Streetsweeper21
15+ Year Contributor
- 140
- 1
- Jan 11, 2006
-
Atlana,
Georgia
Searched tons of threads but cant seem to find answers. I want know what is the Oem 1g Piston ring gaps for stock bore? Thanks.
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STD size pistons dont need to be gapped because the rings are already pre-gapped
STD size pistons dont need to be gapped because the rings are already pre-gapped
Granted it's been a while since I've done a stock rebuild, I've always had to cut OEM piston rings. Sometimes I get lucky and don't have to cut much if any at all but more times then not, I cut them. Factory numbers are in the FSM or even a Haynes manual.
From what I am reading always it is always still good to check....
THANKS Alot and that for 6 bolt correct?Thats true, good technique
From the Mitsu Service Guide
Install the piston ring into the cylinder bore. Force it down
with a piston, its crown being in contact with the ring, to
correctly position it at right angles to the cylinder wall.
Then, measure the end gap with a feeler gauge.
If the ring gap is excessive, replace the piston ring.
Standard value:
No. 1 0.25-0.40 mm (.0098-.0157 in.)
No.2 0.20-0.35 mm (.0079-.0138 in.)
Oil 0.20-0.70 mm (.0079-.0276 in.)
Limit:
No. 1, No.2 0.8 mm (.031 in.)
Oil 1.0 mm (.039 in.)
Standard value:
No. 1 0.25-0.40 mm (.0098-.0157 in.)
No.2 0.20-0.35 mm (.0079-.0138 in.)
Oil 0.20-0.70 mm (.0079-.0276 in.)
Limit:
No. 1, No.2 0.8 mm (.031 in.)
Oil 1.0 mm (.039 in.)
your still in limit, even that your using STD sizes the block has wear, and pluse hone..
for every .001 you open the bore you will gain Pi (3.141)
you said you have appox .025 on #1 Ring and .016 on the #2 ring
you are still within the limit specs so your fine..
we will guess that you have had the bore honed and it had a wear valve of .004
so with .004 x 3.141=.012564 add to your stock ring gap
so if you had the max new ring gap of .0157 + .01256 = .0282 ring gap now
with a turbo engine, it will not hurt to run a wider ring gap, yes you may smoke a lil, but if you run lean, it will keep the rings from butting and braking the ring lands
most of the wear will be in the first inch of the bore, that is where the rings push out the most on the power stroke.
the gap readings you are getting just show how the bore is tapered...
get the block mic'ed...and see what the real bore dia is... you may have to have the block bored and go with new rings and pistons.
normally #1 ring has the larger gap..
are you sure the ring gap on #2 is .020 and not .002 sort of hard to have the #2 gap get larger in the bore further down .. where #1 gets smaller further down
look at the chart DSM-pwr posted... in the first set of values, the #2 ring dose have the smaller ring gap....
No. 1 0.25-0.40 mm (.0098-.0157 in.)
No.2 0.20-0.35 mm (.0079-.0138 in.)
Oil 0.20-0.70 mm (.0079-.0276 in.)
if you get .002 anywhere in the bore .. that is way to tight and you will start braking ring lands..
find where you get the smallest gap, bottom of the bore.. and use that spot to gap your rings
or have the block bored to get the taper out of the cylinder
if you gap at the bottom of the bore, use the gap.. #1 Ring .010 and the #2 ring .008 and yes they will be wide gapped at the top of the block
And you having a thunderbird as your main pic scares me..J.k But yaThe 2nd ring gap being bigger is for ring flutter. I've got .020 and .022 and it doesn't smoke or burn oil at all.
Some blowby at idle but nothing out of the usual.
MitchellOnDemand is an info site that shops pay for, like AllData. Alldata is an autozone company and MitchellOnDemand is own and operated by SnapOn. It supplies shops and DIY(separate site i think for DIY) with factory service, maintenance, and repair information, guides, specs, and procedures. Any specifications on site are pulled straight from factory service manualsI've never heard of MitchellOnDemand but I don't trust any numbers (for a OE rebuild) unless they come from the Mitsubishi Factory Service Manual (FSM).
From the actual '97-99 MITSUBISHI FSM...
Standard value:Not arguing with you biglady, just posting the actual OE SPEC numbers in here from the FSM. Piston ring clearances should be in the SPEC of the piston manufacturer or whatever the engine builder recommends outside of OE.No.1 ring 0.25-0.35 mm (.0098-.0138 in)Limit:
No.2 ring 0.40-0.55 mm (.0157-.0217 in)
Oil ring 0.10-0.40 mm (.0039-.0157 in)No.1, No.2 ring 0.8 mm (.031 in)
Oil ring 1.0 mm (.039 in)
This is correct and is a good way to minimize blow-by. I appreciate the info and input. I only flagged for incorrect OE specs. Occasionally when surfing through the web I come across these old posts that contain incorrect info and I just like to flag for correctional purposes. The info you posted about aftermarket piston ring gap added good info.The second ring is not always larger. I have been using larger ring gaps on the first rings literally for years. I had a very long conversation with Nick Arias about this over the phone. He gave me a game plan and asked me to stick to it and for over 10 years it has not let me down even using the opposite train of thought on 800-1000hp 4g63's. Combustion stays where it is suppose to and we do not have blow by where and when we don't want it.