Section : General

Rebuilding a 1971 GT6 Mk3 how much power 

Posted By : John Schuldt, 07-Jan-2007, 08:10pm

• Rebuilding a 1971 GT6 Mk3 how much power 

  Posted By : Philip Charlton, 07-Jan-2007, 09:27pm

  around 200bhp
  
  you can cam it
  bore it
  stroke it
  balance it
  lighten it
  flow it
  re valve it
  re-ignition it
  
  loads of options
  
  depends how far you want to go, how many mph you want, how much you have to spend etc etc

  • Rebuilding a 1971 GT6 Mk3 how much power 

    Posted By : John Schuldt, 08-Jan-2007, 00:48am

    great
    
    and the drivetrain will handle this much power?
    
    1st...where can i get some of these fun parts?
    
    2nd...where can i get performace / upgrade parts anyways?
    
    thanks

  • Rebuilding a 1971 GT6 Mk3 how much power 

    Posted By : Nigel Gibbins, 08-Jan-2007, 12:55pm

    I think 200 Bhp is extremely optimistic for a medium budget and a need for reliability.
    
    Dave Thompson or Jon Wolfe (Both race GT6s) would be better placed to answer properly but I don't think you can expect more than 180Bhp out of the 1998cc engine. However, with that you lose all drivability and the engine will need rebuilding every 1000 miles (or so).
    
    I would guess that 150Bhp is achieveable without extreme expense and the engine can still be driveable and reliable... I await the afore mentioned oracles comments...

    • Rebuilding a 1971 GT6 Mk3 how much power 

      Posted By : George Ralph, 08-Jan-2007, 01:29pm

      I agree with Nig. I will be putting mine on a rolling road in a few weeks time so I will find out then. It has proved to be gutsy and reliable (4000miles to date) and pretty driveable so I can't complain. I reckon (hope) I have about 150bhp and I have done (carefully) all the mods and I use as lumpier a cam as I can for the road (Kent TH6).
      
      Done properly about 150 would be achievable, torque is more important, and the 1998 revs like a dream (mine will happily exceed 7000rpm so I use a rev limiter).

       

      
      
      Rebuilding a 1971 GT6 Mk3 how much power

       

      • Rebuilding a 1971 GT6 Mk3 how much power 

        Posted By : Mark Hellier, 09-Jan-2007, 02:17pm

        You will not achieve anywhere near 200 bhp with a 1998cc unit on a medium budget that will last and is tractable for road use???
        
        However 140-150bhp (at the flywheel) is more than achievable with standard (excuse the pun) Triumph parts - you've already the 6:3:1 manifold so your half way there in extracting any available power &8211; 6:2:1 manifolds don&194;&8217;t work -best way to get power out of your 2ltr using standard bits + a few bolt on&8217;s is a TR5 35-65 profile camshaft with a well balanced bottom end/damper/flywheel/clutch cover/rods/ flat top pistons @ zero deck + a compression ratio of 10.5:1 if you can find a late 2.5S head then this will give you the best flow characteristics of the stock Triumph parts + some decent flowed valves - fit TR double valve springs and don't waste your money on alloy valve caps - change the standard split exhaust caps for standard inlet ones (i.e 12 inlet caps ) &8211; there is also no direct correlation by using what everyone terms as a TR5/6 150 camshaft in respect to the 1998cc units and achieving 150bhp on the 2ltr &8211; in fact the TR6 was only 142bhp
        
        Standard early 150cd carb&8217;s work well on this set-up - make sure you use stub stacks inside the filters as a bare carb&8217;s face will loose you power ( as in a standard air filter) + TR5 D25 distributor and electronic ignition
        
        As for the Webbers I&8217;d replace them with a set of twin 150/175 CD&194;&8217;s or 1.75&194;&8217; SU&194;&8217;s or better still fuel injection as for road use webbers do little apart from make a noise and tip fuel down the inlet port - which of course is what there designed to do - but things are different on the track and the road - Webbers are fine in either the on or off position i.e. full throttle - again you need match your the camshaft carefully to make the best use of Webbers - you can tell I don&8217;t like Webbers!!!! you need high lift cam with Webbers &8211; this configuration doesn&194;&8217;t lend itself to a smooth tractable unit that produces power/torque low down which is ideal for a road engine - also the TR5 camshaft doesn&8217;t work well with Webbers and visa versa 150cd&8217;s/SU don&194;&8217;t work well on the TT/Kent profile cams &194;&8211; I don&194;&8217;t like TT/Kent cams either.
        
        Last raced in 94 on a 2.3 fuel injected lump with 170 bhp at the wheels &8211; that cost money and didn&194;&8217;t last long between strip downs, since then performed the above mod&8217;s on 4 1998cc units with power outputs all up at constant 150bhp &8211; you'll get more power (upto to 160bhp at the flywheel) by uping the compression to 11.5:1 and running a longer duration camshaft and with fuel injection should get you around 180bhp at the flywheel (would be 150 bhp at the wheels)- obviously there are other mods you must consider as well regardless of radical mods &8211; ARP rod bolts, decent oil pump, oil cooler, jetting and a good rolling road with someone who understands 150/175CD or SU's
        
        Apart from that the rest of the drive train will handle the power with a few basic mod&8217;s &194;&8211; the Spit 3:63 diff is the strongest &8211; pre 74 dolomite 1850 3 rail j type gearbox and some decent UJ&194;&8217;s and donuts &194;&8211; also remember you have to stop the car as well?
        
        

        • Rebuilding a 1971 GT6 Mk3 how much power 

          Posted By : John Schuldt, 09-Jan-2007, 02:56pm

          thank you for that info
          
          now to go out an start pricing / finding parts.
          
          will post some pics once i get my camera back.