Need a Carb recommendation

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Joined
Dec 11, 2015
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Location
Philadelphia
My Car
73 Mach 1
My factory carb could use a rebuild but from what I hear it's better to just upgrade from the 4300d. I've also hear that you can't just drop any old carb on top of the factory intake due to the spread bore. As i've mentioned in my intro...the carb world to me is completely new so please forgive my ignorance when asking some questions that might seem simple.

I've heard good things about holley carbs and I'd like to keep my factory intake if possible. I plan on keeping the car close to stock with the exception of long tube headers and exhaust. If the motor ever went then I'd put a mild cam in it. So if it's possible to have a carb that would be ok for stock but would also allow me to grow into it if I had to that would be better. I intend to use the car as a weekend cruiser with some spirited street driving. No track or autocross. The motor is a 351C 4v with a 4 speed top loader. Currently the gears are 3:89 but I might chicken out and put 3:50 3:55's unless you guys think I should stick with the 3:89's? Thanks

 
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Part# 0-80459SA holley spread bore 750cfm carb.would be a good fit for stock or mild build.Keep the 3:89's if you want to add a mild cam look at the Comp Cams Dual Energy cam 275DEH 2000 - 6000 RPM range.

 
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Part# 0-80459SA holley spread bore 750cfm carb.would be a good fit for stock or mild build.Keep the 3:89's if you want to add a mild cam look at the Comp Cams Dual Energy cam 275DEH 2000 - 6000 RPM range.
Isn't that Holley a square bore? I had once tried a square to spread bore adapter to keep my original intake and really didn't like the performance. I would just go with a performer manifold now.

 
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I'm sure holley makes a good matching intake for the carb that would be suggested correct? Would those part number be? Do I have to worry about any clearance issues? Just wondering what everyone else has used with success?

 
An Edelbrock Performer intake and a Quick Fuel ss-680-vs carb will work with your current combo and the carb will not be a limiting factor for future upgrades.

 
That Holley won't bolt to the 73 spreadbore intake. A good option to keep it mostly stock would be a 70-71 M-code iron intake with a carb of your choice. You may need to run a small spacer for the butterflies to clear the bores on the mounting pad.

 
From what you indicate as using the car for a cruiser and spirited occasional driver, there isn't any major advantage in keeping the 4300D spread-bore manifold on the engine insofar as performance. Changing to an Edelbrock performer manifold (or similar) will open up the choice of carbs that can be easily bolted on. The change will probably be a major wake-up in terms of ease of starting, off-the-line performance, and improved gas mileage. Keep the stock 4300D manifold and carb on the shelf to either sell outright or include with the car if you ever get an offer that can't be passed up.

On the other hand, if you have the carb professionally rebuilt by someone who knows what they're doing (may take some research to find someone, and this forum can assist with recommendations) you can run the 4300D for a long time with decent performance. The cost of a 4300D rebuild will be about the same as changing the manifold and carb to standard square-bore configuration. You will have to learn a few things about carbs as it is (how to set cold start choke, warm idle fuel/air mix, etc) but it's not all that difficult to learn the basics. If an engine rebuild comes due, then would be the time to discuss changing the intake/carb set up with the engine builder to meet the goals of the rebuild. With that in mind, the condition of your current 4300D should have bearing on any decision. One issue the 4300D is prone to is a cracked base plate. If that occurs, or something like internal passage erosion is evident, then changing to an aftermarket setup is the way to go.

 
I don't mind doing the aftermarket intake with a new carb I just need to know what combo works the best for my intended use. Which would be spirited weekend cruiser. Plus it would be nice to allow for a mild cam upgrade down the road. What CFM would you say 650 at the very least? Is it cool to do an eddy intake with Holley carb or just do Eddy/ Eddy? I just don't know whats good these days? I've been out of the performance market for about 10 years and this is my first carb car.

 
There's another thread about carb/intake decision going on, and here's my input to that (post 13): http://www.7173mustangs.com/thread-decision-time-advice?page=2

600 cfm is really about all you'd want without warming up the rest with a performance valve-train (cam, rockers, head work, etc.) and higher-flowing exhaust (headers, etc.).

It all works together... simply adding a bigger carb and performance intake will only give you slightly better performance - it's only a small part of the equation for more power. You can only feed the beast so much more before it starts to choke on too much. ;)

 
There's another thread about carb/intake decision going on, and here's my input to that (post 13): http://www.7173mustangs.com/thread-decision-time-advice?page=2

600 cfm is really about all you'd want without warming up the rest with a performance valve-train (cam, rockers, head work, etc.) and higher-flowing exhaust (headers, etc.).

It all works together... simply adding a bigger carb and performance intake will only give you slightly better performance - it's only a small part of the equation for more power. You can only feed the beast so much more before it starts to choke on too much. ;)
Thanks for the link. I will at the very least do a full exhaust along with the new carb setup. Since rockers and springs are kind of easy to do would there be a suggestion to do that also? What are the factory rocker size?

 
When you do the exhaust I highly recommend swapping out the manifolds with headers. Made a huge difference on mine even with just a factory 2v set up.

 
Wow. Cool I am curious how they fit and perform. I went with a set of Headmans uncoated and had my local coating place do cerakote on the outside and a layer of insulkote on the inside. Ended up costing about the same (maybe a few bucks less) than buying them already coated but I know the local guys here and they do a fantastic job. Fitting the drivers side header in was a PITA. Just an FYI if you are doing them yourself. My winter project is to upgrade the ignition and intake side since it is still a 2V. Going with a Holley 300-12 intake I bought from a member here and cleaned up and had it coated as well. Looks great in blue. I am going with the new Street Demon 750 CFM with the composite bowl. I've heard really good things about the primary/secondary design on these in regards to throttle response. Also putting in a Pertronix III.

 
That Holley won't bolt to the 73 spreadbore intake. A good option to keep it mostly stock would be a 70-71 M-code iron intake with a carb of your choice. You may need to run a small spacer for the butterflies to clear the bores on the mounting pad.
sorry about that , thought i gave part number for Holley spread bore carb .

 
If your still running a 4300D then your going to want to change the intake as well. It's been a while but I believe the 4300D uses a Spread Bore pattern and if you go to a Holly the pattern is different. I bought a used intake from a 1970 351 Cleveland that has a Holly pattern and I bought a Holly 715cfm with central pivot floats (Shelby) carb. The 2 seem to work very well on my Q code but parts for that carb are getting harder and more expensive to find.

 
There's another thread about carb/intake decision going on, and here's my input to that (post 13): http://www.7173mustangs.com/thread-decision-time-advice?page=2

600 cfm is really about all you'd want without warming up the rest with a performance valve-train (cam, rockers, head work, etc.) and higher-flowing exhaust (headers, etc.).

It all works together... simply adding a bigger carb and performance intake will only give you slightly better performance - it's only a small part of the equation for more power. You can only feed the beast so much more before it starts to choke on too much. ;)
+1

If you improve the intake flow without doing the exhaust too you will see some improvement. Doing both is ideal. An important thing to remember is that you need to select all the parts that will work together. For example, getting a cam that in its power band at 2500 to 6000 rpm with a rear axle of 2.75 : 1 would not work very well and you will need to be at high freeway speeds for the cam to be in its power band. This is another subject but is important one to consider when getting parts. Best to decide what your overall goal is and then go from there. Will save you $$$ in the end.

 
Given the stated use, 4V heads, 3.89:1 gear, and manual transmission I feel you could use either a vacuum secondary or mechanical secondary carb. I'd consider the Quick Fuel HR series in 750/780 cfm as they have great adjustability for the price, they perform well, and the adjustability and size will work with what you have now as well as you planned upgrades.

I'd consider the Edelbrock Air Gap dual plane intake for the same reasons.

The rocker ratio is 1.73:1. If the valve train is working fine now the benefits of changing to roller rockers would be minimal. The same goes for the springs. The time to consider those changes is when/if you decide to do a cam change and increase the RPM limit. If the heads are 73 4V open chamber heads, you have about 8.0:1 compression ratio that doesn't leave a lot of room for performance cams with significant overlap in my opinion but, everyone's opinion of what a performance cam is varies.

The Hooker comps, not super comps, fit well and work well. Good luck with the improvements.

Chuck

 
Good info here guys. I'm very good with leaving the heads alone for now. I'll only get into the motor if something goes wrong. From there I could get into changing the heads if need be to support the rest of my setup, up to and including getting everything ported. I've see a lot about changing the timing chain gears as a must/standard. If I'm taking the front apart to do that is there anything else I should do while that's apart? Water pump? Flex fan? Any of this stuff worth doing if nothing is wrong and are there good aftermarket parts that are better than factory?



When you do the exhaust I highly recommend swapping out the manifolds with headers. Made a huge difference on mine even with just a factory 2v set up.

Wow. Cool I am curious how they fit and perform. I went with a set of Headmans uncoated and had my local coating place do cerakote on the outside and a layer of insulkote on the inside. Ended up costing about the same (maybe a few bucks less) than buying them already coated but I know the local guys here and they do a fantastic job. Fitting the drivers side header in was a PITA. Just an FYI if you are doing them yourself. My winter project is to upgrade the ignition and intake side since it is still a 2V. Going with a Holley 300-12 intake I bought from a member here and cleaned up and had it coated as well. Looks great in blue. I am going with the new Street Demon 750 CFM with the composite bowl. I've heard really good things about the primary/secondary design on these in regards to throttle response. Also putting in a Pertronix III.
I'll definitely report back once I get them installed. It will be sometime before the spring. I'll match that up with a set of either spintech pro streets or sportsmans. I'm leaning toward sportsman.

 
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If the engine has the OEM timing set, low and mid ranges will be improved my installing a timing set that does not have the retarded crank sprocket.

Chuck

 
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