Rattling during acceleration

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Jul 4, 2017 | 03:31 PM

S.S. Clarence

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Rattling during acceleration

I am experiencing a rattling sound when accelerating in my '67 F-250 with the 4.9l 300 i6. It is most apparent in 4th gear and only occurs when accelerating. The noise has become more prominent and the motor seems to be losing some power. Any one have a suggestion of what I should be looking for? Anyone experience this before and know how to fix?

Jul 4, 2017 | 04:08 PM

mrpotatohead

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Joined: Apr 2006

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From: NAMPA, ID.

Might be spark knock due to low octane fuel, excessively advanced ignition timing, lean fuel mixture, hot air stove valve not closing, burning oil, lugging the engine; or any number of other possibilities. Posting a video that has good audio of the sound will be very helpful in giving a diagnosis.

Jul 5, 2017 | 08:27 AM

KOT390

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I agree with MPH, but specifically with the spark knocking. You might check the vacuum advance can since the sound happens in fourth gear accelerating, i.e. under a load. Check base timing as well.

KOT390

Jul 5, 2017 | 02:03 PM

JEFFFAFA

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Joined: Mar 2013

Posts: 14,255

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From: Phoenix, Az.

Welcome to FTE and the Bumpside Kingdom!

Besides the above good information I will add one more. OLD gas can also cause it. How old is the gas in the tank?

Jul 6, 2017 | 08:37 AM

orich

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Joined: Aug 2003

Posts: 7,592

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From: **** hole San Jose ca.

I will also add one thing if you don't know when your lugging the engine then install a vacuum meter/motor minder gauge.

Then down shift when the meter shows the vacuum has dropped down to far.

For Best mileage learn to drive with the meter/gauge plus you'll do less engine "Damage" to the top of the pistons.
Orich