A Quiet Boom

As I had stated in my post about installing a 3.0SC into my '66 912 in place of the Zenith carbed 2.0E engine my plan was to reuse the Zeniths (originally from a 2.2) on the new engine. I was able to purchase larger Venturi's from Motormeister. I installed them and rebuilt the carbs at the same time. Now for my problem, per their suggestion Motormeister wanted me to contact Lee Marks at their facility to discuss drilling my idle and main jets to work with my combo, I did contact Lee and we spoke in detail about my setup and he gave me suggested jet sizes. The trouble is I have the jets in my hand and the sizes I wrote down just seem way too big. 0.150" for the mains and 0.060" for the idle jets. Currently the idle jets are around 0.006" meaning 0.060" is a 10x increase, the mains are around 0.045" meaning more than a 3x increase. Either I have written down his instructions wrong or their is something I'm not understanding, I have reworked a lot of Holley carbs in the past and I know from experience that doubling diameter of a jet does not double it flow, it's exponential, much more than double which is why I don't understand such large increases. The only way I can understand it in my head is that the venturis are MUCH larger 36mm vs. the stock one I measured at 27.5mm and therefore the "draw" on the jets is substantially less. (larger venturi = less vacuum across the booster) so I suppose 0.150" could be correct for the mains but what about the idle jets? I'm in sort of a jam since I had hoped to get the car running this weekend but I missed contacting Motormeister before they closed and I don't know if they are open on Saturday. Anybody out there familar with this stuff that can give me some insight, I can't stand being without my P-car it's been over two weeks already and these carbs are the only thing left to finish before the first test drive.

Howard

150 mains (1,50 mm) are .059" in diameter , 60 idles are (,60mm) or .024" diameter. Weber was Italian....so it's all metric unlike the Holley carb. mm/25.4=inches You can get jet reamers from Pelican or Performance Products.

A Quiet Boom

[quote]Originally posted by Howard:
<strong>150 mains (1,50 mm) are .059" in diameter , 60 idles are (,60mm) or .024" diameter. Weber was Italian....so it's all metric unlike the Holley carb. mm/25.4=inches You can get jet reamers from Pelican or Performance Products.</strong><hr></blockquote>


/me is a stupid American LOL. I work around machines all the time and I'm stuck on inches. 1.50mm and 0.60mm sounds a whole lot better.