knocking 390fe
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Freshman User
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knocking 390fe
i have a 390 in my 77 f150. the motor was "rebuild" or so the guy i got it from said it was. i got it all together, and started to drive it. things were goin great on my way back from my 2 mile test drive. untill i heard a lot of valve noise. hooked up and oil pressure guage i was only getting 10 psi at 2000RPM. i dropped the pan and i just put the high vol. oil pump in tonight and still have a now LOUD knock on the driver side top end.. any ideas???
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Freshman User
Joined: Oct 2011
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well im gettin about 4 knocks per sec at idle. around 1000 rpm so im guessin a cam speed knock. dam this motor stuff im a body man give me a welder and some bondo im right at home. motors are like speakin chinese to me....
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
i have a 390 in my 77 f150. the motor was "rebuild" or so the guy i got it from said it was. i got it all together, and started to drive it. things were goin great on my way back from my 2 mile test drive. untill i heard a lot of valve noise. hooked up and oil pressure guage i was only getting 10 psi at 2000RPM. i dropped the pan and i just put the high vol. oil pump in tonight and still have a now LOUD knock on the driver side top end.. any ideas???
Do not believe a single word a seller claims! Do some research before you buy. Private sellers can lie just as well as used/new car dealers, lawyers...and politicians.
And, do not assume it's a 390, because on sale day, 360 engines magically become 390's! The bore is the same (4.05"), the stroke is not the same.
Stroke: 360 = 3.50" / 390 = 3.78."
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Freshman User
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well he had paper work for the 390 block and the work to build it its bore .30 over and has mustang heads on it the block its self was out of a 65 merc, trans and transfer case from a 76 bronco. the truck sat for about 10 years after he had the work done i didnt know this till after starting it a few times. when i dropped the pan to replace the oil pump there was about an 1/8" of sludge on the bottom of the pan. and like i said the knock sounds like its the front driver side but its on the top im gonna look into a set of push rods and see if that takes care of it..
Posting Guru
Joined: Sep 2009
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From: Suburbs of Chicago
Before you throw parts at it, pull the valve covers AFTER the engine has been running. You don't need to drive for 2 hours and pull them while its scalding, just make sure that the lifters haven't bled down. Make sure that all of your rocker arms aren't freely flopping around and are properly torqued. If that doesn't solve it, then pull your pushrods and see if any of them are bent, like Josh said. Josh, Sleepy455 and a couple others on here (can't think of their handles) are pretty dern knowledgeable about the FE's.
Pushrods are a valvetrain issue, which would be half cam speed as indicated before. Most valvetrain issues aren't a "knock" but are more of a "tick".
Pushrods are a valvetrain issue, which would be half cam speed as indicated before. Most valvetrain issues aren't a "knock" but are more of a "tick".
Certified Thread Hijacker
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The funny thing about FE pushrods going thru the intake as they do, if something binds and one gets bent it makes a very noticeable "knock" sound as it pounds and scrapes the pushrod bore.
Pretty easy to pull the suspect valve cover and have a looks-see. you can even run the engine briefly with valve cover off to help diagnose.
Josh
Pretty easy to pull the suspect valve cover and have a looks-see. you can even run the engine briefly with valve cover off to help diagnose.
Josh
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Rusty Roller
Joined: Oct 2011
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From: Santa Cruz Mountains
I'm not a expert on 360/90 engines but can't you just bring each cyl up to tdc and rotate the push-rods by hand to see if there is any wobble? They should rotate straight and true visibly without actually pulling the rocker assembly and removing the push-rods? Just a thought; I could be mistaken.
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I'm not a expert on 360/90 engines but can't you just bring each cyl up to tdc and rotate the push-rods by hand to see if there is any wobble? They should rotate straight and true visibly without actually pulling the rocker assembly and removing the push-rods? Just a thought; I could be mistaken.
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That's why I lean towards a bent rod versus a collapsed lifter which would be a loud tapping and not a knock.
Could be something weird too like the oil baffle under the VC came loose an is just slapping around.
Fleet Mechanic
Joined: Nov 2010
Posts: 1,501
Likes: 1
From: Axtell, TX
Loosened the rocker shaft and pulled the pushrods and lo and behold ones bent. It was longer than the rest for some reason. You could see where it had made contact with the pushrod bore causing the sound. Cheap fix and a decent profit when I sold it for very little work.
Cargo Master
Joined: Nov 2009
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From: starship enterprise
Well, another thing to look at is those rocker assemblies. One bolt is special to let the oil through and it had to be in the right place. One more thing is make sure the oil holes are down on that rocker shaft and not up. I have seen the shaft put in with the holes down and it makes for some strange symptoms. As does the wrong bolt in the wrong hole, oil is restricted. If you find one look for the other. Last but not least is look at the valve lash. People take this for granted on hydraulic cams, but on fords there is a spec I have found only in the factory manual that states to assemble the engine and compress the lifters and measure the clearance between the valve stem and the rocker tip. If the heads or block were milled or the cam journals bored or the valve stems are taller, this number will be altered. If it is too little, the valves could never close and if it is too much, the geometry on the valve stems is wrong and instead of pushing straight down on the valve stem, it pushes more sideways and ruins the valve guides.
Fleet Mechanic
Joined: Nov 2010
Posts: 1,501
Likes: 1
From: Axtell, TX
Well, another thing to look at is those rocker assemblies. One bolt is special to let the oil through and it had to be in the right place. One more thing is make sure the oil holes are down on that rocker shaft and not up. I have seen the shaft put in with the holes down (I think you mean UP) and it makes for some strange symptoms. As does the wrong bolt in the wrong hole, oil is restricted. If you find one look for the other. Last but not least is look at the valve lash. People take this for granted on hydraulic cams, but on fords there is a spec I have found only in the factory manual that states to assemble the engine and compress the lifters and measure the clearance between the valve stem and the rocker tip. If the heads or block were milled or the cam journals bored or the valve stems are taller, this number will be altered. If it is too little, the valves could never close and if it is too much, the geometry on the valve stems is wrong and instead of pushing straight down on the valve stem, it pushes more sideways and ruins the valve guides.
https://www.ford-trucks.com/article/idx/8/106/article/FEs_That_Bend_Pushrods_A_Dirty_little_Secret.html
Cargo Master
Joined: Nov 2009
Posts: 2,364
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From: starship enterprise
I know little of FE blocks but have read lots and rebuilt a few, but a small problem can make some strange noises and symptoms, like the rocker shaft being upside down eliminates the oil restriction and iol flows too fast and can't drain out of the valve covers so it starts burning oil through the valve seals, and you get a tick due to the clearance being too great from the oil in the top rather than the bottom. I'm sure it is simple, but finding it is half the battle.
Logistics Pro
Joined: Feb 2011
Posts: 3,522
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From: Townsend, MT
The serial break was in '77 wasn't it? All hiboy's had FE's, right? I have seen a few '77 (seller claimed anyway) hiboy's with FE's.
