Piston Direction When Fitting

[DamirGTI 342]

Info regarding engine burn rate :

 

http://guy-croft.com/viewtopic.php?t=97

 

Damir

 

EDIT : and some more with 205 piston/head pics : http://www.guy-croft.com/viewtopic.php?f=1...mp;hilit=squish

Edited April 22, 2009 by DamirGTI

[Miles 331 1 Cars]

I remember that Matt Cony (I think) did this on a TT engine and it was slightly down on power, Was along time ago now so I can't remember it fully now

[DamirGTI 342]

... turned the pistons the other way around with DIST mark towards the dizzy or disturbed the ring gaps by turning them the right way back as they suppose to be ?

 

Damir

[mattbenselin 0]

Miles: down on power because he didn't have the pistons the right way round?

Damir: not sure what you mean by that last comment?

 

Again great info guys and I am aware if done properly there would be more to it than just spinning the pistons round but I suppose I want the easiest fix but not compromising on performance, so ok to go ahead with spinning them round like welshpug said? I think the engine has done only 14k miles since the pistons were put in that way by the previous owner if that helps at all.

[DamirGTI 342]

Damir: not sure what you mean by that last comment?

 

Was asking the same question as i'm not sure on what Miles pointed out ! the rings or the piston crown position ..

 

Damir

 

EDIT : .. anyway i can tell for sure that , during the engine rebuild , i've been turning the pistons (with the ring gaps arranged as they suppose to be) inside the liners and did remove them out afterwards in order to re-do the ring gaps when i spotted that i've made mistake by turning them the wrong way around , i remember that the ring gaps where -> sound , they hardly moved , if at all .. but then again this was with the brand new rings ..

Edited April 22, 2009 by DamirGTI

[wardy18 33 1 Cars]

as I've never fitted pistons etc before but will be soon I have picked that rings gaps keeps being mentioned, I didn't realise there was a certain way the rings should be arranged when re fitting the pistons

 

Can someone please advise??

[Rom 0]

Id have to double check to be exact, but something like 1/3 of a turn apart for the gaps. So they dont all line up and allow blow by. Ill have a look today at work, though sure someone will have answered for sure by then

[James_R 3]

180deg from the next ring along.

 

They move round anyways, but it's still the done thing

[M@tt 77]

I've just fitted a new set of rings to mine and the instructions on the packet siad stagger them 120 degrees apart (ie 1/3)

 

However just to make things interesting the bottom oil compression ring actually came in 3 parts. 2 really thin rings (like thin versions of the other 2) and a sort of serrated effort that goes in the middle. With that you put the gaps in the 2 rings 180 degrees apart from each other and the join in the serrated jobbie inbetween those. I then used the join in the serrated ring as the position marker for the bottom rings position in relation to the other 2 (if that makes sense)

[petert 586]

If you're worried about the rings turning when you rotate the piston, why not just take the liners out and rotate the whole piston/liner assembly 180 deg.? Give it all a good clean up, fit new seals, etc.

 

Ring gap positions, see page 3 - http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf

Edited April 23, 2009 by petert

[mattbenselin 0]

I have just fitted my head and everything built up, almost ready to fire up so ideally I need a solution which does not require me taking the head off again!

So as welshpug said; just take off the rod caps, push the pistons up the liners and spin 180...This is not good because of ring movement? Or can I still do it?

[M@tt 77]

It will be fine, you'll probably find the rings stay where they are anyway as you turn the piston (but obviousy won't be able to see it )

[Tom Fenton 1,542]

Shouldn't matter at all that you disturb the rings, just undo the cap bolts, push the piston up the bore, spin it round and re-attach the cap.

It does matter that you disturb the rings when they have bedded into the bores, as any professional engine builder will tell you.

[mattbenselin 0]

So...move the pistons and risk disrupting the rings (tom f), or move the pistons and all should be fine (m@tt)???

 

Rebuilding if rings have moved and need realigning is not really an option so need to know I can do this from the bottom?

[Rom 0]

I originally read Toms reply says it doesnt matter. Which made me think, seeing as i was the one who orginally said it did... had me second guessing

 

Tbh, its not something ive ever been told. Normally, if pistons are coming out, new rings are going in anyway. I cant think of a time when ive ever moved pistons without rings.

I build engines at work, i have to be fussy, i am meticulous with parts going back where they came from. Valves, lifters, rockers, etc etc, even though a lot of people arent, and when lapped in etc it shouldnt matter, i just dont take chances.

So personally, i wouldnt take the pistons out, or rotate them unless i intended to fit new rings and rehone. Rotating will most likely change the ring end gaps imo, and more wear occurs on the thrust face, so the rings will have beeded in differantly to each area of the bore.

 

For the price of a set of rings, and the time it takes, i wouldnt risk it myself. But as i said, im a bit anal with stuff like this

Edited April 25, 2009 by Rom

[mattbenselin 0]

I dont want to have to take my head off and remove everything I put in (carbs/timing belt/the lot). Had i Known before I would not have rebuilt it leaving the pistons the wrong way round obviously! I just want to know if I can safely whip off the sump and rod caps and turn the pistons round...from you say (Rom) I should not do it that way, but others seem to think it will be ok? I understand what the rings do, thrust faces and their placement etc. But as said earlier in the topic my squish area is wrong so should really move the pistons to get it all right. If I have to take the head off and removed the pistons/liners I will I suppose.

 

I'm not saying you are wrong Rom far from it, just that there is a lot of differing opinion on this so presumably some people have done it or similar, do you think the rings will be all out of place if I try?

 

If I take the pistons out could I just swap for some 1.9 ones, I have had a head skim of 40thou to bring CR up from 9.2 (DKZ pistons) to 10.2 ish. So I presume new CR would be 10.6ish?

 

More thoughts please thanks

[Rom 0]

Its hard to say really. I build engines, but this isnt something i learnt at college, nor something ive encountered.

 

Everyone will have differing views. Myself, i cant see how you could turn a piston in the bore, without the rings being disturbed. You have no way of knowing if they turned all the way, and maintained the correct end gaps, or if they turened partially, disturbing the end gaps. Or they could even not move at all.

Im just thinking out loud here, i could well be wrong.

We know rings need to be set at correct ends gaps. It doesnt make sense to me, to think that the rings wont be disturbed.

do it myself. Without seeing the ring gaps myself, i wouldnt be happy they are correct.

[Tom Fenton 1,542]

Its not just the ring gaps, the main issue is you are potentially moving the rings from where they have bedded into the bores.

 

To be honest if you are going to change them I'd want to fit new rings and hone the liners, cost approx £70.

[mattbenselin 0]

What about taking head off, sump off, oil pump out and rod caps off, pulling the liners up and out, turn 180 degrees, new o rings on liners and put it all back together??

 

Any thoughts on using 1.9 pistons instead?

 

Thanks