Cylinder hone after 10k km 2

[Deividas]

Hello,

Half year in weekends I was rebuilding my old Alfa Romeo engine. Cylinders were re-bored and honed, new larger pistons with new rings installed, main and conrod bearings replaced, new valves, valve guides, valve stem seals installed, all other seals and gaskets replaced. And, as it was my first engine rebuild, in break in period I used 5w40 synthetic oil, and as I found out later, it was not good idea. Oil was changed after 1000 km to same 5w40. Right after rebuild, engine was using oil, I thought maybe it's due to break in period, but now, after few thousands km, engine still consumes a large amount of oil, about 1,5 - 2 litres for 1k km.
I can't understand where is the problem and I planning to try disassemble engine again after winter, when it gets warmer outside. I think, that there can be issues with oil rings, and my question is, do I need to get cylinders honed again, if I will replace piston rings? I know, that it's recomended to hone cylinders when changing rings, but if cylinders were honed few thousands km ago?

 

[TugboatEng]

That is literally called the "Italian tune-up". The thought is that running an engine under heavy load clears out carbon buildup and deglazes cylinder walls.

Honda has a recall out on their engines currently. It calls for replacement of piston rings. I don't think they recommend honing the cylinders.

 

[gruntguru]

Not the Italian tune-up - this is the age old procedure for initial bed-in of new rings. From a reputable source Link

BTW the Italian tune-up does work. Also known as a dyno decoke. Apply full load at peak torque rpm until the exhaust clears. Follow up with oil change and new spark plugs.

je suis charlie

 

[CWB1]

Machine shops without HVAC are pretty rare stateside anymore, and OEs haven't selectively fit pistons in ~40 years that I know of. Regardless, if a shop is measuring pistons then they're not following piston manufacturer's spec for bore size (clearance) or finish so I wouldn't expect high quality work.

I still suspect that your problem isnt in the long-block. If you somehow were burning 1.5-2 liters tho, I wouldn't expect break-in to solve anything and would start by checking the condition and orientation of the rings. That said, if your 2k kms has been mostly short stop&go trips around town then its far from broken-in. I usually recommend new engines be babied on a nice long 2k+ km, mostly freeway roadtrip or motored and run-in via a dyno if money allows. Slamming transients on new ring packs is a great way of destroying engines and verboten in development.

 

[TugboatEng]

Most of my experience with select fit pistons is in dirt bikes. The Japanese OEM's have A through D sizes for pistons and cylinders. You can't order a specific sized cylinder so you would need to order a cylinder, check the stamp, then order the correct piston. Instead the dealers stock the smallest D size piston and that gets used in all cylinders.

 

[Tmoose]

"if a shop is measuring pistons then they're not following piston manufacturer's spec for bore size (clearance) or finish"

logical fallacies - causal fallacy or maybe false dichotomy ?

 

[CWB1]

Neither, due-diligence.

 

[Deividas]

Today I saw video on Youtube and decided to try my luck, when it gets warmer outside, and try to change valve stem seals without removing cylinder head. I think simple method with rope/shoelace inserted in cylinder through spark plug hole with piston at TDC should work just fine, so this way I can save my time and money. And if new seals won't help, then it will be clear, that problem is with piston rings or cylinders

 

[3DDave]

I thought the usual trick was a spark plug adapter for an air compressor to hold the valves closed while replacing the seals.

You might also be able to hear/feel air leaking past the valve stem seal.

 

[Deividas]

3DDave - yes, method with air compressor also should work, but I don't have air compressor in my garage and I don't want to buy it just to use it once for this job

 

[3DDave]

They are available for rent.

 

[Deividas]

3DDave - yes, I know, but i don't see difference between these two methods

 

[3DDave]

You don't need TDC with the air pump and you can confirm the valve stem is leaking without replacing it.

 

[TugboatEng]

Is that worth the risk? Any loss of air pressure means the head is coming off.

 

[Deividas]

3DDave - how You can see valve stem leakage with compressed air in cylinder if valve is closed? Cylinder head was checked before installation, and there was no leakage between valves and valve seats

 

[TugboatEng]

Valve stems will leak with compressed air. They are not meant to seal.

An observation I have made working with 2-stroke diesels. They have an air box between between the combustion chamber and crankcase. There is no path for combustion gasses to get to the crankcase through the piston rings yet the oil still turns black. As it turns out, the majority of the blow-by is through the valve guides. I think you will find that this holds true for most engines, especially turbocharged engines.

 

[Deividas]

Hello to all,

So, as I planned, I changed valve stem seals without removing cylinder head, almost all of them were not "fully seated" and also found intake manifold gasket oil leak (there is variable valve solenoid on intake manifold), so replaced this gasket also.
Assembled everything as it was, mounted timing belt, and... Surprise! Engine spins so hard with wrench, that I thought that something fall inside cylinder and blocked piston. Before dissasmebling head I checked timing marks and engine was spinning as it should, without too much force.
Removed timing belt, placed piston between tdc and bdc and tried to rotate camshafts by hand, and intake camshaft was very very hard to rotate.
After this I removed camshafts and hydraulic tappets, installed camshafts without tappets again, so now they not touching valves and should spin freely, but intake cam spins quite hard compared to exhaust cam. Tried to remove intake camshaft caps and even with one cap installed it still turns quite hard.
Any ideas what happened?

Edit:
Found the problem - damaged camshaft journal

 

[Deividas]

Hello,

After few hundreds km valve stem seals popped off again. First time I used oil to fit them, second time I installed them dry, because I thought that maybe they popped off because of being lubricated inside. Both times I installed them with socket and they fit pretty easy without too much force. Anyone had similar situation? Because I don't know what to do, to keep them in place

 

[Pud]

Have these seals got a wound spring retainer to hold and retain an internal rib in a corresponding groove in valve guide?

Politicians like to panic, they need activity. It is their substitute for achievement.

 

[Deividas]

Pud - no, there is no spring on seals to hold them in place. Also there is no groove on valve guide. Valve guide surface is smooth

 

[Tmoose]

What model and year Alfa?
The ones I'm //familiar// with would have had replaceable liner kits. 1950, 1960s, 1970s.

Did you say at the rebuild the valve stem seals were found out of place?

regardless, I wonder if the "new" guides were machined properly.
Diameter within .002", and groove type features.
Possibly just a roughened surface, although I think that would be wishful thinking for seal retention.

Did you use genuine OEM valve seals?

What is the un-installed seal OD? If the genuine seals have no clamping/booster springs on the OD. maybe a few coils cut from the appropriate size fine wire coil spring could be ddded.

Glue. I'd look for one that has a forever operating temp over 300° F.