trummy2500 Posted September 30, 2010 Share Posted September 30, 2010 Right guys (and gals), my first post on this Forum - There will be many more to come! - so thought I would give you something technical to chew over......I am rebuilding a MK2 2500 Saloon for track days, autotesting & hillclimbing events. I have a low milage 2500 bottom end out of another MK2 Saloon (year unknown) & have been offered a semi race spec cylinder head but I have no idea if it will fit the engine I have. All the details I have been given are "Straight six Triumph gas flowed cylinder head, year or model unknown. Casting number 516816"The head is 150 miles away from me in Watford so don't fancy a road trip to find it won't go on my MK2 2500 bottom end .... Can anyone tell me what Triumph this head is off & if it will bolt onto the engine I have? I am very ready to be corrected on this as I am new to Triumph engines but are there two different head bolt sizes too that could cause a problem?I know of a few people that have interchanged 2500/2000 heads & blocks in Hillclimbing so in therory this head MIGHT fit my block but they keep the details close to their chests so no joy getting the info I need out of them! Anyone help? Link to comment Share on other sites More sharing options...
Freek76 Posted September 30, 2010 Share Posted September 30, 2010 Head # (stamped) 516816Height nominal (inches) 3.400Applications Mk1 PI & Mk2 PI to MG50000. 2000 low compression 7:1. TR5/6 to CR 2845Exhaust valve (mm) 32.0Push rod length (inches) 8 1/8 Link to comment Share on other sites More sharing options...
trummy2500 Posted September 30, 2010 Author Share Posted September 30, 2010 Freek76 wrote:Head # (stamped) 516816Height nominal (inches) 3.400Applications Mk1 PI & Mk2 PI to MG50000. 2000 low compression 7:1. TR5/6 to CR 2845Exhaust valve (mm) 32.0Push rod length (inches) 8 1/8 Thanks for the info - Just done a bit of research on the Internet and found the head also fits some early TR6's too with a 9.5:1CR.Fitting the head should in theory be Ok for my bottom end then. I would probably skim the head before fitting anyway to make sure I have a flat mating surface.Has anyone fitted a PI head to a 'standard' carbed MK2 2500 bottom end and got any noticeable power gains? Any reasons why it should or shouldn't?For the rest of the engine, I'm not going mad as I want it to be a reliable fun car rather than expensive and breaking all the time - I was going to fit a mild road/ race cam for torque rather than top end, US Spec TR6 Inlet manifold and HS6 SU's. I was hoping for around 120BHP to start with - Possible?Can't afford the £300 extractor manifold yet and besides, I want to use Triumph 'Parts bin' secondhand/ factory original bits as much as possible to see how much power I can get using interchanged standard parts Link to comment Share on other sites More sharing options...
Freek76 Posted September 30, 2010 Share Posted September 30, 2010 If it's a semi race head it might have been skimmed already.Best to cc it before taking off too much. Link to comment Share on other sites More sharing options...
Alex Posted September 30, 2010 Share Posted September 30, 2010 My mk1 has a 2.5 with a mk2 2000 unleaded head and tr5 cam and goes very well on hs6's! Link to comment Share on other sites More sharing options...
JohnD Posted September 30, 2010 Share Posted September 30, 2010 Fully agree with the Freek.Here's how to: http://www.totallytriumph.net/spitfire/skimming_your_head.shtmlYou may not get much advantage from a "semi race spec cylinder head" unless you do other things to it.EG Exhaust manifold. Tubular, 6-3-1, matched to exhaust portsCam TR5/early6JOhn Link to comment Share on other sites More sharing options...
trummy2500 Posted September 30, 2010 Author Share Posted September 30, 2010 Alex wrote:My mk1 has a 2.5 with a mk2 2000 unleaded head and tr5 cam and goes very well on hs6's!What is your cylinder head number? Have heard that some early MK2 2000 heads work VERY well on 2.5's Link to comment Share on other sites More sharing options...
trummy2500 Posted September 30, 2010 Author Share Posted September 30, 2010 JohnD wrote:Fully agree with the Freek.Here's how to: http://www.totallytriumph.net/spitfire/skimming_your_head.shtmlYou may not get much advantage from a "semi race spec cylinder head" unless you do other things to it.EG Exhaust manifold. Tubular, 6-3-1, matched to exhaust portsCam TR5/early6JOhn I have been told about using a TR5 cam - Is this just a standard grind TR5 Spec cam? What is the advantage over using, say an aftermarket Kent Fast Road cam? Link to comment Share on other sites More sharing options...
andy thompson Posted September 30, 2010 Share Posted September 30, 2010 Very early 2000 Mk2 heads have 3.300" height so give silly CR unless serious chamber mods are made. This is possible - I have a 3.290" head thickness on a 2.7 engine - but it does have close to 11.1 CR which is only possible with a long duration cam and preferably strnger pistonsWorth asking the seller of the head what is its overall height Link to comment Share on other sites More sharing options...
Alex Posted September 30, 2010 Share Posted September 30, 2010 2660 wrote:What is your cylinder head number? Have heard that some early MK2 2000 heads work VERY well on 2.5's Mines a 218225 not sure how old but its an old dome top head.The numbers are all herehttp://www.triumphclub.co.nz/technical.html Link to comment Share on other sites More sharing options...
andy thompson Posted September 30, 2010 Share Posted September 30, 2010 2660 wrote: I have been told about using a TR5 cam - Is this just a standard grind TR5 Spec cam? What is the advantage over using, say an aftermarket Kent Fast Road cam?TR5 profile is designed for Triumph head flow characteristics -they were developed with a lot of thought as Triumph engineers were a lot wiser than some give them credit for - Kent cams are not - they are mostly designed for crossflow heads with no combustion chamber where high lift shortish duration works much better than in a Triumph175bhp is possible with a TR5 cam with correct mods.Check Steve Attenboroughs blog - he got 145bhp from a 2 litre with a standard PI cam Link to comment Share on other sites More sharing options...
trummy2500 Posted September 30, 2010 Author Share Posted September 30, 2010 lagerzok wrote:Worth asking the seller of the head what is its overall heightSorry, forgot to add that detail - it's 3.400" height head with 38cc Chambers. Don't know if this is standard height and chamber size though, as said I am a newbie to Triumph engines.What CR do you think that would give on my standard 2500 bottom end/pistons? Link to comment Share on other sites More sharing options...
andy thompson Posted September 30, 2010 Share Posted September 30, 2010 9.5:1 Link to comment Share on other sites More sharing options...
trummy2500 Posted September 30, 2010 Author Share Posted September 30, 2010 lagerzok wrote:9.5:1Thats good for me really as I can still use normal 'pump petrol' - I was a bit concerned with all this talk of very high CR that I would have to look at racing only fuel!Is 3.400" height and 38cc Chambers standard size then?Would you say the head could go down to 3.300" for a bit of extra CR or would the disadvantages outweigh the plus points? Link to comment Share on other sites More sharing options...
Lord Sorbington Posted September 30, 2010 Share Posted September 30, 2010 Alex wrote:Mines a 218225 not sure how old but its an old dome top head.The numbers are all herehttp://www.triumphclub.co.nz/technical.htmlThe early mk2 2000s have flat top pistons and a 9.25:1 compression ratio. Mine is fine on normal unleaded. Link to comment Share on other sites More sharing options...
Hugh Posted September 30, 2010 Share Posted September 30, 2010 Would a TR6 head and fast road cam be worth fitting to my 1971 GT6 MKII engine :) Link to comment Share on other sites More sharing options...
Richard B Posted October 1, 2010 Share Posted October 1, 2010 908 wrote:Would a TR6 head .... be worth fitting to my 1971 GT6 MKII engine :)No, not unless you took it out to 2.5. Link to comment Share on other sites More sharing options...
Deleted User Posted October 1, 2010 Share Posted October 1, 2010 Stick 99 Octane and a shot of octane booster in it… vrooooom! Link to comment Share on other sites More sharing options...
JohnD Posted October 1, 2010 Share Posted October 1, 2010 2660 wrote:What CR do you think that would give on my standard 2500 bottom end/pistons? trummy, I gave you a link above to my own article on how to work out the CR. With great respect to Andy, who may have worked it out, work it out for yourself, then you can't blame anyone else!It's not quantum chromodynamics.Quoted from HughWould a TR6 head .... be worth fitting to my 1971 GT6 MKII engine Quoted from RichardNo, not unless you took it out to 2.5.OR, skimmed the head down, a rather lesser job, which would give you...... Tantarara! A GT6 head!If the water jacket has not suffered from plug shift.In which case you get......Huzzaa! A boat anchor.John Link to comment Share on other sites More sharing options...
trummy2500 Posted October 1, 2010 Author Share Posted October 1, 2010 JohnD wrote:work it out for yourselfIt's not quantum chromodynamics.It was last night after half a bottle of whisky ! ;D Link to comment Share on other sites More sharing options...
TimW Posted October 5, 2010 Share Posted October 5, 2010 i have a 2.5 with pi head (standard) a set of hs6 su's, 6-3-1 manifold and a tr5 cam. I get 131bhp and 151ftlbs of torque at the flywheel. I get max torque at 2400rpm IIFC Link to comment Share on other sites More sharing options...
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