bren_1.3 1 Posted March 25, 2006 according to haynes peugeot employed a numbering and lettering system to allow for manufacturing tolerances; and i quote "pistons and liners are seperated into three size groups. the size group of each piston is indicated by a letter (A, B or C) stamped onto its crown, and the size group of each liner is indicated by a series of 1 to 3 notches on the upper lip of the liner." (it is permissible that the letters rather than notches are cut into the liner lip) so mixing and matching my TU24 and my TU3S;we discover the TU24 has two 'B' group pistons and two 'c' group pistons. While the TU3S has four 'B' group pistons. there are no visible notches on the TU3S liners nor can i see any letters stamped onto them! i assume that they are all group 'B' liners??? to quote further from the haynes manual "ensure that each piston and its respective liner are both of the same size. it is permissible to have different size group piston and liner assemblies fitted to the same engine, but never fit a piston of one size group to a liner in a different size group." as im banking on using the TU24 pistons in the TU3S block, i now have a problem as i have two 'C' group TU24 pistons trying to fit two 'B' group liners. ive run a search and nothing hs come up.. i typed in "liners" "liner" and "liner selection" without any reference to what im now typing. so i guess if anyone has any ideas on the matter than ill be hunting for a couple of 'C' group TU3S liners! bummer..... i doubt peugeot will be willing to sell me liners on thier own either! Share this post Link to post Share on other sites
trogboy 17 Posted March 25, 2006 Hey Bren Just so we all know what tolerances we are talking about: Cylinder bore diameter: Size group B 75.010 to 75.020mm Size group C 75.020 to 75.030mm Piston diameter: Size group B 74.970 to 74.980mm Size group C 74.980 to 74.990mm The fact that the pistons are size group C means that they are slightly too big for the size group B liners. The pistons are all used now thought aren't they so perhaps there may be some wear around their circumference? have you tried measuring the current diameter of the pistons to see what size they are now? Similarly are the liners worn at all? Do they still perform to size group B tolerances Looking at the figures you can see that as a minimum the bores only have to be 0.03mm larger than the pistons and if your have a bit of wear all round then they may well be. If the pistons and the liners are all within their original tolerances perhaps there is the potential for getting the pistons turned down a smidgen to fit with in the B tolerences? I don't know the answers - just throwing some ideas into the mix. Hopefully someone who does will be able to help you out further. Share this post Link to post Share on other sites
christopher 5 1 Cars Posted March 25, 2006 Bren are these the mahle pistons you are fitting or standard TU24 Items? Share this post Link to post Share on other sites
bren_1.3 1 Posted March 25, 2006 (edited) trogboy, the TU24 pistons have been used although i dont know how many miles they've done, i have new piston rings for them, and there's no indications of severe wear on them. similarly the TU3S pistons are of unknown mileage, and again theres no signs of severe wear on them. the TU3S liners are in need of rehoning so maybe they could be bored out to 'C' group specification??? i think that idea needs to be cleared with the person rehoning the liners, but i cant see any reason why they couldn't be bored out to 'C' group specification. your only talking .020mm max to be taken out of them! christopher im talking about standard TU24 pistons. the mahle pistons i have very little info on. i have no piston group markings on them, nor do i have any piston rings for them, the standard TU24 oil ring fits fine but the two rings on compression are slightly thinner than standard items. EDIT: the mahle pistons have the numbers 74,94 stamped into them on the outer edge of the piston where the gudgeon pin slots through. so i guess that would be undersize of even 'A' class pistons!!?? there are also the numbers 89664 and the numbers 701/1, but ive no idea what they mean. ooo btw trogboy, hows your hybrid engine coming along?? Edited March 25, 2006 by brens_1.9_wide_arch Share this post Link to post Share on other sites
