[tvanlant]

I have an 850 vac secondary holley on my ZZ502. I am going to switch to a Barry Grant 850 Speed Demon. What are the differences in the two carbs? Will I need to change anything (ie. fuel hookups, ect)? What are the main differences between the two carbs? Does the barry grant have a power valve? Any other info is appreciated

[lluciano77]

They should be a direct swap. You may need to change a vacuum line, but it is unlikely.

Barry Grant Carbs are almost exactly like Holleys. They have Holley powervalves. Most of their parts are Holley interchangeable.

I suggest if you run a BG or a Holley, you should learn as much as possible about their components and how to tune them. There are plenty of good books out there that will tell you everything.

A vacuum guage is also necessary. It is the most accurate way to tune the idle mixture. I don't leave home without one. Mine has a permanent place in my trunk.

[tvanlant]

what about fuel inlet thread size? are they the same? or will I have to get a new fuel feed line?

[lluciano77]

If you have the 7/8" or whatever it is fuel line I think it will fit. The 3/8" fuel line won't if I am not mistaken. Either way the local parts house should have a fuel line that will work.

[Tech @ BG]

You will need to purchase a new dual feed line as our inlet fittings, and center to center distance are different than on a Holley. You will also need to either modify your exsisting air cleaner, or get one specifically designed to fit a Demon. The choke towers are larger on a Demon to increase the air flow, so the air cleaner has to clear the choke linkage. Other than those two things the rest of your items should interchange. If you have any questions, please contact our technical department at (706) 864-8544.