High Idle
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6th Gear
Joined: Mar 2023
Posts: 6
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High Idle
351m,Fresh Rebuild,30 over,Straight up timing set
2150 Rebuilt professionally,Adjusted for Max 17/18 Vac Gauge
Headers, but otherwise Stock,8* BTDC
Using Manifold vac I cant seem to bring the idle below !000 rpm
Using Ported Vac I can get 750/800 rpm
Should i stay with Ported? And can someone explain why this might be?
2150 Rebuilt professionally,Adjusted for Max 17/18 Vac Gauge
Headers, but otherwise Stock,8* BTDC
Using Manifold vac I cant seem to bring the idle below !000 rpm
Using Ported Vac I can get 750/800 rpm
Should i stay with Ported? And can someone explain why this might be?
Desk Jockey
Joined: Sep 2021
Posts: 1,070
Likes: 427
From: Raleigh, NC
Stock setup is manifold. At idle there is no vac so you distributor vac advance is not activated. See my diagrams at link below
https://www.ford-trucks.com/forums/1...-attached.html
Check your timing (vac adv plugged) with RPM at 650. Engine at operating temp. Adjust idle screw to CCW to slow idle. You should be around 10 deg. Hook up vac advance and set curb idle to 650-750.
https://www.ford-trucks.com/forums/1...-attached.html
Check your timing (vac adv plugged) with RPM at 650. Engine at operating temp. Adjust idle screw to CCW to slow idle. You should be around 10 deg. Hook up vac advance and set curb idle to 650-750.
Logistics Pro
Joined: May 2015
Posts: 4,474
Likes: 974
From: Tri Cities, TN
Before you start changing a lot of stuff. Check the choke high idle adjustment screw. It may need re-adjusting and could be holding the throttle plates open and preventing the curb idle screw from being able to control the idle speed.
Hotshot
Joined: Feb 2004
Posts: 10,839
Likes: 2,612
From: The Shenandoah Valley
Mine is always on ported vacuum ... I only ever unhook and plug it to set my timing. Ported vacuum is open to manifold vacuum only after the throttle is opened some. Manifold vacuum is the vacuum in the intake manifold always. Why yours will idle lower on ported vacuum is simply because there is then no vacuum on the vacuum canister on the distributor.
As far as I know, stock was ported vacuum, but many years ago folks started running the dizzy off manifold vacuum so they could idle with a more closed throttle, but it often results in "run on" or low speed spark knock. I even tried it, it's not good.
As far as I know, stock was ported vacuum, but many years ago folks started running the dizzy off manifold vacuum so they could idle with a more closed throttle, but it often results in "run on" or low speed spark knock. I even tried it, it's not good.
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civicmindeddogooder
1961 - 1966 F-100 & Larger F-Series Trucks
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Feb 6, 2013 12:06 AM
