LS3 stock rebuild ring gaps and piston to wall too loose?
01-22-2013, 01:13 PM
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LS3 stock rebuild ring gaps and piston to wall too loose? Honed cylinders in shop, cleaned up old pistons, put in stock GM rings (factory gapped, not file to fit, so they fell as they fell), all new bearings.
.017-.020 top rings gaps
.025-.030 second ring gaps
Piston to wall clearance is up to .004 in some cylinders. But at least the cylinders are true now (were pretty wobbly before on the bore gauge).
The skirt coating is mostly worn off the stock pistons.
Should I be worried about blowby, oil consumption, piston slap?
.017-.020 top rings gaps
.025-.030 second ring gaps
Piston to wall clearance is up to .004 in some cylinders. But at least the cylinders are true now (were pretty wobbly before on the bore gauge).
The skirt coating is mostly worn off the stock pistons.
Should I be worried about blowby, oil consumption, piston slap?
01-23-2013, 11:12 PM
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Well... The ring gaps are right at the high end of the range, so I guess I'm ok with that:
Piston Ring End Gap - First Compression Ring - Measured in Cylinder Bore - Service 0.0067-0.0173 in
Piston Ring End Gap - Second Compression Ring - Measured in Cylinder Bore - Service 0.0126-0.0272 in
But the piston to wall clearance is way out, if I'm up to .004:
Piston to Bore Clearance - Service Limit with Skirt Coating Worn Off 0.0022 in
Now this is really strage:
Piston to Bore Clearance - Production -0.0019 to +0.000 in
Negative cearance??? How the hell does that work??
Any real world experiences with piston to wall clearance of .004"? I measured near the bottom of the skirt. Some cylinders / some spots get tighter, around .003", but the max of .004 sounds scary. I know race pistons run with much wider clearances, but then those alloys have different expansion rates than these stock pistons.
At this point it's basically a moot point, because I'm not gonna tear it up again, bore it, and buy new pistons and rings... It's pretty much together now. Truth is, I didn't expect the shop to take this much material off the bores. But I'm curious as to what I should expect. I know these engines like to piston slap even with factory tolerances, so I'm a little worried...
Piston Ring End Gap - First Compression Ring - Measured in Cylinder Bore - Service 0.0067-0.0173 in
Piston Ring End Gap - Second Compression Ring - Measured in Cylinder Bore - Service 0.0126-0.0272 in
But the piston to wall clearance is way out, if I'm up to .004:
Piston to Bore Clearance - Service Limit with Skirt Coating Worn Off 0.0022 in
Now this is really strage:
Piston to Bore Clearance - Production -0.0019 to +0.000 in
Negative cearance??? How the hell does that work??
Any real world experiences with piston to wall clearance of .004"? I measured near the bottom of the skirt. Some cylinders / some spots get tighter, around .003", but the max of .004 sounds scary. I know race pistons run with much wider clearances, but then those alloys have different expansion rates than these stock pistons.
At this point it's basically a moot point, because I'm not gonna tear it up again, bore it, and buy new pistons and rings... It's pretty much together now. Truth is, I didn't expect the shop to take this much material off the bores. But I'm curious as to what I should expect. I know these engines like to piston slap even with factory tolerances, so I'm a little worried...
01-24-2013, 07:29 PM
#6
Well... The ring gaps are right at the high end of the range, so I guess I'm ok with that:
Piston Ring End Gap - First Compression Ring - Measured in Cylinder Bore - Service 0.0067-0.0173 in
Piston Ring End Gap - Second Compression Ring - Measured in Cylinder Bore - Service 0.0126-0.0272 in
But the piston to wall clearance is way out, if I'm up to .004:
Piston to Bore Clearance - Service Limit with Skirt Coating Worn Off 0.0022 in
Now this is really strage:
Piston to Bore Clearance - Production -0.0019 to +0.000 in
Negative cearance??? How the hell does that work??
Any real world experiences with piston to wall clearance of .004"? I measured near the bottom of the skirt. Some cylinders / some spots get tighter, around .003", but the max of .004 sounds scary. I know race pistons run with much wider clearances, but then those alloys have different expansion rates than these stock pistons.
At this point it's basically a moot point, because I'm not gonna tear it up again, bore it, and buy new pistons and rings... It's pretty much together now. Truth is, I didn't expect the shop to take this much material off the bores. But I'm curious as to what I should expect. I know these engines like to piston slap even with factory tolerances, so I'm a little worried...
Piston Ring End Gap - First Compression Ring - Measured in Cylinder Bore - Service 0.0067-0.0173 in
Piston Ring End Gap - Second Compression Ring - Measured in Cylinder Bore - Service 0.0126-0.0272 in
But the piston to wall clearance is way out, if I'm up to .004:
Piston to Bore Clearance - Service Limit with Skirt Coating Worn Off 0.0022 in
Now this is really strage:
Piston to Bore Clearance - Production -0.0019 to +0.000 in
Negative cearance??? How the hell does that work??
Any real world experiences with piston to wall clearance of .004"? I measured near the bottom of the skirt. Some cylinders / some spots get tighter, around .003", but the max of .004 sounds scary. I know race pistons run with much wider clearances, but then those alloys have different expansion rates than these stock pistons.
At this point it's basically a moot point, because I'm not gonna tear it up again, bore it, and buy new pistons and rings... It's pretty much together now. Truth is, I didn't expect the shop to take this much material off the bores. But I'm curious as to what I should expect. I know these engines like to piston slap even with factory tolerances, so I'm a little worried...
01-25-2013, 02:41 PM
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X2, loose is fast but don't plan on the ring seal to hang around forever. I would put it together and run the **** out of it, and save for a set of over sized pistons and rings to put in a year or two.
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01-29-2013, 12:41 AM
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I would'nt run it if it were Me ,,,,,,,,I would do it right this time ,,,,,,,,,if You do run it ,,,,,,You'll probably want to create a little extra clearance in the bearings and then run Valvoline 60 wt. racing oil and maybe some Lucas additive ,,,,ha ha ha and it might be quiet 4 a while
01-29-2013, 04:42 PM
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Yeah, sorry for the lack of update. From feedback on other forums, I decided to redo the whole thing. .004 is a bit much even for 4032 forgings, but hypereutectic won't expand, and it'll likely never stop slapping.
The block's at another shop as of today. I'm putting in 20 over Silvolite hypereutectics, hastings rings, and calling it a day. Should be good for a stock rebuild.
If all goes well, and they don't screw me again, I can finish it up and drop it in this weekend, and I'm without a car for one extra week only...
The block's at another shop as of today. I'm putting in 20 over Silvolite hypereutectics, hastings rings, and calling it a day. Should be good for a stock rebuild.
If all goes well, and they don't screw me again, I can finish it up and drop it in this weekend, and I'm without a car for one extra week only...
