I'm Stumped?

[Anonymous]

Hey all!

I have been hovering around here for a while but havn't posted much lately. Been busy with school!

I have been driving the mustang around and noticed a slight ticking comming from the engine. Sounded like a clacking rocker or something. Well I adjusted all the lifters and started it up and there was a loud clacking when the valve cover was off. I was not rythmatic like a rocker ticking but more intermitant. So I thought the port divider was loose. Opened the header, and changed the gasket and made sure that it was in there good. Got everything buttoned up and I was still ticking. Took off the valve cover and It had the same intermitant loud ticking. With the valve cover on, the loud ticking cannot be heard but the rythmatic rocker ticking remained. It is more noticable when downshifting at 2000 to 1500 rpm. Doesn't do it above that or below.

What the heck could this be? It has stumped me all day long and I worked on it for hours! Could a lifter have collapsed? or is the port divider somehow moving? I just don't get it!

Please Help ME!

Later,
Paul

 

[80broncoman]

I would pull plug wires one at a time to see if it maybe a rod knock. But I hope I am wrong. Also look inside your rocker cover to see ifmaybe it is holding somthing that is loose. It is worth a shot.
Jim

 

[BIGREDRASA]

One other possibility is a worn fuel pump or cam eccentric.

 

[Anonymous]

The cam was replaced just reciently. Comp 260. Fuel pump was new when I rebuilt it over 4 years ago...But would that make a louder noise when the valve cover is off? And I don't see how the valve cover could be holding something loose? But I will check all of these things tomorrow.

I pray that it is not a rod knocking!!!!!!

Later,
Paul

 

[BIGREDRASA]

I had that experirnce with a worn out fuel pump on an old 260 bent 8. The sound could resonate through the internals with the cover off.

 

[Anonymous]

oh one more thing...

I just went to the store and when I got back, i let it idle for a few seconds, and then punched it to WOT and it backfired once. Hasn't done that in a while! Other than that, it seems to be running just fine.

Timing is set via manifold vacume pressure, sparkplugs are brand spankin new, and it was rebuilt 4 years ago but only run for 3.5 yrs. I know it is not pinging because it is knocking durring deceleration from a range from 2000 to 1500 rpm.

Later,
Paul

 

[BIGREDRASA]

"I know it is not pinging because it is knocking durring deceleration from a range from 2000 to 1500 rpm."
Now you have me mystified. "Knocking," preignition and "pinging" are really the same thing. Any banging or clanging sound during decel sounds more like a bad con rod bearing or wrist pin. One of the other "experts" here can probably shed more light on which. The troubleshooting section of any Chiltons' will give you the steps to eliminate the various sources of banging/clanging sounds. They tend to involve disconnecting one spark plug wire at a time. When you pull the plug wire on the delinquent cylinder, the noise stops.

 

[Anonymous]

ok guys...

I got a new fuel pump but have not installed it yet. I pulled the plugs on each cylinder and none of them made the noise stop. But the #4 and #6 made the engine run rougher when unplugged. One more bit of help is that it seems to not do it as badly when it is cold. Worse when it is hot. And again, only durring the specified rpm range and durring deceleration or holding it at that rpm while under load. I talked to the guy at NAPA and I had him stumped. He thought it was a bad lifter but they are brand new or only about 4 months old!!?

Anyways, Ill change the pump and see what happens.

Later,
Paul

 

[addo]

Your mechanical advance is probably sticking. Check it with a tach and timing light, at the factory RPM "steps".

 

[Anonymous]

Retorque your exhaust manifold...ZZ

 

[Anonymous]

First off, thanks for all the replies and all the ideas.

Now the more I listen to it, it sounds like a rocker ticking and the port divider still loose. The only thing that makes me think that a lifter is bad is the fact that it only ticks from 1500 to 2000 rpm. The other knocking could be the port divider but that is still up for debate. As for the rockers, any suggestions on how to check to see if a lifter is bad? Can I tighten them down to the point where I can't move the rocker with my fingers without damaging the pushrods? This way of adjusting always seemed a little to tight to me, but that may be the cause of the ticking. I have always been tightening them down to where it first comes in contact with the lifter and then adding an extra 3/4 of a turn.

Anyways, I am going to take it apart again tomorow and recheck everything.

Thanks for all the help!

Later,
Paul

 

[addo]

So long as you were doing it on the cam lobe base circle, your tappet adjustment method is fine. A sticky lifter will free up in most cases after 15-20 minutes running.

A few initial measurements will help you. Check your manifold vacuum, compressions (hot), advance curve and the plug appearance. See if any of that stuff is outa whack.

Cheers, Adam.

 

[Anonymous]

I may have found the culprit!

After taking the top end apart again today, I found that the loud knocking noise was solved by advancing the timing more. I need to get a timing light to see what it is now but it was not pinging under acceleration when I drove it.

Now for the bad news. While I was inspecting everything, i noticed that a rocker piller or stud or what ever they are called, was cracked by the bolt hole. So i cursed for a while and then took all the stuff off the shaft and found 2 studs were cracked. One was cracked on the top all the way through. The other was half way through. Now I got to find some more studs. Anyone know where to find new ones? I tried NAPA and other stores and couldn't find them. Does Gary at Rocker arm specialists have new ones?

Anyways, i put it all back together and drove it home and parked it for the weekend. Good thing I got a truck now so I don't have to rely on the mustang all the time!

One last thing, after I reinstalled everything, I noticed that the ticking that was made durring the 2000 to 1500 rpm was reduced to 1500 to 1000 rpm. It still sounds like a rocker ticking but it could be from the studs. But they seemed pretty tight when I put it back together. I don't know!?

Later,
Paul

 

[Anonymous]

Now I am getting angry. I don't think you will like me when I am angry!



No but seriously, I went to the junk yard today and found a mavric with what seemed a 200 in it. But NOOOO! It was a 250 and the rockers were non-adj. So I thought I might just change the pillers from one to the other, but NOOOO! They are different sizes. One was 0.78" and the other was 0.80"!!! About 0.02" different!!! Next closest parts car is over 60 miles away! (According to the junk yard people )

I just can't get a break now!! What did I do to deserve this?!

Sorry about that...I just had to vent my frustration right now!

 

[Anonymous]

I finally got everything back together. It runs now but still has that ticking sound from the top end. I think I narrowed it down to the #3&4 cyl exhaust rockers. This makes me think that the port divider is still loose in there but it still sounds like it is a rocker ticking to me. Guess I'll have to have it looked at by someone else because I can't figure out the stupid thing!

Thanks for the help!

Later,
Paul

 

[Anonymous]

Well, my uncle and I cannot figure this one out. We took it apart the other day and welded the port divider in so it won't ever come loose. Checked everything...vacume is good and steady, cyl compression is good at all cylinders, valves are adjusted correctly(quadruple checked), and IT IS STILL TICKING. I have managed to narrow it down to the #3 cylinder. Under closer inspection, when the plug wire is pulled, the ticking goes away. My suspition is that it is piston slap! I am going to try a thicker oil and see if that does any good because I never had this problem when I was using dino oil. (Just switched to synthetic 3000 ago. So maybe that will solve the problem. Other possibilities might be a stuck valve or something of that nature so I might have to rebuild a spare head I have laying around.

Anyways,

Thanks for the input and have a great Turkey Day!

Later,
Paul