Engine experts...Whats the consensus on worn cylinder liners?

O2 sensor operation and fuel trim does not change with a bad header. It is not detectable by any electronic engine parameters.

We have repaired many 355's with bad injectors. At this point in their lives it is quite common. None have resulted in cylinder wear issues.

 

Too much choke ...

Pete

 

With a bad header the cylinder is ingesting a lot of debris. The flow in the pipe is not one way.

 

I'm still not 100% clear on this one. Is it the header or is there another common cause for the cylinder liners wearing? I'd love to know if there is something we should/shouldn't be doing to help preserve them?

 

That's interesting. Most cars I have worked on with a pre o2 exhaust leak will send that bank to max positive fuel trim.

Is it because the 355 heat shielding seals up well enough so it doesn't pull in much ambient air?

 

When my header cracked, the slow down 1-4 light came on and shut down that side of the engine. After the header was repaired, no slow down light, everything functional.

 

Don't know, don't care.

The dealers and the factory tried every possible way to determine electronically if a running problem was caused by a header. We studied parameters on normal cars and sent reams of printouts of those parameters to the factory. In the end no method was found.

 

I have replaced or overlooked replacement of hundreds of headers and have never seen that.

 

I was up at Competizione today and brought this subject up. Richard is very cautious with his words and I trust him completely but I left with the impression there may be several factors involved but the primary focus being on the headers. It seems people that get the headers fixed early may not see the problem versus someone that drives their car a long time with a bad header which can greatly accelerate the wear.

This alone may not help you since the 355 engine is a very complex thing and there are several contributing factors but it was pointed out that cars that had their headers replaced early on after finding a problem with them don't seem to see the problem as quickly or as often as cars that may have header issues over a longer period of time.

Net, if you know you have a header issue I would recommend parking it until you get it fixed.

 

Clean pistons are not caused by fuel washing. Excess fuel causes excess carbon and makes them dirtier. Bad ring sealing allows oil around the circumference and cleans the piston. It is very common in many Italian motors. We used to see it all the time in Alfa 1750 and 2.0 motors.

 

All true.

 

Unfortunately, I'm no expert by any stretch, but my take from reading around and folks like Brian who are very experienced, is that no-one really seems to know what causes these issues, including the factory. There are obviously causes but no concrete link formed, and that's after a considerable number of rebuilds and thousands of header failures and the like.

I had to have a rebuild on my 355 due to liner wear, one pot in each bank. Both headers had been replaced, and the issues spotted with those fairly quickly and not run on them etc. One thing I noted prior to any issues, was that sometimes on cold starting it would run rough for 20 seconds or so and quite petrolly. Oil cleaning the pistons is spot on in my case as well, the pistons with worn liners had failing oil rings and the car was using a lot more oil than normal. I just wondered if some petrol wash previously at points could possibly damage the liners/rings, and then you get the oil use and shiny piston syndrome??

On mine everything electrical/injectors etc was found ok, changed none the less as I really didn't want to face that again and although errors etc weren't found, I'm guessing it's virtually impossible to test everything to simulate 5-10k of motoring. Nothing problematic was ever found though that you could say, yep, that little b#gger caused the prob. Not the most confidence inspiring. The onset symptoms I noticed were very quick to arrive, and started with smell of burning oil when backing off acceleration under braking. 150-200 mls later I think, the engine was in pieces.

 

That would do it. Petrol is a fantastic abrassive.

Has anybody worked out whether there is a correlation between vehicles with little user versus vehicles that are used as a car?

Short trips with the computer running the engine rich due to it being cold is a bad thing ... heck with my motorcycle (because it has carbs) pretty much as soon as I can I put the choke in. That is usually within 100 metres or so ... sure its not 100% happy but that is better than washing the bores.
Pete

 

Would anyone mind telling me what constitutes a bad header? The cracking? Or is it something else?

 

I am operating under the assumption that it is a hole or crack in the header tube.

 

This is what it looks like! These tubes are from my 1995 355.
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Wow, thats just insane!

They all cant get THAT bad, can they?

 

You should get an engine conpression test done if you are worried about bore wear. This should be done on a cold and hot engine. Also, it is always worth getting a cylinder pressure test via compressed air, this will show of excessive leak back, (excessive crankcase pressure), past the piston rings and also if the valves/seats are sealing correctly.

Unfortunately, most exotica's dont get used much and because of that injector clogging from varnish and other by products in the fuel does not help. This can deposit around the injector needle and can cause all sorts of fuelling issues. I have seen many injectors on my injector test rig fail the spray pattern and flow rates because of this.

Also to note, injectors are a serviceable item, repair kits which include filter strainer, seal and spacers etc are available for most fuel injectors.

Wrong engine oil can also cause excessive bore wear, oil viscosity is very important as this determines how well the oil will flow at various temperatures. i have also seen some engines fail due to 'sticky' piston rings, this is caused by the oil by products/carbon gumming up in the piston ring groves and makes the rings stick to the piston wall, causing low compression and also wear on the liner.