Which carb to go with?

[Sask84gt]

Hey all. Trying to decide which carb to throw on my fox. 84 with a 91 302 motor, edlebrock rmp intake and bbk shorty headers to off road h-pipe to flowmaster American thunder 40 series dual exhaust. Right now I have the stock holley 4180c on it. My 85 that's pretty much going to be a parts car has a 4160 600cfm. Number on the carb is 80457-7 and was manufactured in either 88,98,2008. Would the 600 be better fit for my car than the 4180? As in a bit more hp, tunability etc?

[bwguardian]

No, stick with the 4180c as it has annular primaries. Do a search on here for a couple tweaks you can do to it for better performance.

[lwelchx2]

Consider dropping to a smaller carb even. Based on the cubic inches, the optimal cfm for a 302 is somewhere around 524 cfm. It all depends on the application and where you want the powerband at. I suggest a 500 on street/strip and a 600 on a racecar.

[Sask84gt]

Consider dropping to a smaller carb even. Based on the cubic inches, the optimal cfm for a 302 is somewhere around 524 cfm. It all depends on the application and where you want the powerband at. I suggest a 500 on street/strip and a 600 on a racecar.

Hmm not sure where I want the power band actually. Never thought of it as I'm new to all this. I think I definitely want more low to mid power than upper range. Also I am planning on adding a decent set of heads and a cam eventually so would a 500cfm still be good?

[lwelchx2]

A 500 will allow you to go more aggressive cam and heads because it'll put the powerband lower. In my eyes, its all about the application. The more performance gains that are made, it may affect streetability. Like putting a really aggressive cam in a car. It sounds like its gonna stall at idle because that cam is made for high rpms. Theres a lot of variables and it starts to get confusing, but it comes down to application.

Personally, I have a street-strip and I'm gonna put a 500 summit carb on it. I have no need to have my power hit at 4000rms or higher because most of the time, Ill be driving at 2000ish and punch it every now and then. But for a drag car, most of the time you're in the 4000-6000 range, so a bigger carb comes in handy.

Sorry for changing the topic, but I thought mentioning the carb size could be a gamechanger in your decision

[Sask84gt]

A 500 will allow you to go more aggressive cam and heads because it'll put the powerband lower. In my eyes, its all about the application. The more performance gains that are made, it may affect streetability. Like putting a really aggressive cam in a car. It sounds like its gonna stall at idle because that cam is made for high rpms. Theres a lot of variables and it starts to get confusing, but it comes down to application.

Personally, I have a street-strip and I'm gonna put a 500 summit carb on it. I have no need to have my power hit at 4000rms or higher because most of the time, Ill be driving at 2000ish and punch it every now and then. But for a drag car, most of the time you're in the 4000-6000 range, so a bigger carb comes in handy.

Sorry for changing the topic, but I thought mentioning the carb size could be a gamechanger in your decision

Np man I'm glad you said something. I had no idea really about any of it. I just figured my stock 4180 was like a 570cfm or something and the 85 I have has a 600cfm so that's what I should go with. I got stuck in the whole it's a bigger cfm so it must be better lol. Like you I have no real reason for my power to hit at 4000+ either. I will be driving pretty much same as you. Funny you mention the summit carb as i was looking at buying that one. Seems to have great reviews. Just wish i could get it in black with electric choke and vacuum secondary. Lol Thanks again for info

Edit: just to be sure, what hp could I run with a 500cfm before I'd have to switch to a bigger carb?

[BaconB8]

If you’re not concerned with originality there’s nothing wrong with the 600 cfm Holley. The 4180 is fine too. The 600 is a good choice sine the replacement Holley kits are available everywhere. The 4180 not so much.

[richpet]

The 570 Street Avenger worked great for my mild build for years.

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[Walking-Tall]

For the ability to verify without a doubt (cleaner, air pressure with a blow gun) that any and all gook and debris is all clean and clear throughout out of a carburetor before installing, "throw on" the 80457-7, hands down. Due to your future plans of upgraded heads and especially more camshaft (although I would suggest the following right now anyways)... look for a good old Holley LIST-3310, a very early base 3310 or -1 with down-leg boosters (780), or -2 or later straight-leg booster (750) vacuum secondary, the older the better. A 750 installed on my own 306 made a night and day power difference as compared to a 600 that was installed, and right now with the dialed-in Holley 950 3-barrel vacuum secondary on it, it's another large notch up, with crispy throttle response, no lack of bottom end torque, noticeably increased peak torque and hp, as well as average increased across the board (area under the curve) torque and hp (even with only 3.08 gears, it pulls hard, bottom to top, like gangbusters). There is NO SUCH THING as "too much carb". Don't believe? Challenge me, I'll show ya.

[Sask84gt]

For the ability to verify without a doubt (cleaner, air pressure with a blow gun) that any and all gook and debris is all clean and clear throughout out of a carburetor before installing, "throw on" the 80457-7, hands down. Due to your future plans of upgraded heads and especially more camshaft (although I would suggest the following right now anyways)... look for a good old Holley LIST-3310, a very early base 3310 or -1 with down-leg boosters (780), or -2 or later straight-leg booster (750) vacuum secondary, the older the better. A 750 installed on my own 306 made a night and day power difference as compared to a 600 that was installed, and right now with the dialed-in Holley 950 3-barrel vacuum secondary on it, it's another large notch up, with crispy throttle response, no lack of bottom end torque, noticeably increased peak torque and hp, as well as average increased across the board (area under the curve) torque and hp (even with only 3.08 gears, it pulls hard, bottom to top, like gangbusters). There is NO SUCH THING as "too much carb". Don't believe? Challenge me, I'll show ya.

Lol well now I don't know what to believe. I'm going to follow your advice though and put the 80447-7 on and see how she goes. Your pretty much the go to guy around here for carb advice so I trust your opinion. Just wished you lived closer so you could rebuild it for me LOL. Thanks Mike
Edit: Just noticed your rebuild site, any chance your going to do a 80457-7 rebuild on there? Noticed you had a 80447-8 is that pretty much the same?

[gt4494]

Whatever carb you go with find someone that has the know-how to tune it properly. I went with a 600cfm and it was a dog. Then I hooked up with a friend that was a drag racer and had all the holey jets, power valves etc. about two hours of tuning and the car is a different car!!

Engine is the stock 302 with a dual plane manifold, E7 heads and shorties with 2 1/2 from the manifolds out. no cats and a single chamber muffler. put 225 hp and 225 torque to the wheels. Not bad for "almost" stock.

[Walking-Tall]

Lol well now I don't know what to believe. I'm going to follow your advice though and put the 80447-7 on and see how she goes. Your pretty much the go to guy around here for carb advice so I trust your opinion. Just wished you lived closer so you could rebuild it for me LOL. Thanks Mike
Edit: Just noticed your rebuild site, any chance your going to do a 80457-7 rebuild on there? Noticed you had a 80447-8 is that pretty much the same?

Disassembly, cleaning and blowing all out, and rebuild... if it turns out it seems to need it, you can do it.
That -8 was another of many reasons I tell people that they'd be best off to get something that is "the older, the better". I outline some of the quality and detail issues that the "new and improved" carburetors are plagued with on that -8 thread. Your -7 should be similar or basically exactly the same... each newer dash number is sometimes just something cosmetic. I don't like it when float level isn't externally adjustable, like that -8 was, but it is adjustable inside.

[Sask84gt]

Disassembly, cleaning and blowing all out, and rebuild... if it turns out it seems to need it, you can do it.
That -8 was another of many reasons I tell people that they'd be best off to get something that is "the older, the better". I outline some of the quality and detail issues that the "new and improved" carburetors are plagued with on that -8 thread. Your -7 should be similar or basically exactly the same... each newer dash number is sometimes just something cosmetic. I don't like it when float level isn't externally adjustable, like that -8 was, but it is adjustable inside.

My brother also has a model 6619-1 2321 that he was going to give me. What's the difference between this one and the 80457-7 carb?

[Walking-Tall]

My brother also has a model 6619-1 2321 that he was going to give me. What's the difference between this one and the 80457-7 carb?

Mainly, "reverse-idle". The idle mixture screws, blunt nose more course adjustment taper, function opposite of conventional idle mixture screws (sharp tip finer adjustment, clockwise~lean, counter-clockwise~rich), and the metering block has larger mixture screw tip passages for the blunt nose screws... if the stickers are gone from the 6619-1, they would have indicated with counter-clockwise lean arrows, which is opposite of conventional idle mixture screws. Opening the "reverse-idle" screws, counter-clockwise, admits more air into the idle/off-idle circuit, as opposed to more fuel conventionally. Fully in with "reverse-idle", clockwise, is full rich, and limited to as rich as it can be as is it is internally calibrated. As well, the 6619-1 will have the same troublesome brass with o-rings accelerator pump circuit transfer tube that is supposed to seal between the metering block and the main body, as is within the 4180... most everything else is physically the same, these 600 vacuum secondaries we are talking about...

You should snatch that freebie 6619-1, if for nothing else than for the externally adjustable needle and seat float bowls.

[Sask84gt]

Mainly, "reverse-idle". The idle mixture screws, blunt nose more course adjustment taper, function opposite of conventional idle mixture screws (sharp tip finer adjustment, clockwise~lean, counter-clockwise~rich), and the metering block has larger mixture screw tip passages for the blunt nose screws... if the stickers are gone from the 6619-1, they would have indicated with counter-clockwise lean arrows, which is opposite of conventional idle mixture screws. Opening the "reverse-idle" screws, counter-clockwise, admits more air into the idle/off-idle circuit, as opposed to more fuel conventionally. Fully in with "reverse-idle", clockwise, is full rich, and limited to as rich as it can be as is it is internally calibrated. As well, the 6619-1 will have the same troublesome brass with o-rings accelerator pump circuit transfer tube that is supposed to seal between the metering block and the main body, as is within the 4180... most everything else is physically the same, these 600 vacuum secondaries we are talking about...

You should snatch that freebie 6619-1, if for nothing else than for the externally adjustable needle and seat float bowls.

Ok, thanks for the help Mike. I will most likely put the 80457-7 on.

[Sask84gt]

Removed the 80457-7 carb from my 85 and took some photos. Doesn't look to bad to me but then again I'm not sure what I'm looking for LOL. Pictures are not the best.
Attachment 136320

[854vragtop]

I've had my '85 GT convertible since 1990 and have run the stock 4180c, and aftermarket Holley 1850, and the Summit 600 CFM vacuum secondary carb. Hands down the best carb has been the Summit carb. Tunes exactly like a Holley, comes with some genuine Holley parts on it, and seems to be an exact copy of the Holley 4010 carb.

Annular boosters on all 4 barrels
Comes with green accelerator pump cam
One piece bowl with easy access to change gets
Glass fuel bowl sight windows
Holley Quick Change Vacuum Secondary Spring Kit bolts right on
Best throttle response of all carbs listed above
No hesitation when shifting and getting back on the throttle
Absolutely the best cold weather driveability. I can start it and drive off cold with no stalling, bucking, etc.

You will have to relocate your coil to the A/C pump support bracket because of the dual feed line.

[Sask84gt]

I've had my '85 GT convertible since 1990 and have run the stock 4180c, and aftermarket Holley 1850, and the Summit 600 CFM vacuum secondary carb. Hands down the best carb has been the Summit carb. Tunes exactly like a Holley, comes with some genuine Holley parts on it, and seems to be an exact copy of the Holley 4010 carb.

Annular boosters on all 4 barrels
Comes with green accelerator pump cam
One piece bowl with easy access to change gets
Glass fuel bowl sight windows
Holley Quick Change Vacuum Secondary Spring Kit bolts right on
Best throttle response of all carbs listed above
No hesitation when shifting and getting back on the throttle
Absolutely the best cold weather driveability. I can start it and drive off cold with no stalling, bucking, etc.

You will have to relocate your coil to the A/C pump support bracket because of the dual feed line.

Thanks for your opinion. Ya if and when I buy a new carb I will definitely look into the summit ones. I've read nothing but great things about them. My coil is located on my driver side shock tower so I would be alright with the dual feed.

[ragtopjr]

Thanks for your opinion. Ya if and when I buy a new carb I will definitely look into the summit ones. I've read nothing but great things about them. My coil is located on my driver side shock tower so I would be alright with the dual feed.

I am running a 680 Black Diamond from Quick Fuels Technology, but at this point if I was going to have to spend the money on a new carb I would go to a Holley EFI , at some point on the ragtop I hope to have the cash to upgrade to that.....
Over the years I have run Holley 600 Double Pumpers with great results, moved up to the Black Diamond for a couple of different reasons....
1 - It was Black and Beautiful...
2 - It was a Vacuum Secondary w electric choke, and was looking a little better drive ability when first started...