New Stroker Running Rough Daul Quad Quick Fuels on RPM Air Gap Final Answer

[falcongeorge]

Of course Joe.... yet I still see people suggesting .015 clearance between the arm and adjusting screw, it's a pretty common bit of misinformation.

It's SUPPOSED to be .015 away from bottoming the diaphragm @ WOT, NOT .015 clearance on the base circle of the pump cam! BIG difference.

[falcongeorge]

Of course Joe.... yet I still see people suggesting .015 clearance between the arm and adjusting screw, it's a pretty common bit of misinformation.

It's SUPPOSED to be .015 away from bottoming the diaphragm @ WOT, NOT .015 clearance on the base circle of the pump cam! BIG difference.

Another thing I'll mention here, if you run #330 pink or sometimes even the blue cam, it will bottom the diaphragm at WOT, and you won't be able to get the specified clearance. The way around this is to take another old diaphragm and cut the center out, and place it between the diaphragm and the pump well in the float bowl. Now you can adjust it properly, and you will get all the shot these two cams have to offer.

[Thumperbird]

Finally had a chance to remove the BJ/BK clones from Carl's and take some measurements.
They both look to be the same but data is for BK only so far, primary carb with choke.
My numbers should be within a thou. of actual, used high precision QB pins to mic holes.
Not super impressed with casting quality and machining, a bit of minor flash here and there on some of the ports and channels.  If you happen to read this Drew, might still take you up on sending to you for review, just playing myself for now, I like to roll my own as much as I can.

Going to beat these things into submission if it kills me and dial in every little item.
Biggest surprise for me was 60 mains, wonder what the 70's I bought will do.
Never had good idle control (RPM's yes but a little rough and always rich), starting to think the power valve was maybe open causing my very rich idle.
Going to change to a 3.5 PV
Adjustable bleeds
Remove the choke
Might hack off the air horns to aid flow in my scoop
Spacers need a little work to reduce turbulence as much as possible
 
Thanks and here are my numbers:

List number        Set came from Carl's Ford
C3AF-9510-BK List 2804 and C3AF-9510-BJ List 2805
Type            2x4 4160's

Primary   
Float            non-metallic, side hung
Booster            .142 Straight leg
Pump nozzle          shipped 0.025, 0.032 now
Pump type and cam      Don't recall as shipped, White #1 now
Idle air bleed         .067
High speed bleed      .034
Metering block#         Nor sure on this, casting id is 34R 12683B
Main Jet         60
Power valve         6.5
PVCR            .032
Emulsion         2 @ .027+ in each airwell
2 @ .027 in upper dogleg (1 in each) feeding emulsion tubes
Kill Bleed         Not sure
Idle Feed restriction      .027 in idle well
Needle and seat         .097
Venturi size         1.20"
Throttle plate size      1.50"

Secondary 
Metering plate marked as 34R 9716B #6 stamped in it
Mechanical or Vacuum?      VS
Spring color         Don't recall shipped, lightest now
Diaphragm length      1.95" (to rod pin hole center)
Float            non-metallic, side hung
Booster            .142 Straight leg
Pump Nozzle         na
Pump type and cam      na
Idle air bleed         .027
High speed bleed      .032
Metering block/plate#      #6?
Idle Feed Restriction      .030
Jet size or Main restriction   .065
Needle and seat         .097

[Thumperbird]

Finally had time to finish up a few mods left over from winter, a quick update on things and though I know you all ar probably tired of the questions, I kindly ask for some dual quad tuning feedback again, let me know what you think.

Went to 12" converter, about 2600 stall, love it compared to the 10" 3100 stall.
Installed proper pushrods for rocker geometry.
Got rid of my intake oil leak and installed a pcv.

As you may recall I had custom offset spacers to accomodate holleys on an Edelbrock dual quad, these consisted of a 1 inch offset spacer and a 1 inch 4 hole spacer(2" tall), never had the low end or smooth running motor I expected.  Photos attached show new spacers that have a center divider to preserve the dual plane all the way to the carbs.

Quick fuel 600's vacuum seconday, no mods so far other than turning screws
Best performance has come from no slip linkage, carbs tied 1:1.
Secondaries cracked a tad on both to set idle, primaries closed off .
Idle screws out about 1/2 turn out each.
Here's how it behaves, what next?

First, with 2nd carb set to come in at 1/3 1st carb throttle it was very rich all the time, I felt like it needed more air so here is what came next, I'm close to a nice runner at all RPM's albeit not a conventional setup I suspect but not there yet under medium hard throttle.

Idle is smooth but a little rich, AF 12/13, if I turn in idle screws I go more lean but tip in stumble is evident.  Launches fairly hard, nice low end torque now.
Cruise between 1500 and say 3000 rpms is AF of 13.5 to 15, nice and smooth.
If I get on it a bit at a cruise speed there is a very brief lean out then it will go quite rich to say 11/12, will recover to ~14 after RPM's come up a bit to match the throttle position.
Quik Fuels have adjustable secondaries, does not matter much if I have them set to fast or slow I still see the rich behavior on moderate acceleration and hard acceleration until my RPM's get to say 4500 then it starts to pull very well.  Timing is ~20, ~ 34 all in by 2500.

It is never a dog but definitely rough sounding at least on hard acceleration until RPMs get up there, I suspect due to rich fuel.  I like the idle and cruise, very top end seems strong as heck as well but that middle ground like a downshift and put my foot in it goes rich and I can tell it is just not a clean acceleration.

What do you all think should be next move(s)?

[My427stang]

The first thing I would say is that your idle a/f is likely reading incorrectly due to overlap from a healthy cam.  I would start by adjusting Idle for all barrels to be equal and best vacuum, ignore the numbers because the O2 sensor is seeing raw fuel

If it’s still fussy, I might consider a slightly smaller IAB if you think it’s not pulling on the t slots, if you thing it’s a slow booster, then I would likely get into the metering block

Of course, the battle axe bandaid could be a blue Holley pump cam, it hides a lot when it drops the hammer, but that’s sort of a Viking solution to a precision weapon problem. I have seen it do wonders though

[Falcon67]

>Idle is smooth but a little rich,

By gauge or by nose?  If it "smells gassy" as you described way back, that's lean - not fat.  Also agree that with some overlap, your A/F or Lambda is going to bounce around.  Dash gauges are dampened, using a meter right off an older heated O2 sensor shows you can't tell whats going on LOL.  When I had a tunnel ram on the 302, idle/low speed performance was in the 12.5 or a bit less range.  But those carbs were Eds and not a lot of overlap.  Eds typically do a better job at idle/low speed operation than most Holley units because of the primary booster arrangement.

[Thumperbird]

Thanks for the feedback guys, plan to tune to vacuum this afternoon, 85 out though.
I also remember I forget to check pump setup after the last round of playing.
Puffing a little dark smoke when I idle and AF is under 11 that is why I was thinking AF might not be that far off.

What are some thoughts on the medium acceleration rich situation?  Drop the mains on both from say 66 to 62?
As long as I'm in there open up the power valve port a bit?
Wanted to get a little closer before messing with bleeds.
 
Thanks.

[Drew Pojedinec]

A savy eye will note the throttle plate and venturi size disparity between the original BK/BJ and the reproduction.

One is a 600cfm carburetor and one would be closer to 500.

[Thumperbird]

Drew:

I should have compared the bk/bj clones I have to the slayers before installing, did not do that, not that smart.
The slayers behave much better with minimal tweaking so far but of course with the new spacers who knows what was what.

The setup is quite different, so far finding that 1:1 linkage works best but I think I am a little over carburated now in the mid range when configured this way.

Trying to figure out why someone has not come up with an adjustable main, power, and bleed systems, does not seem that hard, too impatient to be going in all the time or drilling blanks all day.

 

[67428GT500]

Drew is in possession of my BJ/BK carbs from Carl's Ford Parts. Perhaps he can unravel the mystery of crappy carbs for us all.

[Thumperbird]

In honor of Alex Trebek, Final Answer on the carb setup for the Tbird (almost).
Good A/F and response for all scenarios, a bit rich at 80 mph cruise (14), pulling like a freight train at end of an 1/8.

Just thought I would post more or less final configuration for Quick Fuel 2x4 setup using custom spacers on RPM Air Gap.  Maybe it will be good reference for someone some day, I know everyones help from here got me to where this is a fun toy, thank you.

445 stroker, 10:1, good internals, wide ratio C6, 12" 2600 stall converter, limited slip 3.5 rear end.
Timing is 20 initial 37 all in.
Cam = Dur (050) 233 int., 241exh., Lift .563 int., .574 exh..
Carbs = Quick Fuel Black Diamond 600cfm, vacuum secondary.  1:1 throttle linkage, idle set with secondaries, both carbs set up identical.
Custom 2" offset spacers using standard spacer plates on either side, dual plenum is preserved up to the spray bars in top plate.  Bottom end torque is strong, suspension work this winter to reduce tire spin on idle launch.

Primary   
Float            non-metallic, side hung
Booster            Stock
Pump nozzle          0.031
Pump type and cam      White #1, (added slight delay, likes a split second (A/F) before the squirt when you stomp it)
Idle air bleed         .058  (stock 74)(got me to more smooth idle nice transition and 7/8 turn screw)
High speed bleed      .033 (stock 31)
Metering block#         Stock
Main Jet         0.062 (stock 66, good cruise A/F 16/15 for 30 to 70 mph, goes to 14 at 80/85)
Power valve         6.5
PVCR            .042 (stock 51)(will likely bump this up a couple with nitrous use. 51 was rich when you hit it)
Emulsion         stock
Kill Bleed         Not sure
Idle Feed restriction      .027 (stock 30, helped lean out transition, cruise up to 40 is in transition)
Needle and seat         Stock
Venturi size         Stock
Throttle plate size      Stock

Secondary
Metering plate   Stock
Mechanical or Vacuum?      VS (adjustable)
Spring color         N/A
Diaphragm length   N/A
Float            non-metallic, side hung
Booster            Stock
Pump Nozzle         0.031
Pump type and cam      White, #1 (stock pink)
Idle air bleed         .042 (stock 33)
High speed bleed      .033 (stock 46)
Metering block/plate#     Stock
Idle Feed Restriction      .027 (stock 31)
Jet size or Main restriction   0.070 (stock 74 but measured 77)
Needle and seat         Stock

Thanks and happy winter!

[Drew Pojedinec]

Good deal!

Love you calibration template btw, genius

[TomP]

I wondered how you did the carb adapters, those look really tall and are they just an open area in the middle or 2 or 4 angled bores?

I looked at putting Holleys on my Air Gap but to clear a distributor the front carb can't be moved forward and that leaves the back carb barrels completely beyond the flange area.

[Thumperbird]

Total height is 3" including 2 each 1/2 inch spacer plates.  Bottom plate is open, top plate is spray bar equipped.
Riser portion of spacers are 3/8" plate stock, 2" tall, 1.125" offset each.
Bottom plate and riser have internal partition extending the dual plenum, this is 1/8" sheet stock, so 2 rectangular angled bore plenum extenders if you will.  All internal edges have radii and are blended to the purchased spacer plates, spacer plates are matched to manifold plenum.

Carbs stay cooler for sure and combined with the air gap the whole thing takes a good 10 minutes of cruising to get warmed up.
For the build I wanted the height did not matter.

[6667fan]

Like the engineering. What is the WOT A/F? Or are you still breaking in? The 14 @80mph, is much of a load taking place or is that no load cruise due to your combo?
Thanks for update.
JB