Help me identify this engine noise..

[proporsche]

Ok...the sound come most from the middle when you moving to the right.
1.is it there when cold or hot
2.what was the last time you adjust the valves.
3.it does not sounds like an exhaust leak but just look under if you see some black marks on cylinder heads.
4.It is possible the you have one valve(cyl.no 1) spring broken if the sound is there when cold already.


let us know ..remove the valve covers and inspect.i`d start with left intake..

Ivan

[nhs15]

Yes it seems loudest in middle or perhaps slightly left of middle when facing the engine from the rear.
It there on start up and when hot. Seems better when driving at speed.
Valves were adjusted when engine was rebuilt maybe 5 years ago. Haven’t driven it that many miles.
Ok will do. Thank you!

[FA-18C]

Ivan, could that be a tensioner?

[ahh911]

nhs15, it's such a delicate sound, have you popped off the rotor cap (noise is strongest there) and checked to see if there is play on the distributor shaft? Also, automotive stethoscopes are cheap and can at times be very helpful.

Phil

[917_Langheck]

With the sound most pronounced when passing by the non-operating fan, I'd venture a loose or lost head stud on the intake side of the cylinder.

You can run a compression test easy enough. Leak down would work too.

[proporsche]

yes as 917 Lang..mentioned
Did you have the 1000 miles inspection done after the rebuild? That will include the torque heads among other things like double checking the rocker arm shafts..
Do you have any oil leak under?

Ivan

[nhs15]

Not sure if I've even done 1,000 miles! but it has been a number of years. Need to drive it more. No specific inspection done by the engine rebuilder, just usual service.
Yes to oil leak. Always had a tiny one but has grown with time.
I'll check the rotor cap distributer shaft and for black marks on cylinder heads.

[proporsche]

when you clime under it take a picture of the place where the cylinders meet the case..let` see it

Ivan
it is kinda necessary to do post rebuild check mainly for the loose heads and rocker shafts..

[nhs15]

Pulled rotor cap off and distributor shaft seems to have negligible play.

[proporsche]

That is the other side of the noise..remove the intake valve cover set it on Z1 rotor facing other side of the no 1 cylinder and see how is the play on the valve adjustment....
What is the up date ?Have you started again or not i`m leaning toward hanging valve in the valve guide...
Ivan

[proporsche]

Originally Posted by FA-18C

Ivan, could that be a tensioner?

All is possible but i have personally never heard this from tensioner..It is a metal clamping -like with your hands- metal to metal
As i mentioned one valve hanging up in the valve guide..i`d would go drive it ...
Ivan

[nhs15]

I'm waiting for the feeler gauge from pelican to arrive..

[proporsche]

Originally Posted by nhs15

I'm waiting for the feeler gauge from pelican to arrive..

meanwhile you can practice using a hand feel for adjustment-I do it like this since the 1980`s;-)
have a look...some peeps say it is easy with the engine out it is actually easier with the engine in since you get some support for your hand..
Ivan
https://www.youtube.com/watch?v=O_ypBn_u7g8

[nhs15]

Ok I'm back. Feeler gauge was backordered. Valve covers are now off, spark plugs are out. I'll say spark plug for cylinder 3 was nearly stuck and took some time. Left lower valve cover was leaking. What else should I look for while I'm here.

[nhs15]

[nhs15]

[nhs15]

Originally Posted by proporsche

meanwhile you can practice using a hand feel for adjustment-I do it like this since the 1980`s;-)
have a look...some peeps say it is easy with the engine out it is actually easier with the engine in since you get some support for your hand..
Ivan
https://www.youtube.com/watch?v=O_ypBn_u7g8

Finally have an update - valve adjustment done - wasn't that off. New spark plugs, re torqued head studs - and put if back together. And the sound still remains. There when cold upon startup. No better or worse. Any other places to check?

[ahh911]

Originally Posted by nhs15

Those oil trails at the cyl/head interface, that seems odd. When my headstud was loose the sealing surface allowed for some leakage in that area. Tightened it up and there is still mild weepage that I wipe down every oil change with brake cleaner to keep it clean, though not a drop of oil on the floor.

Where do you think the oil is coming from?

Phil

[nhs15]

Not sure. Its been there for some time. Seems tacky almost. Never has hit the ground. I wiped it up so lets see if it ever returns.

[Jim2]

Sir, do you know how to use a screwdriver as a stethoscope? Simple yet effective way to narrow down mechanical noises, bad bearings, clatter etc. A cheap ~15" long thin screwdriver, grip with your thumb over the end of the handle then press your ear against your thumb. Put the tip of the screwdriver against the object in different locations. You need to listen to the individual cylinder heads from under your car, chain cases L and R from above and below, cam housings left bank vs right bank, etc.

Normal mechanics stethoscopes are frequently too loud and drown out detail, I find a simple screwdriver does the trick. Hope you can narrow it down!