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The close the throttle butterflies as much as reasonably possible without theĮngine dying. How much you have to turn the screw to open the throttle butterfliesĮnough for the engine to idle while it's cold.
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Turn the idle speed screw to increase the RPM, again taking note of exactly Position the throttle butterflies and idle mixture needles as described above,Īttach the manifold vacuum gauge to the vacuum port and start the engine. Though more involved, way to setup the idle system. If your distributor has a mechanical advance system there is a much better, One final note: Make sure your timing is set correctly before starting this
BIG CAM 350 CRACK
When you just crack the throttle, you should be good to go. At this point if the idle is stable and the engine responds quickly
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If any motion hurts manifold vacuum, you know that needle is set Original position near the bottom of the transfer idle slots.Īs a final check give each idle mixture needle a slight turn in then a slight Presumably you'll be able to pick up enough idle speed by optimizing the idleįuel mixture that you can close the primary throttle butterflies down to their Manifold vacuum is as high as you can get it) repeat the process with the Stabilize each time, until it starts to decrease. If manifold vacuum increases repeat the process, letting the idle Turn while you're watching the vacuum gauge. With the engine idling, pick one of the idle mixture needles and turn it in 1/4 Opening at least somewhat without the engine dying. Warms up it should gain rpm, so you should be able to reduce the throttle Throttle butterflies to the position you originally set them at. The whole idea is to be able to return the Since throttleīutterfly position is critical, count the turns and fractions of turns so you'll Screw to increase the RPM to get it to idle while it's cold. If it dies, which is likely, you'll have the turn the idle speed setting Work the throttle a few times then start theĮngine. Without touching the carburetor, turn the engine over until you have Remove the plug, attach a good vacuum gauge to the port and position the This vacuum portĬonnects with a passage in the throttle body that 'sees' manifold vacuum. Hopefully you'll see a little tube, covered by a rubber plug. Reinstall the carburetor and setup your idle system.īefore you start the engine, examine the fuel bowl side of the throttle body. Them out 1 1/4 turns, which is a good baseline setting. Idle fuel mixture difficult to set with any accuracy. Excessiveįorce here will damage both the needles and metering block and make the Next, turn the idle mixture needles in until they are lightly seated. Idle slot at curb idle is absolutely critical for maximum acceleration. Positioning the throttle butterflies near the bottom of the transfer Don't worry about measuring anything - your eyeball is goodĮnough. 020" from the bottom edge of the transfer Turn the idle speed setting screw to set the bottom edge of the To start with, invert the carburetor and check the position of the throttleīutterflies. One method of setting up your idle system is a follows: Earl Parker wrote a nice paper on setting the idle mixture/initial timing that I copied. The initial timing is based on what the engine likes at idle. Your total timing should be independent of the idle speed, and is set at a point at which the distributor is at max advance.