Dual quads on my motor

[DanEC]

My motor came to me from the builder with two Holley carbs sitting on a LR 427 dual quad intake. I'm building a street roadster w/o a hood scoop. At the time I didn't get into any particulars with the builder as to particular carbs to install or not install. He wanted to use 600 cfm carbs and that was pretty much the extent of the discussion.

In looking at them they both appear to be the same model carbs. The air horn markings on both are F 1850-12 and 1230. This motor is pretty much old school and built to be streetable with 9:1 compression, 4.25 in crank, iron heads, 230 deg plus cam with about .570 lift.

The motor seemed to rum pretty well on the dyno but I'm wondiering how these carbs will be on the street. Max power alone isn't my main objective. Strong power with good driveability is more important. Anyone have any experience with a similar setup?

Thanks

[Bobcat]

Dan ... not on my ERA , but I do have a dual quad setup on my 63 1/2 Galaxie 427 with a close ratio top loader .... and it`s very streetable . Try to get hold of an old Ford shop manual ( 1960 to 1964 ) as it has very clear instructions on how to adjust the linkage and the carbs . I adjusted mine about 4 years ago and haven`t touched them since . Sounds like you have the 1850 List carbs ... which is what I have , except mine were highly modified by Competition Fuel out in Tuscon some years ago .

Bob

[elmariachi]

I don't have much experience with 2x4s beyond the original medium riser set I have (Holley list 3300/list 3301, also known as the BC/BD set). I love them, and I believe Ford must have spent a lot of time selecting their carbs for these engines. Though these are based on the 4160, they don't seem to have many common parts to other models.

I have had great luck running the original setup so if it were me, I'd buy a set of the original Holley BJ/BK reproduction low-riser carbs tuned for your intake from Carl's Ford Parts. The original linkage is available from Greg Donohue Restorations. They are very straight-forward to setup and tune and are very street able. Also, lots of good info on this subject over on the FE forum.

[DanEC]

Originally Posted by elmariachi

I don't have much experience with 2x4s beyond the original medium riser set I have (Holley list 3300/list 3301, also known as the BC/BD set). I love them, and I believe Ford must have spent a lot of time selecting their carbs for these engines. Though these are based on the 4160, they don't seem to have many common parts to other models.

I have had great luck running the original setup so if it were me, I'd buy a set of the original Holley BJ/BK reproduction low-riser carbs tuned for your intake from Carl's Ford Parts. The original linkage is available from Greg Donohue Restorations. They are very straight-forward to setup and tune and are very street able. Also, lots of good info on this subject over on the FE forum.

I believe it's the BC/BD carbs that I recall reading recommendations on before, although I forgot they were for the MR motor. Sounds like the BJ/BK carbs are what I should have been thinking. My current carbs appear to basically be 4160 non-emissions, street/competition carbs according to my Holley book.

What are the BJ/BK carbs and how do they mostly vary from the later 4160/1850 carbs I have?

Thanks

Except for a last measure of original appearance, is there any reason I shouldn't expect the 4160/1850 carbs to perform well on the street? I have the Blue Thunder reproduction throttle linkage on the motor.

[Barry_R]

As another supplier of FE 2x4 carbs I could tell you that the 1850's wont work. BUt that would not be true. They will work pretty well once you sort out a couple things.

The linkage needs to be tweaked. The factory Ford linkage was progressive and does not readily mount ot the 1850's universal style side plates. You need to either add a hole or to fabricate a spacer for one of the links.

The throttle plate on the 1850 has a PCV valve fitting that extends out from the center. This fitting needs to be removed, plugged and milled flush. The passage below gets uncovered on some intakes causing a vacuum leak. I still catch this sometimes on my carbs if the guys "forget" and use a normal base plate.

You need to make certain that the throttle plates are well centered in their respective bores and very nearly closed all the way - you should only see a very small amount of the transfer slot from underneath - perhaps .020". Too far open and you'll have a high idle speed and unresponsive mixture screws.

Once sorted out the 1850s will be just fine.

[DanEC]

OK - that gives me a few things to check out. I remember he seemed to have some trouble brinnging the idle down on the dyno so I'll check the throttle plate openings. What about the secondary side - are the throttle plates adjustable on this model so they can be closed down to compensate for the primary throttle plate setting a little? The linkage seemed to work smoothly but I'll take a closer look at how it's hooked up.

Thanks

[Bobcat]

Dan , as Barry mentioned , you will have to spend some time sorting out the 1850`s . That`s why I had mine modified .... every circuit is tunable from idle to hi speed . The secondary throttle plates are adjustable , but you have to turn the carb upside down to get to them . It`s a small screw and sometimes they can get frozen and have to be broken loose . Follow what Barry said and you`ll be ok . PB Blaster can be your best friend here .
The .020" Barry mentioned on the primaries .... don`t try to actually measure ... I found that if the slot opening looks like a small square , then that is very close to the .020" .
Make sure the butterflies don`t hang up on the intake at full throttle .... cycle them before starting the motor if you have had the carbs off .

Bob

[mreid]

The 1850 is Holley's cheapest vacuum secondary carb. I guess it could be said that there is not a performance bone in its body. Single feed with transfer tubes, side hung bowls, drilled metering blocks, etc. However, they can be made to work well on a street driven car and they fit properly on the manifold without significant linkage fabrication. With the suggestions above, yours should work just fine on the street.

[DanEC]

Originally Posted by Bobcat

Dan , as Barry mentioned , you will have to spend some time sorting out the 1850`s . That`s why I had mine modified .... every circuit is tunable from idle to hi speed . The secondary throttle plates are adjustable , but you have to turn the carb upside down to get to them . It`s a small screw and sometimes they can get frozen and have to be broken loose . Follow what Barry said and you`ll be ok . PB Blaster can be your best friend here .
The .020" Barry mentioned on the primaries .... don`t try to actually measure ... I found that if the slot opening looks like a small square , then that is very close to the .020" .
Make sure the butterflies don`t hang up on the intake at full throttle .... cycle them before starting the motor if you have had the carbs off .

Bob

Thanks - I'm fairly familiar with that much tuning on Holley carbs anyway, after sorting out the issues on my 66 Corvette with a replacement L88 motor. The cam was too much to prevent uncovering the idle slots and losing ability to tune the idle. I ended up drilling the primary throttle plates to compensate. Later, I realized the secondary throttle plate setting was adjustable and could be used to slightly open them and avoid drilling the pri-plates. But, anyway drilling the plates did work, it's fully tunable and runs very well.

These are all brand new carbs, fuel log, linkage, even the manifold was professionally restored and re-skinned. Shouldn't be any frozen or worn out parts to deal with.

[elmariachi]

The BJ/BK carbs had 4033 metering blocks in front, plates in rear. They were 600 CFM to match low riser heads. They BC/BDs were 710 CFM and came with the medium riser heads and intake and had 5731 metering blocks in front and plates in rear.

Excessively high idle (if not inducing timing advance) can come from an attempt to set the idle position equally on both carbs. Everything I have read says to set transition slots to square on the bench and then set the idle with the front carb once mounted.

[DanEC]

Originally Posted by elmariachi

Excessively high idle (if not inducing timing advance) can come from an attempt to set the idle position equally on both carbs. Everything I have read says to set transition slots to square on the bench and then set the idle with the front carb once mounted.

OK - that's interesting. I figured the objective was to tune the idle settings for both cars to achieve the higest idle speed, and then back the idle adjustment screw down on both carbs equally to a curb idle setting. Your way sounds easier.

Dan

[elmariachi]

I did a bunch of reading so don't quote my way as the best or only way. On my car if I have the idle screw turned in too much the carb will stumble as it transitions from idle to acceleration. If I set both carb idle screws so that the slots are .020 square, the car will start and run (once warmed up) at about 650 rpms with my 294 Comp Cam. To get it to idle where I want it at 850 rpms I adjust the front carb only. I then hook up the linkage, then adjust the back carb idle screw in until it starts to raise the rpms, then I back it up a tad until its at 850 rpms. Once you check your vacuum and idle mixture you may have to do this all again one time. Lastly I set the float bowl levels so that fuel is just below the holes with the bowl sight plugs out.

One other thing to check with them on the bench...make sure you have discharge needles in the well beneath the discharge nozzle/squirter. The exploded diagram shows a check ball, a weight and a needle in that hole. You either run a needle only, or a ball and weight but not all three. Lots of times when carbs are rebuilt these items get overlooked. The missing needle will cause the carbs to continue sending raw fuel up through the squirter nozzles when you let off the gas, impeding a smooth and quick deceleration.

[SuperHart]

Just an addition here if I may. The box stock Holley 1850s come through with the "universal" throttle arm on the primary throttle shaft. When used in a dual quad setup using the original Ford FE dual quad linkage which is a progressive setup, the secondary carb must open at a quicker rate than the primary carb. For instance, the primary carb opens 100% beginning with the first depression of the accelerator pedal and ending with the pedal to the metal position. The secondary carb begins to open when the accelerator pedal is approximately one-half way through its travel and must be open 100% when the pedal is fully depressed. Therefore, the radius (distance) between the pivot and the trunnion (stud that the linkage attaches to) must be shorter on the secondary carb to allow for a quicker opening. I hope that makes sense.

Anyway, I had the same problem on my 351W using a Price Motorsports dual quad intake and a pair of 390 cfm Holleys and FE medium riser dual quad linkage which externally have the same dimensions as the 1850s. I actually swapped the throttle arms from the universal ones to Ford pattern arms and the setup works beautifully. Rather than post everything here, if you are interested in what I did just click on the link to Page 6 of my Cobra Build Site and scroll down about half the page. I purchased Ford style throttle arms direct from Holley. You would need access to an accurate drill press to drill into the end of the primary throttle shaft but the end result is well worth the effort. Your carbs will both look and operate correctly. Below are the photos of the primary and secondary throttle arms so you can see the difference in the placement of the trunnion position. Placing the trunnion closer to the pivot point causes the secondary carb to open at a faster rate than the primary carb.

PRIMARY THROTTLE ARM


SECONDARY THROTTLE ARM


UNIVERSAL THROTTLE ARM REPLACED WITH FORD THROTTLE ARM

[DanEC]

Does anyone see any problems with this linkage set up? It works smoothly and is progressive. The rear carb starts to open after the front one is roughly half way open - and they are both full open at full throttle. It looks good to me - no binding or mickey mouse hookups.

Looking down the throttle bores I do see some misalignment between the intake and carb bores. At this point I'll probably just try to shift them slightly on the mounts to see if some of it will go away. There's no binding of the throttle plates on the intake bores.

Again - these are all new components except for the manifold.

[ERA Chas]

Dan,
You may want to stage the rear carb at about 1/3rd of the front instead of 1/2. If you feel a flat spot during heavy throttle application, the rear carb needs to come in sooner.
Mine is set at about 20% of the lead carb but I have a lot of cam and 2.25" valves.
You should not feel anything except a strong, even pull of the RPM when properly staged.

[DanEC]

Originally Posted by ERA Chas

Dan,
You may want to stage the rear carb at about 1/3rd of the front instead of 1/2. If you feel a flat spot during heavy throttle application, the rear carb needs to come in sooner.
Mine is set at about 20% of the lead carb but I have a lot of cam and 2.25" valves.
You should not feel anything except a strong, even pull of the RPM when properly staged.

OK - that is something else to look at. I'm guessing on the half throttle as about where the rear carb starts to open. I'll take a closer look at it and see if there is any adjustment in the linkage to play with.

Dan

[elmariachi]

My car had a dead spot in the acceleration curve if I let #2 come at the halfway mark of #1. The primaries are between 1/4 and 1/3 open when #2 starts coming in. They both then hit the WOT position stop at the exact same time.

[ERA Chas]

Originally Posted by elmariachi

My car had a dead spot in the acceleration curve if I let #2 come at the halfway mark of #1. The primaries are between 1/4 and 1/3 open when #2 starts coming in. They both then hit the WOT position stop at the exact same time.

What I tried to say only much more clear...

[DanEC]

I looked things over a little more and as near as I can judge with an angle indicator, my second carb is starting to open with about 15 deg opening of the front carb - so that looks pretty good.

And, my primary throttle blades are nearly closed in the idle setting. A whole lot of the idle transfer slot is left above the throttle blade on both carbs - nearly all of it - but I haven't actually pulled a carb to look at it from the underside. It appears that the rear carb is actually cracked open a little more than the front one. I wouldn't think they would mess with those after taking the motor off the dyno so I guess that is how it was broke in and run. I may have some fiddling to do with that.

[racco]

I have mine set to run together, no flat spots what so ever. Gas mileage.. nevermind.