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Post by elsiefan on Jan 20, 2023 12:54:53 GMT 1
Hi all, I'm looking for some thoughts before proceeding any further with my rebuild. I ordered up some new pistons and on opening the boxes, it appears they are different (see picture) Same boxes - Mitaka, Made in Japan - Same size - 64.5mm - but inside, one piston has a black coating on it and one doesn't, and the rings are from different manufacturers. Does/will this make any difference when I fit them? Can I just mod the 'tang' for the LC and fit them? Or should I contact the vendor and request a replacement one to match, and return the 'odd' one? Thanks in advance  IMG20230120111813 |
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Post by oldelsieboy on Jan 20, 2023 13:32:33 GMT 1
Send them back and ask for LC pistons not YPVS.
OEB
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Post by Chewie01 on Jan 20, 2023 13:33:16 GMT 1
Regardless of them being compatible or not, I would want to be fitting matching pistons for a rebuild.
I wonder if they are the same weight?
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Post by elsiefan on Jan 20, 2023 13:40:21 GMT 1
Send them back and ask for LC pistons not YPVS. OEB I did order PV pistons, as a try out for the larger intake windows compared the the LC ones and was going to remove the 'tang' before fitting. My question was around them looking somewhat different and whether this was an issue or not. |
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Post by elsiefan on Jan 20, 2023 13:41:50 GMT 1
Regardless of them being compatible or not, I would want to be fitting matching pistons for a rebuild. I wonder if they are the same weight? I don't have any scales that accurate, only bathroom ones, would you know anyone who might have scales that accurate? 😉 |
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Post by Chewie01 on Jan 20, 2023 13:46:42 GMT 1
Regardless of them being compatible or not, I would want to be fitting matching pistons for a rebuild. I wonder if they are the same weight? I don't have any scales that accurate, only bathroom ones, would you know anyone who might have scales that accurate? 😉 I wouldn't possibly know anyone who sells things that would need an accurate scale  |
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Post by Robbieben on Jan 20, 2023 13:47:02 GMT 1
Send them back and swap for the correct piston, have a word with the supplier they may not even know they are sending out mixed pistons.
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Post by Norbo on Jan 20, 2023 14:36:04 GMT 1
They would make no difference the black coating comes of after a few hundred miles any way if they are the same size it does not matter both good pistons same make by the looks of it just some have black and some do not the rings again both jap makes both good . People fit pistons 1 or 2 sizers bigger in 1 side to the other will no ill effect theys will be the same weight i would fit them and dont worry about it .
They are YPVS pistons so you will have you remove the small tab at the bottom on the skirt under the windows ,.
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Post by elsiefan on Jan 20, 2023 14:57:16 GMT 1
They would make no difference the black coating comes of after a few hundred miles any way if they are the same size it does not matter both good pistons same make by the looks of it just some have black and some do not the rings again both jap makes both good . People fit pistons 1 or 2 sizers bigger in 1 side to the other will no ill effect theys will be the same weight i would fit them and dont worry about it . They are YPVS pistons so you will have you remove the small tab at the bottom on the skirt under the windows ,. Thanks for clarifying that for me Norbo 👍 The engine was built by Dave W and originally came with PV pistons in, so I wanted to do a like for like. |
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Post by chrisg on Jan 20, 2023 15:21:05 GMT 1
Heads up: jewlers have accurate scales.
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Post by reedpete on Jan 20, 2023 17:27:39 GMT 1
They would make no difference the black coating comes of after a few hundred miles any way if they are the same size it does not matter both good pistons same make by the looks of it just some have black and some do not the rings again both jap makes both good . People fit pistons 1 or 2 sizers bigger in 1 side to the other will no ill effect theys will be the same weight i would fit them and dont worry about it . They are YPVS pistons so you will have you remove the small tab at the bottom on the skirt under the windows ,. It might not matter ‘that much’ … but to buy two identical pistons new, from the same supplier and get ones from a different batch or different subcontractors is surely… ‘not preferred’… doesn’t give you a warm feeling that whoever sent them out had their finger on the pulse.. |
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Post by oldelsieboy on Jan 20, 2023 17:37:21 GMT 1
Send them back and ask for LC pistons not YPVS. OEB I did order PV pistons, as a try out for the larger intake windows compared the the LC ones and was going to remove the 'tang' before fitting. Correct me if I'm wrong but surely for the larger piston windows to have any effect you'd also need the larger YPVS reed valves and inlet rubbers fitted. OEB |
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Post by dougw on Jan 20, 2023 17:44:29 GMT 1
In the 80s and 90s ran Power valve pistons in my various 4L0s with the "Tang" in place, that never gave me or any of my mates any issues , road and race.
While others appear to have had problems with the "Tang" catching, I`m wondering how much wear has to present to cause the problem ?
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Post by dougw on Jan 20, 2023 17:49:38 GMT 1
I did order PV pistons, as a try out for the larger intake windows compared the the LC ones and was going to remove the 'tang' before fitting. Correct me if I'm wrong but surely for the larger piston windows to have any effect you'd also need the larger YPVS reed valves and inlet rubbers fitted. OEB "Proddie" tuned 4L0s had the backs of the pistons removed round the windows, and ran the standard rubbers (mostly as the PV ones where no, strictly allowed, and the rubbers and reed blocks where modified too) |
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Post by dougw on Jan 20, 2023 17:49:58 GMT 1
I did order PV pistons, as a try out for the larger intake windows compared the the LC ones and was going to remove the 'tang' before fitting. Correct me if I'm wrong but surely for the larger piston windows to have any effect you'd also need the larger YPVS reed valves and inlet rubbers fitted. OEB "Proddie" tuned 4L0s had the backs of the pistons removed round the windows, and ran the standard rubbers (mostly as the PV ones where no, strictly allowed, and the rubbers and reed blocks where modified too) |
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Post by Gitram on Jan 20, 2023 18:02:31 GMT 1
Heads up: jewlers have accurate scales. Bother.. I was going to say that.. lol marti |
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Post by elsiefan on Jan 20, 2023 18:02:31 GMT 1
I did order PV pistons, as a try out for the larger intake windows compared the the LC ones and was going to remove the 'tang' before fitting. Correct me if I'm wrong but surely for the larger piston windows to have any effect you'd also need the larger YPVS reed valves and inlet rubbers fitted. OEB You could be right or wrong, I wouldn't know, though as I mentioned "The engine was built by Dave W and originally came with PV pistons in, so I wanted to do a like for like." It's a long story that has been played out in parts on here, so I won't go any further and bore everyone. |
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Post by elsiefan on Jan 20, 2023 18:05:14 GMT 1
In the 80s and 90s ran Power valve pistons in my various 4L0s with the "Tang" in place, that never gave me or any of my mates any issues , road and race. While others appear to have had problems with the "Tang" catching, I`m wondering how much wear has to present to cause the problem ? The engine came from Dave W with PV pistons and no 'tang' so that was what I wanted to put it back to. I've been practising material removal on the old piston skirts, before modding and fitting these ones. |
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Post by elsiefan on Jan 20, 2023 18:10:05 GMT 1
They would make no difference the black coating comes of after a few hundred miles any way if they are the same size it does not matter both good pistons same make by the looks of it just some have black and some do not the rings again both jap makes both good . People fit pistons 1 or 2 sizers bigger in 1 side to the other will no ill effect theys will be the same weight i would fit them and dont worry about it . They are YPVS pistons so you will have you remove the small tab at the bottom on the skirt under the windows ,. It might not matter ‘that much’ … but to buy two identical pistons new, from the same supplier and get ones from a different batch or different subcontractors is surely… ‘not preferred’… doesn’t give you a warm feeling that whoever sent them out had their finger on the pulse.. Hi again 😁 and thanks for your help earlier 👍 I understand your comment, but placing the two boxes unopened, side by side, there is zero difference between them and you would never know, so not down to the vendor. More likely a change somewhere in the Mitaka supply chain. A bit like wallpaper I suppose, made in batches with slight cosmetic variations. |
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Post by Tobyjugs on Jan 20, 2023 19:21:06 GMT 1
I did order PV pistons, as a try out for the larger intake windows compared the the LC ones and was going to remove the 'tang' before fitting. Correct me if I'm wrong but surely for the larger piston windows to have any effect you'd also need the larger YPVS reed valves and inlet rubbers fitted. OEB I will do my best  It's all to do with the movement of your fuel/air mixture. Off the top of my head i think the windows should match the inlet port at 80 degrees after BDC as there is movent in piston causing flow in the fual/air mixture. So it's not only size. |
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Post by jon on Jan 21, 2023 10:05:00 GMT 1
To be honest I would have thought there was negligible difference in performance using a YPVS piston as opposed to an LC? We only did it for years because a dedicated LC piston was not available.
The old tang debate roundabout again. I’m in the remove it camp. Why not?
As for the OP question, I think it’s more about the niggling feeling if those pistons were fitted rather than the fact I doubt any real world difference would be seen.
I do question though why not just inform the seller you want a matched pair?
Jon
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Post by muttsnuts on Jan 21, 2023 19:30:49 GMT 1
YPVS pistons would have been fitted because for a good while you couldn't get LC pistons, but that has changed now and they are readily available. If I can get hold of LC pistons I always fit them, only fit YPVS ones when I can't, clearly removing the tang always
Weight wise, nowt in it (yes I do have scales accurate enough!), both make of rings are fine, both are Jap made, the black coating as mentioned is a friction reduction coating, wears off after a few hundred miles, LC pistons don't come with it on
As regards the windows in the pistons, they don't make much difference unless you spend time matching the port timing, open up the inlets and improve the reed blocks on the LC
I've just done some rebores today on some LC barrels, some had YPVS pistons in when they came, but I've fitted the proper LC pistons now since I can get them
HTH
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Post by steeley on Jan 23, 2023 7:46:29 GMT 1
Heads up: jewlers have accurate scales. So do car body repair paint shops . |
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Post by shaunthe2nd on Jan 23, 2023 8:30:32 GMT 1
Heads up: jewlers have accurate scales. So do car body repair paint shops . ... and drug dealers.... |
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Dave B
Drag-strip hero
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Post by Dave B on Jan 23, 2023 10:31:12 GMT 1
Heads up: jewlers have accurate scales. And so do people who do baking. Digital kitchen scales are accurate to 1 gramme for comparisons, although the absolute figures may not be spot on . |
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