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Unread 04-05-2014, 03:24 PM   #1
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Default 1984 F-150 spark timing

I have a 1984 F150 with a 5.0L 302CI engine.

The sticker under the hood says to set spark timing to 12 BTDC. The truck does run at this setting, but poorly. The engine runs much better at around 22 BTDC. Why?

Yes, I am taking the vacuum hose off the distributor and plugging it while setting timing. Yes, my timing light is working correctly. Yes, the harmonic balancer is installed correctly. Yes, the valve timing is set properly.

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Unread 04-05-2014, 07:06 PM   #2
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When you say it runs but runs poorly, do you mean at idle or when driving?

If it idles fine but drives poorly, maybe your mechanical advance isn't working. Not uncommon to have seized and you have no advance.

When you have the vacuum hose off, watch the timing marks with your timing light and rev it up. The timing should advance. If not remove the distributor cap and see if the rotor/shaft advances. I don't know what direction distributor rotation is, but it should feel springy in one direction when you twist it back and forth.
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Unread 04-05-2014, 09:55 PM   #3
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I think it's counter clockwise ?
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Yeah. Should hold up fine, long as you don't drive like a primate.

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Unread 04-07-2014, 11:24 AM   #4
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Where's our resident F-150 expert?
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Unread 04-07-2014, 12:57 PM   #5
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It idles poorly and drives poorly when set to 12 BTDC.

When revving, it does advance by a few degrees.

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Unread 04-07-2014, 03:53 PM   #6
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Quote:
Originally Posted by VegaObscura View Post
When revving, it does advance by a few degrees.
WITH the vacuum advance hose connected, or without? You need to check both.
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