AdamP 0 Posted March 7, 2008 I've been offered a 106 Rallye S1 head, thats one of a 1300 TU. Firstly... what are the differences between it and a 205 XS head? Plus what's the cam like and what will i need to do to get it on a TU3S block? Adam Share this post Link to post Share on other sites
Sandy 191 Posted March 7, 2008 It's a better head (sensible valve sizes and nice inlet ports, exhaust ports a tad small, and a pretty good cam. But the bigger combustion chamber means that you need to review the pistons in the TU3S bottom end to get proper compression ratio and the inlet port spacing is different (significantly), so you'll be iunto different induction too. It's the way forward, but only really as part of a holistic engine build really. Share this post Link to post Share on other sites
Rippthrough 98 Posted March 7, 2008 So what you should do is buy then swap it for my reworked Tu3S head Share this post Link to post Share on other sites
AdamP 0 Posted March 7, 2008 (edited) It's a better head (sensible valve sizes and nice inlet ports, exhaust ports a tad small, and a pretty good cam. But the bigger combustion chamber means that you need to review the pistons in the TU3S bottom end to get proper compression ratio and the inlet port spacing is different (significantly), so you'll be iunto different induction too. It's the way forward, but only really as part of a holistic engine build really. Well as I'm planning a full engine build with my spare XS engine with 40mm mikuni carbs that shouldn't be too much of a problem. Is it a case of skimming head/block or is it definately a piston change needed? Adam Edited March 7, 2008 by AdamP Share this post Link to post Share on other sites
Sandy 191 Posted March 8, 2008 Flat topped or ideally domed pistons are needed. Decking down the 106 1.3 Rallye pistons is the popular way. Share this post Link to post Share on other sites
AdamP 0 Posted March 8, 2008 Are there any more 'off the shelf' options? The chap who's selling it had been running a 106 rallye head on a 1.4 205 Rallye block before... are we look at big power losses with the lower compression? Share this post Link to post Share on other sites
Sandy 191 Posted March 9, 2008 I've done it on bodies, with a skim to try and raise CR, but the engine was limp compared to what it should be with decent CR. Don't do it for the sake of it, you'll be wasting time and money. If you fancy building an engine from the ground up, then it's the better head to use by far (compared to TU3S head), but otherwise no. Share this post Link to post Share on other sites
