Philip Blank Posted February 28, 2005 Share Posted February 28, 2005 can anyone advise on the optimum size of exhaust valves on a mildly tuned 2500, bored to approx 2680? std 2500 head has small (29.3?) valves but my tuned 2000 engine has the 32mm triumphtune jobs. i realise that the smaller valve assisted the torque on the 2500, and i do want torque, but on the other hand i also want it to rev sweetly to say 6k on a regular basis. (i shouldn't have the need to do the 7k of my 2000). i'm being told not to use the 32mm valve and wondered what you racers out there think. the engine will have basically a TR5 cam, HS6s with K & N, 6:2:1 exhaust, 9.5 comp, very slightly ported head, balanced with lightened flywheel, no engine fan, lumenition. i primarily want the car for rallying, not track work, tho it will get a bit of both. if it was for track work only we'd clearly want the bigger valve for constant high speed pull. will be fitted with 3.7 diff. any thoughts out there? i'd bet good money that mr thompson in particular will have some ideas. regards, phil blank. Link to comment Share on other sites More sharing options...
Deleted User Posted February 28, 2005 Share Posted February 28, 2005 Have a look at the valves Chris Witor is doing,think he does a 31mm? for a mark 1 which allows 20% more flow blah blah etc etc! cant remember but have a look at www.chriswitor.com Link to comment Share on other sites More sharing options...
Deleted User Posted February 28, 2005 Share Posted February 28, 2005 http://www.chriswitor.com/Chris_Witor_Price_List.pdflooks like a 30.3 mm ex valve is the one he does Link to comment Share on other sites More sharing options...
Deleted User Posted February 28, 2005 Share Posted February 28, 2005 If you are building a new head... use 2500S head (219016 part no) skimmed by about 80 thou.Use biggest inlets you can (approx 38mm) Use 30 or 31mm exhaust valves.. 32mm wastes real estate for inlets and contributes very little to bhpThe key to HP and torque is cylinder filling , the exhaust gets sucked/ blown out The inlet ports are slightly too big for even the biggest inlet valves so use the availible space for inlet area!!!Triumph fitted smaller exhaust valves on later cars for reliability Link to comment Share on other sites More sharing options...
Philip Blank Posted March 3, 2005 Author Share Posted March 3, 2005 thanks to both of you guys, most appreciated. i'm right at the stage where my engineer is about to install valves, so most well timed. andy, i was advised by chris witor to get that head as well, but i don't have one handy. i have late 2500tc heads - will i be missing a lot in using one of them? i'm not after the ultimate performance, mostly mid range power. i already had 38mm inlet valves in my 2000 head which i'll use here. i was going to go for about 31.5 exhaust but from what you say i should be going smaller. my engineer, who admittedly is more of a ford man than a trump guy, was a bit diffident about going as small as 31 but sounds like i should be. thanks again, phil. (and yes, i owe you even more beers now)! Link to comment Share on other sites More sharing options...
Philip Blank Posted March 3, 2005 Author Share Posted March 3, 2005 hi again, have just looked at the specs on chris' site. i see his performance exhaust valve is shown as 31.25 so we're not too far out maybe. however, i guess there is an advantage in keeping the diameter down if you don't need it, given the lack of land between inlet and exhaust. Link to comment Share on other sites More sharing options...
Deleted User Posted March 3, 2005 Share Posted March 3, 2005 I really don't think 0.5mm makes much difference to the scheme of things... so go with the easiest to obtain... The 2500TC head should be the same as 2500S... check the number stamped at the front above ports for 1 and 2The latest Oz heads had a drilling for EGR which can be blanked off (219021 I think)I will be in Auckland from Sunday for a week or so... Link to comment Share on other sites More sharing options...
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