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Classic Goldwing Technical Forums
Engine & Fuel System Modifications
So what port are you using for the vacuum advance ??
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<blockquote data-quote="IBAJIM" data-source="post: 139442" data-attributes="member: 3676"><p>I have read on this post that the right port is the "vacuum port" that the vacuum advance should be attached to.</p><p></p><p>I looked where the hole in the bore for the right port is located. It's below the throttle plate, so it's the "manifold vacuum" source.</p><p></p><p>The hole in the bore for the left port is located above the throttle plate, so it's the "ported vacuum" source.</p><p></p><p>Found an interesting article that claims using the ported vacuum source for the vacuum advance results in less bog & better idle.</p><p></p><p>For those of you with the single carb, it might be worth switching to the left port to see if it makes an improvement in idle and transition from off idle. You might have to turn in the idle speed screw, if the "manifold vacuum" source is adding advance at idle. When switching over to "ported vacuum" , the idle speed may decrease if it results in less vacuum advance. See the quotes below the Article link.</p><p></p><p><a href="https://www.stromberg-97.com/tech_center/pdfs/stromberg-stromberg-stromberg-vacuum-advance-2.pdf" target="_blank">https://www.stromberg-97.com/tech_center/pdfs/stromberg-stromberg-stromberg-vacuum-advance-2.pdf</a></p><p></p><p>Quotes : " We posed this same question to top carb modifier and Stromberg consultant, Norm Schenck. He said, " My experience with vacuum</p><p>advance on modern street engines has been that most run better with ported vacuum than with manifold vacuum to the distributor." </p><p></p><p>And : "On most hot rod engines, modern vacuum advance distributors are designed for ported vacuum. If you use manifold vacuum with them,</p><p>it pulls full distributor advance at idle. My 355ci Chevy had a hesitation on the dyno, during the transition to full throttle, with both the 4-barrel and prototype</p><p>‘BIG 97’ carburetors, when the vacuum advance was not hooked up. In the car, with the ported vacuum advance connected, there was no hesitation. With manifold vacuum connected, there was a big off-idle hesitation.</p></blockquote><p></p>
[QUOTE="IBAJIM, post: 139442, member: 3676"] I have read on this post that the right port is the "vacuum port" that the vacuum advance should be attached to. I looked where the hole in the bore for the right port is located. It's below the throttle plate, so it's the "manifold vacuum" source. The hole in the bore for the left port is located above the throttle plate, so it's the "ported vacuum" source. Found an interesting article that claims using the ported vacuum source for the vacuum advance results in less bog & better idle. For those of you with the single carb, it might be worth switching to the left port to see if it makes an improvement in idle and transition from off idle. You might have to turn in the idle speed screw, if the "manifold vacuum" source is adding advance at idle. When switching over to "ported vacuum" , the idle speed may decrease if it results in less vacuum advance. See the quotes below the Article link. [url]https://www.stromberg-97.com/tech_center/pdfs/stromberg-stromberg-stromberg-vacuum-advance-2.pdf[/url] Quotes : " We posed this same question to top carb modifier and Stromberg consultant, Norm Schenck. He said, " My experience with vacuum advance on modern street engines has been that most run better with ported vacuum than with manifold vacuum to the distributor." And : "On most hot rod engines, modern vacuum advance distributors are designed for ported vacuum. If you use manifold vacuum with them, it pulls full distributor advance at idle. My 355ci Chevy had a hesitation on the dyno, during the transition to full throttle, with both the 4-barrel and prototype ‘BIG 97’ carburetors, when the vacuum advance was not hooked up. In the car, with the ported vacuum advance connected, there was no hesitation. With manifold vacuum connected, there was a big off-idle hesitation. [/QUOTE]
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Classic Goldwing Technical Forums
Engine & Fuel System Modifications
So what port are you using for the vacuum advance ??
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