Seems like there are several ring-end-gap theories out there & kinda going opposite directions:
some say that the top ring should have the biggest gap since it is the first one to take the beating & the heat (therefore expansion)
(ie: 0.018-0.020 first ring & 0.014-0.016 second ring for a 4.030 302)

& that makes sense.....

Others say that in order to prevent ring floating (making sure that the top ring stays seated at the bottom of the first groove at all time) & inter-ring pressure build-up, the first ring should be set tight (ie: 0.014-0.016/First & 0.020-0.022/second)

And that makes sense too

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Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

quote:

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Originally posted by Moneymaker:
Last time I looked (about a minute ago)there were quite explicit, and specific ring gap instructions in the box.
Why would you want to deviate from the ring manufacturers recomendations? Especially on a street car?

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Well, being new to this hobby I have actually never touched/seen a set of ring nor the box it comes in & I try to be very cautious about every steps (may be too much sometime, all right )

I have received the gap specs from my piston manufacturer speed pro (mail I sent you and you OKed them) & it seems to be opposite to the one of the ring manufacturer that summit gave me over the phone later on !

I will mostelikely cover my *ss and follow the specs of the ring manufacturer but returning a broken engine ain't cheap to me so I am trying to understand why specs can differ so badly !!

I figure that the manufacturer knows a helluva lot more about metalurgy than I do, so I've always gone with the 'looser' top ring as per spec

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1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9"

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Alex Denysenko
Co-Administrator and Moderator

NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00,'01,'02,&'03
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl

Any way, depending on the type of engine you have and what you are going to be using it for, determines what you should set you're "ring-end gap" to.

As somone stated before, the top compression "ring-end gap" should be greater than the 2nd 3rd etc. The main reason for this is heat and piston movement.

The top piston ring is going to see more heat than the other rings because it's closer to the flame. Also, when the piston rocks back and forth in it's bore, the top ring is subjected to more movement than the other rings.

As far as what to "gap" the rings to.

In a 4" bore...Top ring

-supercharged
.022-.024

-Normally aspirated
Street-strip .016-.018
Nitro-street .024-.026
Nitro-drag only .032-.034

2nd ring

Supercharged
.012-.014

-Normally aspirated
Street-strip .010-.012
Nitro-street .018-.020
Nitro-drag only .024-.026

*Note: These specs. are not set in stone. There are other factors that come in to play, but it gives you a good idea on what to set you're ring-end gap to.