danno 128 Report post Posted June 13, 2019 I have had poor mileage, and it could be because I have the wrong 2100 carb in my car. What is the correct venturi diameter of a stock 2100 on a 302 in 1969? I think I have one that is too large. I have 3 of the carbs, and I am guessing the smallest one is correct. Quote Share this post Link to post Share on other sites
69RavenConv 286 Report post Posted June 14, 2019 The 1.08 was correct for a 302 manual transmission car. I think the automatic got a bigger one. Quote Share this post Link to post Share on other sites
Jwb5858 1 Report post Posted June 14, 2019 My stock 302 manual has a 1.08 with size 50 jets. Quote Share this post Link to post Share on other sites
danno 128 Report post Posted June 14, 2019 I have an automatic, so maybe 1.14 inch? That is what I read on another discussion on this forum. Do I measure it with a caliper across the plates that open with the throttle? If that is true, all 3 of the carbs I have are large. The smallest is 1.43. Another question... there is a place where the mains inject to the air. Are those little holes supposed to be completely above the throttle plates when at idle? Mine are a bit below it, so it looks like I am injecting into the air even though the plates are closed. Quote Share this post Link to post Share on other sites
69RavenConv 286 Report post Posted June 14, 2019 I'd agree about the 1.14 being right for an automatic 302. The size should be embossed on the carb body. I used to see boxes of 2100's at swap meets but as time goes by not so much. FI Fox bodies are the new classics now. I found the following chart on the internet, I can't vouch for it's accuracy. 0.98 = 190 CFM 1.01 = 240 CFM 1.02 = 245 CFM 1.08 = 287 CFM 1.14 = 300 CFM 1.21 = 351 CFM 1.23 = 356 CFM 1.33 = 424 CFM Quote Share this post Link to post Share on other sites
Brian Conway 264 Report post Posted June 14, 2019 From the Shop Manual: Quote Share this post Link to post Share on other sites
1969_Mach1 333 Report post Posted June 14, 2019 13 hours ago, danno said: I have an automatic, so maybe 1.14 inch? That is what I read on another discussion on this forum. Do I measure it with a caliper across the plates that open with the throttle? If that is true, all 3 of the carbs I have are large. The smallest is 1.43. Another question... there is a place where the mains inject to the air. Are those little holes supposed to be completely above the throttle plates when at idle? Mine are a bit below it, so it looks like I am injecting into the air even though the plates are closed. The venturi (not the boosters) is the hour glass shaped portion inside the main body. The specified dimension is the smallest diameter portion of the venturi. That's the location of maximum air velocity as it passes through the carb. You might have to get creative to find a way to measure it. Quote Share this post Link to post Share on other sites
danno 128 Report post Posted June 14, 2019 I found the stamping on the side of the carb with the size. All autolites have it stamped on the side. That makes it easy, nothing to measure. For 30 years I have been running with a 1.23, and that could be the problem with poor gas mileage and overheating. I still have the 1.14 that was removed 30 years ago, I will rebuild it and put it back on. The jets with the 1.23 were 50F, I will insure the 1.14 has the correct jets. If this fixes it, it is great knowledge for others. All 2100 carbs are not the same, there are probably a hundred differences. Venturi and primary jets are the largest hidden difference. Thanks, I will follow up with results. I want this fixed! Quote Share this post Link to post Share on other sites
