AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,911
- Reaction score
- 12,263
I know you like short answers so;
on the forward half of the throttle valves,between the T-slots and the Idle ports, and about 1/3 of the way back towards the center point
BTW, if you put a 4-corner idle carb on a SBM, with a 223* or smaller cam, don't even bother trying to get the secondary idle circuits working. If you do, the primaries will likely be too far closed on the transfers, and you know what that leads to.
The long answer;
Well, I've been lambasted a few times for promoting the holes. But I've seen it done from the factory on all kinds of small equipment, especially outboard marine engines. I can almost guarantee you that nearly every piece of lawn and garden equipment, that you own, that has an idle position, has a butterfly with either a hole or a trimming.
And unless your 4bbl carb has a 4-corner idle system on it, the only correction for bypass air that I know of, is with either drilled holes, or PCV flow manipulation. I tried the PCV flow deal, but that didn't work out very well for me.
Since I wanted the bypass air to mix with the transfer discharge/idle discharge as quickly as possible, that's where I put my holes. Namely on the forward half of the throttle valves,between the slots and the ports, and about 1/3 of the way back towards the centerpoint. Mine was a Holley. The learning curve hit me hard. I kept drilling and tuning and drilling and tuning, and suddenly, the holes were too big; from 7/32 to 8/32 I found out, is a big change! Yeah I had to figure out how to make the solder stick, and made a mechanical joint by chamfering both sides. The plugs are still in there, since year 2000 I think.
on the forward half of the throttle valves,between the T-slots and the Idle ports, and about 1/3 of the way back towards the center point
BTW, if you put a 4-corner idle carb on a SBM, with a 223* or smaller cam, don't even bother trying to get the secondary idle circuits working. If you do, the primaries will likely be too far closed on the transfers, and you know what that leads to.
The long answer;
Well, I've been lambasted a few times for promoting the holes. But I've seen it done from the factory on all kinds of small equipment, especially outboard marine engines. I can almost guarantee you that nearly every piece of lawn and garden equipment, that you own, that has an idle position, has a butterfly with either a hole or a trimming.
And unless your 4bbl carb has a 4-corner idle system on it, the only correction for bypass air that I know of, is with either drilled holes, or PCV flow manipulation. I tried the PCV flow deal, but that didn't work out very well for me.
Since I wanted the bypass air to mix with the transfer discharge/idle discharge as quickly as possible, that's where I put my holes. Namely on the forward half of the throttle valves,between the slots and the ports, and about 1/3 of the way back towards the centerpoint. Mine was a Holley. The learning curve hit me hard. I kept drilling and tuning and drilling and tuning, and suddenly, the holes were too big; from 7/32 to 8/32 I found out, is a big change! Yeah I had to figure out how to make the solder stick, and made a mechanical joint by chamfering both sides. The plugs are still in there, since year 2000 I think.
all I asked was for a picture!
