The Ford Barn

Kilohertz · 01-17-2021, 10:40 PM

I was able to run the flathead engine today until the T-stats opened and everything seemed to find it's happy place. I was able to set the timing just so and played around with the vacuum advance and I made an interesting observation. I am using my modified GM distributor and vacuum advance can which currently advances 14* at idle, a little too much but for now it's okay.

When I first started the engine a few weeks ago it had that classic flathead sound out of the open headers, you know the burble....today I made some comparisons with and without vacuum advance at idle. With the vacuum can disconnected, the idle sounded rough, the exhaust was quite loud from the open headers, ran fine, just sounded a little...well, unhappy. I connected the vacuum advance (manifold) and the engine just seemed to sigh a happy sound and it just ran smoother, and was very much quieter out of the exhaust. I know it's to do with the timing of the firing and firing 14* before the exhaust opens will be quieter than opening them at 2* BTDC, I was just amazed at how much different the engine ran. I plugged and unplugged the line a few times during the recording.

I thought some of you might enjoy this analysis.

Cheers

https://www.dropbox.com/s/vpgcd0rf9y...acuum.mp3?dl=0

01-17-2021, 10:40 PM	#1
Kilohertz Senior Member Join Date: Jan 2021 Location: Slightly left of Vernon, BC Posts: 155	Manifold vacuum at idle... vs without...interesting observations I was able to run the flathead engine today until the T-stats opened and everything seemed to find it's happy place. I was able to set the timing just so and played around with the vacuum advance and I made an interesting observation. I am using my modified GM distributor and vacuum advance can which currently advances 14* at idle, a little too much but for now it's okay. When I first started the engine a few weeks ago it had that classic flathead sound out of the open headers, you know the burble....today I made some comparisons with and without vacuum advance at idle. With the vacuum can disconnected, the idle sounded rough, the exhaust was quite loud from the open headers, ran fine, just sounded a little...well, unhappy. I connected the vacuum advance (manifold) and the engine just seemed to sigh a happy sound and it just ran smoother, and was very much quieter out of the exhaust. I know it's to do with the timing of the firing and firing 14* before the exhaust opens will be quieter than opening them at 2* BTDC, I was just amazed at how much different the engine ran. I plugged and unplugged the line a few times during the recording. I thought some of you might enjoy this analysis. Cheers https://www.dropbox.com/s/vpgcd0rf9y...acuum.mp3?dl=0 Last edited by Kilohertz; 01-17-2021 at 11:56 PM.