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what course of action is indicated?

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PHAT69AMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/10/2021 at 12:59pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote bikerfox Quote  Post ReplyReply Direct Link To This Post Posted: Apr/10/2021 at 4:46pm
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.


1969 Rebel SST (1970-1987)--SOLD
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1969 SC/Rambler (owned 2011-2019)--SOLD
1970 Javelin (2019 to ?)--"Jane"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/10/2021 at 5:55pm
Good to see the improved A/F Ratio results, Thanks !


Edited by PHAT69AMX - Apr/10/2021 at 10:54pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bikerfox Quote  Post ReplyReply Direct Link To This Post Posted: Apr/10/2021 at 6:24pm
Originally posted by PHAT69AMX PHAT69AMX wrote:

Good to see the improved A/F Ratio results, Thanks !
Was the .067" Jet drill dia. ( #64 Jet equivalent ) Plate Stamped 8, 23, 16, 9, or 36 ? 9
Was a stamped #6 Plate, .070" Jet drill dia. ( #69 Jet equivalent ) removed ?...
A .071" jet drill diameter ( also a #69 Jet equivalent ) Jet Plate would be stamped #35.

All that I have read over decades says DRILLING Holley Jets or Jet Plates is a No-No.
The lead-in, chamfer or not, orifice length, surface finish, corner treatment, etc all come into play.
And if a Jet or Jet Plate IS drilled, please, mark it with a Vibra-Etch Pen ! stating such.
Or break it or crush the jet, or something, or throw it away, imho.

The .067 plate was already drilled to .071--idk what drill size he used.  too late for regrets.
1969 Rebel SST (1970-1987)--SOLD
1968 AMX (2005-2011)--SOLD
1969 SC/Rambler (owned 2011-2019)--SOLD
1970 Javelin (2019 to ?)--"Jane"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/11/2021 at 9:16am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Apr/11/2021 at 9:45am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/11/2021 at 12:58pm
All take and no give
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/11/2021 at 3:01pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote bikerfox Quote  Post ReplyReply Direct Link To This Post Posted: Apr/11/2021 at 10:19pm
Originally posted by BassBoat BassBoat wrote:

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

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.
1969 Rebel SST (1970-1987)--SOLD
1968 AMX (2005-2011)--SOLD
1969 SC/Rambler (owned 2011-2019)--SOLD
1970 Javelin (2019 to ?)--"Jane"
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