After replacing 3 slightly bent pushrods in my 390 I have been driving it around a its running a little rough.Really it only runs rough when I am idling in gear then when I go to take off its rough kinda sounds like a small miss.I have checked everything out that I can every thing seems ok.Is it possible that replacing these bent pushrods is causing this.A friend said that when you replace a pushrod it will take a little bit for the lifter to adjust is this true.

 

Your lifters might be going bad. I would probably replace
the cam and lifters.

Glenn

 

Did you make sure the pushrods where all the correct length? Ive seen this happen before.

Nathan

 

I did get the same length pushrods.But even if there was a small difference the lifter would adjust to it right.I don't think my lifter or cam is worn the truck ran fine before no problems at all I just happen to see a bent push rod when I was fixing a leaking valve cover gasket.

 

Jon, Did you read the FE bent pushrod article in the Tech article of this site?

John
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I read an article for disassemble and assyemble of rocker arms is that the article your speaking of.I would still like to know if the lifters will self adjust to the new pushrods.I got the same length as the old ones by comparing them side by side so there could be a hair of a difference but if there was would'nt the lifter self adjust.And also when I had the rockers off the lifter would expand some how long does it take for them to get back to normal.

 

[font size="1" color="#FF0000"]LAST EDITED ON 20-Mar-01 AT 02:20 PM (EST)[/font][p]To answer your question, yes, assuming your lifters are in good working order they will adjust to your new pushrods, and should have already. My questions are: did you replace all your pushrods or just the 3 that were visually bent? If no, did how did you check true of the others, visually or by gauge? What with this being an FE engine, and you already had 3 visually bent, its probably others were bent if not as noticably. Are you sure you tightened down the rocker assembly in the proscribed manner? This is often done incorrectly. Personally, I always replace my lifters when I replace pushrods, its cheap insurance. I wouldn't neccesarily worry about a worn cam, while its possible, bent pushrods are not uncommon on these engines and not particularly indicitive of a bad cam. Finally, although I know this sounds obvious, slap a vacuum gauge on your engine and make sure you don't have any vacuum leaks. Sometimes something can get knocked loose when you work on your engine. If you end up beating your head against a wall with no luck I would replace your lifters, mic all of your pushrods, and double check the tightening sequence of your rocker arm assembly. Good luck and let us know how it turns out.

If your knuckles ain't bleeding you did something wrong.

'72 F-250 "Hi-Boy" 4x4, Dana 60/HD44, FE390 @ 400hp(purt near!), 4-speed, custom suspension w 4" lift, mud on black.

 

I just replaced the rods that were visualy bent the others I just looked at yes I tightend the rockers in order.If it does'nt straight out I am going to replace all pushrods and lifters.When I go to do this is there any special length rods I should get or just stock size pushrods with new lifters.

 

You should try to determine what bent those push rods. You may have bent a valve enough to affect the on or two of the cylinders. You may consider checking compression on those compared to the rest.

 

maybe the valve seats??guides??seals?? could be a vaccum leak that was waiting to happen

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77'FORD F150 XLT 400

 

I found out today that number 2 cylinder is dead.I let it run for a couple of minutes and felt the headder pipe and it was just a little warm.I have checked the plug wires and plugs all are good.
I pretty sure the compression is good because I dont burn any oil at all and it just started running rough like this after I replaced the bent rod.tomarrow I am going to check the valve make sure it isnt stuck then I will check the lifter to see if maybe it didnt collaspe.

 

do a compression test, man!

Greg

P.S. I heard of a trick for determining compression leak causes... if you squirt about a teaspoon of motor oil in the offending cylinder's spark plug hole, then do a compression check, it can tell you the following.

Corrected temporarily = bad rings
no correction = valve(s) not seating or blown head gasket, leaking wall, etc
but a blown head gasket would either cause low compression in two adjacent cylinders (break from cylinder to cylinder), or cause pressurization of the water system (break to water jacket).

Any additions?

 

okay Guys I have'nt done a compression test yet but will as soon as I get a gauge.But today I pulled of the valve cover and watched the pushrods work as I turned the engine over heres what I found out.Everything apears to be working fine the valves on the dead cylinder apear to be opening and closing correctly.But still yet the cylinder is dead.It is not getting any gas into the cylinder.what would stop this from getting gas in it if the valves are opening.Remeber before I changed the pushrods it ran fine on dead cylinders only after is when this started.thats why I the compression is fine but as soon as i get a gauge I will check it.

 

maybe there is no spark on the dead cylinder.