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Old 11-02-2004, 05:09 PM
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Holley 4777 carb. questions.

This carb. is recommended to me by the machinist who is building my 383. I understand that is a 650 CFM,mechanical secondaries,known as a double pumper.

I guess the machinist had good experience with this specific carb. hence his recommendation. Apparently a carb. with excellent throttle response and superior HP output...He told me also that this carb. would need to be gone-through at about every second year or so. My questionning is what kind of tuning this will be! I'm no carb. enclined neither knowledgeable...my biggest attempts at this level being having had changed few rods and springs on my edelbrock...I don't mind reading and trying to learn but don't want to spend next summer having to fiddle with the thing everytime I want to go for a drive! The initial carb. tuning will be perform at the machinist shop where the engine will be fired-up soon.

I'm questionning myself about how the 4770 compare with other holleys at levels of frequent maintenance work? Would some other holleys,with vacuum sec. as an example, be less demanding in terms of maintenance schedule?

I understand the 4770 is recommended as a strip or track carb....is this recommendation based mainly on the extra gaz consummation or what?

I've asked him about the edelbrock 750 and he told me that whatever tuning you would try it would always be a too rich carb. for my 383 and the 600 too small! So that puts edelbrock aside.

My car is a street used one for short nice days summer trips so milleage is not a big point here.

So is this choice of carb. a good one or not?

thanks,

Ron.

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Old 11-02-2004, 06:16 PM
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Carbs

I would opt for a vacuum secondary for the street myself. Double pumpers have a richer idle circuit than a vacuum secondary which will cost you in fuel. Not to mention that if you don't have a stall converter and a low gear you will not be as happy as you would with the vacuum secondary carb. Besides that...If you use the blue re-use gaskets you will not have a problem with any hollley. The one thing that is a problem with ALL Holley carbs is the idle air and high speed bleeds (located inside the air horn just above the boosters) they will need to be kept clean. Once every 6 months or so I start up the engine and spray some carb cleaner down these bleeds to keep them clean.
I don't want to throw you off the idea of a double pumper. I use one myself on my car but I also have a stall converter and a 3.91:1 gearset. I am just saying that the double pumper has a richer idle circuit and sometimes only 2 fuel circuits. The Vacuum secondary carbs have 3 fuel circuits which gives you a smoother transition between the various throttle angles that you have when driving a street car. In all cases you can bet that what works for me might not work for you. I would install several carbs and let your seat of the pants make your mind up. If I were building your engine I would recommend a 3310 holley with a Purple spring in the vacuum chamber. I am interested in reading what others have to say about this post because this is the most asked question in hot rodding, What kind and what size carb should I run. By the way I have a 406 Chevy with alum heads and roller cam and I am running a Holley 800 Double Pumper.
Good Luck!
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Old 11-02-2004, 08:02 PM
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Cuztomcar,

Interesting comments about the 4777...thanks.

I don't know up to what point the machinist took in consideration the gear ratio the car has...it's a light 2500 pounds car with doug nash 5 speed,direct final ratio,and the diff. ratio is 3.08...and 14 inches tires..so that is easy to take off.

Your comment about the smoother transition in favor of vacuum sec. surprises me I was under the impression there is a kind of bug time associated with vacuum versus as very snappy mechanical.

This car will see (under my ownership anyway) most of its time strolling around 2500 RPM,65-70 MPH so maybe the idea of the 4770 is more about the machinist aiming for max.power than my own goals...I'll have to talk with him about this.

I'll check the 3310 and ask him what he thinks?

thanks, Ron.
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Old 12-21-2005, 12:35 AM
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4777

I run a 4777 on my 350 and like it.Very good off idle throttle response,no bogs,pulls nice to top end and very low maintenance.It did need to be tuned out of the box ofcourse,primary jets,power valve and mod for more idle air bypass.So IF your mechanist sets up the carb RIGHT -----that will be the key.
Mike
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Old 12-21-2005, 03:52 AM
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Had a 4778 , 700cfm on my 383. Worked flawless. My car really liked the 1:1 linkage instead of the progessive.
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Old 12-21-2005, 07:55 AM
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The 650 would be just fine. I recommend you use the 3310 vacuum secondary carb. It will idle smoother, get much better mileage and will provide just as much throttle response. If you need the additional cfm under WOT is then there otherwise you get an infinately better streetable setup.

The secondary opening of the 3310 can be set to provide smooth opening and NO bog or hesitation. Out of the box it will work just fine on stock or highly modified. I sold and installed many of them over the years. The edelbrock carb may be too rich initially but I am sure it is TUNEABLE too.

BTW, there is no such thing as a maintenance free carb. You will need to clean it every now and then. Since the removal of lead from gasoline, I have noticed that carbs need cleaning less often. Also today there is less dyes in the gas and they are not as prone to the creation of varnish which is a whole other problem. If you plan on occasional use, make sure you keep some stabilizer in the gas to keep it from sludging up and causing problems. Also, an inline filter is worth every $$ you spend as they allow you ease of changing.
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Old 12-22-2005, 08:07 AM
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Vacuum vs. Mechanical Secondary Carburetors

Normally with a high stall converter or a manual transmission you're going to get better throttle response, acceleration, and throttle control with a mechanical secondary carburetor.

Vacuum Secondary carburetors work based upon air velocity, and engine load. As air travels through the front barrels of the carburetor it creates a low pressure (or vacuum) signal this is what opens the secondary butterflies. Depending on how you drive the vehicle (aggressive or not) you can run into a scenario where the secondary butterflies are opening and closing at inopportune times making driving more difficult.

As far as the circuits go both mechanical secondary and vacuum secondary carburetors use the exact same circuitry. Idle circuit, Transition circuit, Accelerator pump circuit, and Main Metering circuit. There is not an additional circuit in a Vacuum Secondary carburetor. Generally if you're comparing carburetors of the same size and series in both mechanical secondary and vacuum secondary the calibrations will be all but identical as well.
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Old 12-22-2005, 08:56 AM
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I always use the mechanical secondary carb. The 4 barrels don't open unless I want them too. So what extra fuel I burn at a red light, I save going up hills and rural route driving. Not needing to fool with vacuum springs is one less step in tuning the carb. It is easier to tune a Holley than an Edelbrock. The 4779 will work on a 383 but not a 350. The 4777 is great on a 350 but I use the 4779 on my 400. You are in a grey area with a 383. When in doubt the smaller carb is the best choice but Holley recommends the 4779 for the 383.
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Old 12-24-2005, 08:11 AM
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holly 4777

over the years I.ve used both doubles and vacuums and had good proformance with both. I suspect the vacuums are best for an auto trans. I'v always had 4 sps so I can not comment from experience with Ats. A hotrod with an A.T. to me is the 8th deadly sin. But "you spends your money how you wants". I've also learned over the years that most guys go too large on the carb. This is the 9th deadly sin. Bigger is not better in this case. The "secret' with the holley vacuum carbs is using the right secondary throttle cam. they are cheap so buy a few and swap them uot until you get the best one for your engine. A test that worked for me was to back off the throtle slightly at the upper rpm limit of the engine. If you feel the car pick up some speed or rpm, your carb is too big.
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Old 12-24-2005, 02:02 PM
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I've heard you can run a vac secondary holley 100 cfm larger than a mech. I've only run d/p'ers though, I also run the 1.1 linkage, slighty modified. I also 4 cornered my4777, and she's pretty rich at idle. How do you tune the idle circuit without modifying the air bleeds? I get 14in's at 800 rpm. and she reaks like fuel. idle screws, 2/3rd's out.

Sorry if I jumped in here, I have worked mainly worked with q-jets, and have much to learn about holley's
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Old 03-08-2009, 12:07 AM
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first of all sorry that i am jumping in here....i have a 351w that was in a 86 mustang...i had a 600 vaccum second. carb and was not impressed...but agree that it is a better choice for an auto.....i put a 750 double pumper on it and picked up over a second on the track...i have since pulled the enigne and stuck it in my 88 bronco and have found that the double pumper does run too rich for the at but i am looking at the 4777 for it as well. with the setup you have and the manual i think you will love the double pumper...especially if you arent worried about the fuel mileage. I dont care for what holley recommends cuz they told me i should run a 550cfm...no way i could get the power out of it. the 4777 i noticed aint designed for fuel mileage but it is designed as a streetable carb....let me know how it works for you.
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Old 03-08-2009, 05:48 AM
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Quote:
Originally Posted by TVR383
This carb. is recommended to me by the machinist who is building my 383. I understand that is a 650 CFM,mechanical secondaries,known as a double pumper.

I guess the machinist had good experience with this specific carb. hence his recommendation. Apparently a carb. with excellent throttle response and superior HP output...He told me also that this carb. would need to be gone-through at about every second year or so. My questionning is what kind of tuning this will be! I'm no carb. enclined neither knowledgeable...my biggest attempts at this level being having had changed few rods and springs on my edelbrock...I don't mind reading and trying to learn but don't want to spend next summer having to fiddle with the thing everytime I want to go for a drive! The initial carb. tuning will be perform at the machinist shop where the engine will be fired-up soon.

I'm questionning myself about how the 4770 compare with other holleys at levels of frequent maintenance work? Would some other holleys,with vacuum sec. as an example, be less demanding in terms of maintenance schedule?

I understand the 4770 is recommended as a strip or track carb....is this recommendation based mainly on the extra gaz consummation or what?

I've asked him about the edelbrock 750 and he told me that whatever tuning you would try it would always be a too rich carb. for my 383 and the 600 too small! So that puts edelbrock aside.

My car is a street used one for short nice days summer trips so milleage is not a big point here.

So is this choice of carb. a good one or not?

thanks,

Ron.
Ron,
Why don't you post your entire combo and I will give you a recomendation for carb size....I'm looking for:

CR ratio, cam, dist, intake, header & exhaust size,tranny & stall, gears, and % of street / strip use.

The 4777 650 cfm is a bit small for a 383 and a 4779 750 cfm M/S is a better starting point.

The 4777 650 features straightleg boosters which are the least efficent booster design and the 4779 750 has more modern & efficent downleg bosters.

The 4779 also features 4-corner idle mix screws which make for more precise tuning.

The 3310 is also good unit but it does not feature 4-corner idle.
Jeff

Last edited by Shaker455; 03-08-2009 at 06:01 AM.
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Old 03-08-2009, 06:21 PM
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I too have a 383sbc with a 4778 , 700DP with 1:1 linkage. It works great!
That 1:1 linkage was the best $8 I spent on my car. I was pretty disappointed with my engine before I swapped the linkage.
I don't understand why a DP would run rich unless the powervalves are blocked. Mine is not rich at all , factory jetting.
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Old 03-08-2009, 08:27 PM
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afr NEVER uses vac sec carbs, 4779 is the best choice, but 4777, or 4778 will work...
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Old 07-02-2009, 11:06 AM
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I have a '69 Camaro with the below engine specs. The car ran well until I took it in the body shop and they took 30 months doing the body work. Since I got it back, I've done a lot of work such as new fuel filter, drained fuel and refilled with fresh fuel, new plug wires, new coil, retimed engine, and done some adjustments to Holley carb...which is where I still need help.

Specs:
302 DZ chevy (original Z28 engine)
11:1 compression
Hi rise edelbrock aluminum intake
Holley 4777 carb
Dart II small cc heads
Factory "Duntov 30-30" solid lift cam
Tremec 5-speed with OD
4.11 12 bolt rear end
Mallory Unilite distributor
MSD blaster coil

I have the car running after doing the above work. However, it now won't idle properly. In order to keep it from stalling at idle, I must have the idle speed set way up at around 2,000 RPM. I believe the issue is in the carb, but not sure where to start. I've backed the idle mixture screws out to 1.25 turns from the seat. Once I get the car warmed up and out on the road...it runs "decent", but when I come to a stop sign or light it just stalls.

The carb was rebuilt 4 years ago...but I'm wondering if the fact that it sat for 30 months without being started has "gummed up" some of the really tiny idle passages in the carb.

If this is so, is there a simple way to clear these other than a complete removal/teardown? Any other suggestions?

Thanks,

Dave
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