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Old 02-09-2021, 11:20 AM
dplidr@gmail.com dplidr@gmail.com is offline
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Overhaul 1976 RWC A4 cylinder hone?

Word back from my machinist that the block passes magnaflux test (and it shows very little rot for its SaltWaterCooled age so I'm relieved about that). One exhaust valve is toast - he recommends replacing all 4 exhaust valves. Was able to glass-bead the intake valves clean to re-use.

Crank bearing surfaces are close to standard so I'll need to replace the main bearings with the std size (one side of bottom half on each bearing pair shows some weird pitting)

Cylinders are close to spec - but worn approx 5-6 thousands (more toward the top of the cylinder) Bottom of cylinder is closer to spec. The next size up for rings or pistons is 10 thousands over. That would require honing.

My Question (how much effort does this really require?):
1) Can I get away with leaving the pistons and rings and cylinders as is?
2) Is it worthwhile to do minimal honing and just use the next size up rings or will that risk too much piston slap?
3) Do I need to hone and upsize both pistons and rings?

I'm worried that honing may weaken the cylinder walls to the point I then need to sleeve - which will be approx $1000 all by itself (not counting any piston or ring replacement)

What is the minimum investment on the cylinders/pistons required? - thank you!

PS - Prior to teardown this A4 started instantly and ran well, but had decreasing power all the last season each time out. Valves were way out of adjustment and a broken spring needed replacing. Once pulled engine and fuel tank was able to remove the 13 foot wet exhaust hose and found it rotted and collapsed in three places. Decided to resurface head and block, clear out the fully plugged water jacket, and gaskets all around along with a series of minor upgrades before re-installing.
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Ishmael22DPL
C&C-33 1976 A4-RWC
Peason35 1969 FWC Yanmar3HM
Evelyn 26 OOD 1979

Last edited by dplidr@gmail.com; 02-09-2021 at 11:31 AM. Reason: adding background for overhaul
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bore, cylinder, hone, piston, rings

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