Correct PISTON RING GAP position (part one)

[MandarinaRacing]

Ok here's one for the experinced engine builders.....what is the correct positioning of the piston ring gaps when they are being installed....I found this diagram but I'm not really sure if I understand it correctly...

Maybe someone can help me get rid of my shadetree mechanic ideas and give me some pointers....

Alex

 

[80broncoman]

myself I have always installed the compression ring gaps at 9 and 3 o'clock looking at that diagram. i have also always put the oils rings at 6 and 12 o'clock. I have never had a problem doing it this way. I don't know why one would put the compression rings gaps so close together. i think maybe they are just trying to get the oil ring gaps as far away from the compression gaps as much as possible.
Jim

 

[addo]

Now here's a curly: If you reverse your pistons like a race motor, do you still index off the front of the block, or off the piston notch?

 

[DYNOED250]

wouldnt that cause all weird things to happen, .. as the pin is on the wrong side now, are they noisie ?

 

[broncr]

Look at each piston as having 5 ring parts to assemble, with the oiling ring comprised of three of them. I would begin by relabeling the diagram A,B,C,D,E. Leave "A" alone, Change one "B" to "C", Change the "C's" to "D" and "E"

Place the oiler ring spacer on first, with the gap at the "A" position, as shown.

Next place the lower wiper ring, gap at the "B" position.

Then place the other wiper ring, gap in the renamed "C" position.

You should now have the oiler ring assembled.


Next, install the lower compression ring (middle ring) with the gap in the (renamed) "D" position. There is usually a dot to mark which side of the ring is up!

Finally, install the top comp. ring with the gap in the (renamed) "E" position.

You should now have one piston ready to install.


Repeat this five more times and you should be ready to install your pistons. I've got 30K on my rebuild (so far) with this configuration. I don't expect any problems...

Broncr

 

[MandarinaRacing]

80broncoman said:

I don't know why one would put the compression rings gaps so close together.

My thoughts exactly...

Thanks for the pointers guys!

BTW I got this diagram from a link I found on the BB Six forum...

http://www.cybrrpartspro.com/Chilton Manuals/8828m/8828CH03_30.HTML

Alex

 

[addo]

D250, my comments on the reversed pistons are based on the fact that the pins are offset to reduce piston slap and running noise. If you put them in "back to front" you actually transfer the force more directly to the rods; the offset is now beneficial to power. But it gets noisier!

 

[80broncoman]

I really have never looked at a diagram on this before, I always just put the two oil ring gaps 180 degrees apart and the same for the compression rings too. I dont think anyone will see a difference between 180 degrees or 160 degrees.
Jim

 

[Thad]

As Bronco said oil rings 180* to each other, compression rings 180* to each other and 90* out of phase to oil rings.
Never noticed any consistance in ring position from engine when torn down. Also I think, in time, there would be some change in position. If not why would the rings be pinned in a piston port 2 cycle.

 

[SuperMag]

I always alternated the ring gaps at 12 & 6 o' clock. Dunno if it actually makes any difference, but I was never fond of putting the ring gaps on the "thrust" side of a piston.

 

[broncr]

I've heard of a lot of ways to position ring gaps, and now - even more. I was taught (by a WW2 era mechanical whiz) to seperate gaps 120*, exactly 1/3. The man had rebuilt hundreds of engines and focused/taught me by analyzing the failures that had brought the engines to him in the first place. There was often some evidence of human error in assembly, though just as commonly evidence of abuse. Often they were just plain worn out.

That said, I don't recall any evidence of failure due to improper ring gap positioning. The diagram pictured is in my Chilton's Bronco Manual. I let the 150* vs 120* spacing slide. Maybe we can all compare notes in ten years or so and see if there is any significant difference in gap position...

One thing I do know (believe), you SHOULD stagger ring gap position & do it the same for each piston.

Broncr