Cylinder hone after 10k km
Cylinder hone after 10k km
(OP)
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?
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?
RE: Cylinder hone after 10k km
Otherwise, it is standard practice to run a home through the cylinders when replacing rings. If anything, it cleans the cylinders.
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
What's the piston-to-cylinder clearance? Cylinders checked for out-of-round or taper?
What did the machinist say about piston ring selection and break-in?
How are compression and leak-down?
What do the sparkplugs look like?
Is there evidence of one cylinder being responsible or are things reasonably even across all cylinders?
I presume you've checked the silly stuff. Crankcase venting, valve stem seal installation, etc.
I have an oil-burner engine myself, but given that the vehicle it's in isn't worth what it would cost to professionally repair, and the amount of oil consumption is remaining stable (about 1 litre per 1200 - 1500 km) and it runs well otherwise, I have just consigned myself to frequently checking and topping up the oil until something big goes wrong with it.
RE: Cylinder hone after 10k km
Unless there is damage to the cylinder walls visible on a borescope or other obvious issues I would start with an exhaust gas analysis to confirm that oil is being burnt and not lost elsewhere, then troubleshoot accordingly.
RE: Cylinder hone after 10k km
I'm guessing "old" is not old enough to have replaceable liners.
How was the block , especially the cylinder bores, cleaned for assembly?
Honing grit can tear up rings permanently. Sometimes the rings and cylinders die together.
Some heavy throttle in short bursts is needed to force the rings against the cylinders for a good break-in.
https://www.us.mahle.com/media/usa/motorsports/mms...
Depending on the results of thorough compression and leak-down tests, performing te following steps of the break-in from the above MAHLE link is worth a try.
75% of max rpm. Then engine brake with the throttle closed, back to 25% max rpm. Repeat
this 5-6 times.
Example: 8000rpm max would start at 2000rpm and accelerate to 6000rpm then
engine brake back to 2000rpm.
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
Who assembled the engine ?
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
Were the ring gaps checked?
Are you certain the compression rings were installed the correct way up?
Check with the supplier of the rings. Some modern low tension rings can be difficult to bed.
Ask the machine shop about their honing procedure - grit sizes, honing steps etc. Presumably they are performing an appropriate "plateau hone". Make sure this aligns with the ring-suppliers recommendation for honing.
je suis charlie
RE: Cylinder hone after 10k km
That said, any shop that wants the pistons onhand to bore the block begs the question - Why, are they not boring to spec?
RE: Cylinder hone after 10k km
Also, most OEMs use a "select fit" process with multiple piston sizes to select the best fit for the bore.
I bought this engine knowing it was an oil burner. No smoke, was getting hard to start due to valve recession, burned a similar amount of oil.
RE: Cylinder hone after 10k km
je suis charlie
RE: Cylinder hone after 10k km
P.S. sorry for my English
RE: Cylinder hone after 10k km
Unless the parts were wrapped in plastic and had labels explicitly saying "clean enough for assembly" I would doubt they were CEFA.
Actually I prefer to do my own cleaning prior to assembly.
Cylinder bores in particular need to be very clean. Most solvents are insufficient.
A thorough scrub brush and hot soapy water has long been popular.
A final test is a white rag damp with clean engine oils MUST stay white after being rubbed in the cylinders.
Older Alfa cranks had complicated drilled oil passages, with intersections and some holes plugged with soft plugs pounded into place.
https://www.alfabb.com/attachments/p1110064-medium...
Trying to flush all the grit out of a ground crank is futile. The plugs must be removed. Tapping the holes in the hardened crankshaft for threaded plugs to be installed after proper cleaning is challenging. Over 2 score years ago a friend had is Alfa 2 liter engine rebuilt. The assembler did not clean the freshly ground crank properly. When the oil pressure went to hell after a way less than 1000 miles it was a very sad day.
https://www.mahle-aftermarket.com/media/homepage/f...
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
Next, start at 25% of the max rpm with light throttle and accelerate at wide open throttle to
75% of max rpm. Then engine brake with the throttle closed, back to 25% max rpm. Repeat
this 5-6 times.
Example: 8000rpm max would start at 2000rpm and accelerate to 6000rpm then
engine brake back to 2000rpm.
je suis charlie
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
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.
RE: Cylinder hone after 10k km
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
RE: Cylinder hone after 10k km
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.
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
logical fallacies - causal fallacy or maybe false dichotomy ?
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
You might also be able to hear/feel air leaking past the valve stem seal.
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
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.
RE: Cylinder hone after 10k km
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
RE: Cylinder hone after 10k km
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
RE: Cylinder hone after 10k km
Politicians like to panic, they need activity. It is their substitute for achievement.
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
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.
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
Do your seals lack that kind of feature?
https://alfa-restoration.co.uk/shop/images/thumbs/...
https://www.kmotorshop.com/document/shop/701.289/t...
https://www.ebay.com/itm/263719475450
https://www.bestpartstore.co.uk/engine/valve-stem-...
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km
Since the engine shop tossed the original parts it's not possible to know if the replacements were a match for them. It's possible it's now a frankenmotor.
RE: Cylinder hone after 10k km
RE: Cylinder hone after 10k km