Engine noise experts

[Stewart]

Engine's making an intermittent expensive sounding noise. Does not do it when cold and has been intermittent when warm but is becoming more frequent. Only does it between 700 and 1k rpm. Oil pressure is still great at a needle width above the 75 mark hot at cruise and half way between 50 and 75 at hot idle. I've pulled the plugs wires one by one and there is no noticeable change in the noise. I have not seen any metal in the oil as of yet though the filter may be catching it. Oil was clean at the last oil change 500 miles ago.

[equiprx]

Engine's making an intermittent expensive sounding noise. Does not do it when cold and has been intermittent when warm but is becoming more frequent. Only does it between 700 and 1k rpm. Oil pressure is still great at a needle width above the 75 mark hot at cruise and half way between 50 and 75 at hot idle. I've pulled the plugs wires one by one and there is no noticeable change in the noise. I have not seen any metal in the oil as of yet though the filter may be catching it. Oil was clean at the last oil change 500 miles ago.

You need to invest in a mechanics stethescope. They are really cheap unless you go for the electronic type. I have a couple and use for lots of stuff.

[Steve Simmons]

Check the valves lately?

[Stewart]

valve's were checked and set about 90 miles ago. The noise is a lot louder than the video lets on. I've tried using a long ratchet extension and a hose for pin pointing the noise but the clacking drowns out anything useful.

[Stewart]

Have it narrowed down to a slightly loose harmonic dampener and possibly a bad timing chain tensioner as there is a lot of slack on the far side of the chain though it may be normal. The noise did deminish abit but did not completely go away when the bolt holding the dampener was tightened. For a bit I was having visions of a full rebuild in my near future which I really didn't want to do.

[Steve Simmons]

Did you check the valves before or after the noise started? Almost sounds like a valve hitting a piston, but it's hard to tell from a video. Sticking valve maybe?

[Stewart]

after. Top end of the motor is like a quite sewing machine.

[VWNate1]

Interesting , THANX for posting the sound video ! .

For what it's worth , the timing chain isn't loose ~ the tensioner is hydraulic and so doesn't do much unless the engine is running .

That being said , those single run timing chains and sprockets are notorious for two things : rapid wear and the fact that the cam timing is 4° retarded by dint of the cam sprocket being cut thata way as a pollution control measure .

I'd change out all there ASAP for a correct , DuPlex timing chain and sprockets .

Have you yet tried running the warm engine briefly without the belts ? ~ it's been many a year since I fooled with superchargers but I remember them making a racket as they began to die , ditto alternators , water pumps and so on .

Yes , I am aware the noise sounds rather more like a bottom end rod typ noise but I prefer to look and test before ripping into an engine willy - nilly .

Does the knock get louder if you hold the throttle up to say , 3,200 RPM's then release it suddenly ? .

Don't forget to come back and up date this same thread when you figure it out .

[Stewart]

Noise goes away after 1k rpm or so. I've had the belts off and the noise remained. I did get lucky and did have a dual timing chain setup in the parts bin. New chain was about an 1/8 or slightly more shorter than the old. New chain has been installed but I need to get a new tensioner before I can start buttoning stuff back up.

[Steve Simmons]

To satisfy my own curiosity, I'd pull the plugs and look at the piston tops. If you're sure it's in the bottom end then I would probably start worrying. Bad thrust bearing? Have you tried moving the crank fore and aft?

Just for giggles, are you sure it isn't external? Have you tried steadying the engine while running?

[Martin Keller]

Just a shot in the dark but a rist pin will sound that way when loose in a piston and will get quiet when RPM increases to a certain point but will still be their.
Hope it is something simple like a loose tappet.

[Stewart]

Well its all back together and has been driven. New dual row timing chain and tensioner were installed. The noise is gone and hopefully will remain gone. On a side note the timing with the single row went from 13º to 11º with the dual row chain.

[Steve Simmons]

Good eye on the single row chain, Nate. Those things never last. I can't see that noise coming from the timing chain, but then again I'm watching / listening to the video on a cell phone because the laptop is broken. Here's hoping the problem is gone!

[Stewart]

One thing I noticed was the harmonic dampener has a bit of play on the woodruff key when the bolt is loose. I'm leaning towards it was loose as the impact gun just spun it right off vs when I did the supercharger install it took quite a while for the nut to break loose.

I'm guessing the pulses from the engine were causing harmonic dampener to bounce off the woodruff key causing the banging noise. When I tightened up the bolt before tearing every thing down the noise did mostly go away however there was still noise coming from the area. What I think was happening with the timing chain being loose it was going slack briefly and then being pulled tight and repeat.

Of course I could be completely wrong.

[VWNate1]

Stranger things have been known to happen ! .

I'm sure the 2° improvement on the ignition timing feels better as does the proper valve timeing , not so much more power as ' crisper ' in the power application at any given RPM / load .

Is the crank walloed where the woodruff key fit ? or just the damper ? .

I'd scrap that damper if it's keyway is even slightly loose as in time it'll wallow out the crankshaft and couse you serious greif .