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 QFX 1050 tuning 
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Joined: Wed Mar 01, 2017 5:39 pm
Posts: 14
Recently did a 2 circuit conversion on my 4710 QFX 1050 carb. I am now in the tuning stage. Trying to get the idle right before moving on to intermediate and WOT tuning.

Set transfer slots square before installing carb. Had to back off sec idle all the way. Pri idle srcew 1 turn in.
Idle mixture screws 2.5 turns out. If i turn them in anymore the car dies when put in gear.

Idles at 1500 rpm in neutral Drops to 1000 when put in gear.

No vacuum leaks.

The idle mixture screws are too far out and 500 drop in rpm is too much. Should I try a smaller IAB?

Also, the sec acc pump shooter dribbles fuel at times. The slow dribbled fuel creeps on the top of the carb body, slowly flooding the air bleed area with fuel. I was thinking a tube type shooter would fix this?

Carb specs:
QFX 4710 1050
BLP 2 circuit billet metering blocks
EM 1-.028 2-plug 3-.028 4-plug 5-plug
TSJ .055
IFR .040
MAB .028
IAB .065
PVCR .070 PRI
PV 4.5 PRI
Pri MJ 82
Sec MJ 92

Engine:
540 BBC 10:1 compression
Dart 345 Heads
Super Vic Intake
2.125x 3.5 headers
Cam: 268/278@.050 .722/.709 lift 108/104


Tue May 30, 2017 8:28 am
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Joined: Fri Feb 08, 2013 5:50 pm
Posts: 2302
Go to .042 for the idle jet, must be lower feed as well. With the QF body .040 doesn't work.


Tue May 30, 2017 9:42 am
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Joined: Thu May 08, 2014 7:47 pm
Posts: 206
Also, try stepping down the restriction size of the IAB, and readjust the idle mixture screws.


Tue May 30, 2017 11:09 am
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Joined: Wed Mar 01, 2017 5:39 pm
Posts: 14
Thank you, I will try the suggestions and get back to you guys with results.
The idle feed is already in lower position.


Tue May 30, 2017 2:33 pm
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Joined: Wed Jul 02, 2014 6:17 pm
Posts: 530
Caster67 wrote:
Recently did a 2 circuit conversion on my 4710 QFX 1050 carb. I am now in the tuning stage. Trying to get the idle right before moving on to intermediate and WOT tuning.

Set transfer slots square before installing carb. Had to back off sec idle all the way. Pri idle srcew 1 turn in.
Idle mixture screws 2.5 turns out. If i turn them in anymore the car dies when put in gear.

Idles at 1500 rpm in neutral Drops to 1000 when put in gear.

No vacuum leaks.

The idle mixture screws are too far out and 500 drop in rpm is too much. Should I try a smaller IAB?

Also, the sec acc pump shooter dribbles fuel at times. The slow dribbled fuel creeps on the top of the carb body, slowly flooding the air bleed area with fuel. I was thinking a tube type shooter would fix this?

Carb specs:
QFX 4710 1050
BLP 2 circuit billet metering blocks
EM 1-.028 2-plug 3-.028 4-plug 5-plug
TSJ .055
IFR .040
MAB .028
IAB .065
PVCR .070 PRI
PV 4.5 PRI
Pri MJ 82
Sec MJ 92

Engine:
540 BBC 10:1 compression
Dart 345 Heads
Super Vic Intake
2.125x 3.5 headers
Cam: 268/278@.050 .722/.709 lift 108/104


I just built one for a 582 BB Chevy 850+ HP street car and here's what worked for him and you can check out the vids of the red Nova on my FB page Dominic Thumper.

.084-.092 jets QF 6.5 p/v .076 pvcr's
.070 ib(tried .067's and was too rich)
.028 hi bl
.040 ifr's
.026 kills
emulsion #1 and #4 @ .028
.059 t-slot
.035 squirters
.132 BLP needle n seats
.angle channels .160

Will test at an 1/8 mile track soon I hope.............. :thumbr:


Wed May 31, 2017 11:08 am
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Joined: Wed Mar 01, 2017 5:39 pm
Posts: 14
Thumperdart wrote:

I just built one for a 582 BB Chevy 850+ HP street car and here's what worked for him and you can check out the vids of the red Nova on my FB page Dominic Thumper.

.084-.092 jets QF 6.5 p/v .076 pvcr's
.070 ib(tried .067's and was too rich)
.028 hi bl
.040 ifr's
.026 kills
emulsion #1 and #4 @ .028
.059 t-slot
.035 squirters
.132 BLP needle n seats
.angle channels .160

Will test at an 1/8 mile track soon I hope.............. :thumbr:


Thank you for the suggested tune.

Great fb page, lots of good carb mod photos.


Thu Jun 01, 2017 4:15 am
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Joined: Wed Jul 02, 2014 6:17 pm
Posts: 530
Caster67 wrote:
Thumperdart wrote:

I just built one for a 582 BB Chevy 850+ HP street car and here's what worked for him and you can check out the vids of the red Nova on my FB page Dominic Thumper.

.084-.092 jets QF 6.5 p/v .076 pvcr's
.070 ib(tried .067's and was too rich)
.028 hi bl
.040 ifr's
.026 kills
emulsion #1 and #4 @ .028
.059 t-slot
.035 squirters
.132 BLP needle n seats
.angle channels .160

Will test at an 1/8 mile track soon I hope.............. :thumbr:


Thank you for the suggested tune.

Great fb page, lots of good carb mod photos.


Thankxxx and this site along w/others and tons of tuning on my 9-second Dart has opened up doors I never imagined............ :thumbr:


Thu Jun 01, 2017 11:07 am
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Joined: Wed Mar 01, 2017 5:39 pm
Posts: 14
With the BLP billet 2 circuit metering blocks, do you turn the emulsion set screws in till they stop? Are they only tapped so deep so you cannot block the main well?
They are the standard 3/16 long brass emulsion jets that BLP sells.

I had to tap the lower IFR location a little deeper than BLP did. The set screw was flush with the metering block gasket surface. Its now about 3 threads deep from the block face. Standard 3/16 long brass set screw. Is this too deep that it may block the passage below it??


Fri Jun 02, 2017 3:29 pm
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Joined: Wed Jul 02, 2014 6:17 pm
Posts: 530
Caster67 wrote:
With the BLP billet 2 circuit metering blocks, do you turn the emulsion set screws in till they stop? Are they only tapped so deep so you cannot block the main well?
They are the standard 3/16 long brass emulsion jets that BLP sells.

I had to tap the lower IFR location a little deeper than BLP did. The set screw was flush with the metering block gasket surface. Its now about 3 threads deep from the block face. Standard 3/16 long brass set screw. Is this too deep that it may block the passage below it??



On the BLP blocks I use only 6-32x 1/8 and they stop in the e-well just fine and of course fit nicely in the lower ifr's.......... :thumbr:


Fri Jun 02, 2017 3:35 pm
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Site Admin

Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1701
I use 3/16" and they work fine. You can measure with a drill bit through the jet and gauge how far it is to the far side of the passage behind the jet. I think you will find it is OK.

I just turn the tap until the tip hits the far side of the idle well and because the point of the tap bottoms in the hole and the threads don't cut all the way to the end of the tap (unless you used a bottoming tap...??) the thread doesn't go in far enough to let the set screw bottom out. The set screw tightens in the progressively shallower cut of the thread in the lead in portion and usually does so about three turns in from the gasket face.


Fri Jun 02, 2017 6:05 pm
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