Graeme Posted June 24, 2003 Share Posted June 24, 2003 Hi again, drove the beast yesterday for its maiden voyage. It was wet and I was very careful not to get to excited. But I dont think the seconadaries are opening properly. There is a vacuum line at the font bottom of the carb that is blocked off, and also a pipe into the manifold is blocked off. Do these two connect up to allow the secondaries to operate? The carb is a holley 750 dp vacuum secondaries,model 3310-3. Any help would be great. Quote Link to comment Share on other sites More sharing options...
dmyntti Posted June 24, 2003 Share Posted June 24, 2003 These lines don't run the vacuum secondaries. There are two vacuum connections on the front of the carb one on each side. As I recall one goes just above the throttle plates and the other goes just below them. The reasoning is depending on the distributor vacuum advance you want you either pick the one from above the throttle plates giving you more advance as the throttle is opened further or less advance as the throttle is open for the one below the throttle plates. As for the pipe on the manifold it could go to a number of differnt things (auto-trans, brakebooster, emission controls, etc.). These plugged vacuum ports are pretty common especially on engines with aftermarket carbs and etc on them. Most likely they were designed for some part of the emmision control system or some other thing you are not using (i.e. automatic trans modulator, etc.) The vacuum secondaries are operated by a vacuum servo on the sideof the carb. There should be a short vacuum line coming out of it and going to a vacuum port on the baseblate of the carb. I am working off of memory here, it has been several years since I worked on a Holley. How do you know the secondaries are not opening. Hope this helps. Quote Link to comment Share on other sites More sharing options...
Guest greimann Posted June 24, 2003 Share Posted June 24, 2003 If you indeed have secondary tuning issues, then there is a kit of springs available that regulates the opening characteristics. You just pop off the top of the spring pot and replace them, but be sure your tuning issues are not something else entirely. Quote Link to comment Share on other sites More sharing options...
Graeme Posted June 24, 2003 Author Share Posted June 24, 2003 Thanks guys , I will do the paperclip trick in the secondary to see if they are opening under load. The dissy has been modded and has no vacuum on it so I will block off the holes again. And it used to run with an auto so i wont need them seeing i have a 5 speed man. With a modded dizzy what should I be running the timing at? I have it at 8 btdc. Quote Link to comment Share on other sites More sharing options...
Guest greimann Posted June 25, 2003 Share Posted June 25, 2003 8 degrees is a good start, but optimal timing depends on the motor. Cam timing, compression, etc.. all contribute to tuning needs. If you have a "hole" in the throttle response, try advancing the timing a few degrees. Listen for detonation and back it off if you knock. Quote Link to comment Share on other sites More sharing options...
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