Fuel Recommended Carb Size?

Motorsport71

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So I have an '85 Mustang GT with a 302 automatic and 3:73 gears. I replaced the engine with a roller motor I purchased from Blueprint Engines. The dyno sheet that came with the engine showed 9:1 compression, 308 hp and 344 ft/lb torque (at the crank). I put a Holley 4160 600cfm with vacuum secondary's on it some time ago but I've had a stumble on hard acceleration. Timing is set properly. I had a shop verify it's correct. He's super busy so he can't get me in until the spring for an all around 'tune'. I was parked across the street from a guy who works on only vintage cars. An employee of his came over to look at the car (I had the hood up and he was a foxbody guy too) I mentioned the stumble and he said to go see his boss. Long story short he said right off the bat that its not getting enough fuel on takeoff. So I have a couple of options. I can take the car to him and have my carb refitted with bigger jets etc, or I can change the carb all together.

Would I be better to go with a something like a double pumper vs the vacuum secondary?
Would I benefit from a larger carb like a 650 or maybe bigger?

Thanks for looking,
Motorsport71
 
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CarMichael Angelo

my rearend will smell so minty fresh,
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So I have an '85 Mustang GT with a 302 automatic and 3:73 gears. I replaced the engine with a roller motor I purchased from Blueprint Engines. The dyno sheet that came with the engine showed 9:1 compression, 308 hp and 344 ft/lb torque (at the crank). I put a Holley 4160 600cfm with vacuum secondary's on it some time ago but I've had a stumble on hard acceleration. Timing is set properly. I had a shop verify it's correct. He's super busy so he can't get me in until the spring for an all around 'tune'. I was parked across the street from a guy who works on only vintage cars. An employee of his came over to look at the car (I had the hood up and he was a foxbody guy too) I mentioned the stumble and he said to go see his boss. Long story short he said right off the bat that its not getting enough fuel on takeoff. So I have a couple of options. I can take the car to him and have my carb refitted with bigger jets etc, or I can change the carb all together.

Would I be better to go with a something like a double pumper vs the vacuum secondary?
Would I benefit from a larger carb like a 650 or maybe bigger?

Thanks for looking,
Motorsport71
If the car is just experiencing an initial stumble when you mat the pedal, it’s just a simple pump squirter upgrade.
If the guy is worth his salt and can truly make the carb work based on the plethora of tuning options there are for a Holley carb, then let him do it. There really isn’t any carb that youre gonna put on any engine that’ll be perfect right out of the box, but a mild hesitation during acceleration is an easy fix.
 
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Motorsport71

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If the car is just experiencing an initial stumble when you mat the pedal, it’s just a simple pump squirter upgrade.
If the guy is worth his salt and can truly make the carb work based on the plethora of tuning options there are for a Holley carb, then let him do it. There really isn’t any carb that youre gonna put on any engine that’ll be perfect right out of the box, but a mild hesitation during acceleration is an easy fix.
Thank you. That's what i'll do then. He's been around forever and has a good reputation. Thanks again.
 

General karthief

wonder how much it would cost to ship you a pair
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Are you running an auto or stick trans? I'm guessing a stick, just curious really, the holley carb is (was) one of the most 'tuneable' carbs out there and they have several videos on their website that helps with common issues, I do agree with Mike that the squirter needs looked at, sometimes it's an adjustment, sometimes a bigger one is needed.
 

CarMichael Angelo

my rearend will smell so minty fresh,
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Are you running an auto or stick trans? I'm guessing a stick, just curious really, the holley carb is (was) one of the most 'tuneable' carbs out there and they have several videos on their website that helps with common issues, I do agree with Mike that the squirter needs looked at, sometimes it's an adjustment, sometimes a bigger one is needed.
He says its an auto, stop guessing ;)
 

7991LXnSHO

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Do not go for a double pumper on the street. This carb should be easily adjusted to be very enjoyable on the street - plenty of power and better mileage. It will be easier to fix than this stuck italic font. A quick change vac secondary spring kit it worth the $ if you do not have one. That will tune how many CFM is used based on engine demand. A double pumper will open all the way and compensate with an extra accelerator pump snd more fuel.
Besides the pump size and squirter size, there is a pack of pump cams and A/B holes to mount them in that make different accelerator pump shots. It just takes some reading and experimentation.

Edit: the bar at the top works today!!! Italics are gone.
 
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Wayne Waldrep

Before I post a pic, do you have one of yours?
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Do not go for a double pumper on the street. This carb should be easily adjusted to be very enjoyable on the street - plenty of power and better mileage. It will be easier to fix than this stuck italic font. A quick change vac secondary spring kit it worth the $ if you do not have one. That will tune how many CFM is used based on engine demand. A double pumper will open all the way and compensate with an extra accelerator pump snd more fuel.
Besides the pump size and squirter size, there is a pack of pump cams and A/B holes to mount them in that make different accelerator pump shots. It just takes some reading and experimentation.
Fixed.....lol.
 

Monkeybutt2000

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So I have an '85 Mustang GT with a 302 automatic and 3:73 gears. I replaced the engine with a roller motor I purchased from Blueprint Engines. The dyno sheet that came with the engine showed 9:1 compression, 308 hp and 344 ft/lb torque (at the crank). I put a Holley 4160 600cfm with vacuum secondary's on it some time ago but I've had a stumble on hard acceleration. Timing is set properly. I had a shop verify it's correct. He's super busy so he can't get me in until the spring for an all around 'tune'. I was parked across the street from a guy who works on only vintage cars. An employee of his came over to look at the car (I had the hood up and he was a foxbody guy too) I mentioned the stumble and he said to go see his boss. Long story short he said right off the bat that its not getting enough fuel on takeoff. So I have a couple of options. I can take the car to him and have my carb refitted with bigger jets etc, or I can change the carb all together.

Would I be better to go with a something like a double pumper vs the vacuum secondary?
Would I benefit from a larger carb like a 650 or maybe bigger?

Thanks for looking,
Motorsport71
Curious,did Blueprint state what carb was used when it was dynoe'd?