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what course of action is indicated? |
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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imho the Holley 9776 is a compromised design. It baffles me they still make and sell them.
Edited by PHAT69AMX - Apr/10/2021 at 10:53pm |
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4473 |
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wow, thanks Phat, for that historical perspective....it's not often that one learns
about the history of anything as "esoteric" as a carburetor, esp. one that one is using! last update on this saga: went back to the dyno facility and i'd already installed the .067 sec. metering plates. first dyno run showed a near flat curve of the a/f ratio and this metering plate was the ticket! a/f went from a 10:1 at its richest point to an approx. 12.2:1 at highest rpm. supposedly, i gained 20 hp! i'm done! the techs said to ignore the large "humps," as that's when there's supposedly a rush of air into the sensor area when full throttle is applied. the fairly "flat" curve was not able to be duplicated by the same guy after we drilled the plates to .071 for just a little bit more fuel. |
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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Good to see the improved A/F Ratio results, Thanks !
Edited by PHAT69AMX - Apr/10/2021 at 10:54pm |
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4473 |
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6909 |
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Very nice! Assuming it's the 134-9 metering plate used, it also changes the idle signal. Did the Primary butterflies get reset with this metering plate?For the $35, I'd tend to put a 134-9, or what was originally installed, back in without the drilling the from 0.067" to 0.071". That leaning out to above 16:1 may cause problems with fuel changes.
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BassBoat
AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1719 |
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So you had a plate that was drilled or you pin checked at 071 and you replaced it with a plate that was 067 drilled or pin checked? So simply a matter of leaning out the secondary? Did you change anything in the primary?
Regardless, your AFR looks much better now. Glad you got it sorted out BB
Edited by BassBoat - Apr/11/2021 at 10:12am |
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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All take and no give
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6909 |
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Have to agree PHAT69AMX. What ever happened on the blocking plate with the flatter curve was quite good. I'd be very happy if it were my car going back to that and call it a day.
I wonder what would happen with a little more carburetor also, see what the original design specifications resulted in. I should add I've never seen or worked on an STR11 and certainly could not afford it or the carburetor (paypal) setup. I do have an 1x1850 at home though! The concern about the lean was many years ago seeing the Chrysler crossrams go "boom". That's a lot of air/fuel in that big intake and any possibility of a backfire should be avoided at all costs. One of the biggest is running the things leaned out. They used to install relief valves and such to prevent catastrophic failure on Chryslers. Never seen or heard of the STR11 catastrophic failure ... but I would tend to go a cautious route. Edited by Trader - Apr/11/2021 at 4:11pm |
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bikerfox
Moderator Group Joined: Aug/02/2009 Location: USA Status: Offline Points: 4473 |
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The sec. metering plate was manufactured @ .067. It was decided to drill to .071 to slightly enrichen the flow. Primaries jets were originally .062 and were replaced with .059 jets for a slightly leaner flow. Thanks for your feedback.
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1969 Rebel SST (1970-1987)
1968 AMX (2005-2011) 1969 SC/Rambler (2011-2019) 1970 Javelin (2019 to ?)"Jane" |
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