BK/BJ reproductions

[Drew Pojedinec]

So Keith here sent me his reproduction BK/BJ's to check out for him.  He says they weren't running right.  I have been wanting to look at these for some time to compare them to the originals.
At this point I have restored roughly 25-30 sets of BK/BJ's, and rebuilt or tested many others, so I feel I have a pretty good idea of the calibration and what they are all about.

In the past I had only seen pictures of the repros, obviously the plating colors are not correct, and certain things like the main body casting, the VS top castings, and the bowls are not like the original.  This is understandable as I doubt Holley would remake dies for a very old carburetor like this.

What amazed me was what follows:

List number         2804/2805
Date            none
Type            4160
Primary            
Float            side hung nitrophyl
Booster            .120 Straight leg
Angle Channel         .118
Pump nozzle         .025
Pump type and cam      30cc white#1
Idle air bleed         .070
High speed bleed      .034
Metering block#         none
Main Jet         60
Power valve         6.5
PVCR            .030
Emulsion         2 @ .028
Kill Bleed         .027 to nonexistant emulsion tube (will plug)
Idle Feed restriction      .027
Mixture screw hole      .062 one side, .063 the other
Needle and seat         .097
Venturi size         1 3/16, 1 1/4
Throttle plate size      1.5 107/116

Secondary
Spring color         Stiff plain
Diapghram length      2.2
Float            side hung nitrophyl
Booster            .120
Angle Channel         .118
Pump Nozzle         na
Pump type and cam      na
Idle air bleed         .027
High speed bleed      .034
Metering block/plate#      #6plate
Idle Feed Restriction      .031
Jet size         .067
Secondary leak hole      .021      
Needle and seat         .097

Notes:
1. Floats set WAY too low indictating high fuel pressure or bad sealing needles.
2. Both Primary Throttle plates very uneven on transition slot, one was .020 off and the other carburetor was .010 off
3. Secondary throttle plate adjuster changed from flat head to allen head set screw for easier adjustability
4. Bowl vent whistle installed incorrectly resulting in the whistle being loose in the bowl.
5. Idle mixture screws out 1.75 turns and cork gaskets not fully seated.  My experience with carbs of this size, 3/4-1 turn out is where they normally end up.
6. Neither vacuum secondary pot will open while dry testing on the bench. Changed both springs to lighter ones, both open on the bench.
7. Emulsion tube feed drilled, but no emulsion tube.  will plug with 4-40 set screw, this will often delay initial main flow and cause instability once flow is initiated, this is normally noticed as a light surge at cruise.
8. Secondary carb, primary throttle closed too far, primary carb/primary throttle open too much.
9. Primary Idle air bleeds on primary carb both .070, secondary carb had two different ones, .070 and .061
10. Very bad casting flash at vena contracta
11. High speed air bleed is excessive at .003-.006 too large
12. With the exception of the High Speed air bleeds, these are an exact replica of an 1849 or a C3AE-9510-C, NOT BK/BJ carburetors.  The original carburetors were 600cfm each, these are realistically closer to 525-550cfm each.


Emulsion feed hole:
IMG_1640 by Drew Pojedinec, on Flickr

Float level when dissembled:
IMG_1639 by Drew Pojedinec, on Flickr

When the float is set this low to counter higher fuel pressure it does seal at idle tho blowing past the needle is a greater possibility.
Also when WOT happens, the fuel level in the bowls drops, the needle tries to refill the bowl to the proper level, with high fuel pressure the float cannot drop very much as it is already low, this picture is the float at full drop when running 6.5psi of fuel pressure, Keith's carbs were set higher still:

58779054_453691662036237_1750090549102116864_n by Drew Pojedinec, on Flickr

With 4-5psi of fuel pressure, the float can seal the needle at a much higher level as not as much force is required to shut off the lower fuel pressure.  At full drop the needle and seat looks like this:

58577549_453691675369569_7572358759704428544_n by Drew Pojedinec, on Flickr

Obviously it is much more open and less restricted.  Typically with high fuel pressure the engine may run alright at idle and off idle, but when heavy throttle is applied the carburetor runs out of fuel.

[Drew Pojedinec]

Corrective actions:

Notes:
1. Floats set WAY too low indictating high fuel pressure or bad sealing needles.

*I will reset floats to the proper level, advise owner to run lower fuel pressure, will also test carburetors to assure no leaks.

2. Both Primary Throttle plates very uneven on transition slot, one was .020 off and the other carburetor was .010 off

*Adjusted throttle plates for proper alignment

4. Bowl vent whistle installed incorrectly resulting in the whistle being loose in the bowl.

*Will install whistles properly

5. Idle mixture screws out 1.75 turns and cork gaskets not fully seated.  My experience with carbs of this size, 3/4-1 turn out is where they normally end up.

*Change cork gaskets, reset needles

6. Neither vacuum secondary pot will open while dry testing on the bench.

*Changed both springs to lighter ones, both open on the bench.

7. Emulsion tube feed drilled, but no emulsion tube. 

*will plug with 4-40 set screw

8. Secondary carb, primary throttle closed too far, primary carb/primary throttle open too much.

*reset to a good dry settings of JUST covering the transfer slot, idle speed adjustments will be made with the secondaries.

9. Primary Idle air bleeds on primary carb both .070, secondary carb had two different ones, .070 and .061

*Drilled .061 Idle air bleed to .070

10. Very bad casting flash at vena contracta

*Nothing done, if I was restoring it I would use a sandroll to smooth the flash out.

11. High speed air bleed is excessive at .003-.006 too large

*Will advise owner, I can change, .028 HSAB suggested.  Secondary high speed should also be downsized to .025

[Stangman]

Love the way you explain things Drew, you make things easier to understand. As far as the low float how do you know it’s low from high fuel pressure, maybe part of the reason it wasn’t running right was the float being to low from not being set right in the first place. We’re they both that low? So you think 4.5-5 on holleys and Quick fuels. I happen to set mine at 5.5-6 do you think reset and readjust. Also on the primary transition slots you said one was 20 off the other 10 what do you consider the proper adjustment. Do you always adjust the idle with secondary set screw or just certain applications. I would think an engine with a bigger cam that needs to idle higher then going the secondary route would be beneficial.  Sorry all the questions I just like and respect your thought process.

[Drew Pojedinec]

In this thread the things I am saying are in regards to 2x4 setups.
With a 2x4 setup you have a massive amount of air leaking into the engine due to 8 venturi, so such getting the idle low enough is more of an issue than anything.  Exposing too much transfer slot, or really any causes the very common rich at idle issue.  This is an issue with tame engines that have an 8V, often the lowest we can get the idle speed is 900-950.
When I first statically set the primary plates, I hold the whole baseplate up to the light.  I can just barely see where the transfer slot is.... that is a very good setting for idle (with 2x4's).  Transfer slot covered but still just barely seeing some signal.  Being closed too much will cause a possible stumble when you roll into the throttle.
When I spoke of .020 and .010 off, what I meant was with one carb, one primary was closed and the transfer slot was not visible, the other was .020 exposed.  The secondary carb with one transfer slot not visible the other transfer slot was .010 visible.  Best to get them as close as possible.  You aren't always able to by swapping around plates or wiggling, them.  In extreme cases I will light bend the throttle plate just a hair to get them even.  This is a setting that should be checked whenever the carbs are taken off the engine.  I have seen backfires bend the plates, especially with the modern "super thin" stainless plates.
With 2x4's and to a lesser extent 4v setups, yes, I get the transfer slot correctly set and I set the idle with the secondaries.  The only instance I do not is on very radical engines, these require opening both the secondary and primary to get the idle at the right speed.  Be very careful about exposing the secondary transfer slot, if any is showing, yes it'll get the idle right, but at a cruising speed it will pull a ton of fuel.....  Think about it, the radical engine makes 4inches of vacuum at idle, but at cruise, lets say it is pulling harder on that slot.

To the float:
How do I know why the float is low?  Previously given information from the owner.
Yes, you can run 5.5-6, yes you can even run 7-8, but as pictured, the lower you run the pressure, the less bouyancy required of the float to seal the needle/seat, as such you allow more float drop.  I have never tested the extreme low of pressure, but I have never found 4.5psi to be too low, so that is why I suggest it.  It is one of those things that seems counterintuitive, but is really basic hydraulics.

No need to apologize, this would be really boring if I kept this info secret or didn't get questions.....  I posted this specifically to show my thought process in the hopes that someone would benefit from it, and not have to go through the expense of sending me their carbs, me do this procedure and then send them back.  Frankly, I'd rather you tune your own stuff and let me get back to plating (which is what I'm still doing at 11pm in my shop).

[Drew Pojedinec]

Oh, and the main reason I posted this thread at all is because I have been hearing forever that the reproduction bk/bj's are just like the originals. 
They are not even the same size, you could get much closer with an pre -3 1850, just reduce IAB to .063 and you pretty much have BK/BJ calibration.

[67428GT500]

Drew: I appreciate you taking care of them. Too many things made no sense.  The fuel pressure is about 5.5LB. Rich as hell at idle and would fall on it's face on hard acceleration. You also touched on something I forgot to mention. If I was just running over idle in first gear like moving through a parking lot the car would jerk like you were on and off of the accelerator. Are these things made in China now? Pretty screwed up being never touched out of the box. I was considering going back to 4.5 on the power valve. I have about 14" of vacuum at idle. I would have ran more of a cam but I didn't want to do so at the detriment of the power brakes.
                                                                                                             -Keith

[Barry_R]

Looks like the idle settings were all jacked up chasing after the characteristics that were caused by the screwed up bleeds and slot/blade relationship.
I find that I end up resetting throttle blade closed position really often on all the dual quad carbs - no matter what the brand.
Just do not understand why they cannot seem to get that close to correct at the manufacturer level anymore.
At one point in time closed throttle airflow measurement was a spec item to check.

[Thumperbird]

On my slayers I started with closed primaries and used secondaries for idle.
This as Drew stated resulted in a stumble at tip in so I worked secondaries down and primaries up until no stumble.  Had to turn idle mixture screws out a bit as well as this adjustment technique progressed.  Remember mine are currently a no slip linkage arrangement, setup seems to prefer some contribution from both carbs all the time.

Running rich with moderate acceleration though, wondering if as Drew stated secondaries are exposed too much?  Maybe this is a case for drilled plates?  I forgot to install a small manifold vacuum port on one of the carbs while playing but it sure liked that leak!

Fun stuff, thanks all for the informative exchange. 

[Drew Pojedinec]

I wouldn't change the PV opening point.  If anything I like to go the other direction and use the smallest jet possible while getting the PV to open sooner, enlarging the power valve restrictions as needed.  This requires tuning on the car tho.  It can be done fairly easily with a vacuum and O2 gauge while driving around.  For an engine like yours the 6.5 works sufficiently well in almost all situations.

I don't know where they are made, if I had to guess I would say cast in china and assembled here.
As Barry mentions, the real issue isn't the manufacture, it is the assembly and checks made, ie quality control.
I could honestly make a living just blueprinting brand new carbs   Sad tho, and many of the issues present on new parts like this are beyond the scope of the typical customer's troubleshooting skills.  This is why I never ship a carb without testing it out.  Sure, you might have a problem here or there, but I can at least say in good faith that it ran well for me.

I mentioned above how important closed air flow is on a carburetor, well things you can get away with on a 4V installation you absolutely cannot get away with when using an 8V setup, it is almost like any small issue is 4times worse when running two of these.

Anyhow, I'll change the high speed air bleed, and finish screwing these together tonight.  Hopefully I will get to test them out and find no other issues.

[Drew Pojedinec]

Running rich with moderate acceleration though, wondering if as Drew stated secondaries are exposed too much? 

Rich at cruise, yes, it could be the secondary slot.  Rich at moderate acceleration is often how the high speed air bleed and emulsion is set up, if I recall, 600cfm Slayer carbs often have large HSAB (.034?) and upper emulsion bleeds (.031?)

[cjshaker]

Glad you're back, Drew. Great post, as always. I think the only thing that makes these "reproductions" is the throttle linkage and lack of choke on the second carb....and marketing 

[BattlestarGalactic]

Awesome information Drew.  Thanks.

Doug, agreed.  Wrong bowl screws and lots of stuff that Drew mentioned, but it has that "right part number" that some people want to have I suppose?

I've run just regular 1850's on all my stuff.  The black car got a set of 660's now that seem to work okay, but still needs some midrange tuning.  I built a set of 735's for the wagon, but those step boosters make it near impossible for me to drive around or do a burn out.  Way too responsive, thus they got removed.  Think I might try them on black car or maybe the pickup.

My pickup needs some attention.  I'm guessing it's just age, as I seem to need to go through them about every 4-5 yrs.  They start screwing up, idle erratic, mid range surge/miss kind of thing, leaking on the manifold pretty bad.  Ugh.  To much sitting around, then the random driving just takes its toll.

[Drew Pojedinec]

Glad you're back, Drew. Great post, as always. I think the only thing that makes these "reproductions" is the throttle linkage and lack of choke on the second carb....and marketing 

Been gone a good bit in the Gulf with no cell service, or very little service.  I was often able to read some of the stuff here, but posting was a problem.  Was fun tho, salvage work on old oil platforms.  Get to blow up the 200ft long legs, etc.  Underwater demolitions make fishing much easier.

In no way shape or form do I mean to be bashing on Carl's reproductions, they certainly fill a void where the car show enthusiast needs the correct number, and that is cool.  In truth, with some minor work, these should in theory work better on a driver quality car as they are smaller.  I was doing the same with 1848 and 1849 carbs as dual 600's were often hard to keep the idle at stock levels for folks with 390 engines and small cams.  I just don't want people to think they *need* these or their car won't run right.

660's are awesome Larry, tho having a primary power valve would be nice.  I imagine those 735 bell boosters pull hard during a burnout, they are really for metering well at low airflow, think roundtrack or dumptruck usage would be most appropriate.  Oddly the factory tunnelport 652 AC/AD's used them, I'm not certain why, perhaps a way to correct lazy air/fuel mixtures?

[BattlestarGalactic]

I think overall quality in lots of things are falling short.  Carbs are just one of them.  They just keep hacking away at things trying to cut costs.

Ya, fuel mileage is not a concern, but the 600's were much more friendly!!!  The 660's have a "bog" in midrange.  You can't flat foot it while cruising under load.  It falls on its face.  It's not a lean pop, just noses over, then goes like stink.  Not a real issue, so haven't really done anything to fix it.  It drives fine overall and if you launch it, it pulls hard(if not blazing the tires).

Yes, trying to hold an rpm for a burnout(I don't use a 2 step), it was near impossible with the 735's.  It would zing to infinitely or near stall, no in-between.  They were a touch fat on the one pass I made, so they needed some tuning anyway.  I just used some 1850 secondary plates as I had them laying around.  Don't know what the number was on them?  Don't know what kind of jetting the secondary side needs, but apparently it's too much as is.  I might throw them on the pickup and see how they are driving?  Might be too touchy there also?

[67428GT500]

I think it might have been better to have Drew make a set with the throttle shafts for dual quads. These have got expensive for what they are. They're about 1500.00 currently. While filling a void, they have an incredible amount of issues. As Drew pointed out, I have never had an issue getting a single quad to run well but these damn things could make a shy bald Buddhist plot mass murder. 
What I know made no sense and to add insult to injury I am in the middle of assembly on another engine because of piss-poor machine work.
I found a great machinist that is an FE specialist and a very competent machinist. Some of you may know Charles Eller of Charles Machine.
The work is beautiful and he was very helpful. My C6AE-R heads were done by Kim Barr racing engines. 
With me taking the engine out for the third time and getting rid of the heavy TRW forged pistons I had cut to flat tops and going with JE pistons and dropping the compression to 9.9 Vs 11.4. I bought a set of Edelbrocks.. If they ever get here. 2.19 intakes and 1.75 exhaust valves and replacement springs. The last thing I want to do is take this damn thing back out and I sure didn't want a rich situation washing the oil off the cylinders.
I admit this situation has left me woefully out of my depth and  Drew bragged that they would be so close to running as returned that a caveman could do it. 
I am glad that my pain and frustration has helped bring light to the "what's in the box" mystery of the 1500.00 BJ-BK's that aren't and the data will help others with the issues and specifications these carburetors exhibit.
Anyway hopefully, all will be well and I can enjoy the fruits of years of labor for a while without having to wrench for a while.
                                                                                            -Keith