Lark ring gap

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Cadillac-ack-ack

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Got all my needed part (we'll see about that) and just today got a little bit of assembly work started. New pistons on perfect original pins with new wristpin bearings. Got to checking the new piston ring's gaps and could not get them into the cylinder. I'm not sure how much would have to filed from the ends to get them in even if butted. The NOS P/N is correct but the ends actually overlap when fitting into bore is attempted. I really think there would not be enough notch left for the pin location if I filed enough for correct gap. Are they oversize rings I wonder?
 
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racerone

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Something is wrong.----Do new pistons fit into the bores ?----Part # of the new rings ?
 
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Cadillac-ack-ack

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racerone said:
Something is wrong.----Do new pistons fit into the bores ?----Part # of the new rings ?
Click to expand...

Yes, new pistons, P/N - 378695, are perfect. Rings, P/N - 378433, are supposed to be correct. The company I'm dealing with lists original rings, P/N - 0378430, as unavailable. That number supersedes to NEW, P/N 0380108. For quite a lot less money, they offer NOS, P-N 0378433. This last P/N, the ones that are too big are supposed to supersede the original's.
 
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Cadillac-ack-ack

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Confirmed that OEM rings, P/N 378433 are indeed oversize. Have some NOS, P/N 0378430 on the way.

By the way, in an earlier thread I questioned whether or not it was necessary to replace all the needle bearings even they they looked real good. Many of you said "yes" so I have. The only ones installed so far are for the wristpins but the fit is better with noticeably less side rock in the piston to rod. Good call!
 
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racerone

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???----0.05 mm is not very much gap at all.-----Surely a misprint here.
 
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Cadillac-ack-ack

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Book says .007" - .017" (.18 mm - .43 mm).
Quick question on gaskets though. I know head gaskets get no dressing. Does that stand for all the others? I didn't see any evidence of any cement upon disassembly.
 
Bosunsmate

Bosunsmate

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i dress the ones where the faces are not looking very good, which ends up being the majority on older motors.
Choose your crankcase sealant wisely and put it on liberally enough
 
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Cadillac-ack-ack

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Just for S's & G's, I received the NOS std rings and they measured up with a nice .010 gap. Don't really know if anyone is really interested in this build but I like to think up-dating on projects is appreciated by folks that have contributed to past questions. Block is back together, new pistons and rings installed, crank with new bearings sitting pretty in the case half. Nicely tightened up I must say. Got some 518 today and next spare time available will avail my self to bolting the half's together. I've been reading a lot of threads in this Johnson/Evinrude forum and it seems as though a lot of posters ask for advice and then just go away. I may bore you'll to death sometimes but I intend to keep anyone who's interested appraised of my admittedly slow progress, - Pete
 
Texas Prowler

Texas Prowler

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It would be interesting to hear how this turns out. Hope it runs good. Did you hone the cylinder?
 
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David Young

David Young

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I read almost every Thread and Post on this Forum. I don't know very much about boat motors but have learned a little. I'll be reading on what you do :)
 
C

Cadillac-ack-ack

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Texas Prowler said:
It would be interesting to hear how this turns out. Hope it runs good. Did you hone the cylinder?
Click to expand...

I did hone the cylinders. Established a nice cross-hatch. There is some light scoring that is still present but the cylinders measured up fine and I felt it was better to leave the marks rather than keep honing and risk a sloppy piston fit in over honed bores. - Pete
 
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