460 rough underload
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Cargo Master
Joined: Nov 2010
Posts: 3,244
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460 rough underload
Hey guys figured I would ask the pros I'm out of ideas. Stock motor outside of straight uptchain. Holley 4160 600cfm vac secondaries. Man trans. New ds2 box dizzy plug plug wires and accel coil. I found vaccumn leaks other day that was messing up idle. I corrected those and tested again none to be found. Idles pretty good around 700 to 900 rpms give or take. Is good while idling small bit of vibration but nothing crazy. When I get on it it vibrates quite a bit more. I've got brake booster running to tree at the back of the motor. Pcv to holley port at front of carb. Va to timed spark side of holley no vac at idle. The last plug on the front is hooked to manifold vac. Two other plugs on manifold are capped off. Any ideas why this would be happening?
Junior User
Joined: Sep 2009
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Hey Gm,
Not a pro, but maybe fresh questions will help. "Vibration" is kind of hard to narrow down from your description. So,
You Triple-checked the firing order? Straight up timing set - the marks were aligned for sure? #1 cyl at TDC matches the timing mark at 0 deg? (or you set a new mark)? Ignition timing set 8 deg BTDC with vac adv plugged, 800 rpm? Your vac hose routing resembles the diagrams in this post?
https://www.ford-trucks.com/forums/1...e-routing.html
Can you describe "vibration" differently? Do you smell too much gas, or too little gas? Hear popping or sucking when you goose the throttle? Have you tried turning the distributor a little while running to see the effect? If it gets rougher as you rev it, what if you hold it at higher rpms? Smooth out, or worse?
Not a pro, but maybe fresh questions will help. "Vibration" is kind of hard to narrow down from your description. So,
You Triple-checked the firing order? Straight up timing set - the marks were aligned for sure? #1 cyl at TDC matches the timing mark at 0 deg? (or you set a new mark)? Ignition timing set 8 deg BTDC with vac adv plugged, 800 rpm? Your vac hose routing resembles the diagrams in this post?
https://www.ford-trucks.com/forums/1...e-routing.html
Can you describe "vibration" differently? Do you smell too much gas, or too little gas? Hear popping or sucking when you goose the throttle? Have you tried turning the distributor a little while running to see the effect? If it gets rougher as you rev it, what if you hold it at higher rpms? Smooth out, or worse?
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Cargo Master
Joined: Nov 2010
Posts: 3,244
Likes: 40
Firing order has been checked for the second on third time. I am pretty confident it was dot to dot on tdc #1 cylinder, 0 on the balancer.
This vibration its like a rough idle basically. Imagine this concept at true idle (kicked down from fast idle) if I were to have a cup of coffee on my dash you would see some ripples in the surface of it. Nothing crazy, but pretty smooth overall.
When I get on it either real quick or hold it steady it would be quite a bit more vibration and bucking.
What do you guys say about a video? I'll take one today and put it on here.
This vibration its like a rough idle basically. Imagine this concept at true idle (kicked down from fast idle) if I were to have a cup of coffee on my dash you would see some ripples in the surface of it. Nothing crazy, but pretty smooth overall.
When I get on it either real quick or hold it steady it would be quite a bit more vibration and bucking.
What do you guys say about a video? I'll take one today and put it on here.
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