1964 Ford 4000 4 cyl gas vacuum reading.

[Grateful Farmer]

Hi All,
I have been working on refreshing a 1964 Ford 4000 4 cyl gas ( 172 cu ) that ran but had low compression. Alot of work has been done.
I have bored out the cylinders to .040 over, new pistons, rings, bearings, seals, cam shaft, cam shaft gear, turned cranked, flattened the deck, new valves, valve guides, springs, reground and lapped valve seats, new coil, and distributor, etc... I got the engine back together timed correctly and running. After it ran a few gallons of gas through it, I checked the compression and now it was 125psi on all 4 cylinders - awesome! When checking the vacuum at the port above the carburetor at the Intake, I get a vacuum of approx. 19 in Hg, but the needle is bouncing. It bounces approx 2 in Hg centered on 19 in Hg at idle and higher rpm's. I can't find anything on the web showing vacuum readings above the updraft carburetor to see if this may be normal. I see a lot of info on classic cars when the vacuum should be steady, otherwise it probably indicates a mechanical issue. But I have already addressed all the mechanical issues. Could this be a carburetor adjustment issue, or is it a none issue ?
See the attached video.

 

[used red MN]

Remember what Elmer Fudd used to say? Be wery, wery quiet I’m hunting a “wabbit”! So if you don’t tell your engine it has a problem it is going to plow, disk, plant, bale the back 40 or whatever you want it to do for you for years and be non the wiser. A vacuum gauge can be a helpful tool to diagnose a problem if you have one. A vacuum gauge can be very definitive in diagnosing some problems such as showing a low vacuum at steady RPM which would indicate a plugged exhaust. The quivering needle identified by a vacuum gauge can have very subjective outcomes. As said above, no need to look for a problem that is not evident.

 

[Grateful Farmer]

Thanks used red MN! I'm sure that you are right that it probably doesn't matter. I guess I will try to move on and leave my vacuum gauge in the toolbox, but I was curious if anyone out there has had a similar experience. Does anyone see a steady vacuum reading on these updraft carburetors at the intake manifold? ( 2N, 9N, 8N, 601, 801, 2000, 4000, etc?) Or is a fluttering vacuum completely normal? Thanks All !

 

[sotxbill]

Guessing valves not sealing or rings not seated.. but the compression test seems to say otherwise. I would guess that after a couple hours of running it will smooth out some more. guides will loosen up, and seats wear in.

 

[Grateful Farmer]

OK, Thanks guys!