pparaska Posted July 28, 2005 Share Posted July 28, 2005 Glad you finally figured it out. But let me tell you my experience. I tried a 750 vac sec, then a 600 vac sec. The 750 made more power (I tuned both of them for the 327). The 600 would idle much better and had better low speed response. Then I got a like-new 650 DOUBLE PUMPER (12 dyno pulls only) very cheap and tried that. NIGHT AND DAY difference to both the vac sec cars. Lesson I learned: Most of the 'net knowledge and HOTROD mag articles say "DON'T USE A MECHANICAL SECONDARY CARB ON THE STREET". That's because they are talking about a big muscle car that weighs 5-700 lbs more than most V8 Z's. Sure, a mechanical secondary carb can cause bog, but only if you do something stupid like mash the pedal in top gear at 40 mph. The Lesson IS: GO AHEAD AND USE A MECHANICAL SECONDARY CARB ON ANY V8Z. Even an automatic car that has the kickdown setup correctly. Quote Link to comment Share on other sites More sharing options...
SportZ2 Posted July 28, 2005 Author Share Posted July 28, 2005 I'm thinking that I will go to a mechanical secondary carb anyways. I'm still getting a hesitation when I hit the pedal after the car is warmed up. It's not the diaphram spring because I have tried just about all of them. My guess is maybe I need to rejet to get more fuel or I'm getting a slight vapor lock. I did put on the heat shield/spacer and will see if that makes a difference. The carb came with .060 all around and on another post someone mentioned that they might be too small for 5000 ft. The local dyno shop owes me some pulls so that should be a big help in getting this thing tuned. Quote Link to comment Share on other sites More sharing options...
pparaska Posted July 28, 2005 Share Posted July 28, 2005 I'm not sure what about the mechanical secondary carb made the difference that I noticed - but the effect was to cause the car to have IMMEDIATE response from having the throttle punched! Finally, the car felt like the beast it should have been all along! Maybe it was the instant opening of the throttle blades, but most likely it was that along with the immediate extra shot of fuel from the accelerator pump on the secondaries. Anyway, my 327 with a lumpy cam loved it, and an engine with even more cubes should love it more! Quote Link to comment Share on other sites More sharing options...
blueovalz Posted July 28, 2005 Share Posted July 28, 2005 I'm still getting a hesitation when I hit the pedal after the car is warmed up. I'd also check on the size of the accelerator nozzle. I've had set-ups that required a 40 size nozzle, but then others that worked fine with a 25. Right now I run a 32. It sounds to me like you could experiment with a large nozzle. Quote Link to comment Share on other sites More sharing options...
pparaska Posted July 28, 2005 Share Posted July 28, 2005 I'd also check on the size of the accelerator nozzle. I've had set-ups that required a 40 size nozzle, but then others that worked fine with a 25. Right now I run a 32. It sounds to me like you could experiment with a large nozzle. Agreed. I found that I needed to run a larger than stock nozzle as well. I also played with the different pump cams, but the default one was close enough. Oh, get a hollow nozzle screw if you're upgrading the squirter nozzle. Just filling in a different value for accel enrichment in the Megasquirt computer is SO much easier! Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted July 30, 2005 Share Posted July 30, 2005 I recently got my seconds working right. My problem was that when I lightend the spring, I didn't get the diaphram seated write. I went to tighten the screws and caused it to fold in on its self. This caused a vac leak. FYI Quote Link to comment Share on other sites More sharing options...
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