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I’m looking at a 2000 hour stock Lycoming IO-360 piston I have in my hangar, and the ring bevels are clearly facing up as well, There are no P/N’s or dots visible on these rings but it appears that they are oriented correctly because the bevel is also on the top (crown side) of the ring lands and the rings definitely cannot be installed upside down (bevel down) because they won’t sit all the way into the land grooves.
Not a problem as long as you measure and respect the ..007” clearance in the top of the choke.
I am familiar with the general guidelines. However, those are for water cooled engine blocks and that is a bare minimum. Most small block chevys are in the 025-028” range. The block is A huge amount of mass that sheds heat readily. Therefore, we assume that the bore will not grow. We know that the ring will expand from the heat and therefore must provide an allowance in the ring gap. This is all heat based. Your guidance is for normality aspirated. Add boost or nitrous and the gap needs to be even bigger due to the extra combustion heat involved.
Sorry. I guess you didn't like my Flintstone comment.
Did they get a technical rational? The choke/wall profile has been validated for the better part of a century. Would seem the risk of ring material fatigue has been increased.
In water cooled, large mass blocks, the bore size never expands from heat (at least not of significance), however, the rings and pistons do. Therefore we need a good sized ring gap to accomodate that expansion, lest the ring becomes larger than the bore and you get what the OP here got and more likely a cracked ring. An 1/8" thick Lycoming cylinder WILL expand from heat, along with the rings and pistons, and therefore, in theory, we need less gap than our water cooled siblings; Not more.
RE the Superior end gap info-I have found this same info from various other sources. All reprints of Superior information. The parallel valve 360 in most cases uses the same pistons and rings as 0 320, 160 hp. So why does the 320 use .045 minimum and the 360 in the text specifies .0075 minimum and no maximum. One possibility is that Lycon misread the .045 minimum and used .0045 instead.
Could you please explain those number to me?
Poor documentation. Superior considers the 320 steel cylinders to be the no choke version and therefore the ring gap is different. See my explanation above. Clearly this is not correct though. While it is poorly documented, you MUST know whether your cylinder is profiled with or without a choke taper before sizing the ring gaps, as the clearance and measuring points are different. Pretty much everything new is tapered. Don’t think they have made straight bores for many decades.
Call the cyl diameter 5” for simplicity and assume no ring gap in the choke. The rings circumference (the linear outside length) is Pi r2. 3.1414*(2.5*2.5)=19.634” at the top of the barrel. Circumference at the bottom of the barrel, assuming an 005” taper is 3.1414*(2.5025*5.25025)=19.673”. So, a 0 gap in the choke grows to 0039” gap outside the choke. Going from a 0 gap to an 005 gap will double that to 0078”. You can do the math on that one.
Larry........We are not looking for the area of a circle. We are looking for the circumference of a circle
Sorry late at night. Data is almost the same though.
Did you ever check to see if the cam was installed right. One tooth off is like 7 degrees of cam timing. + or - .
Your concerns here assume that the cyl bore remains the same size. See my explanations above about the cyl expanding as well.
You measure the 0.0075 with a feeler gauge. If it fits you're good to go. Cylinder variance is why you measure the ring gaps. One of the worst things you can have happen is for the rings to close.
and would probably be reflected by some hi CHTs right?
The Superior protocol for measuring ring gap is state of the art WIERD. Approximately is not a word I want to see for something this critical. Is the Superior starting point 1.2 or 4.0 from the bottom of the cylinder?? The Superior cylinders have a reputation of running significantly hotter than Lycoming. The higher temperature combined with inadequate ring gap is the cause of this.
As I measure it, the taper in the cylinder would have to be about 0.012 to make the ring gap clearance meet the spec of the chart minimums.
Approximately is not good enough for end gap at top.
OP said. "I did not check the ring gap, as this was done by LyCon. The 8130 says “rings were fit”
The Lycoming cylinders and the Superior cylinders use different processes for casting the cylinder heads. Lycoming are rough surface which results in good cooling. Superior are smooth which results in less efficient cooling. The Superior cylinders with too narrow ring gap are much more likely to self destruct.
I checked the ring gaps after disassembling the engine and they were all fine, but perhaps they are fine now that the cylinder bores are majorly worn?
I always wondered how close superior cuts it on the choke ring gap. I installed their cylinders on my 540 when i overhauled it. I was pretty careful with the ring gaps. At my first ci, one cylinder blew 50/80. Pulled the cylinder and the top ring was cracked. Fortunately superior sent my a new one under warranty. My suspicion is that their hone process is not very tightly controlled and on that cylinder, the taper starts much lower in the bore than it should have (the lower you go, the less it expands from heat). I still have the cylinder, as it was still in great shape, and one day will measure it with the bore gauge. Also, my chokes were tighter than normal, as all my lower bore ring gaps were in the 055-060+ range after i got the upper gap to 008”. At that time, the spec was 045-055. I think because of this production issue, they changed the spec to 045 minimum, to prevent calls like mine, saying I can’t get my ring gaps in tolerance.
Superior just may be a different head/barrel dimension delta at room temperature prior to assembly. The process today is undoubtedly different than my observation 40 yrs ago, but then the heads were in a 400F oven and the honed barrels (as a cylinder) were dipped into a pool of liquid nitrogen until the boil was happy for the operator. He then spun the chilled barrel into the hot head. When thermally equalized his would then shrink the barrel at the head interface and create the "choke" . The process is likely more controlled than the past, but dimensions for various reasons could easily be different.
Because superior doesn't stand behind their products
I believe you misplaced your decimal above. Should be 0.025 and 0.055 and 0.015.
This is ring land clearance, so the values are correct. 2.5-5.5 thou, not 25 and 55. In the end I don’t think this was of consequence
He was referring to ring side clearance and it is 0.0025 to 0.0055. And we both found the side clearance to be tight (around 0.0015 or less).
