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Re: 70RR Carb replacement?
[Re: varunner]
#3308945
05/31/25 12:57 AM
05/31/25 12:57 AM
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Joined: Feb 2016
Posts: 216
PA
Scully
enthusiast
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enthusiast
Joined: Feb 2016
Posts: 216
PA
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Those were good carburetors. They are very lean in factory configuration. One could go through the unit and fix any issues with leaking, but swapping out the original metering block for an 1850 and running around #70 primary jets would make it run very nicely. I agree. After digging into this carb, I've learned quite a bit. The IFR in the carb is small, .022", that can be opened up along with the idle bleed. Some may disagree, but this carb flows over 700 cfm, depending on pressure drop. I've given up looking for a factory cfm rating, but I believe its' somewhere between a 715 -735 cfm rating. If anyone can find that holley spec, please post it. I have 4 of these carbs and without a good air cleaner base which adds close to 20 CFM, on my flow bench as is, untouched, one flowed 724 the other 746 CFM, the similar looking but smaller one I flowed from a 71 440 was 644. The two 340/383 AVSs I flowed were 625ish.
Last edited by Scully; 05/31/25 01:01 AM.
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Re: 70RR Carb replacement?
[Re: Scully]
#3308947
05/31/25 06:31 AM
05/31/25 06:31 AM
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Joined: Jun 2006
Posts: 760
Virginia
varunner
super stock
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super stock
Joined: Jun 2006
Posts: 760
Virginia
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[/quote] I have 4 of these carbs and without a good air cleaner base which adds close to 20 CFM, on my flow bench as is, untouched, one flowed 724 the other 746 CFM, the similar looking but smaller one I flowed from a 71 440 was 644. The two 340/383 AVSs I flowed were 625ish. [/quote]
You would think the carb for the 440 would be better than the one for the 383. But clearly the one for the 383 is better. Specs in the FSM show this, and the 383 secondary boosters are down-leg, opposed to the straight-leg for the 440. Factory mix-up ??
I'll have to get a couple different base plates tested.........
Last edited by varunner; 05/31/25 06:32 AM.
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Re: 70RR Carb replacement?
[Re: calrobb2000]
#3311205
06/13/25 11:58 AM
06/13/25 11:58 AM
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Joined: Aug 2004
Posts: 2,214
New Mexico
JMCFAN
OP
top fuel
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OP
top fuel
Joined: Aug 2004
Posts: 2,214
New Mexico
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hi
nice original carb , i would restore it or replace it with an original from a 440 for more performance [i have several ]
also your throttle spring is on wrong , long end hooks between cable clevis end .
Spring go like this?
Last edited by JMCFAN; 06/13/25 11:59 AM.
68 Charger 383/ AT Green/Green VT
70 Roadrunner 383/4sp Purple/Black VT
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Re: 70RR Carb replacement?
[Re: Scully]
#3314737
07/04/25 11:43 AM
07/04/25 11:43 AM
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Joined: Jan 2004
Posts: 9,457
fredericksburg,va
cudaman1969
Itch Nutz
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Itch Nutz
Joined: Jan 2004
Posts: 9,457
fredericksburg,va
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Those were good carburetors. They are very lean in factory configuration. One could go through the unit and fix any issues with leaking, but swapping out the original metering block for an 1850 and running around #70 primary jets would make it run very nicely. I agree. After digging into this carb, I've learned quite a bit. The IFR in the carb is small, .022", that can be opened up along with the idle bleed. Some may disagree, but this carb flows over 700 cfm, depending on pressure drop. I've given up looking for a factory cfm rating, but I believe its' somewhere between a 715 -735 cfm rating. If anyone can find that holley spec, please post it. I have 4 of these carbs and without a good air cleaner base which adds close to 20 CFM, on my flow bench as is, untouched, one flowed 724 the other 746 CFM, the similar looking but smaller one I flowed from a 71 440 was 644. The two 340/383 AVSs I flowed were 625ish. Agree, the best Holly Chrysler put out. (Back half of a 3310). 70 Cuds and Challengers running super stock pick the 383 engine because of this carb. I picked up 3 from a pile a guy had and Im sure they would work well on a 440.
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Re: 70RR Carb replacement?
[Re: Kudakidd]
#3314926
07/05/25 09:10 AM
07/05/25 09:10 AM
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Joined: Aug 2004
Posts: 2,214
New Mexico
JMCFAN
OP
top fuel
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OP
top fuel
Joined: Aug 2004
Posts: 2,214
New Mexico
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Save the original and throw on a Holley #4778 (700 cfm) Just to update the outcome. Scott was 3 mos out on a rebuild. Local took a look. Metering block needed replacemnt.... re jeted.. found the power valve loose as hell.... base plate slightly warped.. also secondaries were not functioning correctly Runs like a diferent car now.... Well worth the $40 he charged me..... LOL Gave him $80
Last edited by JMCFAN; 07/05/25 09:11 AM.
68 Charger 383/ AT Green/Green VT
70 Roadrunner 383/4sp Purple/Black VT
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Ya can't beat that!
