What's my engine saying to me?

[Del in NE Ohio]

Since returning from the BRP, I haven't had much chance to "get back in the saddle". When I finally did, I found my engine making a strange noise.
Having witnessed first hand the "carnage" along the parkway, my anxiety level went right up. So, in an effort to get in front of things, I dropped the pan on my 9K mile engine and checked all the rods and mains. Babbitt looked good. Clearances all looked good. Back together for test drive, noticed an intermittent click..click...click in the vicinity of #1 cylinder. It was especially noticeable when I would slightly open the throttle and release. Then when I grounded the #1 plug, the click was constant and more defined! Pulled the valve cover and all valve clearances were OK.. Restart = same noise! Engine has touring grind cam, Brumfield head, FSI distributer. Compression 110-120 lb on all cylinders. I am especially stumped since the noise increases with the shorted plug on #1. Other plugs make no difference.

What am I missing?

[James Rogers]

Sounds like piston slap to me. Did you overheat the engine on any of those hills?

[Del in NE Ohio]

I may have touched 190-200 degrees once or twice.

[KGBnut]

Couldn't hurt to check your timing gear. When they get sloppy, as the fiber ones sometimes do, they induce clicking/knocking noises. A broken timing gear plunger spring can do the same.

I can't explain the increase when grounding #1, but mine was very noticeable when I would punch and release the throttle.

[MikeK]

Piston slap. Possibly exacerbated by a stiff piston pin. Next time you drop the pan see how much left-right rock you get on the piston skirt. It is possible to expand the skirt diameter a few thousandths with the piston in-place by peening the inside just above the bottom edge.

[H. L. Chauvin]

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Always a challenge to diagnose engines from a distance when one cannot "see" & "hear" exactly what is going on; above advice is good.

If it were mine, I would:

1. First, either get a mechanics stethescope, (under $10.00) or use a wood dowel placed on your ear to re-try to re-pinpoint the exact location of the click.

2. Second, if click is near #1 piston, remove #1 plug, put a few squirts of regular engine oil in cylinder #1, & start engine "without" #1 plug connected & immediately listen -- if far less clicking noise, possible piston slap -- if same clicking noise possible "no" piston slap.

3. Third, if possible "no" piston slap, I would call Mr. Dan McEachern in CA to order an aluminum timing gear -- why?

4. Touring cams like yous offer far more resistance with much higher lifts for a fiber cam gear to rotate than turning an 80 year old cam that is well worn.

5. It could be play between gear teeth or play between metal center of timing gear & fiber outer part -- how much play? -- play about the thickness of a frog hair can make an engine with a high lift cam sound like a corn grinder with hard walnuts in it.

6. All of the above is less than $100.00 -- from far away, in trying to guess at your problem, that is what I would try first -- at the very least, the best part is that you will change out (5) mufflers before your aluminum timing gear wears out.

Hope this helps.

[Kurt in NJ]

Piston slap is usually louder cold, loose wristpin noise is usually louder hot--and is a double noise (top of stroke, bottom of stroke), and can be louder with the plug shorted ---
The tight pin/loose piston scenario of MikeK could possibly be seen through the plug hole by rocking back and forth in 3rd looking at the top of the piston with a small mirror or borescope.

[BRENT in 10-uh-C]

I was thinking along the lines of Kurt while also thinking like Mr. Chauvin in that lack of hearing always places us at a disadvantage. I also factored in the added possibility of a bent rod.

[Del in NE Ohio]

Thanks for all the replies. I tried applying pressure with timing pin with engine at idle and made no difference. The timing gear is a laminated std gear that was installed last fall when a fiber/metal gear was the problem.

Just now removed #1 plug, squirted oil in chamber. Re-installed plug (no wire). Started engine.. no noise.. I shut it off, re-connected plug wire. Started and noise is reduced somewhat, but when short out plug it's back.

[H. L. Chauvin]

Hi Brent,

Very keen observation in reply #8 for noticing that all of our guesses are on equal terms -- never thought of it that way!

For example, when one is trying to diagnose an engine problem by listenng from a thousand miles away, an older guy with terrible hearing loss can hear the problem engine running & clicking just as well as the other guy one thousand miles away who has absolutely no hearing loss. LOL

[H. L. Chauvin]

Hi Del,

All repair manuals were written by engine manufacturers selling expensive engine services & selling expensive parts, thus indicating only the "creme de la creme" costly type of repairs.

Even though it may appear odd, many of the "poor folk" mechanical remedies work; but, were never written in the manuals.

May be possible if "only" piston slap is the "only" problem, the split skirt may be opened to make up for wear, rocking, & slapping; however, for a one (1) time fix, better to bring piston & rod to a machinist type mechanic to test alignment, piston pin movement, & make recommendations for peace of mind & to avoid future wearing out of your oil pan bolts trying to find the clicking problem.

Hope this helps.

Others no doubt will have other good suggestions.