Register Login
Shop4Parts - UK's largest online superstore for FIAT and Alfa Romeo parts
Reply
 
Thread Tools
Old 16-03-2018   #1
Join Date: Jun 2009
Posts: 746
Thanks: 59
Trader Rating: 0
United Kingdom 
Damage to piston skirts

Any thoughts on what has caused this sort of damage to the piston skirts? There appears to have been friction with the cylinder .
Attached Thumbnails
Click image for larger version

Name:	image.jpeg
Views:	28
Size:	1.78 MB
ID:	189096  
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

Toshi 975 is offline Reply With Quote Quote 
Old 16-03-2018   #2
Join Date: Apr 2017
Posts: 1,785
Thanks: 123
Trader Rating: 0
United Kingdom 
Re: Damage to piston skirts

Ouch .
Oil starvation , over heating causing pistons to expand excessively , or piston to bore clearance insufficient .
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

jackwhoo is offline Reply With Quote Quote 
Old 16-03-2018   #3
Join Date: Dec 2014
Location: Ripon
Posts: 578
Thanks: 27
Trader Rating: 0
Bleeding Knuckles has donated!
United Kingdom 
Re: Damage to piston skirts

Quote Originally Posted by Toshi 975 View Post
Any thoughts on what has caused this sort of damage to the piston skirts? There appears to have been friction with the cylinder .
Hi Dave, I have had the same nearly identical marks on my pistons
The attached pic shows my old 80.0mm BIS piston which my engine man commented as 'over heating' and 'excessive piston to bore clearance' I forget what the actual figures were, but could find out if you need a steer.

Ian.
Attached Thumbnails
Click image for larger version

Name:	IMG_20160810_164948_hdr.jpg
Views:	13
Size:	1.87 MB
ID:	189108  
__________________
Si dice in Sicilia non c'e nulla di piu pericoloso di una Donna con fucile da caccia.

Abarth - Piccola ma Wicked
Bleeding Knuckles is offline Reply With Quote Quote 
Old 16-03-2018   #4
Join Date: Jun 2009
Posts: 746
Thanks: 59
Trader Rating: 0
United Kingdom 
Re: Damage to piston skirts

Quote Originally Posted by jackwhoo View Post
Ouch .
Oil starvation , over heating causing pistons to expand excessively , or piston to bore clearance insufficient .
Thank you for your input.
These are first oversize (0.2mms) Pistons from a 594ccs engine that only ran for 50 miles. Now fitted with new pistons and running well. There was an issue with lubrication as the wrong big end shells had been fitted so some oil squirt jets in the con rods were blanked off. However the performance con rods that are available for the 500 & 126 engines do not have these jets and I am told that they rely on the splash effect in the sump to lubricate the bores so that puzzles me. Not sure about overheating but the engine before strip down did turn over quite freely.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

Toshi 975 is offline Reply With Quote Quote 
Old 16-03-2018   #5
Join Date: Apr 2017
Posts: 1,785
Thanks: 123
Trader Rating: 0
United Kingdom 
Re: Damage to piston skirts

It could well be the piston to bore clearance was tight but not noticeable when engine cold. When engine heated up the piston expansion could have taken up all the clearance.
The pic posted by Ian shows some wear marks toward the bottom of the piston skirt rather than centre.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

jackwhoo is offline Reply With Quote Quote 
Old 16-03-2018   #6
Join Date: Apr 2017
Posts: 1,785
Thanks: 123
Trader Rating: 0
United Kingdom 
Re: Damage to piston skirts

Is damage on both sides of pistons or just the thrust side?
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

jackwhoo is offline Reply With Quote Quote 
Old 16-03-2018   #7
Join Date: Jun 2007
Location: Christchurch
Posts: 136
Thanks: 8
Trader Rating: 0
New Zealand 
Re: Damage to piston skirts

I had exactly the same marks on one of my engines.

It was in a 500F I bought from my neighbour which had an engine in it that was overhauled by a "Fiat expert" in Palmerston North, NZ. I forget the exact figure, but the book says there should be something like 0.020" piston to cylinder clearance.... I found 0.005" when I pulled it apart! That and the loose bolts I found all over the internals of the engine led me to believe that this idiot was in fact an expert..... X being an unknown quantity and a spurt being a drip under pressure.

New pistons, rings and a quick hone put it all right again.

Chris
Thanks jackwhoo thanked for this post
Likes jackwhoo liked this post
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

looigi is offline Reply With Quote Quote 
Old 16-03-2018   #8
Join Date: Apr 2017
Posts: 1,785
Thanks: 123
Trader Rating: 0
United Kingdom 
Re: Damage to piston skirts

Nice info looigi.
More likely to be 0.002 inch (2thou) normal.
0.0005(half a thou) would be very small clearance on an air cooled motor.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

jackwhoo is offline Reply With Quote Quote 
Old 17-03-2018   #9
Join Date: Jun 2007
Location: Christchurch
Posts: 136
Thanks: 8
Trader Rating: 0
New Zealand 
Re: Damage to piston skirts

Quote Originally Posted by jackwhoo View Post
Nice info looigi.
More likely to be 0.002 inch (2thou) normal.
0.0005(half a thou) would be very small clearance on an air cooled motor.
No Jackwhoo, you have the decimal in the wrong spot. The piston to barrel clearance on my engine was 0.005" (5 thousandths) when I pulled it apart.

It should have been, and now is 0.059" (59 thousandths). Actually mine is half a thou under, but I can live with that.

Chris
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

looigi is offline Reply With Quote Quote 
Old 17-03-2018   #10
Join Date: Apr 2017
Posts: 1,785
Thanks: 123
Trader Rating: 0
United Kingdom 
Re: Damage to piston skirts

Thanks chris , I don't have the correct specs for this engine.

I think there may be confusion between mm and inches . 0.059 inch is about 1.5mm.

The important thing is you have direct experience of similar air cooled engine with insufficient piston to bore clearance.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

jackwhoo is offline Reply With Quote Quote 
Old 20-03-2018   #11
Join Date: Jun 2007
Location: Christchurch
Posts: 136
Thanks: 8
Trader Rating: 0
New Zealand 
Re: Damage to piston skirts

I have been thinking about this today, so I checked.

I was wrong in my earlier assertions and I apologize. The correct piston to bore clearance is 0.03 - 0.05mm (.012" to 0.020").
Thanks jackwhoo thanked for this post
Likes jackwhoo, Franko500, fiat500 liked this post
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

looigi is offline Reply With Quote Quote 
Old 20-03-2018   #12
Patinated Peter
 
fiat500's Avatar
Join Date: Mar 2005
Location: Nairn
Posts: 4,305
Thanks: 213
Trader Rating: 0
fiat500 has donated!
United Kingdom 
Re: Damage to piston skirts

Quote Originally Posted by looigi View Post
I have been thinking about this today, so I checked.

I was wrong in my earlier assertions and I apologize. The correct piston to bore clearance is 0.03 - 0.05mm (.012" to 0.020").
Nicely said; plenty of people simply sidestep the matter when they make inaccurate assertions.
I think many of us, with a non-engineering background, find these micro-measures a nightmare to deal with,
Likes jackwhoo, Franko500 liked this post
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

fiat500 is offline Reply With Quote Quote 
Old 20-03-2018   #13
Join Date: Apr 2017
Posts: 1,785
Thanks: 123
Trader Rating: 0
United Kingdom 
Re: Damage to piston skirts

Quote Originally Posted by looigi View Post
I have been thinking about this today, so I checked.

I was wrong in my earlier assertions and I apologize. The correct piston to bore clearance is 0.03 - 0.05mm (.012" to 0.020").
No need to apologize , you have shared good practical experience.

0.03mm is about 0.0012 inch
0.05mm is about 0.002 inch
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

jackwhoo is offline Reply With Quote Quote 
Old 20-03-2018   #14
Join Date: Apr 2017
Posts: 1,785
Thanks: 123
Trader Rating: 0
United Kingdom 
Re: Damage to piston skirts

1 inch is 25.4mm.
25.4mm divided by 1000 =
0.0254mm.
one thousandth of an inch is 0.0254mm
Likes fiat500 liked this post
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

jackwhoo is offline Reply With Quote Quote 
Old 20-03-2018   #15
Patinated Peter
 
fiat500's Avatar
Join Date: Mar 2005
Location: Nairn
Posts: 4,305
Thanks: 213
Trader Rating: 0
fiat500 has donated!
United Kingdom 
Re: Damage to piston skirts

Quote Originally Posted by jackwhoo View Post
1 inch is 25.4mm.
25.4mm divided by 1000 =
0.0254mm.
one thousandth of an inch is 0.0254mm

Aaaaaaaaghhhhhhhhh!!!!!!!!!:bang :
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

fiat500 is offline Reply With Quote Quote 
Reply
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump
Similar Threads
Thread Thread Starter Forum Replies Last Post
(T) Piston damage grapeman Punto (Mk2/2b) 18 20-06-2015 23:42
(G) multipla 1.6 piston damage Deejwatson Multipla 4 03-09-2013 17:48
(T) Punto 1.1 Fire engine, Piston damage Simples31 Punto (Mk1) 9 05-10-2011 23:52
(T) Piston damage, what has casued this? ralphnz Uno 4 02-12-2008 17:14
how can i repair this? (damage on plastic skirts) beau Bodyshop 8 09-03-2006 01:15