Vacuum gauge

[Mike..Yorba Linda]

'36, 21 stud stock engine, dual 94's, Bubba set up dizzy. Trying to set up the holley's and the dial of vacuum gauge flutters. I've tried two different gauges. Is this normal? It's not even close to being still. Any suggestions? Might be able to post a video later. Thanks.....

[drolston]

Just put a vacuum gauge on my rebuilt 59A/B. It pulls 15 to 16 inches at idle which I believe is normal for an engine with a mild street cam (Schneider 248f) and three 97's. There is just a little fluctuation; less than 1 inch). I assume you are picking up vacuum at the manifold fitting that goes to the distributor and wipers. How much fluctuation are we talking about? Is the idle smooth, fluctuating, or sputtering?

First thing to do is to check for vacuum leaks around the manifold gasket, throttle bases, throttle shafts, and vacuum line. Then ensure that the carb linkage is adjusted so that all 4 throttle plates are completely closed at the same time, do not stick or bind, and that there is no spring or slop in the linkage that connects the two together. If any of that helps, it is your lucky day. In the unlucky department, valves sticking or not sealing is the most onerous cause of fluctuation. Try drizzling a pint of MMO through the carbs while bumping the rpm up and down a little to see if that unsticks the valves and steadies the vacuum. If not, we will need to road test for other symptoms.

[Talkwrench]

Sounds a bit like a leak but how much fluttering are we talking?

[Tinker]

http://members.iinet.net.au/~phatcar...%20SMALLER.jpg

[41LjH]

I have a a dedicated vacuum gauge on my truck. I remains steady unless I depress the accelerator.
My 8BA is modified, has a Isky Max 1 cam, headers, unilite, and a Weber 1403.
Check your connections and make sure you are using engine vacuum. Also make sure you are not loosing vacuum at the dizzy connection.
Good luck

[Mike..Yorba Linda]

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Good info.....I'm taking the reading from the manifold ...From the chart above it looks like my plug gaps are to close or the carbs are out of adjustment. It's a good start... I'll also do the spray trick to check for leaks first....Thanks guys!

[Talkwrench]

Normal rule of thumb with multi carbs is to disconnect the link to them, tune carbs separately then reconnect.