Posted By: JonC
Ring end gap - 05/26/11 11:19 PM
I'm putting my 340 +.040 engine back together. What ring gap should I use? Cast pistons .040 over, Moly rings.
Ring end gap
Posted By: RapidRobert
Re: Ring end gap - 05/27/11 12:01 AM
top-.016". 2nd-.012"
Posted By: 1_WILD_RT
Re: Ring end gap - 05/27/11 12:13 AM
Quote:
top-.016". 2nd-.012"
Current thinking is second ring gap should be wider than top gap... It has been found that the second ring can trap pressure between the rings and cause the top ring to flutter in it's groove losing ring seal....
I'd set the second @ .018..
Posted By: JonC
Re: Ring end gap - 05/27/11 12:24 AM
That's a bit of a difference between the two answers. 
Posted By: RapidRobert
Re: Ring end gap - 05/27/11 12:29 AM
Old school was .004 per inch of bore on the top ring and .003 on the 2nd comp ring as the top ring is closer to the fire and will expand more. New thought is the opposite. The old has worked for decades & is my pref 
Posted By: Von
Re: Ring end gap - 05/27/11 12:30 AM
Id file them the same, 1st and 2nd groove.
IMO, ring gap, (as long as its not tight) isnt that big of a deal.
IMO, ring gap, (as long as its not tight) isnt that big of a deal.
Posted By: 1_WILD_RT
Re: Ring end gap - 05/27/11 12:33 AM
Nothing wrong with old school, it's worked well for me in the past also... But learning new tricks from guys that have results to back it up isn't a bad idea either... 
Posted By: RapidRobert
Re: Ring end gap - 05/27/11 12:34 AM
Jonc we're not helping you today are we 
Posted By: JonC
Re: Ring end gap - 05/27/11 12:50 AM
Quote:
Jonc we're not helping you today are we
Ha Ha, but I just want to get it back together. I guess it wouldn't hurt a street car to do it old school.
Posted By: Dcuda69
Re: Ring end gap - 05/27/11 01:27 AM
Quote:
Id file them the same, 1st and 2nd groove.
IMO, ring gap, (as long as its not tight) isnt that big of a deal.
If in doubt fail on the big side. N/A I would do .016-.018 on both and run it!! 
Posted By: buildanother
Re: Ring end gap - 05/27/11 01:57 AM
That'll work
Posted By: court9155
Re: Ring end gap - 05/27/11 02:29 AM
I go with the .0045 and .0035 all motor rule and .006 and .0045 for nitrous or low boost.
http://www.totalseal.com/TechPage.aspx#trTSFAQ
http://www.totalseal.com/TechPage.aspx#trTSFAQ
Posted By: court9155
Re: Ring end gap - 05/27/11 04:39 AM
Wow did some research and I dont believe everything I read but:
http://blogs.hotrod.com/piston-ring-gap-194.html
http://blogs.hotrod.com/piston-ring-gap-194.html
Posted By: dOc !
Re: Ring end gap - 05/27/11 04:58 AM
Quote:
Wow did some research and I dont believe everything I read
...and you should REALLY question ones who are Really TemperMENTAL
JC ...what do you have for ring gap now? uNless you bought specific OVERsized rings .... normally - very little filing will be necessary.
Posted By: JonC
Re: Ring end gap - 05/27/11 01:54 PM
Quote:Quote:
Wow did some research and I dont believe everything I read
...and you should REALLY question ones who are Really TemperMENTAL
JC ...what do you have for ring gap now? uNless you bought specific OVERsized rings .... normally - very little filing will be necessary.
I never thought to measure the old rings, I'll do that today.
Posted By: MoparforLife
Re: Ring end gap - 05/27/11 02:34 PM
Also in this case I believe in the old adage too much is better than not enough. Read this. http://www.kb-silvolite.com/features.php?action=read&F_id=62
Posted By: Anonymous
Re: Ring end gap - 05/27/11 04:20 PM
That "flutter" deal may be true for a full out high RPM RACE engine--but for a street unit old school is still a great way to go--doing an 8500RPM Drag small block go the other way. Get the rings on right side up and no matter what you do it will be fine
Posted By: dOc !
Re: Ring end gap - 05/27/11 04:32 PM
Quote:
I never thought to measure the old rings, I'll do that today.
THAT would be an interesting # to see ... but what I am talking about is the NEW rings .. in the NEW bore. And like was said above .. it is BESTer to have the gaps a tad fat .. than toooo tight.
NASTY things can happen if the ring ends butt and then break.
Posted By: JonC
Re: Ring end gap - 05/27/11 11:04 PM
Old top ring is .025, new top ring is .016.
Old second ring is .027, new second ring is .017. The engine bore has not changed in this rebuild, all I did was have it balanced.
Old second ring is .027, new second ring is .017. The engine bore has not changed in this rebuild, all I did was have it balanced.
Posted By: RapidRobert
Re: Ring end gap - 05/27/11 11:09 PM
You have 016 and 017, I'd run em. OT; Jon What did you do to the bore finish?
Posted By: JonC
Re: Ring end gap - 05/28/11 12:57 AM
Quote:
You have 016 and 017, I'd run em. OT; Jon What did you do to the bore finish?
I ran a hone down each cylinder just to break the glaze. I am at my campground right now and can't tell you the grit.