Something else to remember with the Spitfire is that there were two distinctly different ZS manifolds. The very common small runner, and the much rarer large runner. I strongly suspect that the manifold is the strangle, not the ZS carburetor. If you do the math, you will see that a 1.75 ZS has nearly the same throat area as the dual HS2 SU setup. yet the HS2 (or 4) far out performs the typical ZS.
John Kipping has stated that his experience running HS6 on the non-US (small runner) manifold yields nearly identical results as the various dual SU setups. I have also encountered early squaretail Spitfires running the single ZS that ran quite well. These early squaretails quite possibly were using the larger runner manifold. Fwiw, it doesn't seem that top speed is much changed on my Spitfire in going from the single ZS and small runner manifold to the HS2 and manifold from an earlier 1300 Spitfire. What has dramatically changed is how relaxed the engine feels at speeds about 40 mph. Granted the RPM's are the same, but the engine is no longer straining the way it once was. With the ZS highway driving was a rotten experience, with the engine always sounding and feeling like it was killing itself trying to keep up with traffic. With the HS2's, the engine is relaxed and not straining, while still buzzing like a top at the same RPM's. I do now have a large runner ZS manifold, and may some day install it for some comparisons. >>> Glenn Trunnell <[EMAIL PROTECTED]> 06/01/02 07:44PM >>> Hi everybody, The work on my SU HIF6 conversion continues apace, but I wanted to find out what kind of performance other peopler saw with their Spits. My main question is this: previously with the single ZS my car would turn about 5300 in fourth gear. Will anybody's pull the full 6000 with the stock carb and emissions? How about with Dual 1.5 SUs or one of the various webers? I previously owned a couple of MGBs. The first a 74 was good for about 105 mph with dual HIF 4s the second an '80 wit a ZS 175 topped out at 85 mph. The only difference between these two cars was the carburettion. So I am curious about a baseline for the Spit as I have only ever driven mine. /// [EMAIL PROTECTED] mailing list /// Send admin requests to [EMAIL PROTECTED] /// or try http://www.team.net/cgi-bin/majorcool /// Archives at http://www.team.net/archive /// Send list postings to [EMAIL PROTECTED] /// Edit your replies! If they include this trailer, they will NOT be sent.
