Ford 3600 Engine Knock on Startup

rghatfield

New User
I have a 1978 Ford 3600 three cylinder gas that knocks right after startup if it sets for a long period of time. Any suggestions on how to fix this?
 
Hard to tell without hearing it in person. Does it sound like a pre-detonation type of knock, or like the valves tapping?

If it is a true pre-detonation type of knock then I would suspect the timing. If it is the valves making a tapping noise I would suspect that the valve lash needs adjusting.
 
(quoted from post at 15:52:56 01/23/18) Hard to tell without hearing it in person. Does it sound like a pre-detonation type of knock, or like the valves tapping?

If it is a true pre-detonation type of knock then I would suspect the timing. If it is the valves making a tapping noise I would suspect that the valve lash needs adjusting.

I would describe it as a wrist pin knock or lower end knock. If you bring the throttle up it will quiet down. Once the tractor warms up it goes away. Come back the next day and start it and it's not there. Let it set for two weeks and it's back.
 
If it knocks for a few seconds, then I would guess oil drain back, if it knocks until warmed up, then piston slap.
 
Change your oil. Try Rotella T 5w-40 full synthetic, recommended as that is what I use in most of my equipment! I had a 1988 Ford 5 liter
that was no way worn out but did that on dyno 10w-30. Went to Mobil 1 10-30 and the problem disappeared. Seems the syn left a better
residue on the moving parts that the dyno oil didn't.

With that oil change , Motorcraft FL-1A is what I used for a filter in most of my Ford products over the years which has an anti-drainback
seal to improve startup oil flow.
 

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