Aight Bewy.......

Just for kicks, I relocated the vacuum advance to a manifold outlet tonight. Made zero difference in idle RPM. But with only 6hg vacuum idle, I didn't think it would make much difference if any and it didn't Haven't driven it yet.

What I have discovered though, in driving it the last few times is, it has a light spark knock right at cruise tip in. It stops immediately after going on into the gas. Even lugging it hard in high gear at low RPM only produces a slight rattle at tip in, but nothing when I really plow into it. My first thought was the vacuum advance. Disconnected it and no change. I haven't driven it since I changed to full manifold vacuum at the can, but I see no reason why that would make it stop.

The change I made that I THINK caused it......I had a 1.5" thick carburetor adapter on the Offenhauser manifold. I got the correct 1/2" thick Offenhauser adapter and that's when Kitty noticed it was doing it. I'm really hard of hearing in the higher frequencies, but once she pointed it out, I heard it.

I did go from the 3.5 power valve back to my 9.5 power valve thinking it was a lean tip in, but no change. Now, Kitty and I talked about it and I asked her if she thought it was possible it's been doing it the whole time and she said she didn't think so. It was the first time we drove it after I changed the adapter that she noticed it. I can give it tip in and hold it and as soon as the car speed picks up and matches the extra pedal, it stops doing it. If I bend the floor board with the gas pedal, it does it for a split second and then stops. I've tried going from 23.5* initial down to about 17.5* initial with no change. I have a friend getting me a couple of gallons of 114 race gas just to see if that stops it. If it does not, I will rule out it being spark knock. I'm almost to that point now. It doesn't sound like any spark knock I've ever heard. It's very high frequency. Kitty pegged it when she said it sounds like a glass jar full of marbles being shaken for a second. And that's what it sounds like. It's not metallic like spark knock....but I know it can sound different in every engine so.......I'm open to suggestions. I'm thinking maybe even trying a size or two up on the primary jets. I don't want to back off the initial anymore because 1) I don't think it's the initial timing, since that didn't change it and 2) I don't want to start losing power backing the timing off.