This is a repost copy from an eBay listing I am watching. I was not aware of this information, but I think I will follow their advice... take it for what it is worth...
"We're still cleaning off our shelves here at Jet Racing and getting rid of some old inventory. You can find some really great deals by looking at all of our listings. Here we have a Barry Grant Throttle Bypass for a Holley Style 4BL Carb.
This is a Linkage controlled bypass with plate mounts under carburetor. Positive response from valve returns unneeded fuel to cell. Use with block mounted 15 psi Six Valve fuel pumps for alcohol.
Do not use with a belt-driven pump. Throttle bypasses were designed to operate with block-mounted pumps and, similarly, diaphragm bypasses with belt-driven pumps. Never use a throttle bypass with a belt-driven pump - they must function in pairs and are not to be mismatched. This is a common mistake and one that will definitely cost you.
You can browse our entire inventory at
www.jetracinginc.com - the home of 6 IMCA Modified National Championships! Get your championship car from the best!"