Hi all, I'm looking at my options for cylinder #3 as it's been giving low compression for a long time and we're discussing whether I should change it now or at overhaul. I bought the plane about 2 months ago - 2011 RV9, IO-320-B1A with 1750 SNEW, chrome-plated cylinders. It's about 50/50, some people say toss it, others say wait till OH, no one has mentioned lapping or solvent flush. I have a new steel cylinder (not chrome-plated) in stock waiting for a decision. Here's the cylinder's history.
Oct 18 2019, 1242.2 SNEW - 78/78/68.76
Sept 17 2020 1294.3 SNEW - 77/76/65/78
May 20 2021 1330.4 SNEW - 78/79/76/79
May 30 2022 1436.3 SNEW - 74/77/67/78
Apr 26 2023 1563.6 SNEW - 76/78/58/77 - #3 exhaust and intake valves lapped due to leakage
Feb 12 2024 1597.0 SNEW - 78/78/50/78 - borescope valves/piston face/cylinder NORMAL
May 19 2025 1678.1 SNEW - 78/71/52/76 - borescope sent to SavvyAnalysis and signs of uneven heat distribution exhaust #3 and #4 to monitor.
Apr 30 2026 1714.1 SNEW - 76/77/50/77 - borescope sent to SavvyAnalysis and signs of uneven heat distribution exhaust #3 and #4 to monitor.
As it stands right now, #3 has a leak through the intake valve and through the rings per the pre-buy inspection. As far as I understand they only tried to lap them in 2023 but didn't look for much else. Engine data has been sent to SavvyAnalysis in 2023, 2025 and 2026 with no recommendations other than to monitor through borescoping.
How about #4 which has no compression loss? Just monitor the valve?
Pictures below are Savvy report from 2025 and the most recent pictures of #3 and #4. Individual pictures are from pre-buy in May 2026.
If I do swap #3 out, what do I do with the old cylinder? Most people have told me that since it's chrome plated, it's only good for trash.
Oct 18 2019, 1242.2 SNEW - 78/78/68.76
Sept 17 2020 1294.3 SNEW - 77/76/65/78
May 20 2021 1330.4 SNEW - 78/79/76/79
May 30 2022 1436.3 SNEW - 74/77/67/78
Apr 26 2023 1563.6 SNEW - 76/78/58/77 - #3 exhaust and intake valves lapped due to leakage
Feb 12 2024 1597.0 SNEW - 78/78/50/78 - borescope valves/piston face/cylinder NORMAL
May 19 2025 1678.1 SNEW - 78/71/52/76 - borescope sent to SavvyAnalysis and signs of uneven heat distribution exhaust #3 and #4 to monitor.
Apr 30 2026 1714.1 SNEW - 76/77/50/77 - borescope sent to SavvyAnalysis and signs of uneven heat distribution exhaust #3 and #4 to monitor.
As it stands right now, #3 has a leak through the intake valve and through the rings per the pre-buy inspection. As far as I understand they only tried to lap them in 2023 but didn't look for much else. Engine data has been sent to SavvyAnalysis in 2023, 2025 and 2026 with no recommendations other than to monitor through borescoping.
How about #4 which has no compression loss? Just monitor the valve?
Pictures below are Savvy report from 2025 and the most recent pictures of #3 and #4. Individual pictures are from pre-buy in May 2026.
If I do swap #3 out, what do I do with the old cylinder? Most people have told me that since it's chrome plated, it's only good for trash.
