Head Tapping Sound Not valve guides
 

Hey friends

I've been scratching my head trying to figure out what this loud tapping sound from the intake side cam shaft is ill give you my data and maybe someone will have an idea.

I don't have a tappet stake down kit installed, I have one as parts though.

Adjusted valve clearance, all within spec. All guides tidy and tight, can't move them with my hands.

Rechecked clearances again and valve guides still good.

Compression is "good" 170psi, all cylinders pretty close. So I'm assuming no bent or damaged valves. Maybe a bit high so I expect there is some carbon build up.

The tapping comes from the intake side only, speeds up with engine speed and only really kicks in once warmed up or right I blip the throttle after starting. Once it starts it doesn't really stop.

The tapping is slower then what I'd expect from an issue with one valve though. As in, I think the each valve would be opening and closing faster then the tapping sound is. Therefore the sound should be faster if it was a valve issue? Unless it's only tapping on every second rotation of the cam shaft.

My thoughts are that it could be a bad valve spring and maybe one of the valves is "floating" rather then closing closing fast enough to meet the cam lobe again to be smoothly pushed open once again.

Maybe a fuel injector but I'm pretty sure that I've pulled those off one at a time while the engine is running and it still made the sound. It would have to be a really loud fuel injector to be louder then the engine though I guess.

What are your thoughts? I'm trying not to pull the head if I can avoid it.

I am still thinking bucket guide.

I seriously doubt you would move them with your hands, as originally they are a press fit in the head.

Eventually they get worse, and get clobbered by the cam lobe, then they are easy to identify. There is always a loud "double" CLACK when that happens. One when the lobe belts it, and the 2nd as it slams into head upon reseating itself.

Exhaust is common, but I have had many, many on the inlet side.

The top timing chain can be a deceiving clattering noise if it is adjusted too loose, and a strange "whirring" noise if too tight.

Wild card:


A busted valve spring!!!


Carl

Hey thanks for the replys.

Yea it could be a busted valve Spring, seeing as there are no marks on the valve guides. I'll have to do both a set of valve springs and the stake down kit.

As for the loose guide, it's a evenly spaced tap not a double tap. But then again that doesn't mean it's not that.

I'll pop the cam covers off again and crank the engine over and see if any of the buckets act strange. Then I guess it's off with the cam shaft and get those springs out haha.

Any other ideas from others?

Long shot but it could be a gunged up valve/ bucket. There's a hydraulic valve cleaner additive (I think it's a Wynns product) which might resolve it.

This one Wynn's Hydraulic Valve Lifter 350ml

Thanks again guys. Also I forgot to say that when I turn the engine over by hand it gets real tight and hard to rotate at one point per engine revolution. Could this be related to a bad valve Spring or similar?

Sorry if that's a stupid question.

Harry,

Only stupid question is the one that was not asked.

That is NOT normal, even on a rebuilt engine.

Something is out of whack.

Remove the sparkers, and try again, just for giggles, sometimes a compression "high" can give that binding feeling.

If that proves the same, it is mechanical, and I am thinking the cam timing is AWOL. It does happen, especially if the previous adventurer did lock things up correctly.

Thanks, yea I'll give that a go. I have checked the cam timing roughly with the aid of a cam alignment tool, and both are aligned. However I can't remember if I referenced that against the timing marks on the crank shaft damper. I'm pretty certain that cylinder #6 was TDC when I checked them so all that seems to be in place.

I guess it could be time for the ol' cam timing/valve springs and stake down at the mechanics giant bill situation haha.