Posted by Dan in TN [172.68.73.45] on Friday, August 25, 2023 at 15:27:10 :
I'm trying to track down the source of a vacuum fluctuation in my freshly rebuilt 1946 230. It has about 3.5 hours of run time since the rebuild. It starts, idles, and revs up fine, but I'm seeing a fluctuation of about +/- 1" Hg at idle.
It seems too small (and too early) to be a burnt valve or worn valve guide. I've gone around the engine with propane while it's running and haven't noticed any surging that would indicate a vacuum leak. I've also double checked my value clearances and they looked fine (.010 intake and .012 exhaust cold).
I'd also like to double check that the ticking I'm hearing from the engine doesn't sound like something's wrong. This is my first flat head, and I know they're usually a little noisy, but if it's excessive I'll tear back into it and try to get it fixed before I put too much run time on it.
Please take a look at the linked video and let me know what you think, where I should start to track this down, if it's normal and I should stop worrying about it, or if my gauge is just too cheap and I need a better one.
Video if the link doesn't work -> https://youtu.be/d3vq3SL6LTM
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