Technical Freshened 1438 sounds chattery

[Davin]

Hello all,

I'm a newbie here with a '68 124 Sport Coupe that's pretty new to me and is my first Fiat.

I'm having some trouble diagnosing what I think is valve chatter, and I'll bet someone here has a trick or two to share. The car runs great and has less than 2k miles on a refresh of its original 1438 performed in 2016.

The receipts (in Italian) give no detail, but a set of pistons, some of the valves, and 600€ in 'cylinder head reconditioning' are included.

I'll post a video of the ticking in the comments. The message board won't let me post a URL as a newbie.

Using a stethoscope it seems to me like the ticking is coming from the #4 cylinder on the exhaust side. I checked the valve clearances and almost all are right in spec. Oddly one of the few that isn't is the #4 exhaust valve, which was .018" (I would have thought .001" tight would have made it quieter not louder).

I have a shim on the way to get it to .019", but I'm guessing that sure won't make it quieter!

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

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

 

[Davin]

Here's the sound in all its glory: [ame]https://youtu.be/_78M5HJRL68[/ame]

 

[F123C]

One thing you might check for is a worn cam lobe. You should be able to do this with a digital caliper or similar with just the cam cover removed - just rotate the engine as required and measure each cam lobe from the peak of the cam lobe to the back of the lobe (nose to heel) and compare results. I've seen Fiat cams wear out one lobe even though the cams run in plenty of oil. One possible cause of a worn lobe is using a worn shim that is hollow in the centre.

Afaik the reason a worn lobe can result in noise even with the valve clearance set correctly is that the action of the 'quietening ramp' on the cam is compromised with a worn lobe?

Your engine does sound noisy, not so much at idle (these engines often sound 'tappety' even with valve clearances set correctly), but it sounds 'clattery' when the engine speed is raised and again as it slows down - just doesn't sound 'happy'. But, then again, engine noises when recorded often sound quite ominous and may not be in reality.

I'm always suspicious of 'refreshed' engines unless, of course, I'm the person who did the refreshing.

AL.

 

[Davren]

The frequency of the tapping noise in the video certainly sounds like a single lobe or tappet.
.

 

[Davin]

Thank you for the idea, AL. I hadn't thought of that one at all, and will check it out tomorrow night.

Totally agree on the whole mystery 'refresh' thing. These AC coupes are damn hard to find though, and after a long hunt I was very pleasantly surprised that this one *actually* came with any receipts at all. And in Italy no less. Anyway, it's not like I can call the shop and ask in Italian what all they did.

Question for one with experience –*I'm running 10W-40 right now. Could a switch to 20W-50 have a chance at quieting things down, or is that too thick for these little Lampredis?

 

[Davin]

Agree 100%. And it is by far the loudest when I put the stethoscope on the rearward-facing cover of the exhaust cam. Hmm.

 

[F123C]

20W-50 would have been the recommended oil for engine and also the gearbox 'back in the day'. Some garages also recommended an oil treatment such as Wynn's or STP at each oil change.

I ran a '69 AC for a couple of years in the late '70's. At that time the AC was old enough for most of the common problems to have materialized but young enough to still be able to get any parts required.

One thing that is unusual about the 1438cc. engine is that it has 2 oil filters!
A conventional replaceable canister on the left side of the cyl. block and a by-pass centrifugal oil filter built into the crankshaft front pulley.

Many regarded the 1438cc engine as being the 'sweetest' and the most 'over-square' of all the twin cams. In Euro. spec. it developed 90 bhp. Some say they had the 'sportiest' cams fitted. Others say that the AC had the best suspension springs fitted (later cars were softened as well as being heavier!). Be thorough with brake maintenance as they are single not dual circuit as standard (they can be easily converted and well worth doing so!)

AL.