Ticking noise when warm

[Rich76_911s]

Hey everyone,

I rebuild my 930 engine about 500 miles ago and it has had a ticking noise that I haven’t been comfortable with. I’ll add some links to videos of said noise at the end of the post.

The ticking is fairly quite when the engine is cold but becomes more pronounced as the engine warms up. To my ear it sounds as though it’s coming from the #6 cylinder. I’ve tried using a stethoscope on it to attempt to pinpoint the location specifically but I haven’t had much luck narrowing it down. I think my slow motion video below confirms the cylinder though. The ticking does increase in frequency with rpms.

Initially I thought it was due to a shifting rocker shaft that I had on the #6 exhaust side, but I replaced that over the winter, did a valve adjustment and checked the headstuds for proper torque. But much to my disappointment the ticking noise persisted. I checked the #6 and #5 cylinders for compression as well and got 120 psi in each cylinder. (Nickie Cylinders with JE pistons at 7.5:1 compression)

So now I’m seriously considering tearing the engine down to diagnose what is wrong. Do any of you have any suggestions of what else I ought to do?

Here are some videos of the noise.

First one is of a cold engine without the ticking noise:
https://m.youtube.com/watch?v=DqTrqV_HkkY

Second is warm with ticking noise at full speed.
https://m.youtube.com/watch?v=509dKGP6hOs

Third is a longer video in slow motion of the engine warm, in slow motion, with a timing light on the #6 cylinder. Note that I have electromotive ignition that fires on compression and exhaust stroke. I mention this only because as you’ll see the timing of the ticking is in sync with the light.
https://m.youtube.com/watch?v=3sNqPo0O_Dw

The slow motion video makes it sound really bad.

Anyway I’d really appreciate the community’s insight and guidance on fixing this and getting myself some seat time instead of wrenching time. ����

Thanks so much in advance
Rich

[dannobee]

A couple of tips to help pinpoint it.

If you can't narrow it down with a stethoscope, try using a section of garden hose or heater hose, with one end up to your ear.

Armed with a 12v test light and a couple paperclips, ground out each cylinder individually and see which one reduces the ticking. (Of course the engine will misfire when you ground each cylinder.) Carefully straighten out one leg of the paperclip, then sneak that part between the spark plug wire and the boot at the distributor/coil pack. With the engine running, verify that your 12v test light is grounded on the alligator clip side, then touch the pointy end to paper clip on the suspect cylinder.

Be careful not to poke a hole in the boot, otherwise the spark could jump through the hole to something else. And be careful to make sure the test light is properly grounded and the bulb works, otherwise you could get shocked. And for gawds sake, don't touch the paperclips with your flesh, otherwise it's gonna hurt.

It could be something as simple as a loose spark plug, or something like piston slap, although most piston slap noises improve with heat. In any case, killing the spark to the affected cylinder should change the tick, since you seem confident that it's not valve noise.

[Rich76_911s]

Originally Posted by dannobee

A couple of tips to help pinpoint it.

If you can't narrow it down with a stethoscope, try using a section of garden hose or heater hose, with one end up to your ear.

Armed with a 12v test light and a couple paperclips, ground out each cylinder individually and see which one reduces the ticking. (Of course the engine will misfire when you ground each cylinder.) Carefully straighten out one leg of the paperclip, then sneak that part between the spark plug wire and the boot at the distributor/coil pack. With the engine running, verify that your 12v test light is grounded on the alligator clip side, then touch the pointy end to paper clip on the suspect cylinder.

Be careful not to poke a hole in the boot, otherwise the spark could jump through the hole to something else. And be careful to make sure the test light is properly grounded and the bulb works, otherwise you could get shocked. And for gawds sake, don't touch the paperclips with your flesh, otherwise it's gonna hurt.

It could be something as simple as a loose spark plug, or something like piston slap, although most piston slap noises improve with heat. In any case, killing the spark to the affected cylinder should change the tick, since you seem confident that it's not valve noise.

THanks for the suggestions. Man i'd love it to be a loose spark plug.

Just a quick question on your grounding out. Essentially we're just not creating spark in the cylinder and determining if the noise is reduced when the spark isn't generated, right? Which hopefully will help determine the guilty cylinder.

Cheers
Rich

[dannobee]

Exactly. We want to determine which cylinder is causing the noise. If it’s excessive piston to wall clearance, killing that cylinder will eliminate the noise.

[pors1968]

Could be exaust leak

[Rich76_911s]

Alright, my apologies for the long delay here. Took me some time to get out to the garage and complete the assignment.

I did remove spark from each of the 4,5,6 cylinders, and there was no discernable reduction in the noise being produced. (Just FYI I didn't do the paperclip method, I just put a spare spark plug on the end of the wire and grounded it out)

I did also torque all 12 spark plugs to waynes engine build book specs. I think it was 35 ft/lbs but don't quote me on that.

Also did a cold leakdown test on the 4,5,6 cylinder bank, and had very low (sub 5% leakdown on each cylinder). Compression test was also done and each cylinder came in at 119/120 PSI. Engine has a compression ratio of 7.5:1.

I also checked and rechecked valve lash, and still no change. I used the Kirk tool to set the valve lash, and probably erred on slightly tighter than I had previously set them.

[Eagledriver]

The slow motion gives a good clue. There’s 3 clicks per fireing light. Must be valve related not rod related. The engine is making 2 revolutions during those 3 clicks. One for each cylinder on that side. This would imply to me that the tensioner is the culprit. Or some other chain issue on that side.

-Andy

[Rich76_911s]

Andy,

Thanks so much for your taking a look at the slow motion video, and giving your insight. I'll keep digging up there and see what it is.

Thanks
Rich

[VFR750]

I had the same ticking sound. Quiet when cold louder when hot. Sound tracked with rpm.

If it is really three ticks per revolution then it might be the same cause: the cam drive gear is loose on the crankshaft. The ticking sound is caused by the woodruff key getting hammered due to the loads imposed by the valves back feeding from the rockers reacting off the cam lobes.

I had my crankshaft weld repaired and a new gear and key.

Sound has stopped.

[dannobee]

How did the cam lobes look when you checked valve lash?

To me it sounds like it's every crank rotation, but one noise louder than the other. On the slow-mo, I hear a "ta thunk (light), ta thunk (light)." That double tap might be a wrist pin noise. Did you measure piston to pin clearance when you had it apart? Did everything else measure within specs? Did you notice the noise right after overhaul, or did it come later?

[Rich76_911s]

Originally Posted by VFR750

I had the same ticking sound. Quiet when cold louder when hot. Sound tracked with rpm.

If it is really three ticks per revolution then it might be the same cause: the cam drive gear is loose on the crankshaft. The ticking sound is caused by the woodruff key getting hammered due to the loads imposed by the valves back feeding from the rockers reacting off the cam lobes.

I had my crankshaft weld repaired and a new gear and key.

Sound has stopped.

Dumb question. Cam drive gear on the crankshaft. I’m assuming that is the gear that drives the intermediate shaft, right? That is one of the only gears I didn’t replace.

[Rich76_911s]

Originally Posted by dannobee

How did the cam lobes look when you checked valve lash?

To me it sounds like it's every crank rotation, but one noise louder than the other. On the slow-mo, I hear a "ta thunk (light), ta thunk (light)." That double tap might be a wrist pin noise. Did you measure piston to pin clearance when you had it apart? Did everything else measure within specs? Did you notice the noise right after overhaul, or did it come later?

You hear the noise the same as I do.

Cam lobes all look fine. I did notice my #4 intake rocker arm shaft has moved some in its bore. But I don’t think this is causing the problem. I tried to fix it, but naturally the 5mm hex doesn’t want to budge.

I’ve checked and rechecked valve lash so many times that I’m starting to think it may be deeper down. Hopefully not all the way to the crank.

I didn’t measure the wrist pin clearance that I can recall. They were all new on new JE pistons though. Everything I measured came out perfectly fine, and the rods were inspected by the machine shop.

Noise has been present since I rebuilt the engine. Which is the main reason I’ve put very few miles on it since I did the build.

Thanks for all the ideas.

[VFR750]

Originally Posted by Rich76_911s

Dumb question. Cam drive gear on the crankshaft. I’m assuming that is the gear that drives the intermediate shaft, right? That is one of the only gears I didn’t replace.

Yes. That gear.

I had my crankshaft inspected and magnafluxed and that is when they found the loose gear. You have to pull the stack apart to get the gear off. Many people don’t do that.

[Rich76_911s]

Originally Posted by VFR750

Yes. That gear.

I had my crankshaft inspected and magnafluxed and that is when they found the loose gear. You have to pull the stack apart to get the gear off. Many people don’t do that.

I was secretly hoping that you mistakenly put crank instead of cam

Yup had my crank magnafluxed and inspected, but didn't remove and replace that gear or the distributor drive gear. Also the large #0 gear on the intermediate shaft is still original. The others were all new.

Was yours louder on one side than the other? By ear mine sounds loudest near the #6 cylinder, but maybe this is just the acoustics of the engine bay. Stethoscope sounds loudest on 4,5,6 bank, but can be heard throughout the engine, and I was surprised by how clear it sounded on the engine mounted oil cooler.

If I have the same problem as you, I guess I'll be improving my skills by building the engine a second time.