Dug this old post back up to look up a few things and see that it's still taking hits so I'll update the engines progress.
Way back after I got it running I posed a question about whether I should be concerned with a rapidly fluctuating vacuum reading at idle and I'll answer the question as yes, I should have been concerned. The vacuum should be much more steady if not completely steady at idle, even with a hotter cam.
I could never get a good idle so in deciphering the vacuum readings I decided to pull the head and investigate. The readings told me that I either had a sticking valve or a blown head gasket. I found #3 intake would stick and some marks on the #3 piston indicates that it was helping to close it. Thankfully no more damage other a few indentations.
I detailed some other problems I encountered with the valve springs in another thread but will update here. I found the original springs to have a free height of 2.04" - 2.06" and specs called for 2.15" and/or 2.25". I ordered new 2.15" springs and all new intake valves. I lapped them in and installed the new intakes and springs, cleaned up and relapped the exhausts.
They all failed my bench top "fill the ports with gas test" as they all weeped gas when closed before tear down and the exhausts still did after relapping.
Well even though this machine shop shop did a great job on my 216's head I decided to take the head to another machine shop to go completely through the head again. This shop will do a vacuum test to ensure each cylinder seals before they stick a fork in it. The original rebuilder told me the original intakes and springs were fine and only after perhaps 3 hrs of run time I find out one was sticking and the others weren't sealing when closed.
I'll fill the ports again and test before I bolt it all back together, these gaskets kits tain't cheap....
Dave
