> For 9:1 compression on a 1500 motor, you want to replce the US spec > dished pistons with the UK spec flat-topped ones. You may still need to > mill the head a bit, but this will get you close to the stock UK 9:1 > spec.
Roger, I used +0.020 flat pitons and milled the head on my 79 Spitfire to get 9.5:1 CR. Originally, I had asked the machine shop to mill the head for 9.5:1 CR but when I got it back, all they had done was take off 0.012" to flatten the head. When I called them on it, they asked if I knew the answer so I went off reading everything I could on the subject. The most useful was an article by John Davies called "Skimming Your Head For A Higher Compression Ratio". http://www.totallytriumph.net/spitfire/skimming_your_head.shtml Toward the end days of Triumph, there were a lot of different head and piston combinations and you never know if a PO may have swapped heads so it is best to measure the amount empirically. I determined that I needed an additional 0.050-0.060" skimmed. When I got the head back, I believe I measured about 9.3:1 but based on how the engine runs (or doesn't run) on 87 octane and how well it runs on 93 octane, I'm pretty sure it is closer to 9.5:1. If you want to see my struggle with this, check out my website (starting with 23 January): http://webpages.charter.net/eighmy/spitfire/ Gene Eighmy Your messages not reaching the list? Check out http://www.team.net/posting.html === This list supported in part by The Vintage Triumph Register === http://www.vtr.org === Help keep Team.Net on the air === http://www.team.net/donate.html === unsubscribe/change address requests to [EMAIL PROTECTED] or try === http://www.team.net/cgi-bin/majorcool === Other lists available at === http://www.team.net/mailman/listinfo === Archives at http://www.team.net/archive === http://www.team.net/the-local === Edit your replies!
