On 25 Dec 2006 at 13:01, Michael ONeill wrote: > I'm thinking of changing the pistons from the dished out type that have a > 7.5 to 1 compression ratio to the flat type that have a 9.0 to 1 ratio. Do > you think this is a good idea?
Don't know nuffin 'bout pistons, but the 9:1 ratio is nice if you don't mind having to be particular about the gas you run. The '76 engine was 9:1 but the difference was the heads,so they tell me. I say this because my own engine is a '76 in an '80 car. It was spec'ed to use 95 octane gas back then. That's not available easily today, though there are so many other differences in the gas that I'm not sure how much stock to put in that spec specifically. Over the years I've gone through great pains to set my timing to prevent the engine from pinking. Under full throttle in some conditions it still does and I don't think any amount of spark retard will prevent it except unacceptably late. With roughly 20 years since its rebuild this engine is still going strong so it must not be too bad. Of course, that higher comp ratio must be giving me more power, and more power is always good. I don't have any standard by which to judge it, never had a different Spitfire. But as far as the comp ratio is concerned, I'd say it's a good tradeoff. Someone else will have to comment on the pistons. -- Jim Muller [EMAIL PROTECTED] '80 Spitfire, '70 GT6+ 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!
