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| | | | Joined: Feb 2003 Posts: 452 Shop Shark | | Shop Shark Joined: Feb 2003 Posts: 452 | Hi Guys
Just finished cleaning the carb and tried tuning the engine. I used a vacuum gauge to set the idle. The maximum vacuum I was able to achieve was 15.5 in. Hg. The book says I should get between 17-21. Should this low number be expected at Calgary's elevation of 3500' above sea level, or do I need to do more work?
Thanks for the help.
Peter
Current fleet (subject to change w/o notice) \'49 GMC 3/4-Ton , 60 Austin Healey Frog-eye Sprite (some assembly required), 2011 Dodge Avenger, 2015 Jeep Cherokee. No, they don't all run. My other ride is a (B737)no, (B767)no, A320.... Update... was Embraer E190, now Boeing B787. Knowledge is a wonderful thing, but ignorance means you don't know you can't do something.
| | | | | Joined: Jan 2008 Posts: 4,962 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,962 | Expect less vacuum at higher elevations. A lot of vacuum gauges are not all that accurate. If you're worried about a vacuum leak, spray some Diesel or Marvel mystery Oil around the carb and intake manifold gaskets. If you have a vacuum leak, it will suck it in and the exhaust will smoke white. | | | | | Joined: Feb 2003 Posts: 452 Shop Shark | | Shop Shark Joined: Feb 2003 Posts: 452 | Thanks CR.
That's what I thought, but wanted confirmation.
Peter
Current fleet (subject to change w/o notice) \'49 GMC 3/4-Ton , 60 Austin Healey Frog-eye Sprite (some assembly required), 2011 Dodge Avenger, 2015 Jeep Cherokee. No, they don't all run. My other ride is a (B737)no, (B767)no, A320.... Update... was Embraer E190, now Boeing B787. Knowledge is a wonderful thing, but ignorance means you don't know you can't do something.
| | | | | Joined: Jul 2007 Posts: 461 Shop Shark | | Shop Shark Joined: Jul 2007 Posts: 461 | A rule of thumb for manifold vacuum is a loss of 1" Hg per thousand feet above sea level. With that, you could expect 3.5" Hg less than the 17-21 level given. Even with the expected loss from altitude, your level of 15.5" Hg seems low. Make sure your initial timing is set correctly, and the idle speed is 550-600 RPM after setting the timing. The idea that your gauge is off is equally valid, but there isn't a good way to check that without a second gauge or a calibration set-up.
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