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#1
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Engine info - something new I learned
Maybe you folks all knew this...I didn't.
Seems Subaru does not necessarily install the same sized pistons from the factory in any one given engine. Now maybe I'm wrong, but I think this is a pretty unusual practice. Does this work because of the inherent balance of the boxer engine? Anyway, I post this as a caution for anyone thinking of a home rebuild...also might want to provide the info to whatever rebuilder you use if having the job done professionally. Seems like it would be of interest to those balancing/blueprinting as well. So for you shade tree mechanics, watch which cylinder the piston came from...my reference is: http://www.endwrench.com/pdf/engine/...esInfoSp00.pdf |
#3
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So ever cylinder has a diffretn size piston? I never heard of this before, who told you this?
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#4
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#5
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This is clearly stated in the FSM. The pistons are given a grade letter and then the letter is stamped on top of the engine block for each piston. The clearance between the piston and cylinder is very tight on the SVX. That is why the piston has to be matched to the bore. I think it also a good part of the reason as to why the engine is so quite.
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May your transmission live forever. SuperbVehicleXtraordinary Proud sponsor of a 1992 SVX. |
#6
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Subaru has been doing this for a while now on all its models. The "grade" of piston and its location in the block is stamped on the top front of the block. You can not mix and match.
Dave |
#7
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Probably a major reason why the engines last so long -- looks like we get a blueprinted engine from the factory!
-Bill
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Retired NASA Rocket Scientist Most famous NASA "Child" - OSIRIS-REx delivered samples from asteroid BENNU to Earth in Sept. 2023 Center Network Member #989 '92 Fully caged, 5 speed, waiting for its fully built EG33 '92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension '92(?) Laguna, 6 spd and other stuff (still at OT's place) My Locker |
#8
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Down to none |
#9
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manufacturing tollerances.
The bore and piston sizes vary with manufacturing tollerances. Most engine builders selectively fit pistons to bores. Some selective fit crankshaft, slipper bearings also.
Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#10
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Collin 1995 L AWD Locker 1987 Porsche 944 turbo 80k miles. MBC + Chips. Relatively Stock |
#11
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Now I got the FSM here in front of me. The clearance is .0004 to .0012 inches diametrical.
Bore size Piston Grade/ Cylinder bore / piston sizes follows: A 3.8151 to 3.8155, 3.8144 to 3.8148 B 3.8148 to 3.8151, 3.8140 to 3.8144 C 3.8144 to 3.8148, 3.8136 to 3.8140 I wonder if they did this on the piston slapping 2.5 engine?
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May your transmission live forever. SuperbVehicleXtraordinary Proud sponsor of a 1992 SVX. |
#12
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Collin 1995 L AWD Locker 1987 Porsche 944 turbo 80k miles. MBC + Chips. Relatively Stock |
#13
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Re: manufacturing tollerances.
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Are you saying most auto/engine builders do this today, i.e., Toyota, or is this something modern, and good, rebuilders do? |
#14
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On grade B you are looking at a .0004 thru .0011 tolerance On grade C you are looking at a .0004 thru .0012 tolerance those are pretty tight to hold on a cars engine. That is very impressive considering that a human hair on average is .0035 thick. No wounder the EG33 runs so smooth. Steve
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92 SVX AWD 130,000 w/ rebuilt SVX 4.11 97 Audi A4 1.8T (Daily Driver) 03 Ford Expedition(hers) SVXepidia SVX information warehouse Are you in? My Old Locker A 4.11 Founding Father "Tranny #6" I really need a manual Reading IX [SIGPIC][/SIGPIC] Ya I was there
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#15
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SVX-FF, what's with you and the cicadas?
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