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Hello! Sorry if this is not the right place but I didn't think it approperiate to post in the engine maintainance and upgrades forum as I don't have the physical engine (yet). Anyway this became longer than I had imagined. For clarification I will be mainly speaking of 4 different engines by their short engine codes as I can't be bothered to type out the whole engine name. XU10J4R RFV 99kW fitted in the 406, xantia and 806 etc XU10J4RS RFS 122kW fitted in Xara VTS, 306GTI6 etc XU10J4D RFT 110 kW fitted in 306 s16, 405 MI16 etc XU10J4L RFY 112 kW fitted in 405MI16 and 306s16 etc (according to wikipedia, lol) As the RFT, RFS and RFY engines are quite rare to find by themselves or mounted in cars that are affordable/not worth keept running (where I live) I'm looking at a RFV engine upgrade for my 405 (that you may have seen). However, I've spoken with another user briefly about the engine a month or so ago and he said getting performance cams to work in the engine is basically not possible. I don't know specifically which cams he had tried, I have asked but he hasn't responded From what I've gathered from the threads I've read the engines have; -different compression ratios due to a different size dish in the pistons and even different pistons, -slightly different port sizes, -different intake manifold designs, -some variations of (at least) the RFV doesn't have oil squirters -floating pins vs presfitted pins -double valve springs in e.g. the RFS -same conrod length on RFV and RFS but different to RFT (and RFY?) I'm then wondering, since they have so similar architecture could one not just fit stock RFS, RFT or RFY cams in the RFV engine and get somewhat similar performance? I get that clearance might be an issue but since the engines ought to be so similar (in my mind) I have a hard time imagining why. To my plebian brain fitting a slightly thicker gasket or removing 1mm from the pistons ought to fix this, or? if it is of interest to you I'm basically looking to take the RFV engine and -make a custom intake manifold with larger and straight pipes, -mount a 70 ish mm throttle body and 200-300ccm injectors from a 2,5L volvo 960, -put a sport catalytic converter on it, stick with the original 2 inch exhaust or maybe upgrade the pipes to 2,5 inches but keep the mufflers as I'm a cheap. (A lot of NA volvo tuners make their exhausts 2,5 inches since 3 is too big and doesn't create enough back pressure when going just over 200bhp.) - MAXXECU street or sport depending on what my aquaintance has a spare of, he is the local reseller of the ecu system. I'll answer some questions/comments I fear might pop up, at the risk of sounding arrogant. Sorry. Why am I manufacturing parts when e.g. gti6 manifolds are available? Well, I'm a cheap and we have the technology and materials to make manifolds. "this is so expensive for little gain" well, most of the parts I already have and the ECU is the most expensive part which can retroactively be modified to fit another project. "Just buy a used X engine and.. " No. P.s. Is the amount of ticking on my currently fitted XU10J2C (RFX) engine too much, if so what might be the cause? I've tried with starter spray all over the intake manifold but no difference so it's not leaking there. I'd much appreciate your thoughts/feedback/comments on anything and everything. Thank you for reading!