Piston liner measurements seem wrong?

[ssevy]

I've got another thread started describing the rebuild I am doing. I'm at the point of installing the liners and pistons, and thought I would run this by you guys first. My machinist measured everything and here is what he discovered.
The measurements for the pistons and liners are interesting:

                         #1                 #2                   #3
Old Pistons     2.9875            2.9855             2.9855

New Pistons    2.9905            2.9906             2.9908

New Liners     2.994               2.997              2.993

According to the part numbers, liner #2 and piston #2 are supposed to be different from #1 and #3, which are the same. All 3 new liners have a "B" stamped on the top, which the manual says denotes the special liner for cylinder #2. The liners for #1 and #3 are the same part #, and both have 27-11-10 B stamped on top of the liner. Liner #2 has 02-11-15 B stamped on it. All 3 new pistons say ART 510 on them from the casting, and #2 has a green mark on top which #1 and #3 do not. Given the difference in markings, I was looking for similar measurements for #1 and #3, and something different for #2.
I'm not sure how to even chase this down with Triumph, as I tried to call their national headquarters just to get a list of what was in the full gasket set, and the guy they connected me with was utterly rude and not helpful. Dealer can't really answer this, as they rely on Triumph to send them the correct stuff, which they then send on to me.

Anyone have any experience with this?

[Mustang]

were the liners checked with dial bore gauge that reads to -0001 at minimum..................
with accuracy to match ?

if not your pissin in the wind .

as far as the numbers go
the old pistons probably shrunk from age and use
( think lots of heat and cold cycles)

and the new liners are supposed to be like that bigger on #2 by a few thousands
the center cylinder runs hotter

[ssevy]

Yes they were measured with precision. The machinist knows his stuff. Good to go then?

[threepot]

The middle liner does seem to have more clearance. Looks OK?
Triumph do need a kick up the ass! the way they deal with owners enquiries!! When I phoned to enquire why the Super3 inlet valves were different,the guy obviously didn't know . But instead of trying to find out,or making enquiries his end,he just waffled on! Not even two main dealers could answer why?

[Mustang]

the specs for pistons are
measured at 90 degrees from wrist pins
#1 and #3 = 75.98-75.96 mm (2.9913 - 2.9905 inch)
#2 is 75.97 mm - 75.96  (2.9909 - 2.9905)

#2 should be average 1/2 thou smaller (.0005)

the liners should be
#1 & #3 = 76.05 - 76.03 mm   (2.9940- 2.9933 inc h )
#2 is 76.05 - 76.04 (2.9940 - 2.9937)


so #2 hole needs to be bigger by .0005 and the piston is smaller by .0005for a total of .001

these are the service specs btw

I'd remeasure those liners cuz 2 are out of spec

me myself I would use a sunnen gauge .................or at the minumum a dial bore gauge that can read to four places





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[ssevy]

The machinist used a dial bore gauge, not sure of the brand. I measured the end gap clearance for the rings, and they all measured in range, so I went ahead and finished putting the engine back together.
Didn't realize Triumph requires new engine mount bolts and nuts, so just ordered those and will install once they arrive. Fingers and eyes are both crossed :icon_wink: