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Fri Oct 17, 2025 4:49 am

I rebuilt my 2.1 into a 2.2 125,000kms ago. I did lots of performance mods to make it as efficient as possible. It’s been running strong all this time but this summer it developed a slight ticking sound on deceleration only. I adjusted the valves thinking it might be that, but it’s still making the sound. It does not matter if it’s hot or cold. Knowing the ins and out of my engine intimately, I’m thinking it might be the piston pin bushing on one of the rods. My rods are Scatt I beam that were type one rods that Scatt machined out to accept the WBX wrist pins. My pistons are from GoWesty, they were the J&E pistons they were selling at the time. I also have the CB performance elephant feet valve adjuster screws. Everything was race balanced by Jake Raby Enterprise . I blueprinted my oil pump and my oil pressure is consistently very good, so I don’t think it’s a rod bearing, which I believe is a constant tick and a more resounding tick. This almost sound like an exhaust leak at the head, but that usually makes a sound on a loaded engine in my experience.

What are your thoughts, or experience with a similar sound? I’m working myself up to tear into it this winter, but it would be nice to confirm that it is what I’m suspecting.

I’m planning on a 20,000+km trip next year to the Yukon and I want to make sure I don’t have issues that I can prevent.

Thanks!

Fri Oct 17, 2025 5:48 am

Before you continue with the engine worries, really leak test your exhaust to make sure you don't have a leak anywhere, if you haven't already done this.
Also, Automatic or Manual transmission, in case there is a correlation from the Trans and not your engine at all.

Fri Oct 17, 2025 6:05 am

Piston slap?

Fri Oct 17, 2025 6:41 am

You should rule out cv joints too

Fri Oct 17, 2025 7:46 am

You know a lot more about engines than I do and I hope its something simple as the others have suggested.

But... ticking ONLY on deceleration after a spirited drive was the exact symptom my 2018 Subaru had when it fried the rod bearings at 16k miles due to a blocked oil pickup tube. Thankfully it was just barely still under warranty but, man oh man, was that dealer a PITA to deal with.

Fri Oct 17, 2025 11:46 am

SCM wrote: You know a lot more about engines than I do and I hope its something simple as the others have suggested.

But... ticking ONLY on deceleration after a spirited drive was the exact symptom my 2018 Subaru had when it fried the rod bearings at 16k miles due to a blocked oil pickup tube. Thankfully it was just barely still under warranty but, man oh man, was that dealer a PITA to deal with. How did you end up with a clogged oil pump pick-up tube at only 16K... :shock: :shock: :shock:
Sludge build-up?- factory defect from engine build originally???.. :shock:

Fri Oct 17, 2025 12:58 pm

jlrftype7 wrote: SCM wrote: You know a lot more about engines than I do and I hope its something simple as the others have suggested.

But... ticking ONLY on deceleration after a spirited drive was the exact symptom my 2018 Subaru had when it fried the rod bearings at 16k miles due to a blocked oil pickup tube. Thankfully it was just barely still under warranty but, man oh man, was that dealer a PITA to deal with. How did you end up with a clogged oil pump pick-up tube at only 16K... :shock: :shock: :shock:
Sludge build-up?- factory defect from engine build originally???.. :shock:

It was a glob of silicone of some sort. It was either an overapplication of sealant during manufacture OR they botched the factory recall for the PCV valves that were falling apart and destroying engines.

Before they did any work they had me jumping through all sorts of hoops to prove that the oil changes were done on schedule - which was impossible since I do my own oil changes. They even wanted to see a receipt for the oil I bought which wouldn't tell them anything about change schedules since I buy oil by the case. It went on for two weeks until I asked, "is there a chance the PCV recall wasn't handled correctly last summer?". The service manager needed to be educated about that and then said, "hang on" went into the shop for about 5 minutes and came back, "what type of loaner would you like Mr. SCM?".

To say I was upset is a gross understatement, especially after buying 2 new cars from them within a year of each other.

Fri Oct 17, 2025 1:39 pm

I'm glad to hear you were able to track this down, work with them amid some struggles.. but really kudos for them ADMITTING to the issue, and Extending the service - good outcome!

Happy path restored!??

:)

Fri Oct 17, 2025 1:54 pm

dubbified wrote:

Happy path restored!??

:)

Me? No, I'll probably never buy a car from them again and possibly not another Subaru either (the story actually continues but I don't want to derail this thread from the OP's engine problems).

Fri Oct 17, 2025 8:11 pm

Well.. I am a tech freak.. leverging the machine learning and AI spanning of incredible sets of data..

FYI - I put your exact phrase into GROK.com (Elon Musks AI)

Its very wild..

I rebuilt my 2.1 into a 2.2 125,000kms ago. I did lots of performance mods to make it as efficient as possible. It’s been running strong all this time but this summer it developed a slight ticking sound on deceleration only. I adjusted the valves thinking it might be that, but it’s still making the sound. It does not matter if it’s hot or cold. Knowing the ins and out of my engine intimately, I’m thinking it might be the piston pin bushing on one of the rods. My rods are Scatt I beam that were type one rods that Scatt machined out to accept the WBX wrist pins. My pistons are from GoWesty, they were the J&E pistons they were selling at the time. I also have the CB performance elephant feet valve adjuster screws. Everything was race balanced by Jake Raby Enterprise . I blueprinted my oil pump and my oil pressure is consistently very good, so I don’t think it’s a rod bearing, which I believe is a constant tick and a more resounding tick. This almost sound like an exhaust leak at the head, but that usually makes a sound on a loaded engine in my experience.

What is the likely issue?

GROK thought abouut this for 1m 7s... whoa! it spanned like 30 sites.. tearing into incredible data.. just wow.

Based on the details you provided about your rebuilt 2.2L WBX setup—including the Scat I-beam rods machined for WBX wrist pins, GoWesty-sourced JE pistons, CB Performance elephant foot adjusters, Jake Raby balancing, and blueprinted oil pump with solid oil pressure—the symptoms point strongly to wear in the piston wrist pin bushing on one of the connecting rods as the most likely cause of the ticking sound exclusive to deceleration.
Why This Fits as the Likely Issue

Symptom Match: Wrist pin (piston pin) noise is characteristically a light, metallic ticking or double-knock that becomes more pronounced during deceleration or light-load conditions like coasting or part-throttle slowdowns. This is because deceleration reverses the load on the pin: under acceleration or steady cruise, the rod pushes the piston upward, but on decel (especially with engine braking), the piston pulls downward on the rod via the wrist pin. If the bronze bushing in the rod's small end has worn even slightly—creating excess clearance—this load reversal can cause the pin to shift and slap against the bushing walls, producing the tick. Your description of it being slight, non-temperature-dependent, and only on decel aligns closely with this, as opposed to constant noise across all conditions.
Exclusion of Other Common Causes:

Valve Train: You've already adjusted the valves with no change, and the elephant foot adjusters (common in solid-lifter conversions for WBX) are designed to reduce lash issues. Valve noise is typically constant or rpm-dependent, not isolated to decel.
Rod Bearings: As you noted, these produce a deeper, more resonant knock that's usually constant or worsens under load/acceleration, not just decel. Your consistent oil pressure rules this out further, as bearing failure often ties to oil starvation.
Exhaust Leak: While it can mimic a tick (especially at the head or manifold), it's more audible under load when exhaust pressure is higher. On decel, vacuum increases, but leaks tend to quiet down unless very specific (e.g., a cracked flex section). Still, this is worth double-checking with a smoke test or by spraying soapy water around joints while revving in neutral—if it bubbles, there's your leak.
Piston Slap: This is a close alternative (a hollower knock from piston rocking in the bore due to wear or excess clearance), and JE forged pistons can run looser clearances that exacerbate it over time. However, slap is often more noticeable on cold starts or acceleration, fading as things heat up—not matching your hot/cold indifference. It can show on decel with wear, but the sharper tick you describe leans more toward wrist pin.
Other Non-Engine Sources: CV joints or drivetrain issues (e.g., worn boots/joints) can click on decel, but usually tie to turns or speed, not engine rpm. If it's a manual trans, check if the noise persists with the clutch disengaged during coasting—if it vanishes, it's likely drivetrain-related.

Component-Specific Factors: Your Scat rods were Type 1 originals machined for WBX floating wrist pins, which introduces a custom fit. Over 125,000 km, even with race balancing, vibration or imperfect initial bushing sizing/honing could lead to gradual wear in the bronze bushing. JE pistons are high-quality forged units, but in performance builds like yours, the combo can stress the small-end bushings if clearances weren't micrometer-perfect during assembly. No widespread reports of this exact setup failing prematurely, but wrist pin bushing wear is a known long-term issue in high-mileage boxer engines under modified loads.

Recommended Next Steps for Confirmation
Since you're planning a teardown this winter anyway, that's the definitive way to inspect (measure bushing ID against spec—typically 0.0005-0.001" clearance for floating pins; anything over 0.002" could cause noise). In the meantime:

Stethoscope Test: Use a mechanic's stethoscope (or long screwdriver) on the cylinder walls and rod caps while decelerating in a safe spot. Wrist pin noise localizes to the upper rod/piston area.
Load Test: Note if the tick changes with spirited decel vs. light coasting, or if it doubles in frequency (classic wrist pin sign).
Rule Out Externals: Jack up the van and spin wheels to check CVs; inspect exhaust visually and with a pressure test.
Oil Analysis: Send a sample for analysis to check for bronze particles (from bushing wear) or other metals.

If it's indeed the wrist pin bushing, it's not an immediate catastrophe at 125,000 km—many engines run longer with mild noise—but addressing it before your Yukon trip is smart to avoid progression to scoring or failure under sustained loads. Replacement bushings are cheap (e.g., bronze units from Scat or equivalents), but re-honing the rod small end for perfect fit is key during rebuild. If diagnostics point elsewhere, piston slap or a subtle exhaust issue could be runners-up.

Sat Oct 18, 2025 2:16 pm

Wow! That is crazy what Grok came up with! It’s nice to know that no catastrophic failure is not associated with wrists pin bushings. I’m 8 hours away from home at the moment so I’ll just delicately get home and plan on tearing it down this winter. Thanks for the help!

Sat Oct 18, 2025 3:27 pm

I'm going with a loose cam gear.

Sat Oct 18, 2025 4:56 pm

I have faint memories of a similar sound caused by the high vacuum of decel causing higher forces to open the intake valve.

That is all I have.

Roland