Piston ring end gaps

[Maki]

I measured the gap of my new rings in the block and they are too tight.

What would be the right way to enlarge the gap and do it evenly on all of them?

[Guy Croft]

See new article at:

http://guy-croft.com/viewtopic.php?p=3976#3976

GC

[Mats]

What is your view on "gapless" rings?

[Maki]

See new article at:

http://guy-croft.com/viewtopic.php?p=3976#3976

GC

thanks, it helped.
but this article http://guy-croft.com/viewtopic.php?t=254 scared me
I've used second hand opel XE pistons for my zvh project and I didn't even think that ring side clearance means anything. As soon as I get to my garage I'll check that but I doubt the readings will be anywhere near 0.05 mm :(
Now back to the topic about the gaps
Haynes says for the mondeo rings (I've used mondeo block and opel xe pistons with rings for my project):
1 ring: 0.26-0.50 mm (mine shows ~0.22 with opel xe rings)
2nd ring: 0.30 - 0.50 mm (~0.20)
oil control 0.40 - 1.40 mm

what would be your suggested gap here?

M.

[Guy Croft]

Firstly, Mats question on gapless rings. If you mean Total Seal, they are excellent.

Secondly, ring gaps - I need_the_bore_size!

GC

[Maki]

Secondly, ring gaps - I need_the_bore_size!

86.1 mm

[Guy Croft]

With 86.1mm bore size.

Haynes manual says

Top ring: 0.26-0.50 mm or 10-20 thou"
2nd ring: 0.30 - 0.50 mm or 12-20 thou"
oil control 0.40 - 1.40 mm or 16-55 thou

I'd build to:
top ring 14-18 thou"
2nd ring same - 14-18 thou"
3rd ring I don't know really - so much depends on the type of ring, two-piece rings with internal expander spring need more careful attention than 3 pc rings with upper and lower rails and inner expander. What are yours? Photo would help.

GC

[Maki]

What are yours? Photo would help.

mines are 3 pc

[Guy Croft]

Hi,

if I read yur pm correctly the new ring pack is KS and from an 86mm bore application, you are fitting them in an 86.1mm (bigger) bore, so the bottom ring (3pc) should fit without any mods.
A 3 pc ring is not easy to modify - you really have to know that the internal expander rail is for a bore size nearly the same as yours or it will be way too tight - or too loose and the scraper rings won't work well. So I would be looking for +/- 0.2mm variation either way max. In other words an expander rail for an 86mm bore unit (and you can only get that dimension from the label on the packet) would work OK in 85.80 and 86.20mm.

As for the slim rings that fit top and bottom on the expander the minimum end gap wants to be same as top ring - although I have seen them much looser.

I hope this helps. All in all, if your rings are from an 86mm pack, they should not be tight in an 86.1mm bore. The end gaps would tend to be bigger in an 86.1 bore compared with the bore of 86mm they were designed for by ratio Pi x difference in diameter ie: 3.142 x 0.1mm, about 0.013" - assuming I have read understood your data properly.

GC

[Maki]

The end gaps would tend to be bigger in an 86.1 bore compared with the bore of 86mm they were designed for by ratio Pi x difference in diameter ie: 3.142 x 0.1mm, about 0.013" - assuming I have read understood your data properly.

GC

I thought my bore was 86.1 as I was told by the machine shope who did the job. but as I measure it I see that the bor eis even smaller by a bit ... it is almost 86, that's why I have too small gap in the rings as they were ment to be for 86 bore.

[Guy Croft]

Macki, hi

please would you post some good quality photographs of this engine project and identify the engine type and intended use etc.

GC Q&A means nothing to many people without this kind of background.

Thank you,

GC

[Maki]

Macki, hi

please would you post some good quality photographs of this engine project and identify the engine type and intended use etc.

GC Q&A means nothing to many people without this kind of background.

Thank you,

GC

Where would you like me to post it?

[Guy Croft]

Maki, hi

you post right here; there is a box for uploading photos in JPEG or GIF format just below the text box. Just click on 'browse' and the system can be used to navigate to your PC photos folder, OK?

GC

[Maki]

Ok here's the story
At the moment I'm driving Ford Escort RS turbo with original but modified engine. 1.6 CVH with lowered CR to run higher boost. It is chipped by Ahmed Bayjoo and runs at the moment 20 psi of boost producing 191 BHP and 254 Nm of torque. I'm using it for drag racing my record is 8.84 sec on 1/8 mile track and 13.6 sec on 1/4 mile track.
As I wanted to be faster I've began to build new engine. The popular hybrid of 1.6 cvh head and 2.0 mondeo Zetec bottom end. The goal is 280 BHP with MS management. At the moment I'm porting the head which will be fitted with enlarged valves. The bottom end is almost done it¢ž¢s rebored to 86 mm and will be fitted with opel XE pistons ... all the parts are fabricated only assembly is the last step.
Here are some pictures:


compare mondeo oe pistons on the right with XE ones on the left you'll get the Idea what's the point in changing them




valves compared to new stainless ones



The only weak point in this engine are the rods. Orignal zetec ones are very thin but I have no millions to pay for the stainless ones :(
If there are any questions I'll be happy to answer them :)
Ah and this is the car

[Guy Croft]

Some nice photos there Maki, well done!

GC