Carb vacuum port ID
From Crankshaft Coalition Wiki
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Many Holley 4150/4160 carbs will have a ported vacuum port on the side of the metering block. The other vacuum ports will usually be manifold vacuum. | Many Holley 4150/4160 carbs will have a ported vacuum port on the side of the metering block. The other vacuum ports will usually be manifold vacuum. | ||
| + | ==Engine diagnosis using a vacuum gauge== | ||
| + | *'''[[Vacuum gauge engine diagnosis]]''' | ||
| + | *'''[[Finding vacuum leaks]]''' | ||
| + | *[http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm Vacuum gauge chart] | ||
| + | *[http://www.secondchancegarage.com/public/186.cfm How to Use and Interpret a Vacuum Gauge] | ||
| + | *[http://www.gregsengine.com/using-a-vacuum-gauge.html Engine Testing with a Vacuum Gauge] | ||
| − | + | ==Table of diagnostic vacuum readings== | |
| − | + | ||
| − | + | bgcolor="white"> | |
| − | + | <td colspan="3"> </td> | |
| + | </tr> | ||
| + | <tr bgcolor="#CCCCFF"> | ||
| + | <th width="26%">ENGINE RPM</th> | ||
| + | <th width="28%">GAUGE READING</th> | ||
| + | <th width="46%">ENGINE CONDITION</th> | ||
| + | </tr> | ||
| + | <tr bgcolor="white"> | ||
| + | <td width="26%">Smooth and steady idle<br> (800 to 1200 RPM)</td> | ||
| + | <td width="28%">Between 17 to 21 inches</td> | ||
| + | <td width="46%">Engine is in good condition, but perform next test to be sure.</td> | ||
| + | </tr><tr bgcolor="lightgrey"> | ||
| + | <td width="26%">Open and close throttle quickly</td> | ||
| + | <td width="28%">Jumps from 2 to about 25 inches</td> | ||
| + | <td width="46%">Engine is in good condition.</td> | ||
| + | </tr><tr bgcolor="white"> | ||
| + | <td width="26%">Smooth and steady idle</td> | ||
| + | <td width="28%">Steady, but lower than normal reading</td> | ||
| + | <td width="46%">Worn rings, but perform next test to be sure.</td> | ||
| + | </tr><tr bgcolor="lightgrey"> | ||
| + | <td width="26%">Open and close throttle quickly</td> | ||
| + | <td width="28%">Jumps from 0 to 22 inches</td> | ||
| + | <td width="46%">Confirms worn rings.</td> | ||
| + | </tr><tr bgcolor="white"> | ||
| + | <td width="26%">Steady idle</td> | ||
| + | <td width="28%">Intermittent dropping back 3 to 5 inches and returns to normal</td> | ||
| + | <td width="46%">Sticky valves. If injection of penetrating oil into intake manifold temporarily stops pointer from dropping back, it's certain the valves are sticking.</td> | ||
| + | </tr><tr bgcolor="lightgrey"> | ||
| + | <td width="26%">Steady 3000 RPM</td> | ||
| + | <td width="28%">Pointer fluctuates rapidly, increasing engine speed causes more pointer swing</td> | ||
| + | <td width="46%">Weak valve springs.</td> | ||
| + | </tr><tr bgcolor="white"> | ||
| + | <td width="26%">Steady idle</td> | ||
| + | <td width="28%">Fast fluctuation between 14 to 19 inches</td> | ||
| + | <td width="46%">Worn intake valve stem guides. Excessive pointer vibration at all speeds indicates a leaky head gasket.</td> | ||
| + | </tr><tr bgcolor="lightgrey"> | ||
| + | <td width="26%">Steady idle</td> | ||
| + | <td width="28%">Constant drop</td> | ||
| + | <td width="46%">Burnt valve or insufficient tappet clearance holding valve partly open or a spark plug occasionally misfiring.</td> | ||
| + | </tr><tr bgcolor="white"> | ||
| + | <td width="26%">Steady idle</td> | ||
| + | <td width="28%">Steady 8 to 14 inches</td> | ||
| + | <td width="46%">Incorrect valve timing. It must also be remembered that vacuum leaks and/or poor compression can result in a low vacuum reading.</td> | ||
| + | </tr><tr bgcolor="lightgrey"> | ||
| + | <td width="26%">Steady idle</td> | ||
| + | <td width="28%">Steady 14 to 16 inches</td> | ||
| + | <td width="46%">Incorrect ignition timing.</td> | ||
| + | </tr><tr bgcolor="white"> | ||
| + | <td width="26%">Steady idle</td> | ||
| + | <td width="28%">Drifting from 14 to 16 inches</td> | ||
| + | <td width="46%">Plug gaps too close or points not adjusted correctly. Damaged plug or | ||
| + | coil wire</td> | ||
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