Piston "side play" question???
11-26-2005, 11:49 AM
#1
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Piston "side play" question??? I have an LS-1 engine that I am planning on installing in a '69 vette. The motor has 40,000 miles and I was planning on using the bottom end as is. However, after removing the heads I noticed there is a considerable amount of "side-play" (appx. 1/32") at TDC on each piston when pressing side to side. Is this normal for an LS-1 motor?
11-26-2005, 04:22 PM
#3
Mr. Rocket,
What you are seeing is the piston rocking in the bore, not piston to bore clearance.
#1 The top land is smaller in diameter than the rest of the piston so it will not touch when the piston rocks over when the rod comes up to TDC and starts to come down.
#2 Clearance is measured at the skirt, not in the ring area. If you ever measured a piston it is not round. It is slightly oval. That is why the piston maker specifies where to measure it to set the piston to bore clearance. A brand X piston may not measure the same way a brand Y piston. I am looking right now at a JE piston print and they specify to measure 90 degrees from the pin and .5 inch up from the bottom of the skirt.
So what you are looking at is at the opposite end of where you need to be concerned. If the bores look good and there is minimal ridge at the top,(where the piston ring does not ride) run it.
If you still have a questioning mind measure the cylinder taper at the top and as far down as you can get with the piston down and compare.
Rich
What you are seeing is the piston rocking in the bore, not piston to bore clearance.
#1 The top land is smaller in diameter than the rest of the piston so it will not touch when the piston rocks over when the rod comes up to TDC and starts to come down.
#2 Clearance is measured at the skirt, not in the ring area. If you ever measured a piston it is not round. It is slightly oval. That is why the piston maker specifies where to measure it to set the piston to bore clearance. A brand X piston may not measure the same way a brand Y piston. I am looking right now at a JE piston print and they specify to measure 90 degrees from the pin and .5 inch up from the bottom of the skirt.
So what you are looking at is at the opposite end of where you need to be concerned. If the bores look good and there is minimal ridge at the top,(where the piston ring does not ride) run it.
If you still have a questioning mind measure the cylinder taper at the top and as far down as you can get with the piston down and compare.
Rich
11-26-2005, 04:46 PM
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I just checked the "play" and there is appx 2.5/100's or 25/1000's of an inch side to side. This is more noticible when the piston is at TDC then at the bottom of the cylindar. Also, there is absolutely no ridgeline at the tops of the bores.
