79 f150 timing problem
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Joined: Jun 2004
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79 f150 timing problem
I just brought my 79 f150 4wd out to California from Colorado. I realize that I need to adjust the timing to compensate for the elevation change. The underhood sticker is gone and I don't know what to set my timing at or my idle speed. Also, my timing does not change when I plug the vacuum line into the vacuum advance, is this a bad thing? It is a 351M with a 2 barrel carb. Please help.
Logistics Pro
Joined: Jun 2004
Posts: 4,758
Likes: 3,372
From: South Central Utah
Base timing is most likely 6B (I have seen some as high as 12B). Clean the dampner off so you don't set your timing ATDC. Pull the vacuum hose off the advance, rev the engine to about 1500 to 2000 rpm. Make sure there is vacuum at the end of the hose. If there is, check the timing at 2000 rpm and then plug the hose in and recheck the timing again, it should increase. If there is vacuum and no change in timing with the hose plugged into the advance, the advance is bad. If there is no vacuum and the engine is all original and stock, I would suspect the vacuum amplifier that controls the vacuum the the advance. That is a round plastic device that sits on the back of the intake manifold behind the carburetor and has several vacuum hoses attatched. The hoses will also go the the EGR valve. The amplifier was designed to supply vacuum the the EGR valve while the engine is under a load.
Hope this helps.
Hope this helps.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Originally Posted by tjs_79ford
Also, my timing does not change when I plug the vacuum line into the vacuum advance, is this a bad thing?
It is standard practice however to remove the line from the distributor and plug it prior to setting the timing.
