Well I finished swapping in a rebuilt longblock 360.

From the passenger side I'm getting a knock-knock noise that seems to happen in time with the engine cycling. I took the valve covers off already to help pinpoint where the sound was coming from. The sound seems to be coming from around the cylinder 3 or 4 valve rocker area. It is not a clack-clack noise, it's more of a hollow sound, it sounds kind of like if you knocked on the valve covers with your knuckle.

The other weird thing is that the noise stopped for a few seconds, then it came back. So, it seems to be a noise that comes and goes. It's not as loud as the rocker hitting the valve cover.

When I put a stick to my ear and touch it to the rocker shaft support between cylinder 3 and 4 the noise sounds like it's coming from this area.

Any clues? I hope my rebuilt engine wasn't a lemon!

EDIT: I compared the noise to the flash of the timing light and the noise is happening in rythm with the flash, so I think it's valves... cpuld it be lash? My rocker arms are not adjustable so how would I even solve a valve lash problem?

 

A valve noise will normally be a lighter "click or tap or clack" type noise. Any deeper sounds are usually more serious, unfortunately. I would, however, check the simple things-spark plugs, pushrods(properly seated?), plug wires crossed up, exhaust leak, that is all I can come up with at the moment. You might try shorting out #3 and #4 pllugs(one at a time) to see which hole is the source.

 

What you could do, is make sure no rocker arms are loose when their respective piston is at TDC on the compression stroke.

If they are, there are a few things you could do, but we'll cross that bridge when and if we come to it.

You did remember all the wrist pin retainers in the pistons..... right?

 

Rusty, I didn't rebuild this engine I bought it rebuilt from a local engine supplier that supplies rebuild longblocks to many auto parts stores in the area.

Just for more information, I tried shorting each spark plug on that side where the noise is, and it made no difference. Since that made no difference and the noise is in rythm with the timing light flashes, I really think that the noise is a problem with the valves, especially the rockers and push rods.

Anyways, please help me, I think I did something stupid... I have never swapped out an engine, and now I am done swapping in the new longblock... Along the way I kept finding more things that needed replacing so now, there is hardly a part under the hood that I have not replaced! I have even had to re-wire parts of the wire harness that had melted or had other problems.

The point is, I am learning as I go along, and I think I made a big mistake... this engine did NOT come with rockers OR push rods. I took the old rockers off the rocker shaft and bought new shafts because the rockers looked OK to me but the shaft was very plugged up with wax and had grooves worn in it. OK so I have the old rockers on brand new shafts...

But I also re-used the push rods out of the old engine. I was told this was OK by a mechanic friend but I think maybe he was wrong. The thing is, this is a different engine, how do I know the rods are the right length? Also, I am not 100% sure the old rods weren't bent. They didn't look bent but I didn't roll them on glass... I read about that step today, I missed it before when I was working on the engine.

So basically I have the push rods that came from the factory engine but I am thinking, couldn't these push rods be too long or too short for this rebuilt engine?

So, now I am very much stuck because I have no idea how to measure and see if these push rods are the right length. I also don't know what I can do if they turn out to be the wrong length. My rockers are NOT adjustable so what can I do about it if the rods are wrong length?

Anyways sorry for the dumb question but I am finally stuck on this project. At least the push rods and rockers are easy to get to, so I am hoping I can learn what needs to be done and do it somehow. I also hope that by letting the engine idle for a while I didn't ruin something from having rods the wrong length.

Thanks if you can help a stupid noob who is in over his head! The engine sounded so nice besides the unknown valve noise, it makes me so sad that something is wrong...

 

Just do what I said, get #1 at TDC on the compression stroke and check from there. You might even use a very thin feeler gauge. If you can push it between the rocker and valve stem tip, there's your problem!

First we need to verify where the problem is. Then we can do something about it.

Dont worry, this will all turn out in the end.

 

OK I will do that. I can't at the moment because of my job but I will do it ASAP. Probably tomorrow afternoon.

There is something I don't understand though. Wouldn't the rods be all different lengths depending on the different clearances from one valve to the next?

I just don't understand how all this works, I thought you had to check each valve to make sure the rod was the right length. I didn't do any of this I just pulled the old rods out the old engine and stuck them in the new one. I didn't even check if the rods are all the same length. I didn't even check if they are bent!

Anyway I will do the test you said to do.

 

see if pulling #3 and #4 plug wires one at a time makes the noise go away.

 

With the engine at idle run a .010" or .015" feeler gauge between the valve tip and rocker on the suspect valves. When located you may have a lifter with dirt in it making it come and go as something is preventing the check valve inside the lifter from functioning properly, if it were a too short of pushrod it would clack all the time, maybe a different tone cold and hot.
Also check for a stuck lifter internally that isn't allowed to extend or self adjust.
.....=o&o>.....

 

Actually I am not sure if the noise ever goes away but it might change in tone.

Also I tried pulling the spark plug wires on 3 and 4 and no change in the sound.

So a rod being too short could cause this noise right?

But what happens if a rod is too long?

 

How does it run? If it runs OK, and doesn't miss, you don't have a too-long pushrod If it was too long, the valve wouldn't close all the way and that cylinder would miss.

One observation about rocker arms and shafts. If the shafts are worn enough to have "grooves" in them, the rockers might not be much better.

Like everyone else said, check the valve clearances first, and report back.

 

With the motor off and the offending valve at TDC compression pull on the pushrod to the side, if you can unseat it in the cup you lifter may be fully extended where a longer pushrod is needed. If you apply pressure and the lifter collapses within a few seconds the check valve isn't working due to dirt or something inside. Let the fun begin pulling and reinstalling a lifter without removing the intake, it can be done. Remove and clean it inside, sometimes you get lucky and it's only a piece of debris.
.....=o&o>.....

 

When you put in the new engine, did you uas the old fuel pump? Sometimes a weak spring on the fuel pump will make noise like lifter "tap", and it runs with the cam, so the sound will run with the engine timing.
Allen

 

one other thing you could check since it is a new install is take the rockers off and see if there is side to side play on the valve stem. I had a set of heads done for mine and within a year one of the guides were real loose and making noise....these engines don't have alot of oil up top IMO when compared to other engines with oil coming up each pushrod....Neil

 

The fuel pump was re-used off the old motor... but it wasn't making the noise on the old motor. I will check though to see if the noise is coming from there... It sure sounds like passenger valve area though.

Just an update, I called the place where I bought the engine, they said run it for a while longer. The guy says sometimes on a fresh rebuild the lifters will stick at first or take a while to get pumped up or something like that. He said idling for 10 minutes or so wasn't long enough to really get things working right. He said maybe let it idle another 10 minutes.

Is that OK or should I ignore that, and check the clearance first to make sure there is zero lash?

 

I agree, run the engine a little longer, let the oil get warmed up. It my talk a few miles on it to get all the lifters pumped up.