1986 F-250 Progress Thread
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Logistics Pro
Joined: Sep 2011
Posts: 4,491
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From: Algona,WA
So today I drove my truck about 8 miles, ran good but it sounded like it's getting a bit too much gas, sounds like it labors and struggles when you get on it at about 1/4 throttle. After that it pulls very hard and sounds pretty normal. My Edelbrock 1406 has stock jets, stock metering rods with 3" blue step up springs. I have my accelerator pump on the largest shot (that helped greatly with the stumble), base timing is at 12* BTDC. Last time I got a vacuum reading it was with everything stock on the carb at 800 RPM warm idle was 17" of vacuum.
Post Fiend
Joined: Nov 2011
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From: Algona, Washington
I'll sub to it even if i have a Bronco. Mine also kind of labors i guess but it's more like at 1/8th throttle. Barely pressing it and there is a lot of missing and shaking but after i push a bit more it runs fine.
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Logistics Pro
Joined: Sep 2011
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From: Algona,WA
Haha thanks, mine used to do that when the vacuum advance canister was screwed all the way in. I had to screw it out a lot to get that to stop.
Post Fiend
Joined: Nov 2011
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From: Algona, Washington
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Joined: Jul 2010
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From: Northeast, OK
Yep, I'm subscribed. I also read what was said on WHYDTYTT. A vacuum reading of 17" at 800 RPM, which is a fast idle, isn't very high. I say that because a stock engine in good condition should be around 20 or so. Even my 351M with an RV cam is showing 18-19" at 600 RPM, and would be higher at 800 R's.
So, is your engine stock? Have you used the vacuum gauge to adjust the idle mix?
So, is your engine stock? Have you used the vacuum gauge to adjust the idle mix?
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Joined: Jan 2001
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From: Virginia
Where do you guys have the timing set? I have found when I change everything around and go out on my own as far as engine tune, it seems to run better if I disconnect the vacuum advance, and turn the distributor so the initial timing is somewhere above 10 degrees, usually around 14 or so BTDC. It drives good and has good throttle response like that, and then later on you can mess with the vacuum advance unit. The factory puts a lot of vacuum advance in the dist from the factory, but you need to turn this way down if you advance the initial timing. I seem to remember my stock vacuum advance adding up to 20 degrees timing. I drilled a hole and put different sized pins int he vacuum arm to get it down to a more reasonable 10 or so.
For a long time I just ran without the vacuum advance. With the initial timing so high, it didn't have as much noticeable affect on the mileage without it.
For a long time I just ran without the vacuum advance. With the initial timing so high, it didn't have as much noticeable affect on the mileage without it.
FTE Legend
Joined: Jul 2010
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From: Northeast, OK
I'm running 16 degrees of initial advance, and haven't changed the mechanical nor vacuum. And, in probably 2000 miles of driving it that way it hasn't pinged or knocked once. Further, it hasn't kicked back against the starter, although at one point a bad battery cable made it seem like it was.
Moderator
Joined: Jan 2001
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From: Virginia
I'm running 16 degrees of initial advance, and haven't changed the mechanical nor vacuum. And, in probably 2000 miles of driving it that way it hasn't pinged or knocked once. Further, it hasn't kicked back against the starter, although at one point a bad battery cable made it seem like it was.
FTE Legend
Joined: Jul 2010
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From: Northeast, OK
Yes, it is working well. I can see the change on timing when I hook it up to manifold vacuum, although I run it on ported. I don't have any jerking once the engine is warm. But it is temperamental when cold, although I think that is due to the lean jetting.
Having said that, I do hear a slight part-throttle burble at cruise when running the stock jetting, but I was attributing to richness. And, the AFR meter shows it to be rich - about 13 - 14:1.
Having said that, I do hear a slight part-throttle burble at cruise when running the stock jetting, but I was attributing to richness. And, the AFR meter shows it to be rich - about 13 - 14:1.
FTE Legend
Joined: Jul 2010
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From: Northeast, OK
I'm running their adjustable vacuum advance, but haven't played with it.
Well, we've done a good job of hijacking Matthew's new thread. I hope he will tell us about his engine. That low vacuum at high idle worries me. I'm wondering about burned valves.
Well, we've done a good job of hijacking Matthew's new thread. I hope he will tell us about his engine. That low vacuum at high idle worries me. I'm wondering about burned valves.