4V carbs.... vacuum vs mechanical secondaries

[chargerdon]

Anyone care to enlighten me on the pros and cons of vacuum vs mechanical secondaries on a 4V.   My 360 has a Lunati Vodoo 703 in it which i love, but, i have noticed that it bogs a little when punching it before the full power comes on.   Im running an Edlebrock 1405 600 vacuum secondaries.   Looking at getting a little bigger 700-750 range carb and some have vacuum and some mechanical.   So anyone know the characteristics of each?

[torredcuda]

Pretty good read here - https://www.hotrod.com/articles/vacuum-or-mechanical-secondary-carburetor/

[blown motor]

Good article for a greenhorn like me.

[Chryco Psycho]

I like EFI best ...
having said that the Edelbrock carbs are the worst choice / least adjustable & tunable , I always take eddys apart reset float levels & lighten the counter weight on the rear air door as the fisrt step in tuning .
Personally I always use mechanical secondary carbs as they are far more responsive , but not perfect , if you floor a mech carb at too low RPM or with too much load I promise it will bog the engine simply cannot overcome the vacuum drop , but if you punch it half way & roll in it will out perform a vacuum carb everytime , , at higher RPM mech will always outperform the vac carbs so part of the tuning is driver training .
My personal preference is the Proform carbs , they are very responsive & tunable for a reasonable price .

For example the eddy carb has 3 squirter choices small medium & large , they come with medium & i often have to drill them out to overcome a bog as you cannot get enough fuel in fast enough , while Holley type carbs have 14 sizes , also the accelerator pump has a choice of 3 positions for total volume of fuel pumped , where Holley type have 8 - 2 position cams . you also have pumps on both the front & rear not just from on the eddy carbs , there are 7 circuits in a carb a almost all are more adjustable on Holley type carbs

[RUNCHARGER]

I agree totally with CP.

[71-440]

I'm running an Eddy on my setup. Not my choice as that's what it came with. The Proform carbs look to be much more tunable.
If I had a choice I'd go with the Proform. Or as Neil said EFI.

[Racer57]

Anyone care to enlighten me on the pros and cons of vacuum vs mechanical secondaries on a 4V.   My 360 has a Lunati Vodoo 703 in it which i love, but, i have noticed that it bogs a little when punching it before the full power comes on.   Im running an Edlebrock 1405 600 vacuum secondaries.   Looking at getting a little bigger 700-750 range carb and some have vacuum and some mechanical.   So anyone know the characteristics of each?

I had the same 600 Edlebrock on my 383 4 speed and I thought it ran good. Put a Holley dual feed, double pump with mechanical secondaries on it. Puiled out onto road and tromped it. It lite up the rear tires.    Cars change in response was beyond anything I thought possible.

[RUNCHARGER]

You bet: The best carbed setup I ever ran was the mechanical six pack with accelerator pumps in all 3 carbs. No bog, no waiting just instance response, great fuel mileage, great top end power.

[dodj]

A while back on my 440 I had a 750cfm 3310 Holley. Vacuum Secondaries. I bought a Holley kit that had about 7 or 8 different colour springs for the secondary diaphragm. You could definitely change the characteristics of how the secondaries operated. But I was never 100% satisfied with it. Over on the other site CP suggested I pick up a proform mechanical. So I bought a Black Street 850 mechanical secondary unit. Like this one but no purple on it.
https://www.proformparts.com/product-detail/67314/black-street-series-carburetor-850-cfm-mechanical-secondary-black-and-purple

It has proformed far better than my Holley ever did. 
They have them in 650cfm and up.

[kawahonda]

I like EFI best ...
having said that the Edelbrock carbs are the worst choice / least adjustable & tunable , I always take eddys apart reset float levels & lighten the counter weight on the rear air door as the fisrt step in tuning .
Personally I always use mechanical secondary carbs as they are far more responsive , but not perfect , if you floor a mech carb at too low RPM or with too much load I promise it will bog the engine simply cannot overcome the vacuum drop , but if you punch it half way & roll in it will out perform a vacuum carb everytime , , at higher RPM mech will always outperform the vac carbs so part of the tuning is driver training .
My personal preference is the Proform carbs , they are very responsive & tunable for a reasonable price .

For example the eddy carb has 3 squirter choices small medium & large , they come with medium & i often have to drill them out to overcome a bog as you cannot get enough fuel in fast enough , while Holley type carbs have 14 sizes , also the accelerator pump has a choice of 3 positions for total volume of fuel pumped , where Holley type have 8 - 2 position cams . you also have pumps on both the front & rear not just from on the eddy carbs , there are 7 circuits in a carb a almost all are more adjustable on Holley type carbs

I have the same low end lean bog and have 3 accelerator  puzzles to pick from. What do you find is the appropriate size?

[torredcuda]

I`m currently running a Holley 750 DP with a Proform main body which gives me extra tunability. To be honest it`s over-carburated for the street but at the track it runs better ET`s than with the previuos Holleys Ive`d tried on it including a 650, 750 vacuum and others. Gas mileage on the other hand is pretty poor as I`m lucky to get 10mpg even going easy on it. Bottom line if you want the best performance and can take the  time to tune it correctly go manual but if you want better mileage and more of a bolt on go vacuum.

[chargerdon]

so that i understand...   on my 600 cfm eddy performer...  it has a mechanical linkage to the throttle plates, but, a vacuum controlled top door...   Sooo is this still considered a mechanical?   Does all mechanical secondary carbs also have a top door controlled by a weight vacuum?   

[Chryco Psycho]

Yeah it is a hybrid
it has mech secondaries but the air cannot flow without waiting for the air door , I always lighten the counterweight significantly as it is Always too heavy , but it acts a vacuum secondary .
Pure Junk , As Dodj said , even when you think it is running fine you are leaving so much power on the table , I found where mid throttle had 50 extra RWHp with the same size carb going from Eddy to proform

[Chryco Psycho]

I like EFI best ...
having said that the Edelbrock carbs are the worst choice / least adjustable & tunable , I always take eddys apart reset float levels & lighten the counter weight on the rear air door as the fisrt step in tuning .
Personally I always use mechanical secondary carbs as they are far more responsive , but not perfect , if you floor a mech carb at too low RPM or with too much load I promise it will bog the engine simply cannot overcome the vacuum drop , but if you punch it half way & roll in it will out perform a vacuum carb everytime , , at higher RPM mech will always outperform the vac carbs so part of the tuning is driver training .
My personal preference is the Proform carbs , they are very responsive & tunable for a reasonable price .

For example the eddy carb has 3 squirter choices small medium & large , they come with medium & i often have to drill them out to overcome a bog as you cannot get enough fuel in fast enough , while Holley type carbs have 14 sizes , also the accelerator pump has a choice of 3 positions for total volume of fuel pumped , where Holley type have 8 - 2 position cams . you also have pumps on both the front & rear not just from on the eddy carbs , there are 7 circuits in a carb a almost all are more adjustable on Holley type carbs

I have the same low end lean bog and have 3 accelerator  puzzles to pick from. What do you find is the appropriate size?

Sorry I meant to reply to this @kawahonda , if you have a bog off idle you either need to increase the squirter size or raise the float level , if the carb was not taken apart after ship[ping & before installing it the float level is generally wrong , 7/16 is the normal spec but I have found they work better at 3/8"

[kawahonda]

I like EFI best ...
having said that the Edelbrock carbs are the worst choice / least adjustable & tunable , I always take eddys apart reset float levels & lighten the counter weight on the rear air door as the fisrt step in tuning .
Personally I always use mechanical secondary carbs as they are far more responsive , but not perfect , if you floor a mech carb at too low RPM or with too much load I promise it will bog the engine simply cannot overcome the vacuum drop , but if you punch it half way & roll in it will out perform a vacuum carb everytime , , at higher RPM mech will always outperform the vac carbs so part of the tuning is driver training .
My personal preference is the Proform carbs , they are very responsive & tunable for a reasonable price .

For example the eddy carb has 3 squirter choices small medium & large , they come with medium & i often have to drill them out to overcome a bog as you cannot get enough fuel in fast enough , while Holley type carbs have 14 sizes , also the accelerator pump has a choice of 3 positions for total volume of fuel pumped , where Holley type have 8 - 2 position cams . you also have pumps on both the front & rear not just from on the eddy carbs , there are 7 circuits in a carb a almost all are more adjustable on Holley type carbs

I have the same low end lean bog and have 3 accelerator  puzzles to pick from. What do you find is the appropriate size?

Sorry I meant to reply to this @kawahonda , if you have a bog off idle you either need to increase the squirter size or raise the float level , if the carb was not taken apart after ship[ping & before installing it the float level is generally wrong , 7/16 is the normal spec but I have found they work better at 3/8"

Thanks! Yea. I'm trying to measure what I have right now with Jeweler's bits, and then will decide which one of the three nozzles to increase it to....or if the gap is too large maybe drill mine out slightly?

My thinking the fastest way to swap out a nozzle is to remove the choke plate vs removing the air horn. Removing the air horn means removing lots more things. Which is the better route? If I remove the air horn then I can check the float--I followed whatever came with Mike's carb rebuild kit and also what someone else linked to me on here.