Knock when starting

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Oct 9, 2007 | 09:20 PM

mikefender

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Knock when starting

I have a 351M in a 1977 f250 4x4 highboy with a manual transmission. When I start the engine it knocks for a second or two then sounds fine. It doesn't make noise any other time. When i replaced the clutch last spring i replaced the clutch linkage as it was mickey mouse looking and wouldn't adjust properly but i had the knock before and after the clutch was replaced.

Is it possible to replace the rods and mains without pulling the motor? I just want to get a few more miles out of it before I install the 460 I'm building.

Mike

Oct 9, 2007 | 11:57 PM

jonbass40

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you will be fine for quite a while het. The problem is your oil filter is leaking down. How much oil pressure does the truck have when it is warmed up?

Oct 10, 2007 | 12:02 AM

mikefender

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I just have the factory guages, its in the middle to upper range of the guage.

Oct 10, 2007 | 08:39 AM

fmc400

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From: Austin, TX

Jonbass40 is right; it's caused by the oil filter letting the oiling system lose its prime. My '77 LTD with a 351W does that when it's ready for an oil change. It knocks loud for a second after starting and then smooths out. After I change the oil and filter it's fine and doesn't do it until around the time it's ready for the next. Maybe it's time for an oil change anyway?

Oct 10, 2007 | 10:24 AM

jonbass40

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Try a motorcraft filter, from what I hear from a lot if people they dont leak down as much as the fram filters that you are probably running

Oct 10, 2007 | 10:58 AM

Purely Ford

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From: East Bend, Carolina, U.S

Wix filters will solve the problem also.

Oct 13, 2007 | 07:04 AM

danlee

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From: Delaware

Some oil filters have an anti-backflow valve. I think that the cheaper Fram filters do not have this valve. You could try "bobistheoilguy.com" to get a list of filters that have this valve.

It is called an ADBV (anti-drainback valve). I think Wix and Purelator One both have them. Motorcraft is made by Purelator and probably has it also.

One way to tell, is if your old filter is still full of oil after an oil change it probably has an ADBV.

Last edited by danlee; Oct 13, 2007 at 07:36 AM.