98 Silverado Z71

[4x4_guy]

Does a 5.7L Vortec in my '98 Chevrolet Silverado Z71 have gapless rings, and if so, will gapless rings cause a slight pecking sound for the first minute or so on a cold start? Another member of this forum told me that the pecking sound was a piston slap, but I am unfamiliar with that.... I was also told gapless rings could be the reason for the pecking, and that it is normal, most newer engines with gapless rings will do that. There are no performance problems with the truck, I am just wanting to make sure it is mechanically sound..... any input will help. Thank You

 

 

4x4_guy

[GM-Tech]

I hope I'm not displaying my stupidity here, but I never heard of "gapless" rings. How can a ring have no gap? The fit necessary for each cylinder would make that very hard to do. What would create the bit of tension needed against the cylinder wall, and how would one compress the rings to get the piston into the cylinder if there was no ring gap?

 

I've had plenty of pistons out of our engines. The rings looked like they have looked probably for the last 80-100 years or so, i.e. with a gap!

 

Piston slap is due mostly to the skirtless design of newer pistons. Couple that with the fact that they're aluminum and expand at a faster rate than cast iron, they have to have some clearance in the bore. That's why you get piston slap when cold. As the piston heats up and expands (in a matter of seconds really) the noise goes away.

[the mouse]

I hope I'm not displaying my stupidity here, but I never heard of "gapless" rings.  How can a ring have no gap?  The fit necessary for each cylinder would make that very hard to do. What would create the bit of tension needed against the cylinder wall, and how would one compress the rings to get the piston into the cylinder if there was no ring gap?

 

I've had plenty of pistons out of our engines.  The rings looked like they have looked probably for the last 80-100 years or so, i.e. with a gap!

 

Piston slap is due mostly to the skirtless design of newer pistons.  Couple that with the fact that they're aluminum and expand at a faster rate than cast iron, they have to have some clearance in the bore.  That's why you get piston slap when cold.  As the piston heats up and expands (in a matter of seconds really) the noise goes away.

 

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The gapless rings he is referring to are usually used in motorcycles. The last 1/4 inch or so of each end of the ring is reduced to 1/2 of it's thickness. The reduced thickhess ends pass one another in the ring groove of the piston, resulting in a "gapless ring". This helps boost compression, and eliminates ring flutter and breakage from extreme rpm changes.

[GM-Tech]

  The gapless rings he is referring to are usually used in motorcycles.

 

 

Never had a motorcycle engine apart so I'll take your word for it.