New pistons - which way is front?
-
- Posts: 68
- Joined: Thu Oct 03, 2013 10:59 pm
New pistons - which way is front?
I'm about to fit new pistons - Hepolite 14396 030 - but there is no marking on the crown of the pistons to say which way is front. Is this because it doesn't matter? Sorry if it's a stupid question but I'd like to make sure they're the right way round!
- A40FARINAGURU
- Posts: 16413
- Joined: Tue Mar 30, 2010 8:14 am
- Committee Role: A35 Registrar
- Location: Birmingham (Home of the Austin)
- x 21
Re: New pistons - which way is front?
there should be the word 'front' on them at leastskipseyhughes wrote:I'm about to fit new pistons - Hepolite 14396 030 - but there is no marking on the crown of the pistons to say which way is front. Is this because it doesn't matter? Sorry if it's a stupid question but I'd like to make sure they're the right way round!
Nick Bayliss
Club's A35 (Saloon) Registrar, South Midlands Area Contact
Email, a35@austina30a35ownersclub.co.uk
Connected with A30/A35's for 63 years
A30/A35 Member A1372 (since 1981)
Club's A35 (Saloon) Registrar, South Midlands Area Contact
Email, a35@austina30a35ownersclub.co.uk
Connected with A30/A35's for 63 years
A30/A35 Member A1372 (since 1981)
- Neil Evans
- Posts: 12179
- Joined: Tue Apr 15, 2008 1:06 am
- Committee Role: Technical Officer
- Location: Boston, Lincolnshire
- x 11
- x 25
Re: New pistons - which way is front?
Have they split skirts? If so, these go to the non thrust side...
Club Technical Information Officer
A30/A35 Club Member A191 (since 1972)
Father of the club's only love child
A30/A35 Club Member A191 (since 1972)
Father of the club's only love child
- A40FARINAGURU
- Posts: 16413
- Joined: Tue Mar 30, 2010 8:14 am
- Committee Role: A35 Registrar
- Location: Birmingham (Home of the Austin)
- x 21
Re: New pistons - which way is front?
i've just checked a set of 'PEP' pistons, there is no split skirt but no markings of 'front'Neil Evans wrote:Have they split skirts? If so, these go to the non thrust side...
Nick Bayliss
Club's A35 (Saloon) Registrar, South Midlands Area Contact
Email, a35@austina30a35ownersclub.co.uk
Connected with A30/A35's for 63 years
A30/A35 Member A1372 (since 1981)
Club's A35 (Saloon) Registrar, South Midlands Area Contact
Email, a35@austina30a35ownersclub.co.uk
Connected with A30/A35's for 63 years
A30/A35 Member A1372 (since 1981)
-
- Posts: 68
- Joined: Thu Oct 03, 2013 10:59 pm
Re: New pistons - which way is front?
Yes, that's correct, they don't have split skirts and there is no indication of "front"
Re: New pistons - which way is front?
In the absence of any markings, suggest looking at piston gudgeon pins which are slightly offset towards the thrust face. This is the very reason why pistons have a specific correct orientation. Offset is fairly subtle but it can be seen visually or measured using calipers.skipseyhughes wrote:Yes, that's correct, they don't have split skirts and there is no indication of "front"
http://pautomotivemechanics.blogspot.co ... signs.html
Thrust face is viewed from front of engine (ie fan belt pulley) in both drawings...
-
- Posts: 68
- Joined: Thu Oct 03, 2013 10:59 pm
Re: New pistons - which way is front?
Many thanks - I'll get myself some callipers and try that
-
- Posts: 68
- Joined: Thu Oct 03, 2013 10:59 pm
Re: New pistons - which way is front?
My new calipers arrived today so I measured the the distance from the gudgeon pin to the sides of the new pistons. It seems to be 28mm to either side but I'm still a bit worried I might not be measuring accurately enough. The article says the offset might be something like 1.5mm. Is that what it should be for our engines?
Re: New pistons - which way is front?
Yes it will be close to 1.5mm. If you cannot measure a difference, then pistons are probably symmetrical so can be fitted in either orientation, which may explain lack of marking.skipseyhughes wrote:The article says the offset might be something like 1.5mm. Is that what it should be for our engines?
I tried to find specification of Hepolite 14396 pistons but nothing came from the web. Calipers are always a useful tool in your box...
-
- Posts: 5896
- Joined: Mon Apr 21, 2008 1:00 pm
- Location: High Wycombe, Bucks
Re: New pistons - which way is front?
I,m pretty sure that at least some A series are symmetrical because I have assembled several 1275 engines with unmarked pistons and just made sure that they all looked to be the same way round. I do belong to Bodgers Anonymous as a founder member so don,t take my word for it.
Re: New pistons - which way is front?
Sometimes pistons have been skimmed which removes the markings, so it's always worth checking for gudgeon pin offset. Surprisingly even quite small offsets can be detected visually.
If you can't see or measure any offset, then pistons are probably symmetrical...
If you can't see or measure any offset, then pistons are probably symmetrical...
-
- Posts: 68
- Joined: Thu Oct 03, 2013 10:59 pm
Re: New pistons - which way is front?
Many thanks guys - that puts my mind at rest