Overhaul 1976 RWC A4 cylinder hone?

[dplidr@gmail.com]

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.

[dplidr@gmail.com]

update

Cylinders, pistons, and rings are in good enough shape to retain. Moving forward with overhaul project.



-DaveL

[ronstory]

Hmmm... if your pistons are 0.005-6" over near the top, you are on very edge of acceptable.

My thoughts are if you are just using the motor of limited use to get to/from the dock and a bit of motoring... likely good enough. If you are looking towards days of potential motoring in the future, going 0.010" over may be a better choice.

Your boat, your call. ... and this opinion if worth exactly what you paid for it.

[ronstory]

BTW, what was your oil pressure cold and hot before disassembly? My main reason for doing my rebuild was to get consistent oil pressure, which I finally achieved, Woo-hoo!

[dplidr@gmail.com]

1976 RWC overhaul

Thanks Ron,

My oil pressure was good solid 35-45. I'm replacing the regulator plunger anyway. Along with Kaminsky upgrade and the accessory-drive oil-level upgrade and a PCV valve from Indigo.


Yes, day sails, beer can racing, local/coastal cruising. If I end up doing the rest of the list for longer-distance cruising, I'd opt for a diesel for the double range per gallon and to support H/C shower, and heavier electronics load.

That list for needed cruising-comfort upgrades is a long one...

-DaveL

[ronstory]

With oil pressure like that, you are a happy man.

My one last thought would be consider replacing the rings 'just cuz' since it's easy now. Maybe Dave Neptune will offer his thoughts... he is our resident engine professor.

[dplidr@gmail.com]

1976 RWC overhaul

Yep - new rings it is...
Painting the individual parts before I reassemble

Has anyone used any kind of zinc paint or other coatings inside the cooling passage area? on the outside of the cylinder walls inside the water jacket or other?

[Surcouf]

Yep - new rings it is...
Painting the individual parts before I reassemble

Has anyone used any kind of zinc paint or other coatings inside the cooling passage area? on the outside of the cylinder walls inside the water jacket or other?

never heard of anybody trying. I would be concerned of a large paint flake coming out and blocking cooling passage. Pretty usual with rust flake..

[sastanley]

Dave, Any consideration to install FWC while you are going this far? It would help give the block a fighting chance to run another 40 years by no longer pumping saltwater thru it. Also, if you did FWC with an H/X you have opened up options for using the antifreeze to heat the potable water too. I am noodling around in my little brain about how to design this upgrade presently. Couple valves and some hose is really all I need..Mine will be more like an on-demand system..would be nice to wash your hands in hot water, or do the dishes without a kettle on the stove, etc.

[dplidr@gmail.com]

1976 RWC overhaul - FWC upgrade?

Hi Shawn,
I'm not considering adding FWC at this time. I agree with all your points, but putting off that additional cost - easily added later once the engines is back running and proven in the boat.

I've compared the MMI mechanical FWC vs the Indigo electric (half the price). I think I'd go with the Indigo - partly because the mechanical system requires space near the flywheel that is not available in the C&C 33 unless I move the cockpit drain thru-hulls.

[scratchee]

Special request for a favor from the OP: would you be able to get a couple close-up photos of the stud holes (for the head, not the manifold) on the valve side? Your block looks great! I'm tearing down a spare engine and some of the holes are blocked, but I don't know what they're supposed to look like or where the cooling passages go.

Thanks if possible, no harm if not!

[ronstory]

Your pic looks to be the block and not the head, but that looks to me like a threaded hole with "gunk" at the bottom.

Regarding the head, if you have new style engine, Universal reduced the number of cooling passage from the earlier block. If you look overlay the gasket on head, you will see some passages in the gasket are not machined through. Evidently, the were not needed or removing possibly improved the flow through the head.

With all the years of either raw water or coolant, it will corrode the head a bit and could look like a nasty broken off stud, but it it's not one of the 17 head stud holes and has a the gasket hole matches to coolant port on the block, but not the head... that's normal.

I almost drilled mine out, but found the post from IloveRust (Bill's) build where he drill them out... and was congratulated for likely having he first new style head with old style coolant ports.

Now if your engine is an old style, the head should have a port or hole every place where the gasket does.

[scratchee]

Your pic looks to be the block and not the head, but that looks to me like a threaded hole with "gunk" at the bottom.

Sorry for not being more clear (and sorry for the thread hijack... I'll make it quick. )

(EDITED TO MAKE IT QUICK). The photo is my block. Three of the stud holes are very hard and metallic at the bottom, so I think a bit of stud broke off but I don't want to drill until I'm sure.

[dplidr@gmail.com]

1976 RWC overhaul - stud hole bottoms

I found similar blocked bottoms on some of the stud holes in my block. Must all my studs had at least 6-8 threads remaining. A few had only 4-5 left and were corroded. I found out that all the studs do continue thru to the water jacket, however the ones close to the threaded mounting holes on the side of the block (for the coil etc.) did bottom out fairly quickly. I carefully poked the few blocked ones with an awl and then gently drilled open with a slow progression of bits. Finally chased all the threaded holes in the entire block with the right-sized tap to clean up for the old studs and a few new ones. The glass-bead blasting did further open up a few water passage areas I thought were metal.

Will take/post a few pics later this weekend...

-DaveL

[ronstory]

If you have stuff at the bottom of the threaded holes in the block, I would soak them with PB Blaster (or similar)... and then tapping them with punch and hammer. Be careful of the threads and wrap a bit of tape around where they could contract the slides. You are just trying to break the threads lose and not drive them out.

Then do the drill thing, but the tapping may make the process less arduous. ;^)