the 4779 does NOT have 4-corner idle, and it does NOT have adjustable air bleeds.

 

Thanks. Nevr worked on a 4779 and just thought it was odd that it only had 2 corner idle.

 

Carb Number

Carb Model Number

CFM

Idle Air Bleed - LSAB

Intermediat Bleed

High Speed Air Blead - HSAB

Renew Kit

Trick Kit

Needle & Seat

Primary Main Jet

Secondary Main Jet or plate

Primary Metering Block

Secondary Metering Block

Power Valve

Pump Nozzle Size, Primary

Secondary Nozzle Size or Spring Color

Primary Bowl Gasket

Primary Metering Block Gasket

Secondary Bowl Gasket

Secondary Metering Block Gasket

Secondary Metering Plate Gasket

Primary Fuel Bowl

Secondary Fuel Bowl

Throttle Body & Shaft Assembly

Venturii Diameter Primary

Venturii Diameter Secondary

Throttle Bore Diameter Primary

Throttle Bore Diameter Secondary

R4779-5

4150

750

37-485

37-933

6-504

122-70

122-80

N/A

N/S

125-65

0.028

0.031

108-83-2

108-89-2

108-83-2

108-89-2

N/R

134-103

134-104

N/S

1-3/8

1-3/8

1-11/16

1-11/16

 

The 4779 List number is THE original mechanical secondary double pump performance design Holley offered,
The original group was 600, 650, 700, 750, 800, and 850 CFM versions. Model 4150.
All were 2 corner idle in the original design.
#4776 is 600 cfm
#4777 is 650 cfm
#4778 is 700 cfm
#4779 is 750 cfm
#4780 is 800 cfm
#4781 is 850 cfm.

Everything is basic on these, all bleeds and orifices are cast or drilled holes, no removable bleeds back then.
Removable bleeds started out as a custom carb builder trick that got popular in race circles in the 1970's bit didn't filter down to general racers and hot rodders until the late 1980's but didn't get super popular on nearly everything new until the 2000's.

 

I finished up rebuilding this carb, and he got it installed and running. He said it started right up and ran just fine, but when he shut it off, it would not restart. That is the same problem he brought me the carb for in the first place. I went over to his shop this morning to see what the problem was. It started right up from cold and ran OK. The idle screws were 1-1/2 turns out when it came to me, so I set them back like that when I rebuilt it. I went to adjust the idle screws with it running and found that I could almost close both idle screws before it made any difference in the idle quality. I turned them back out to a little less than 3/4, but I think that 1/4 turn would have been enough. It ran just fine on the test ride (burns the tires though 2nd gear). Don't know much about the internals. Solid lumpy cam. Iron heads.
My question is: is there much I could do about giving the idle screws a little more control? Without a changeable IFR jet I don't think there is much. It looks like I could drill and tap the IFR holes for jets. I have done this on several carbs. Would it be worth doing?
I know this carb is really old, but it looks brand new!
As far as the not restarting problem, I must have started it a least a dozen times, and it never failed to start.

 

Holley carbs are generally between 3/4 and 1 turn out

Not responding to idle screws means it's drawing fuel elsewhere.

How are the transfer slots? Are they set to a square?
Fuel level?
Did you chase every passage with fishing line?

 

Holley carbs are generally between 3/4 and 1 turn out

Not responding to idle screws means it's drawing fuel elsewhere.

How are the transfer slots? Are they set to a square?
Fuel level?
Did you chase every passage with fishing line?

Yes, transfer slot is square. I set it when I rebuilt carb. Idle speed was a little low, so I raised it by opening the secondaries a tad. Fuel level is right at the bottom of the hole. And yes I chased every circuit. I should have gauged the idle feed holes before I put it back together. All my QFT carbs have had needed .028 to .031 IFRs.