Tappa tappa tappa from a freshened 1438

[Davin]

Hello all,

I'm a newbie here with a '68 124 Sport Coupe. I'm no stranger to old cars, but this is my first Fiat. I'm having some trouble diagnosing what I think is a single clacking valve or tappet. I've spent hours reading archived threads here and trying all the non-invasive stuff, maybe someone here has a trick or two to share.

Here's the sound: https://youtu.be/_78M5HJRL68

The car runs great and has less than 2k miles on a refresh of its original 1438 performed in 2016 in Italy. The receipts (in Italian) give no detail but a 600€ 'cylinder head reconditioning' is included with a set of valve shims (along with bottom end stuff like pistons and bearings).

Using a stethoscope it seems to me like the ticking is coming from the #4 cylinder on the exhaust side.

What I've checked:
• Valve clearances were all in spec. I changed shims for intake #1 and exhaust #4 because they were on the tight side of the tolerance range. Now intakes are .018 .017 .017 .017". Exhausts are .019 .020 .019 .019".
• Can't find any exhaust manifold leaks
• Timing wheels are metal
• Can't find any play in the cams (hard to be sure when they're under valve spring tension though)
• Compression is great

Unsure about:
• I've read the threads about a hidden crack somewhere in the cam box castings – don't have spares to try sadly, cannot find any obvious cracks with a bright light :/
• My oil pressure gauge has failed and a new sender didn't fix it. Tested continuity of the wiring yesterday and it's good, so next step might be a new gauge? I mention this because my guess is if I had low oil pressure, that spot way up by #4 in the head would get the worst of it. But maybe that's a silly assumption. And the sound does not go away with revs.

I'm leaving soon on a 3-week road trip in this car, and I've gotta eliminate this variable. What would you experienced TC folks do next?

Thank you VERY much in advance for any advice you may have!

-Davin

[Yadkin]

If you suspect poor oil pressure it's never a bad idea to install a mechanical gauge, even as a temporary measure. However I doubt that is the issue.

That sound could be a spark leak. Make sure that you have good connections on your wire-to-plug, and use a small amount of dielectric grease to seal the rubber boot to the ceramic insulator.

It could also be an exhaust leak in that area.

[JohnMc]

You are right on the specs on clearances - of course cold.
I am on my second 1438 and they both kind of made noise. I just my head redone with valve seats for unleaded and cannot tell but might sound like yours. To me they have never been quiet - but what is quiet and what is excessive?
My official FIAT 124 Sport 1970 Manual on servicing instructions states in part, "Excessive tappet clearance causes noise, but if there is no clearance, the valves will remain slightly open: this greatly shortens their life and that of the valve-seats". Doesn't really tell you damn.

On the oil pressure I can only talk on the 1969 and 1970 Spiders. They have a pressure gauge and also a low oil pressure sending idiot light. The low pressure idiot light is supposed to light up when the oil pressure falls to 6 to 12 PSI. On the Spiders the sending units are right next to each other. Also I have always had to tap on the oil pressure gauge to get it moving - though the low pressure idiot light works fast.
Probably not much help - hopefully others have more experience than I.

[blazingspider]

As you seemed to have checked out the most obvious reasons for valve train noise or noise masquerading as valve train noise, I'll throw out a couple of possibilities. Are the shim profiles proud of the bucket recesses? In other word could the cam profile be contacting the lip of the bucket because the shim rides a hair lower? Another thought would be checking for excessive wear on the bore of the cambox for the tappet buckets or the buckets themselves.

[Davin]

If you suspect poor oil pressure it's never a bad idea to install a mechanical gauge, even as a temporary measure. However I doubt that is the issue.

That sound could be a spark leak. Make sure that you have good connections on your wire-to-plug, and use a small amount of dielectric grease to seal the rubber boot to the ceramic insulator.

It could also be an exhaust leak in that area.

Thank you @Yadkin. Interesting idea with the spark leak. I did pull each wire while the engine was running to see if that impacted the sound and it didn't (good news for the bottom end, but rules out the spark leak). For sure when I got the plug wire near ground, the jumping spark made a sound just like this tap-tap-tap. I took your suggestion and added dielectric grease under the boots for good measure.

I wish I could find an exhaust leak, that would be a nice simple solution. Kinda at a loss for a good way to do that though. I used a light to look for soot, and taped a funnel to a piece of garden hose to make a giant listening thingy. Also sprayed soapy water on the mani while it was cold and watched for bubbles as the car warmed up. All with no luck.

When I use the stethoscope it really sounds like a mechanical tap from the rear cam cover on the exhaust side.

[Davin]

You are right on the specs on clearances - of course cold.
I am on my second 1438 and they both kind of made noise. I just my head redone with valve seats for unleaded and cannot tell but might sound like yours. To me they have never been quiet - but what is quiet and what is excessive?
My official FIAT 124 Sport 1970 Manual on servicing instructions states in part, "Excessive tappet clearance causes noise, but if there is no clearance, the valves will remain slightly open: this greatly shortens their life and that of the valve-seats". Doesn't really tell you damn.

On the oil pressure I can only talk on the 1969 and 1970 Spiders. They have a pressure gauge and also a low oil pressure sending idiot light. The low pressure idiot light is supposed to light up when the oil pressure falls to 6 to 12 PSI. On the Spiders the sending units are right next to each other. Also I have always had to tap on the oil pressure gauge to get it moving - though the low pressure idiot light works fast.
Probably not much help - hopefully others have more experience than I.

Thanks JohnMc. Yes, very hard for me to tell what's ok noise-wise since I'm new to these motors. I traveled kinda far today to get a 25-year Fiat/Lancia tech's opinion. My German is not the best so some of the nuance was lost, but he basically agreed that it would be good if it were quieter but that I should not have any major worries about it. So I'm not gonna let it stop my trip – but it still bugs me. It feels like if nothing were wrong it *shouldn't* sounds like that. The tick is too singular and pronounced. Cheers.

[Davin]

As you seemed to have checked out the most obvious reasons for valve train noise or noise masquerading as valve train noise, I'll throw out a couple of possibilities. Are the shim profiles proud of the bucket recesses? In other word could the cam profile be contacting the lip of the bucket because the shim rides a hair lower? Another thought would be checking for excessive wear on the bore of the cambox for the tappet buckets or the buckets themselves.

Thank you for getting creative about it. Whatever this is it's a bit hidden, so I'm open to anything. The shims are all sticking up comfortably above the buckets to my eye. Excessive wear on the bucket bores was something I was wondering about. When they're not under pressure from the cam lobes, I *can* seem to rock some of the buckets back and forth juuuust a hair with my fingers. It's barely perceptible, but I don't know what's normal and I have even less sense for how much movement there would make noise.

I guess a next step would probably be to pull the head and get it to a reputable machine shop to do another run through. No time for that before my big trip, unfortunately.

[Davin]

Here's an idea. I recently did an oil change to 10W-40, based on what the manual said for the summer season. In my previous oldies (BMW, Datsun) I've always used 20W-50.

Could switching to the thicker stuff in theory quiet the valves at all? Or would it be a bit heavy for some of the oil passages? Rookie question, I'm sure!

[grrrdot]

Huh,
Your video sure sounds close to my engine, here's my video:
https://youtu.be/s5fhp7t1wZI
In my case my #2 exhaust was .22. It was not long after I had done the shims and looking at my shim log somehow the clearance on this shim got wider... AFAIK they were supposed to only get smaller! it made no sense but there it was.
New shim and it sounded normal again.

-G

[JohnMc]

Worth a shot on the oil. Other people at the site said they now use 15-40 shell diesel oil and I have starting to use it. I always used to use 20-50 but am in a very hot climate in northern CA.

[TX82FIAT]

I would absolutely change the oil to 15W40 to a 20W50. A thicker oil will quiet down the motor. It actually sounds normal just a little loud to me. Let's have an expert weigh in.

[Davin]

Thank you for the recent replies, all. After reading some threads about oil I ordered up some ZDDP additive. Will change to heavier oil and add that and see how it goes.

I'll also get on the program of using lead substitute. I had thought since this car had cylinder head work they would have installed modern valve guides that don't require lead, but it couldn't hurt to try it for a while and see if thing quiet down.

Will report back. Cheers!

[seabeelt]

My 1608 has had the same noise for 5 years and all of my tappet clearances are right on the money. I drive it like I stole it and haven't broken it yet