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Hi all, I'm in the process of checking the gaps on my new piston rings (Hastings 2M5170), for my Lq4 build. and my top gaps are all coming out at about 0.26. Seemed a little large for me, since its going to be NA for now, but I've read that it is still well within the okay range. Now that I've moved on to the 2nd rings, the first one I measured came out at about 0.19-0.20! Isn't the 2nd ring gap supposed to be larger than the 1st? On summit, there was another comment about this, so I'm guessing this is how they all come?? I have a ring grinder so should I file them down to about 0.28 to achieve the 0.01-0.02 larger than the top rings, as I have heard on the internet? Any help is much appreciated!!
Are you sure you don't have the 1st and 2nd rings switched? The top ring should have a slightly silver finish to it, that's the molybdenum plating. Second ring is usually a dull grey cast iron finish.
This makes me wonder, because I have a set of Hastings rings for a build I'm going to do soon.
Yeah Im pretty sure I dont have them switched, especially because its a 1.2mm top ring and 1.5mm second. Attached is a pic where you can see the shiny thinner top ring, along with the grey second.
Read instructions twice, and make sure your right. Second ring should be .002 bigger gap than top ring to prevent ring flutter, and sealing issues. Cut the second ring and dress it properly to achieve the .002 bigger second ring gap. Take your time.
Yeah, I checked the instructions in the box, but nothing about gaps was mentioned. Unless there's a reason for me to not use these rings, I plan on grinding them to achieve the proper gap. It Just doesn't make sense to me that the bottom rings would come that much smaller than the top rings from the factory. Is there an application where this is the case? if not why would Hastings do this? maybe to let the customer grind to their desired 2nd ring gap ?
Yeah, I checked the instructions in the box, but nothing about gaps was mentioned. Unless there's a reason for me to not use these rings, I plan on grinding them to achieve the proper gap. It Just doesn't make sense to me that the bottom rings would come that much smaller than the top rings from the factory. Is there an application where this is the case? if not why would Hastings do this? maybe to let the customer grind to their desired 2nd ring gap ?
Guess so, iust a little odd to me since on summit it says they are not file-fit rings, yet the bottoms need to be filed to match with the top. Either way, guess I'll get to grinding!
hey guys, So I contacted Hastings to get their opinion on it, and these are the gap specs I got: For street application with Hypereutectic pistons,
AT Bore 4.00" = 2M5170
The gaps my rings came with are within that, but now my question is more if my top ring gap should be larger or smaller than my second? From everything I have read, the bottoms should be about 0.02 LARGER than the top. BUT after asking this, Hastings said: "For Hypereutectic piston applications, the end gaps of the Top rings are higher than the 2nd rings in general. This is to give extra room for ring expansion with the extra heat produced in the engine with hypereutectic pistons."
Unless I am mistaken, my 2007 Lq4 comes with Hypereutectic Cast Aluminum Alloy pistons from the factory. So is this what I should follow?? If so, do I follow the same 0.02 rule? meaning I would gap the 2nd rings about 0.02 SMALLER than the top rings?
I would gap them both the same. Yes, the top ring gets more heat. It will expand more. Once the engine heats up, the top ring gap will be slightly smaller than the second.
hey guys, So I contacted Hastings to get their opinion on it, and these are the gap specs I got: For street application with Hypereutectic pistons,
AT Bore 4.00" = 2M5170
The gaps my rings came with are within that, but now my question is more if my top ring gap should be larger or smaller than my second? From everything I have read, the bottoms should be about 0.02 LARGER than the top. BUT after asking this, Hastings said: "For Hypereutectic piston applications, the end gaps of the Top rings are higher than the 2nd rings in general. This is to give extra room for ring expansion with the extra heat produced in the engine with hypereutectic pistons."
Unless I am mistaken, my 2007 Lq4 comes with Hypereutectic Cast Aluminum Alloy pistons from the factory. So is this what I should follow?? If so, do I follow the same 0.02 rule? meaning I would gap the 2nd rings about 0.02 SMALLER than the top rings?
Thanks again for any info or guidance.
I stand by my above numbers. Hypereutectic pistons do not cause more heat in the engine. Fake news. A Eutectic piston will generally be set up tighter in the bore, due to the material not expanding as much as a typical forged piston material. This tighter setup doesn’t expose the top king as much as it would in a forged piston application, therefore the top ring does not see as much heat as a typical forged piston top ring will. I’d CERTAINLY not set up the top ring smaller than the second, and if anything, cut them to get the same gap. I’ve never seen anything in all my dyno testing that showed a smaller top gap would work well, irregardless of piston material. Hastings obviously has found something that I haven’t.
so what your saying is to follow what Hastings said and either run them equal or run the top gap larger than the bottom? But also, you said above to try to achieve .002 bigger second ring gap?
so what your saying is to follow what Hastings said and either run them equal or run the top gap larger than the bottom? But also, you said above to try to achieve .002 bigger second ring gap?
I’m saying do not cut the top ring gap larger than the bottom. I’d go .002 bigger bottom…always. I’ve seen what a smaller second ring gap can do in a performance application…not good.
ok, that's what I was thinking. cause right now, uncut, my tops are coming in at about 0.26, and my bottoms are coming in at about 0.19. So i guess Ill have to increase the bottoms quite a bit..?
Last edited by 65gmcC10; Sep 19, 2023 at 11:25 PM.
ok, that's what I was thinking. cause right now, uncut, my tops are coming in at about 0.26, and my bottoms are coming in at about 0.19. So i guess Ill have to increase the bottoms quite a bit..?
Yes. It stinks that your top ring is .026 already. How far down the bore are you squaring the rings to measure?
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2nd Piston Ring gap smaller than top? 
