Ring Gap

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Braeden Clark

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I am rebuilding my magnum 360. It has 126k miles when pulled. I decided to only hone the cylinders as they looked mint to begin with. I bought enginetech hypereutectic pistons and the rings they told me to get to go with them. All standard size. The issue I am having is the top ring gap for all cylinders is .024-.027 inches. The service manual says spec is .012-.022 inches. The 2nd comp. rings are all .022-.023. Spec is .022-.030 or something like that.

My question is the top rings. Maybe they are meant to be that open for those specific pistons? The machine shop did not mention any bad wear in the bores. Am I safe using those rings? I read a post where someone had the same exact thing happen with those rings. Same measurements and all. I'm thinking maybe they are supposed to be like this. Thoughts? Would I run into issues? I do plan on opening up the 2nd rings to like .024ish. Thanks
 
The service manual is speced for cast. The hypereutectic need more ring gap. The piston maker should tell you what gap they want. Go by that.
Gotcha. I was told these were pregapped. I will try to find out for sure though. Does the gap I have sound about right though for hypereutectic pistons?
 
Too much gap is WAY better than not enough. There's a thread on the B side where a fresh 440 with KBs broke a piston ringland from not enough gap. If yours have the same accumulator area below the top ring that kbs have.... I would use .030.
 
That gap sounds about right for a hyper piston....but that is just from memory of what I have read in the past. Like others said, check with the piston manufacture to see what they recommend.
 
That gap sounds about right for a hyper piston....but that is just from memory of what I have read in the past. Like others said, check with the piston manufacture to see what they recommend.
Gotcha. Obviously I will check with the piston manufacturer but what would you recommend for the 2nd comp ring gap? Mine seemed a bit tight. Around .022ish. Seems tight to me. Thoughts
 
Too much gap is WAY better than not enough. There's a thread on the B side where a fresh 440 with KBs broke a piston ringland from not enough gap. If yours have the same accumulator area below the top ring that kbs have.... I would use .030.
Here is a picture of the piston. Thoughts? Look similar to the KB's?

Screenshot_20220111-154332_Samsung Internet.jpg
 
Okay, that does NOT have the accumulator of the KB. So, as stated above, find out what your piston maker recommends.
I think I added about .008 to the recommended number on my 440, just in case nitrous should someday accidentally appear.
 
My KB107 hypers froze the engine at the KB street spec factor, and the engine always ran hot. I took it apart and opened it up to the Nitrous/towing factor and that solved it. My top rings went to in the range of .032 to .034. I used a hand-crank ring-filer.
About three Daily-driver years later, I put a one-size bigger cam in it and with no changes, the car went 93 in the Eighth @3457 pounds.
Don't be afraid of a lil extra gap.
 
Okay, that does NOT have the accumulator of the KB. So, as stated above, find out what your piston maker recommends.
I think I added about .008 to the recommended number on my 440, just in case nitrous should someday accidentally appear.
Yea well the issue is the idiot at enginetech is telling me the rings should have the same gap as the stock ones. I don't buy it. Especially when I bought the pistons I was specifically told to use these rings. Maybe there is just a bit of wear in the bores but the machine shop checked it. Plus if there was substantial wear why would the 2nd rings be on the tight side. There is a thread somewhere on this site where someone used the exact same rings and came out with the exact same measurements as me. I'm thinking it's supposed to be like this. I'm checking all my measurements again tonight.

My plan is to have all the top rings gapped around .025-.027 and the second rings gapped to around .024. Thoughts?
 
In my humble opinion, other than all out race, or specialty rings, there are two kinds: rebuilder or standard rings, and file to fit. I have seen rebuilder rings at .035 and things seem to run fine. The guys that run power adders on stock shortblocks open them up to specifically open up the ring gap, then reassemble.
I think I would run the 25-27/24. More, if nitrous is a possibility.
 
In my humble opinion, other than all out race, or specialty rings, there are two kinds: rebuilder or standard rings, and file to fit. I have seen rebuilder rings at .035 and things seem to run fine. The guys that run power adders on stock shortblocks open them up to specifically open up the ring gap, then reassemble.
I think I would run the 25-27/24. More, if nitrous is a possibility.
Here is a photo of all the final gaps. Some of these fit tight though. Anything concerning? Should I open the gap of the second rings at all? I took measurements a couple inches from the top of the cylinders and bottom

20220111_201430.jpg
 
In my humble opinion, other than all out race, or specialty rings, there are two kinds: rebuilder or standard rings, and file to fit. I have seen rebuilder rings at .035 and things seem to run fine. The guys that run power adders on stock shortblocks open them up to specifically open up the ring gap, then reassemble.
I think I would run the 25-27/24. More, if nitrous is a possibility.
As a side note I am pretty sure silvolite makes these pistons for enginetech. They look like the same style as silvolite pistons. Silvolite is also made with KB
 
A trend in recent years is increase [ slightly ] the 2nd ring gap over the top ring. The theory being that as the gas pulse passes through the top ring gap, a larger 2nd ring gap allows for an escape route & the top ring does not unseat.
 
A trend in recent years is increase [ slightly ] the 2nd ring gap over the top ring. The theory being that as the gas pulse passes through the top ring gap, a larger 2nd ring gap allows for an escape route & the top ring does not unseat.
Talked to my machinist tonight. He claims he would like to see a slightly smaller gap. I am not running KB pistons so I don't need the much larger gap. I am also not going to be beating this engine to hell. My machinist (been doing this for over 35 years) would like to see the top ring gap arouhd.020-.022 and the 2nd ring gap to be larger. As you said, he says it allows gases to escape. That's the way these motors cane from factory. I bought new rings from sealed power. Also, all of the specs given above work with what the company that manufactures these pistons recommend (Silvolite). Here is a photo.

Screenshot_20220112-234444_Drive.jpg
 
Braeden,
The bigger 2nd gap is for all piston types, not specifically hypereutectic. Have a look at comments on the net.
 
Imo 3 is still tight. Second should be 4.00x.004= .016 min. The rest look ok. Good luck.
I'm dealing w/ BS from Hastings for my Ironhead Cafe Racer drag bike. The formula you stated is the same info I have read as a guideline for installation. Much less, at op temp, gap can close up, and that ain't purty
 
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