The Ford Barn - View Single Post - Manifold vacuum at idle... vs without...interesting observations

Kilohertz · 01-25-2021, 11:36 AM

So my Dad came over to hear the flathead again after I got her tuned up, and I was mucking about with the timing light trying to figure out the advance curve on the mechanical springs with the vacuum can disconnected and his first comment is..."it sounds like it is retarded". One thing I have noticed is it has a hard time accelerating without stumbling and you kind of have to ease into the throttle to get it up to 2,000RPM, I figured I needed to adjust the accelerator pump. He said no, lets check the timing, but I assured him I had it set to the mark on the crank pulley and he said forget that, lets time it by ear. I loosened the clamp and we spun it around until the idle smoothed right out and when accelerating it jumped right up like it was a new engine! Ran great! So for grins I put the timing light on it and it was at about 10-12* advance at idle, and made it to 21* at 2500 RPM, this was still with the vacuum can disconnected. Well what the heck? My Dad used to hot rod these engines back in the 50's and knows them very well, way to go Dad, thanks!

Now this crank pulley looks like it has been changed, it is new, with a little bit of surface rust on it....is it possible it's marked wrong, or is the wrong pulley? Anyone else find this? I am not sure if I can accurately determine TDC without pulling a head off, and even then, there is a fair amount of crank* movement while the piston is at TDC.

For now I'm leaving it as it as it runs so well, but ultimately would like to know what is going on with the marks on the pulley and why it runs so good at this advance setting.

Cheers

01-25-2021, 11:36 AM	#32
Kilohertz Senior Member Join Date: Jan 2021 Location: Slightly left of Vernon, BC Posts: 155	Runs better now...but why So my Dad came over to hear the flathead again after I got her tuned up, and I was mucking about with the timing light trying to figure out the advance curve on the mechanical springs with the vacuum can disconnected and his first comment is..."it sounds like it is retarded". One thing I have noticed is it has a hard time accelerating without stumbling and you kind of have to ease into the throttle to get it up to 2,000RPM, I figured I needed to adjust the accelerator pump. He said no, lets check the timing, but I assured him I had it set to the mark on the crank pulley and he said forget that, lets time it by ear. I loosened the clamp and we spun it around until the idle smoothed right out and when accelerating it jumped right up like it was a new engine! Ran great! So for grins I put the timing light on it and it was at about 10-12* advance at idle, and made it to 21* at 2500 RPM, this was still with the vacuum can disconnected. Well what the heck? My Dad used to hot rod these engines back in the 50's and knows them very well, way to go Dad, thanks! Now this crank pulley looks like it has been changed, it is new, with a little bit of surface rust on it....is it possible it's marked wrong, or is the wrong pulley? Anyone else find this? I am not sure if I can accurately determine TDC without pulling a head off, and even then, there is a fair amount of crank* movement while the piston is at TDC. For now I'm leaving it as it as it runs so well, but ultimately would like to know what is going on with the marks on the pulley and why it runs so good at this advance setting. Cheers __________________ 1949 Ford F-47 with a '51 8BA Flatty, GM TBI fuel injection system, and a grey shop cat, Spot.