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Piston Rings
paulbeyer - 26/3/03 at 11:02 PM

Tonight I put the pistons into my Pinto block and I've just realised I didn't pay any attention to where the gaps in the rings were. Is that a bad thing or shouldn't it make any difference?

davef - 27/3/03 at 06:19 AM

Hi Paulbeyer, yes your ring gaps should be set at 120 degrees really, to prevent blow through, but having said that you would have to be the unluckiest person in the world to have set them all in line by sheer chance, i would,nt worry carry on with the build. cheers davef.

david walker - 27/3/03 at 07:05 PM

I assume the rings were still OK then Paul? Best of luck with it. Dave

paulbeyer - 27/3/03 at 10:01 PM

quote:

I assume the rings were still OK then Paul? Best of luck with it. Dave


Hi Dave,

The rings were fine. Did what you said and gave everything a good wipe down and re assembled evrything with new seals on the crank and auxillary drive. I got my local ford dealer to remove the cast alloy housing and drive belt pulley off the front of the crank for £4.00 so I could replace the seal.
I'll take the pistons back out tomorrow night and set the rings at 120 degrees as has been mentioned by Davef and my haynes manual. I should RTFM more often, it would save me a lot of grief.
Thanks for your help the other day, I appreciate you help and honesty.

UncleFista - 28/3/03 at 04:26 PM

No need to take it apart, Dave Baker of Puma racing http://www.pumaracing.co.uk said on usenet;

"The same old crap about ring gap positions has been trotted out in Haynes
manuals since the dawn of time by people whose capacity for original thought
has been firmly stamped out of them since birth. It doesn't make a scrap of
difference where the gaps are. Think about what happens to the gas that gets
past the top ring. Will it magically not go through the gap in the second ring
just because that isn't lined up with the top gap? Imagine several engine
cycles have taken place and the space between the top and second ring is filled
with gas at uniform pressure. Any leakage past the top ring will increase the
pressure in all of that space uniformly again. The leakage rate past the second
ring will therefore be the same regardless of where the gap is. It just won't
happen to be the same gas that came past the top ring on the same engine
stroke. Those specific molecules will take a few more cycles to migrate round
the piston to the other side as they get pushed there by new molecules leaking
in.

Anyway - they do rotate so all of the above is academic too."

Dave knows his onions too, so I'd trust him

jollygreengiant - 28/3/03 at 10:57 PM

actually I think that you'll find it's to stop a score line or ridge developing on the bore from having the ring gaps in the same place which would then lead to early failure of the oil control ring.

Think about it.

And no they generally dont rotate thats cam followers.


Enjoy.

[Edited on 28/3/03 by jollygreengiant]

[Edited on 28/3/03 by jollygreengiant]

paulbeyer - 29/3/03 at 12:06 AM

Job done whether it needed it or not only took 20 minutes start to finish.

johnston - 30/3/03 at 07:01 PM

quote:

And no they generally dont rotate thats cam followers


after building and rebuilding a engine a fortnight apart i can confirm they do rotate after a bit of runnin