Solved - bad engine noise!!

[Stevehose]

Took the car out for a carb tuning run this am, on the way back close to the house all of a sudden my engine starts to make noise - the kind of noise that makes the hair on your neck stand up. First I thought it was something hitting the fan because I had taken all the carb induction stuff off and maybe forgot to move something out of the way. I limped home and popped the hood. Sounds like valve/rocker clatter on steroids, increases with revs and consistently-not at random. Pulled a plug on each cylinder to test for rod knock but this made no change. Sounds like it is coming from front half of valve train so I pulled the valve cover and plugs then turned the motor over with the starter. No noise, all valves apparently working as they should. Good oil pressure and volume onto the cam. Exhaust manifolds don't appear to be leaking, the manifolds were honed and refitted with new gaskets when I put my W&N exhaust on last year.

Not enough rpm from starter to replicate the noise? Should I button it back up and post a video? Anything else to check before starting it again? Thanks.

 

[x_atlas0]

Timing chain guide failed? Or the tensioner died?

 

[Stevehose]

Timing chain guide failed? Or the tensioner died?

I replaced the guides when I did my pistons but will check that. The tensioner looks fine and is holding pressure. Thanks.

UPDATE: chain guide looks fine.

 

[Mike Goble]

I had taken all the carb induction stuff off and maybe forgot to move something out of the way.

What exactly did you take off and leave off while you did your carb test?

 

[Stevehose]

What exactly did you take off and leave off while you did your carb test?

I have an airbox for my triple webers that I removed, leaving the fronts of the carbs exposed. Have done this many times before with no issues. I thought maybe a rag or hose was left in the path of the fan but all clear.

 

[Markos]

I know you pulled the valve cover and examined but is the oil bar loose?

 

[Mike Goble]

I have an airbox for my triple webers that I removed, leaving the fronts of the carbs exposed. Have done this many times before with no issues. I thought maybe a rag or hose was left in the path of the fan but all clear.

Are you sure you didn't suck in a rock? Something embedded in the top of your piston will make some real noise.

 

[Stevehose]

I know you pulled the valve cover and examined but is the oil bar loose?

It's tight and wired down.

 

[Stevehose]

Are you sure you didn't suck in a rock? Something embedded in the top of your piston will make some real noise.

Mike I believe this is it, I had an M6 nut on a couple bolts that hold the carb plate on by the throats, 2 are now missing and suspect I likely ate one! Holy shyte! I will boroscope and report back! What a dumbass move!

 

[Barry.b]

Mike I believe this is it, I had an M6 nut on a couple bolts that hold the carb plate on by the throats, 2 are now missing and suspect I likely ate one! Holy shyte! I will boroscope and report back! What a

Hopefully you didn’t cause any permanent damage and can maybe fish out the nut with a magnet or something .
Fingers crossed !!

 

[Stevehose]

Hopefully you didn’t cause any permanent damage and can maybe fish out the nut with a magnet or something .
Fingers crossed !!

Yes I have the magnet ready and it can only be in 2 of the 6 cylinders. I knew someday I'd be rebuilding this engine, just not this soon

 

[Stevehose]

No luck finding anything in the 6 cylinders with a boroscope. Much like searching for the remains of the Titanic. The valves operate correctly so I don’t think anything is wedged into one. Calling it a night and will regroup for another go tomorrow. Might feed the scope down into the intake manifold to see if the nut is hitting the intake valve.

Is there enough valve clearance to allow an M6 nut past and into the cylinder?

The sound is rhythmic and doesn’t sound like a pinball machine.

 

[sfdon]

When anything - even a washer gets sucked in, the noise is loud as hell and a constant rhythm. The item with often get stuck in the top of the piston.
You can hope to retrieve it through the spark plug hole. The two times I have seen this, the head had to come off. You will need to do a compression test afterwards.

 

[x_atlas0]

If something got into the combustion chamber, the boroscope view should have looked like a horror show on top of your piston, nasty gashes everywhere.

 

[Stevehose]

If something got into the combustion chamber, the boroscope view should have looked like a horror show on top of your piston, nasty gashes everywhere.

Agree, I don't see any evidence of destruction

 

[day66]

About 35 years ago a girlfriend had a Mk1 Ford Escort - it didn't run well and I thought it had a blocked jet in the carb ... I dismantled it and unbeknown to me the carb had a ball bearing in it that was part of the accelerator pump mechanism, needless to say that ended up in the engine, and it did indeed make a tappy tappy noise continuously. I had to take the head off to retrieve the ball bearing, the top of the piston looked like someone had taken a punch to it, but I just bought a new gasket and stuck it back together again. It was still running when we split up (not much later)

 

[bavbob]

Should you go magnet fishing anyway? A few shavings or similar may narrow something down for you.

 

[Stevehose]

Should you go magnet fishing anyway? A few shavings or similar may narrow something down for you.

Yes, the magnet retriever I have is on a bendable wire but I can't bend it enough for it to both fit through the spark plug hole and get to the deepest side of the cylinder so I am thinking of a way to get a small magnet onto a more flexible and controllable attachment.

 

[sfdon]

Vacuum

 

[Stevehose]

Vacuum

excellent idea, will give it a go