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Posted by: dumbjim Dec 5 2020, 08:40 AM

I'm getting ready to install a Petronix svda distributor in the next day or so. I emailed them as to which vacuum port I should hook up to on the carb. They replied cylinder 4, yet the install letter they sent me says I should t the vacuum line and run one to each carb. What's your opinion out there? Thanks

Posted by: michael7810 Dec 5 2020, 03:35 PM

You get a lot of vacuum pulsing so T-ing both carbs will smooth that out some. Put a vacuum gauge on it and you’ll see what I mean. I ended up using the anti-pulse valve from Aircooled dot net and it worked OK but still did not have a smooth vacuum signal.

Posted by: Ansbacher Dec 5 2020, 05:05 PM

I'm running dual Dellortos not Webers, but I found being hooked up to just one carb gave the best results. Tried it from both and with the one-way valves but it seemed to instill some weird cross talk and impaired my performance.

Ansbacher

Posted by: Tdskip Dec 5 2020, 07:33 PM

Make sure you have vacuum ports - not all of them do and finding a 4mm thread to add one has proven to be surprisingly difficult.

Posted by: porschetub Dec 6 2020, 12:56 PM

Did the same with 36 drla's seem to work fine,tried to research this on many other forums …just got confused some said ok to run that way and others you must run from two vacuum points.
The Alpha spec Dellorto's only run one pickup per set ,not sure if the ones imported by CB performance years ago had one each carb or none @ all.