normal_post in Rejetted my carb.... WOW ! in Engine, Transmission & Rear End Author Topic: Rejetted my carb.... WOW !  (Read 420 times)

Online Racer57

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Rejetted my carb.... WOW !
« on: September 22, 2022, 08:35:07 AM »
70 Cuda, HP383. manual, Holley 750 dual feed double pump

Car ran and started great, but black "soot" on rear valance so I knew it needed re-jetted.   Suggestions in this forum suggested 2 sizes at a time.  Factory jets were 80/76. They are now 73/70. The difference in response and even the sound is incredible. I would still like to tinker with it a little more, but will have to find another buddy with a more compete jet assortment so I know what to buy after experimenting.   :D 

Linkback: https://forum.e-bodies.org/engine-transmission-and-rear-end/4/rejetted-my-carb-wow/26489/

Offline blown motor

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Re: Rejetted my carb.... WOW !
« Reply #1 on: September 22, 2022, 08:38:24 AM »
Thatís something Iíve been meaning to do as my bumper and valance also get sooty. Just havenít gotten around to it yet. Thanks for giving me a push.
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Online torredcuda

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« Reply #2 on: September 22, 2022, 10:47:23 AM »
There is a lot more tuning you can do with a Holley DP - pump cam selection, position, adjustment, power valve, squirters - all to optimize the air/fuel ratio over the whole rpm range. It will run better and produce more HP so well worth the time spent.

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Re: Rejetted my carb.... WOW !
« Reply #2 on: September 22, 2022, 10:47:23 AM »

Offline Filthy Filbert

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« Reply #3 on: September 22, 2022, 12:39:17 PM »
And with today's advancements in technology... use of a wideband O2 sensor will help tremendously!   

Offline dodj

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« Reply #4 on: September 22, 2022, 02:45:18 PM »
There is a lot more tuning you can do with a Holley DP - pump cam selection, position, adjustment, power valve, squirters - all to optimize the air/fuel ratio over the whole rpm range. It will run better and produce more HP so well worth the time spent.
Yup...went down that rabbit hole....buy lots of bits an pieces (cams, squirters, jets, bleeds...) and spend days messin' with it. Found it fun though figuring out what worked and what didn't. Used an Innovate wideband o2 sensor to help me out.
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Offline DeathProofCuda

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« Reply #5 on: September 22, 2022, 03:11:36 PM »
  Factory jets were 80/76. They are now 73/70.

Are you listing your jets sizes as primary/secondary, or vice versa?  Primary jets are typically smaller than the secondary jets.

I will second, or third, the recommendation for using a wideband O2 meter.  Based on throttle response you are probably in a better place at idle, but you'll also want to make sure that you're not running lean at WOT.

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« Reply #6 on: September 22, 2022, 07:12:16 PM »
  Factory jets were 80/76. They are now 73/70.

Are you listing your jets sizes as primary/secondary, or vice versa?  Primary jets are typically smaller than the secondary jets.

I will second, or third, the recommendation for using a wideband O2 meter.  Based on throttle response you are probably in a better place at idle, but you'll also want to make sure that you're not running lean at WOT.

Ooops. Secondary/primary

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« Reply #6 on: September 22, 2022, 07:12:16 PM »

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« Reply #7 on: September 23, 2022, 04:10:06 AM »
  Factory jets were 80/76. They are now 73/70.

Are you listing your jets sizes as primary/secondary, or vice versa?  Primary jets are typically smaller than the secondary jets.

I will second, or third, the recommendation for using a wideband O2 meter.  Based on throttle response you are probably in a better place at idle, but you'll also want to make sure that you're not running lean at WOT.

Main jets don`t affect idle mixture. I`ve never had an O2 meter or sensor but that would be ideal, or a dyno. I`ve always just tuned by set of my pants, reading plugs and 1/4 mile ETs.

Offline DeathProofCuda

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« Reply #8 on: September 23, 2022, 10:06:28 AM »
  Factory jets were 80/76. They are now 73/70.

Are you listing your jets sizes as primary/secondary, or vice versa?  Primary jets are typically smaller than the secondary jets.

I will second, or third, the recommendation for using a wideband O2 meter.  Based on throttle response you are probably in a better place at idle, but you'll also want to make sure that you're not running lean at WOT.


Main jets don`t affect idle mixture. I`ve never had an O2 meter or sensor but that would be ideal, or a dyno. I`ve always just tuned by set of my pants, reading plugs and 1/4 mile ETs.

Agreed, the point of my comment was really to say that there are multiple circuits of a carb to tune and that it is really helpful to have a wideband meter to see where you are in real-time while utilizing each of those circuits.  Old school tuning certainly still works, but it takes alot longer to get it sorted out and track time isn't cheap.   :alan2cents:

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« Reply #8 on: September 23, 2022, 10:06:28 AM »

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