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Piston ring end clearance

Piston ring end clearance

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Mike Meyer
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What is the gap in new piston rings meant to be when installing pistons in a D2/D4 pilot motor, and where in the bore is the measurement taken, I assume a slightly wider gap is required for the top compression ring?

I have the measurements for side clearance, and ring land clearance behind the rings, but not the end gap, and the new compression rings I have here measure around 22 thou end gap clearance halfway down the bore.
Thanks
Mike
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Mon, Apr 14, 2014 3:02 AM
jmvmopar
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Mike, As long as you have at least 0.010" ring end gap at the bottom bore you will be ok.

Spec is 0.010" to 0.020"
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Mon, Apr 14, 2014 5:29 AM
Mike Meyer
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Reply to jmvmopar:
Mike, As long as you have at least 0.010" ring end gap at the bottom bore you will be ok.

Spec is 0.010" to 0.020"
Thanks jmvmopar, I was wondering if I should be looking for the next ring size up if I have a gap of around 22 thou halfway down the bore, these are new Cat 20 thou oversize rings, I'll double check the gap at the bottom of the bore.
regards
Mike
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Mon, Apr 14, 2014 6:24 AM
edb
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Reply to Mike Meyer:
Thanks jmvmopar, I was wondering if I should be looking for the next ring size up if I have a gap of around 22 thou halfway down the bore, these are new Cat 20 thou oversize rings, I'll double check the gap at the bottom of the bore.
regards
Mike
Hi Mike,
second go at this, lost last post using this crap top Win 7 thing--bring back XP.

Ring gaps are given as :- compression 0.012"--0.022" and oil 0.012--0.020" for the small pony in both J and U SRB's.
for worn bores check at the unworn bottom section of the bore.
If the bore is really tapered you could check at the lowest section of that rings travel in the bore.
For new bores I was taught to check top, middle, and lower.
Scan below is from a Cat Spec Sheet.
Cheers,
Eddie B.
Attachment
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Mon, Apr 14, 2014 7:47 AM
Mike Meyer
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Reply to edb:
Hi Mike,
second go at this, lost last post using this crap top Win 7 thing--bring back XP.

Ring gaps are given as :- compression 0.012"--0.022" and oil 0.012--0.020" for the small pony in both J and U SRB's.
for worn bores check at the unworn bottom section of the bore.
If the bore is really tapered you could check at the lowest section of that rings travel in the bore.
For new bores I was taught to check top, middle, and lower.
Scan below is from a Cat Spec Sheet.
Cheers,
Eddie B.
Attachment
Thanks for the scan, I've printed it off for safe keeping. Found 3" of rain in the gauge when I got home from Adelaide on Thursday night, so I've been busy on the tractor plowing some ground since, should get back on the Cat projects in a few days.
regards
Mike
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Mon, Apr 14, 2014 9:14 AM
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