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| | | | Joined: Aug 2005 Posts: 26 'Bolter | | 'Bolter Joined: Aug 2005 Posts: 26 | I have a 1949 Chevrolet ½ ton with the original 216 engine that has been modified with dual Carter W-1 carbs and an electric ignition.
I am the third owner on the truck after the first owner was a rancher that bought the truck new and sold it to my grandfather in 1955. I inherited the truck in 1972 and drove it original until 2000 when I tore it down to the frame and began a long restoration. The restoration is finally just about finished.
I just brought a 1949 Chevy 216 to life after twenty odd years. The 216 runs well and idles at 450 RPM. The concern I’m having is that the vacuum at idle is 10 inches vs the 20 inches I expected. I put dual Carter W-1 carbs on it. Do you expect the vacuum to drop when you double the carbs?
The compression on all the cylinders are good at around 115 PSI and the timing is on the mark. What do you think? | | | | | Joined: Jan 2000 Posts: 2,074 'Bolter | | 'Bolter Joined: Jan 2000 Posts: 2,074 | I would hook up a vacuum ga, engine running, rotate distributor until you get peak vacuum and lock it down. Let us know if that helps. Best of luck | | | | | Joined: Feb 2004 Posts: 29,881 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,881 | With two carbs you're lucky to get that much vacuum. Be happy with it.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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| | | | | Joined: Dec 2008 Posts: 1,923 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,923 | Adding a carb reduces the idle vacuum by about 29%
2^.5 = 1.414, 1 / 1.414 = .707, 1 - .707 = .29
Adding some initial spark (5 degrees?) may help, just crank it up a bit and evaluate results. The idle speed should go up; relax both idle speed screws the same amount to get the desired idle speed back. Vacuum should be higher. Throttle response may also be better. Road test, listen for pinging.
If it helps, remember to reduce the advance curve by the same amount as added to keep the total constant. | | |
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