vacuum and timing issues

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Mar 10, 2013 | 09:41 PM

dyoungen

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From: Perry Georgia

vacuum and timing issues

We got the 300 six installed in a 1976 F100 that had a 360 originally. The engine had sat for a number of years, don't know exactly but she started right up when everything was in place. Other than moving the distributor, we had run the oil pump to get things oiled, we didn't do anything to it. After running the truck for a day after setting the timing buy the timing mark, I checked the vacuum. The timing is at the farthest mark without going off the mark and she only shows 16 inches of vacuum. Without going off the mark is this reasonable? She doesn't miss and starts right up. From the numbers on the block it looks like it's a 1969 engine.

Mar 11, 2013 | 08:52 AM

BaronVonAutomatc

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From: Earth

Sixteen inches is a little low for a healthy engine. How does the truck drive?

Mar 11, 2013 | 09:28 AM

1986F150six

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From: Sheffield, AL

The timing marks may have shifted due to an old harmonic balancer. Try adjusting the timing by rotating the distributor while the engine is running and watch the vacuum gauge. Make sure the vacuum line is disconnected from the distributor and plugged.

My engine has 20.5" @ 700 RPMs, but I retard the timing until it has ~19 1/4" vacuum, due to slight pinging while under load.

Mar 12, 2013 | 12:03 AM

dyoungen

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From: Perry Georgia

Denny says the truck drives fine. I"m going to see about driving it myself to check out the timing. I used to check out my mustang, 1968 by setting the timing by the marks and driving up a hill till I would get it to ping than back it off. Worked every time. I didn't have a vacuum gage back then but the pinging worked fine.

Mar 17, 2013 | 06:17 PM

muscletruck7379

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From: Harrisburg, NE

i would go with adjusting the timing as well. 16" ain't all that horrible out here in colorado...

Mar 18, 2013 | 10:47 AM

Harte3

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From: Spokane, WA

Use a vacuum gauge to set the timing and adjust the carb. Disconnectthe vac advance line to the dizzy and plug it. Attach the vacuum gauge to a full vacuum manifold source. Turn the dizzy until the highest steady vacuum reading is achieved and then back off 1-2 hg. Adjust the carb idle speed and then the mixture screws the same way the dizzy was adjusted. Go through the routine again...dizzy then carb, dizzy then carb, etc. That gets you at a good starting point for further adjustments if needed after you drive it and gives the engine a tune according to what it "likes" and your manner of driving.

Mar 20, 2013 | 06:54 PM

dyoungen

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From: Perry Georgia

We tried the pinging going up the hill but didn't hear the pinging. When we got back to the shop I checked the vacuum and after adjusting the idle it read almost 18inches of vacuum. When we used the timing light, the mark was way past the mark. The mark on the harmonis balencer is way below the mark on the engine as in almost double the mark looking down from the passenger side. If the end mark is 10 DEGs it looks around 20 DEGS. The engine has the petronics ignition. Would that make a differance?