4779 carb replacement

General engine tech -- Drag Racing to Circle Track

Moderator: Team

amc fan
Expert
Expert
Posts: 598
Joined: Wed Jul 11, 2012 7:03 am
Location: BETHLEHEM PENNA.

4779 carb replacement

Post by amc fan »

I have an old 4779 carb modified by Brad Urban in 1984 with 4 corner idle and holes drilled in the throttle blades it has the stock 4779 metering blocks with no removable air bleeds and with a new cam and intake set up it runs rich at idle. I am looking to replace it with something new and I am looking for something bigger in cfm like 850-1050 . motor is a 427 SBC , 4.125 x 4 inch good heads and intake Stahl step headers 263-268 solid roller. Who makes a carb that I can bolt on and be fairly close and can tweak from there?
ProPower engines
Guru
Guru
Posts: 8686
Joined: Sun Jan 21, 2007 1:16 pm
Location: Victoria BC Canada

Re: 4779 carb replacement

Post by ProPower engines »

I would start with a Quick Fuel 850 they have removable air bleeds as well as in the metering blocks they use emulsion jets that can be changed out as well.

They are way easier then trying to tune an older Holley with out removable bleeds etc
Real Race Cars Don't Have Doors
Tuner
Guru
Guru
Posts: 3184
Joined: Sun Apr 01, 2007 5:26 am
Location:

Re: 4779 carb replacement

Post by Tuner »

I would modify the 4777 for removable bleeds, idle jet, PVCR, etc. An old 4777 is a tough act to follow for a lot of "modern" carburetors. :lol:

You might just need a new carb kit and some wire in the idle jets to lean it a bit.
novafornow
Pro
Pro
Posts: 205
Joined: Mon Feb 04, 2019 2:23 pm
Location: california

Re: 4779 carb replacement

Post by novafornow »

Maybe send the one you have to Mark Whitener.
1980RS
Guru
Guru
Posts: 1636
Joined: Thu Oct 13, 2016 10:03 am
Location:

Re: 4779 carb replacement

Post by 1980RS »

I ran an Holley 830Hp last year that worked pretty well after getting the jetting right. Idles well and car pulls like crazy.
tuffxf
Pro
Pro
Posts: 316
Joined: Wed Dec 20, 2006 7:34 am
Location: Central Qld Australia

Re: 4779 carb replacement

Post by tuffxf »

Gday,
Put a kit in it, wires in the idle jets as mentioned work fine,
I know which carb I would rather have.
Those old ones are awesome, plenty big enough and work properly
Cheers
Walter R. Malik
Guru
Guru
Posts: 6353
Joined: Tue Jul 24, 2012 11:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: 4779 carb replacement

Post by Walter R. Malik »

amc fan wrote: Wed Apr 28, 2021 1:42 pm I have an old 4779 carb modified by Brad Urban in 1984 with 4 corner idle and holes drilled in the throttle blades it has the stock 4779 metering blocks with no removable air bleeds and with a new cam and intake set up it runs rich at idle. I am looking to replace it with something new and I am looking for something bigger in cfm like 850-1050 . motor is a 427 SBC , 4.125 x 4 inch good heads and intake Stahl step headers 263-268 solid roller. Who makes a carb that I can bolt on and be fairly close and can tweak from there?
Is this a race vehicle or street driven vehicle ?
http://www.rmcompetition.com
Specialty engine building at its finest.
amc fan
Expert
Expert
Posts: 598
Joined: Wed Jul 11, 2012 7:03 am
Location: BETHLEHEM PENNA.

Re: 4779 carb replacement

Post by amc fan »

Walter... it is going to be a bracket race car mostly , but will be driven to cruise nights. It is an 86 Hurst Olds. The carb that was first tried on the car was a ( Proform 850 ) it fouled the plugs quickly and it had to be idleing at 1300-1500 to stay running ,we swapped it with the 4779 from my 68 AMX ...which idles rich, but so far it is not fouling the plugs , I need the Holley for my car so He has to fix the Proform or get a better carb.
ProPower engines
Guru
Guru
Posts: 8686
Joined: Sun Jan 21, 2007 1:16 pm
Location: Victoria BC Canada

Re: 4779 carb replacement

Post by ProPower engines »

amc fan wrote: Wed Apr 28, 2021 9:22 pm Walter... it is going to be a bracket race car mostly , but will be driven to cruise nights. It is an 86 Hurst Olds. The carb that was first tried on the car was a ( Proform 850 ) it fouled the plugs quickly and it had to be idleing at 1300-1500 to stay running ,we swapped it with the 4779 from my 68 AMX ...which idles rich, but so far it is not fouling the plugs , I need the Holley for my car so He has to fix the Proform or get a better carb.
So then why not just send the carb to a specialist and get the fuel curves corrected based on the application.
They can then remove the fixed air bleeds and install the more current removable bleeds for faster tuning of the idle issues it has now. The proform carbs are hit and miss from what I have seen and heard from guys that tried them because they are a cheap version of what you really want and need..................a carb that works and preforms well. =D>

Or just get a quick fuel as they come with all the current fuel curves and it would be the same or less then sending the other carb out to a shop that just may say its junk and can't be fixed.
Even a used carb can easily be brought back to life with a kit and an hour of your time and a used QF can be had for much less then a new carb and way better then a 40 year old carb that has been screwed with.

JMO
Real Race Cars Don't Have Doors
BillK
Guru
Guru
Posts: 1745
Joined: Wed Aug 26, 2009 8:30 pm
Location: Beautiful Southern Maryland
Contact:

Re: 4779 carb replacement

Post by BillK »

I would call AED and see what they say. They might be able to make yours work. If not they will sell you what you need. Great guys to deal with and great carburetors.

https://www.aedperformance.com/
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

www.enginerepairshop.com
Walter R. Malik
Guru
Guru
Posts: 6353
Joined: Tue Jul 24, 2012 11:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: 4779 carb replacement

Post by Walter R. Malik »

amc fan wrote: Wed Apr 28, 2021 9:22 pm Walter... it is going to be a bracket race car mostly , but will be driven to cruise nights. It is an 86 Hurst Olds. The carb that was first tried on the car was a ( Proform 850 ) it fouled the plugs quickly and it had to be idleing at 1300-1500 to stay running ,we swapped it with the 4779 from my 68 AMX ...which idles rich, but so far it is not fouling the plugs , I need the Holley for my car so He has to fix the Proform or get a better carb.
If you have the time ... I would send that ProForm carb to a reputable "modifier" and give them time to fix it.

If you need to get one right now ... I have had good luck with a Quick Fuel Q-950; (if it is still available).
http://www.rmcompetition.com
Specialty engine building at its finest.
amc fan
Expert
Expert
Posts: 598
Joined: Wed Jul 11, 2012 7:03 am
Location: BETHLEHEM PENNA.

Re: 4779 carb replacement

Post by amc fan »

Thanks everyone for the suggestions and help. I found some videos on you tube from a guy Randy who says he has 40 years of tuning and modifying carbs, and he shows how to modify idle bleeds on old Holley carbs. I drilled .070 holes in all four butterflies and I measured the IFR on the Proform metering block and .034 pin slid in and out with a slight drag. I will try the carb with just the holes in the throttle blades first, and if it is still rich I will try going down .003 at a time on the IFR and watch what happens.
Tuner
Guru
Guru
Posts: 3184
Joined: Sun Apr 01, 2007 5:26 am
Location:

Re: 4779 carb replacement

Post by Tuner »

amc fan wrote: Sat May 01, 2021 2:27 pm Thanks everyone for the suggestions and help. I found some videos on you tube from a guy Randy who says he has 40 years of tuning and modifying carbs, and he shows how to modify idle bleeds on old Holley carbs. I drilled .070 holes in all four butterflies and I measured the IFR on the Proform metering block and .034 pin slid in and out with a slight drag. I will try the carb with just the holes in the throttle blades first, and if it is still rich I will try going down .003 at a time on the IFR and watch what happens.
Before you change the idle jet size try a larger idle air bleed. What size is the IAB now?
amc fan
Expert
Expert
Posts: 598
Joined: Wed Jul 11, 2012 7:03 am
Location: BETHLEHEM PENNA.

Re: 4779 carb replacement

Post by amc fan »

Tuner
I do not have gauge pins over .060 ,so I used a number 51 number drill that measured .070. So the size of IAB would be .070
amc fan
Expert
Expert
Posts: 598
Joined: Wed Jul 11, 2012 7:03 am
Location: BETHLEHEM PENNA.

Re: 4779 carb replacement

Post by amc fan »

Tuner
I do not have gauge pins over .060 ,so I used a number 51 number drill that measured .070. So the size of IAB would be .070
Post Reply