Technical Holley Carb Question

I have a 670 vacuum secondary
Car runs fine but I need to have the black secondary spring in or it bogs.

I know it is opening and I have read the spring rates that say it may never open with the black spring.(Secondaries)
With a lighter spring I get a bad bog when they kick in but after they open it feels no different between the springs as far as how much they open so I think I'm getting them open the same with any spring in it.
What my question is, when I had a 3310 750 I used the purple spring with no issues so why does the smaller carb need the stiffer spring?

 

Lower cfm equals higher vacuum equals steffer spring to keep secondaries from opening to soon

 

I’ll hazard a guess here- the 670 CFM carb has a stronger vacuum pull through the smaller venturi.

 

Bog isn't necessarily your sec. opening. Could be shooters or accel pump cam .

 

Might want to check if the mechanical advance is sticking and advancing to late

 

I would wire the secondary closed and see what happens. Vac secondarys should never attribute to a bog, is the check ball in the housing port? I think Holley makes an external secondary spring kit, Summit may still sell it. Don't have to take the diaphragm apart to adjust. How many cubes?

 

That's what I was thinking.... Oversize shooter!...

 

Rich Bog...or lean stumble??
I find a lot of guys confuse the two or can't tell the difference unless it is a stumble so bad the engine coughs or backfires into the intake and then they know it is not actually a rich bog.

Richen the pump shot, if it gets worse you know instanly that lean pump shot isn't the issue and just change it back

Most often I find it is not enough pump shot rather than too soon secondary spring.

Check the air bleeds on the secondary side for blockage...if the air bleed gets plugged, it will reatly slow the siphon of fuel through the transition circuit that has to happen when the secondary's start to open, especially the idle feed/air bleed circuit on Vacuum Secondary carbs....the air bleeds are really small to make action happen quick, but if it is plugged they kill it.
Verify rear float level too.

 

What is the model number or list number on the carb.

 

There were some model holley that were to lean in the circuitry of the jet plate.

 

The Holley 670 Street Avengers are noted for being very lean. Really crummy calibration from Holley on those, a lot of complaints.

 

0-83670
I changed the stock jets moved the stock 68 jets from the secondary to primary and added 76 jets to the secondary

 

68 to 76 is a pretty big jump.