I'll try to keep this short. I'm having trouble dialing in a 625 cfm Road Demon carb. The car: a '65 fb 289-2v 3-spd stick. Relevant mods: 4-bbl dual plane, tri-y headers, 2-chamber Flows, Pertronix Ignitor II and coil, 3.50:1 lsd 8-inch. Factory 2-bbl camshaft still in place.
This engine ran well enough on the factory 2-bbl, no smoke or anything, pulled hard to guesstimated 4500 or 5000 rpm.
Road Demon was bought used. For jets, it had 61's in the primaries and 73's in the secondaries. Now it's 61's x 70's. Float levels are slightly below the middle hash mark. Don't know what spring is in the vacuum motor. Choke works properly. I've set idle speed and base timing with a vacuum guage, adjusting both to achieve maximum idle, then backing off the bell crank set screw to slow the idle down to an acceptable level.
The problem: starts and idles, idles rough till warmed up, but settles down. Will accelerate if I ease into it, and will run at steady speed under load, including at highway speeds. If coasting at low speed in second or third, will run slightly rough. I might call it surging if I knew for sure that this term is accurate. But apply any throttle at all and it bogs badly. Will run at steady 60 mph, but always on the verge of a stumble.
Barry Grant's trouble-shooting page says to set the idle screws then readjust the butterflies. I have done part one but not part two. Part two requires to remove carb and turn it upside down and check the transfer slot openings, which should show .020" of the transfer slot. Next, BG says to change the squirter size.
What do you guys say? Do I have an accelerator pump problem?
TIA
Seven
This engine ran well enough on the factory 2-bbl, no smoke or anything, pulled hard to guesstimated 4500 or 5000 rpm.
Road Demon was bought used. For jets, it had 61's in the primaries and 73's in the secondaries. Now it's 61's x 70's. Float levels are slightly below the middle hash mark. Don't know what spring is in the vacuum motor. Choke works properly. I've set idle speed and base timing with a vacuum guage, adjusting both to achieve maximum idle, then backing off the bell crank set screw to slow the idle down to an acceptable level.
The problem: starts and idles, idles rough till warmed up, but settles down. Will accelerate if I ease into it, and will run at steady speed under load, including at highway speeds. If coasting at low speed in second or third, will run slightly rough. I might call it surging if I knew for sure that this term is accurate. But apply any throttle at all and it bogs badly. Will run at steady 60 mph, but always on the verge of a stumble.
Barry Grant's trouble-shooting page says to set the idle screws then readjust the butterflies. I have done part one but not part two. Part two requires to remove carb and turn it upside down and check the transfer slot openings, which should show .020" of the transfer slot. Next, BG says to change the squirter size.
What do you guys say? Do I have an accelerator pump problem?
TIA
Seven
