OAF939M Posted May 30, 2017 Report Share Posted May 30, 2017 My 1974 TR6 has a cylinder head stamped 218225 and cast 312388. A couple of people have said that I have the good head , I have checked and it has either come from a GT6 or a Triumph 2000. Why are they considered better heads? Quote Link to post Share on other sites
TriumphV8 Posted May 30, 2017 Report Share Posted May 30, 2017 I wonder if there is that difference. If you enter the head with a grinder you normally feel differences. Here all I prepared have been similar Some did jobs on the flow bench, that is beyond my capabilities but I have problems to believe the results. Anyway Chris Wittor reports differencies on his website. The main differences are the spacing between the inlets. Aiming for PI this is a topic. Wider spacing is required. Also the carb manifold for the wider spacing looks better for me. The other difference is the exhaust valve size. The smaller exhaust is preferred by me because the core shift between combustion chamber and exhaust port can be compensated better. I prepared several heads with big exhaust valves and after having all grinded to size there was some material missing just under the valve seat area. The smaller exhausts require more cutting and normally end with a nice ported area aroung the valve seat. Also here Wittor is different and claims to use the smaller valve for better flow. Anyway I am a friend of the PI system giving some power over the twin carbs for free without sacrificing low end torque like from wilder cam that has to be collected back by a lot of tricks like compression, head work and proper AFR ratio and ignition timing. The compression ratio and size and shape of the combustion chamber can be grinded and milled to suit with any of the heads. The US versiond require to mill off quite a bit more, thats the difference. Quote Link to post Share on other sites
John390 Posted May 30, 2017 Report Share Posted May 30, 2017 Rimmers say it is a TR6 head: https://www.rimmerbros.co.uk/Item--i-GRID600007 Cheers John Quote Link to post Share on other sites
astontr6 Posted May 30, 2017 Report Share Posted May 30, 2017 My 1974 TR6 has a cylinder head stamped 218225 and cast 312388. A couple of people have said that I have the good head , I have checked and it has either come from a GT6 or a Triumph 2000. Why are they considered better heads? +1 for John. I do not know where your info came from? But my old SAH chart shows that your numbers refer to MK2 PI MG5000 to MG82077 or TR6 CR type, exhaust valve size 32.0 m/m? Bruce. Quote Link to post Share on other sites
OAF939M Posted May 30, 2017 Author Report Share Posted May 30, 2017 Like this? I took this to mean Triumph 2000 saloon 520873 218225 312388 3.400 Mk2 PI MG50001 to MG82077 Flat 32.0 8.125 Yes No Two people from companies who work on injected Triumphs told me it was the good head. Quote Link to post Share on other sites
OAF939M Posted May 30, 2017 Author Report Share Posted May 30, 2017 I've got a pdf open with the info that the head was fitted to these. TRIUMPH SIX CYLINDER ENGINES Mk2 CYLINDER head applications chart Part No. (bare)Head No. stampedCasting No. raisedHeight nominal (inches)ApplicationsPiston typeExhaust valve (mm)Pushrod length (inches)EGR humpRear water slot 520819 218225 312388 3.4 Mk2 2000 from ME50001 to ME86355 -86508. Mk2 GT6 Dome 32 8.125 Yes No So am now really confused. Quote Link to post Share on other sites
openroad Posted May 30, 2017 Report Share Posted May 30, 2017 Yes Triumph 2000 mk2 and GT6 mk2....Chris witor chart, some differences to tr6 true head. Cheers, Conrad. Quote Link to post Share on other sites
OAF939M Posted May 30, 2017 Author Report Share Posted May 30, 2017 Thank you, at least I'm not going mad. The car goes really well and I am not planning to change anything, just interested. Quote Link to post Share on other sites
astontr6 Posted May 30, 2017 Report Share Posted May 30, 2017 Yes Triumph 2000 mk2 and GT6 mk2....Chris witor chart, some differences to tr6 true head. Cheers, Conrad. My TR6 I have owned since new it is a 1973 CR type and has the original head on it. Guess what Listers numbers are exactly the same as mine! and as shown in the SAH list from 40 years ago, as originally stated in my thread #4. That means it is a genuine TR6 type head. If you want to know what the major differences are to the early TR6 type are. Its all to do with thickness of cast iron in certain sections to prevent warping and cracking between valve seats. Lastly, it was to be used with the modified Coopers/Payen ( same company) cylinder head gasket, which was re-enforced on the fire rings and the block counter bored around the bores, to improve compression sealing. Bruce. Quote Link to post Share on other sites
aardvark Posted May 30, 2017 Report Share Posted May 30, 2017 My 1970 CP has the same head as Bruce and Lister. I've always assumed the head was changed because of a problem in the past. So if it is a CR head on a CP am I missing out on anything? Cheers Dave Quote Link to post Share on other sites
Nick Jones Posted May 30, 2017 Report Share Posted May 30, 2017 No. Head may have been changed in the past but no practical difference. I suspect that when people say the "good" head, they mean one with 32mm exhaust valves as many later cars had the 219015 head with smaller, 30mm exhaust valves. This was changed to try and reduce the incidence of cracking between the valves (usually cyl 1 or 6) some consider it affects performance. Nick Quote Link to post Share on other sites
OAF939M Posted May 31, 2017 Author Report Share Posted May 31, 2017 Thank you. Quote Link to post Share on other sites
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