I have a recently rebuilt 400 that started dieseling after I would turn it off, now I fixed the dieseling, but while it is running at idle, I hear a ticking sound on the passenger side of the motor. I don't know whether it is a rocker arm or what. It has a hydraulic cam. lift is .485 intake lift .520 exhaust lift, 282 292 duration. Is the lift high enough to make the rocker arm hit the valve cover? I think the ticking sound is from only one rocker arm because I hear it like it is in a sequence.

 

It might be a leaking or cracked exhaust manifold.

 

thats possible. The mechanic that rebuilt the motor said the manifold was a little loose. and When I had new pipes and mufflers put on it, the guy said the same thing and he said he would fix it, but didn't know how long it would last. I don't know whether to get a spare valve cover gasket and check the rocker arms or check the manifold.

 

I would check the exhaust manifold first.

 

now it aint doing it...????? My motor is weird and mysterious.

 

That crap happens to me all the time.

 

I thinking it might have been something else... like a loose vacuum line or something. If it was a rocker arm, wouldn't it still be making the noise?

 

I usually tell myself that if the noise comes and goes it cant be too bad. If something is broke it usually stays broke and the noise is always there if thats the case. If it comes back grab a big screwdriver and put it up to your ear handle first with the point touching the engine. poor mans stethoscope and move the tip around to track the noise. I am not kidding. just try it and see what I mean. You will be surprised how much noise is transmitted. Just be careful as it must obviously be done when the engine is running so stay away from belts/fans hot things etc.

 

I remember my own rebuilt 400 doing that (ticking at idle from the pass side) never did figure out what it was but I haven't noticed that noise in a while now....

 

that is an awesome tip. You should make a thread of: useful tech tips

 

Tech tip(?) the old screwdriver trick? I must admit I was very sceptical 20 odd years ago when I started my fitting turning appenticeship. I'd heard far too many stories of pain and humiliation from tricks on the boys but a tradie did it on a electric motor in front of me and suggested I try it. He was right. Very occasionally I used to see a tradesman (usually mechanic) with a doctors stethoscope which is obviously a few stages along from the screwdriver but I doubt you'd see many around now with the way the new ones are serviced/repaired/diagnosed. Go and have a play with it it seems like black magic if you haven't tried it or aren't that mechanically inclined, just be care you don't get wrapped up in a set of fan belts/blades!! Ha Ha.

 

You can do the same thing with a stick/wooden broom handle (shorten of course). That way you dont put your head so close to the moving parts.

 

Harbor Freight has a Mechanic's Stethoscope for $5 (and is $4 on sale):



Mechanic's Stethoscope

 

hello, i have the same problem. my 351m in my 1978 f150 was making this noise for a year when i drove it so i parked it and recently bought a 1979 f150 with a 400m that ran great and was supposed to be a crate motor about 15 years ago (was owned by a trailer factory and only used occasionally in the winter to plow their parking lot) the engine ran like a top and made no ticking noise what so ever but the engine looked like any old dirty junk yard motor from the outside and when i tore it down the inside looked brand spanking new, i put a can, valve springs, double roller timing chain, melling hi volume oil pump, edlebrock performer intake, headers, holley 700cfm carb and when i fired it up to do the break in it made a very slight tapping noise and the more i ran it the louder it sounded, it sounds just like the 351m did when it was pulled, but its like everyone else's its only coming from the passenger side ? i cannot figure it out

 

I think it is a rocker arm.... My motor stopped the sound after the break in was thorough.