cammmy Posted August 17, 2009 Share Posted August 17, 2009 Hey GuysI have been told that putting a 2000 head and pushrods in a 2500 will increase the compression.Has anyone done this or seen it done? What compression ratio does it result in and what kind of octane would be needed after?CheersCam Link to comment Share on other sites More sharing options...
andy thompson Posted August 17, 2009 Share Posted August 17, 2009 Early Mk2 (pre 72 ) 2000 head on a 2500 will give about 12:1 CR which with a standard cam and pistons will result in terminal detonation :( . With a race cam and forged pistons you might just get away with it :-/ Link to comment Share on other sites More sharing options...
cammmy Posted August 17, 2009 Author Share Posted August 17, 2009 That is quite high. Thought there was no difference in early heads between the models, and that they used domed pistons to increase the compression for the 2000? Thought the later 2000 heads were the ones that where made shorter. Link to comment Share on other sites More sharing options...
andy thompson Posted August 17, 2009 Share Posted August 17, 2009 Other way round... early 2000's Mk2 <ME50000 have flat top pistons , short pushrods and "thin" head. Later 2000's have domed pistons and heads/pushrods common with 2.5. Dome volume is 8cc btw Link to comment Share on other sites More sharing options...
cammmy Posted August 17, 2009 Author Share Posted August 17, 2009 ahhhhh, thanks.So is machining the way to go for increasing CR? better to try and "deck the block" or take it from the head? Any other way to increase CR? Link to comment Share on other sites More sharing options...
andy thompson Posted August 17, 2009 Share Posted August 17, 2009 Easiest to mill material off the head. Keep a 30 thou clearance between pistons and top of deck on a 2.5 or pistons will hit head if overrevved (rod stretch)PI compression of ~9.5.1 is obtained by having a 3.400" head height - for comparison a 2000 head with flat tops is ~ 3.300" so 100" thinner.Standard 2500 TC is 3.475" high.CR alone does not help power, you need to fit longer duration Cam (TR5?) + good exhaust etc etc Link to comment Share on other sites More sharing options...
cammmy Posted August 17, 2009 Author Share Posted August 17, 2009 Thank you very much for the info. Greatly appreciated.I will be doing other mods. I have 3 engines so I figure I would tear one of the spares down and rebuild it for experience, Figure if I'm doing that I may aswell make it a hot motor too :-). Would be looking at increasing CR, fitting twin 2&3/4" SU's (have 2 sets aready so maybe a triple setup some day), quicker cam, headers and exhaust, any changes needed to make that reliable, maybe lightened flywheel and definately an alloy rocker cover etc etc.Dad is right begind the project so he should be helping in the parts department :-) Keeps going on about his "MGB with Osselli road race engine". Would love to show him some Triumph power Link to comment Share on other sites More sharing options...
cammmy Posted October 2, 2010 Author Share Posted October 2, 2010 Hey GuysI'm going to drag this one up again.I've got a 3.5 RV8 for this now but I will need to rebuild it and sort a whole heap of other stuff out first. In the meantime I was thinking about tinkering with my spare motor and using the 1.75" SU's I have, then putting that in.Coming back to milling the head. Would it be feasible to get 10 or 10.5:1 comp out of this by removing material from the head? How much would I need to remove and would there be much risk of valve to piston contact (i.e would there be enough clearance still)?I would be using 98 octane or 95 in a pinch (with a booster in necessary).What issues would I come accross? Is this a stupid Idea that I should forget about and just go for 9.5:1 ;)CheersCam Link to comment Share on other sites More sharing options...
kenv8pi Posted October 2, 2010 Share Posted October 2, 2010 880 wrote:Hey GuysI'm going to drag this one up again.I've got a 3.5 RV8 for this now but I will need to rebuild it and sort a whole heap of other stuff out first. In the meantime I was thinking about tinkering with my spare motor and using the 1.75" SU's I have, then putting that in.Coming back to milling the head. Would it be feasible to get 10 or 10.5:1 comp out of this by removing material from the head? How much would I need to remove and would there be much risk of valve to piston contact (i.e would there be enough clearance still)?I would be using 98 octane or 95 in a pinch (with a booster in necessary).What issues would I come accross? Is this a stupid Idea that I should forget about and just go for 9.5:1 ;)CheersCamHi Cam To get the compression up on your rv8 you need to change the pistons not milling. milling the head will make the preload on the cam followers wear the cam out plus the vavle will hit the piston at high revs. get a set of piston from a p6 rover or there is a set from sdi of 9.75;1 which cam you use will also effect the compression Regards Ken Link to comment Share on other sites More sharing options...
cammmy Posted October 2, 2010 Author Share Posted October 2, 2010 Hi KenCheers for that. The motor is from a P6B and I have some SD1 head for it too. I meant milling the head on the Trump motor though ;D sorry If I wasn't clear enough about that.CheersCam Link to comment Share on other sites More sharing options...
Glenn Posted October 3, 2010 Share Posted October 3, 2010 Hi Cammy. Here's a "secret". The head on the post '75 2000TCs was also 3.400" so a quick 'n' cheap way to get a 2500S or TC block up to 9.5:1 CR. Use the TC push rods too. 8) Link to comment Share on other sites More sharing options...
cammmy Posted October 4, 2010 Author Share Posted October 4, 2010 Hi GlennThanks for that.The car is a '74 TC2500. Is it possible/safe to go beyond 9.5:1? Say 10 or 10:5?What would be required in the way of lash adjustment for this?My brother is an engineer so it is likely to be easier/cheaper for me to get him mill down the head I have (he has confirmed that he should be able to do this) rather than source and purchase a post 75' 2000 head. Although I will certainly keep that in mind ;)CheersCam Link to comment Share on other sites More sharing options...
Glenn Posted October 4, 2010 Share Posted October 4, 2010 Has your '74 2500TC got SU HS4 carbs? If so, it's comes with the 125bhp PI cam. Using the 3.400" head along with bigger HS6 carbs will give you a sweet, pokey engine it's said!!I'm no expert but I think it would be risky to go for much more of a skim than that. You wouldn't be able to run with as much advance, it might run on more, and generally be more hassle than it's worth. Link to comment Share on other sites More sharing options...
cammmy Posted October 4, 2010 Author Share Posted October 4, 2010 Actually, come to think about it. I don't know what year this motor is! I was thinking about the original motor! Sheesh :PIf I get the numbers from the lump, can anyone here tell me which one it is? Where abouts would I find the markings?It came without carbs but I do have a pair of 1.75" units I'm cleaning up at the mo (planning to use these) Link to comment Share on other sites More sharing options...
Deleted User Posted October 4, 2010 Share Posted October 4, 2010 Rust_Spot wrote:Hi Cammy. Here's a "secret". The head on the post '75 2000TCs was also 3.400" so a quick 'n' cheap way to get a 2500S or TC block up to 9.5:1 CR. Use the TC push rods too. 8) Note to self: Nip down the shed and dig out the 2000TC at the back and check. Link to comment Share on other sites More sharing options...
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