will wear guides since they actually push the valve stem slightly sideways each operation.
For street use, with fresh guides, use the O-rings on all 12. The PC type machine-to-fit positive seals were the best setup for years, but with the horrible gas today, stem to guide clearance needs to be increased, and you need more lubrication up there. Also, instead of replacing the guides, use a K-Line or similar liner in the factory guide, & ream to a minimum .002 clearance.
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