Cliff's Quadrajet Parts and Rebuild Kits

General Category => Quadrajet Carb Talk and Tips => Topic started by: Mike29 on July 11, 2015, 01:15:19 PM

Title: Quadrajet marine carb on secondaries.
Post by: Mike29 on July 11, 2015, 01:15:19 PM

Just wondering if anyone knows the approx rpm for the secondaries to open? Is there a vacuum reading number they open at? My boat with BB Crusader/Chevy motors seems to do best around 3200-3400 rpm. I cant tell by sound if I'm into the secondaries until 3450-3500 when I can hear the wail. I used one of Cliffs kits to do the overhaul and she runs great at all RPM's to WOT. I know Quadrajets were designed primarily for automobile applications where the secondaries only get the short full throttle bursts but I'm talking to more folks with heavy boats that are running the Crusaders into the 3200-3400 range to stay on plane.  Are there any tricks we could do to make them run more efficiently on the secondarie side? Is this covered in Cliffs book?

Title: Re: Quadrajet marine carb on secondaries.
Post by: Cliff Ruggles on July 14, 2015, 04:47:48 AM

The secondaries are mechanical, so based on throttle position not engine rpm's.  The airdoor is spring loaded, so operates on engine demand. 

Marine q-jets are excellent units, not emission calibrated and do very well in Marine applications.  The secondaries are easy to tune, and they still respond well to custom tuning with different secondary metering rods.....Cliff

Title: Re: Quadrajet marine carb on secondaries.
Post by: Mike29 on July 14, 2015, 05:35:51 PM

Thanks Cliff...I need your book.