Rebuilding bottom end, advice wanted.

Model, year, miles covered, leak down/compression numbers, as well as the reason why you're in there to begin with would be of some help here.

 

If you feel like it, then do it!
You'll need new liners if any are out of spec. I think the liners are nikasil. You don't want to bore them. Do the bearings for sure. I'd be surprised if you found any benefit from balancing. If you look at piston and rod specs, you'll find Ferrari has a wide variety of weights they use to obtain near perfect balance.
Just the feeling of cranking that fresh motor is worth it.

 

Take a hard look at it before you get in too deep. It's not too late to leakdown test the pistons. This will give you an idea what you have and how many $$ you need to spend. You might get lucky.

OEM liners, pistons and rings are expensive. They are sold individually.

I wouldn't recommend using anything else on a 355. I've been told that liners can be "re-conditioned" but I'm not aware of who claims to do it and the risks of the project going sideways by doing this is real. The 355 is kind of a fussy girl about these things. Resist the temptation to cut too many corners or you might be doing it all over again. Examine the bearings, you might be pleasantly surprised.

Good Luck!
Image Unavailable, Please Login

 

Generally if there is any perceptible ridge they are past the wear limit. The hardened surface is very thin. Usually if there is perceptible ridge you will also have significant ring wear.

The 355 motor is why most of us have equipped ourselves with leak down adaptors to use after the head is off. It really needs to be done.

 

Just out of curiosity, how many years and miles were on the belt when it snapped?

There is a line where cost exceeds gain, however I would imagine it's harder to determine with these cars since the price of some parts are reasonable and some are insane.
In respects to the bottom end, I would definitely get new bearings and polish the crank unless they simply looked pristine, and maybe have someone look at the liners and rings to give a second opinion. I work with airplanes a lot and it's common to just replace one bad piston or cylinder

 

+100000000

 

Are there general mileage guidelines for f355s/348s and respective bottom-end rebuilds? Do many of you make it a practice to have oil analysis done at change intervals to monitor bearing health?

 

No.

 

To expand on Tims answer these motors generally do not get taken apart and fixed or rebuilt due to wear or failures that can be predicted by oil analysis.

Besides I am not a big advocate for tearing down major components until they are symptomatic. There are a few exceptions to that but I can get nearly any car to fail some kind of test.

As far as the cylinders and rings go though, on the 355 they wear like granite up to a point and once they reach that point it goes downhill fast. That is why many of us hold them to high standards on compression and leakage tests. 0 or 1% leakage is not unusual but 10% is really not a good sign. 10% on a QV is not a big deal at all but not so with these.

 

Gotcha. Thanks, Brian.

 

Don't overthink it. The adapter plate that I use is 1/2" aluminum. I seal it with a piece of rubber gasket material. Tightened enough to seal against 100psig. You're looking for relative differences between cylinders more than absolute numbers. The real trick with leakdown testing is to be as consistent as possible with your technique for each cylinder. As Brian said, ideal leakdown would be 1%. You're probably not gonna get that here unless you replace everything. This (combined with a visual inspection) should give you an idea where the bad holes are and if you can live with some of them the way they are now.

 

Has anyone measured how thick the coating in these cylinders is? about generally. Has anyone tried a boring those liners and go for custom pistons and rings in uncoated cylinder?

 

The cylinder coating is about 80 microns thick.

If you want to bore the cylinders take them up to 86mm (from 85). Then be sure the ring package is designed for a steel liner, and don't expect the same longevity.

 

You sound like you r talking from experience. Have you done this?

 

well it sounds strange that coating wears of just 25k, it would be strange if it wears in 50k. pistons and rings should always wear before that coating. obviously scoring in the cylinder walls would be bad.

but, there should be no issues what so ever running modern pistons/rings in traditional uncoated liners and make 30-40k on the clock before any significant wear on cylinders, in street use. Tho I'm just a newbie in ferrari world

 

It didn't wear out, it was killed. It is almost a certainty it was the result of an burned out header pipe and it went unaddressed. It is a pattern failure in the 355.

 

Luckily my 348 liners are in excellent condition. But if I had to refinish them I would use Millennium Technologies.

I have had over 50 Ducati cylinders bored and replated over the years. Excellent quality and service.

Millennium Technologies

 

Subbing to this want to know how replating goes

 

if you use their coating be sure to post your impressions.