Quad carb setup information help

-
rod7515

rod7515

Well-Known Member
Joined
Jul 18, 2013
Messages
1,738
Reaction score
589
Location
Red Lion PA
I've asked many questions about putting my TR5 intake and carbs together on my 408 Dart. Got a ton of great help here. But now its time for the next step.
I finally got all the fittings in place and sealed up. I have 6.5 psi of fuel pressure with switch on but engine not running and with engine running its holding right at 6 psi. Its winter here and I can't get the car out on the road because theres salt everywhere. But the car fired right up and actually settled into an idle better then it ever did with the single 4 bbl on it.
Now it seems rich. I'm using 2, 600 cmf holleys that are supposed to be performance carbs. Here's a few things about them. The factory jetting was 65's. Because of using them as a dual quad setup I down jetted them to 62's in the primarys. I also have 6.5 power valves. These carbs are mounted sideways. The front and rear bowls do not have adjustable float settings without taking the bowls off which i dont understand the reason for that if there performance carbs. Once the engine warmed up good I tried to adjust the air screw by turning it in but it made no difference going all the way in. I'm guessing its because the second carb over rides the adjusting? Again it sounds good and seems very responsive but the exhaust is very rich smelling.
I realise I can't do anything with the secondaries until I can get it on the road which is at least 2 months away once spring arrives.
My question is where do I start making any adjusting with the carbs. I could possibly have the floats a slight bit to high and maybe that's another reason turning the air screw made no difference.
I watched a video the other week about starting by balancing the carbs using an Edelbrock balancing tool which I have no problem buying and fitting up to balance the 2 out but is that the right place to start? Should the air screw made an idling difference? Does no change when I turned that one screw in mean another problem. With one carb I would be checking for vacuum leaks to start but not sure that its the same procedure.
I'm including a video if the site allows me. And of course it won't let me do the video. Its only 11 seconds long but it won't work. So here's some pics of what I got.
I'm ready to learn so throw some suggestions my way. And thanks for all the help.
Rod
20220201_174311.jpg
10-adjusting-holley-carburetor-vacuum-secondaries.jpg
20220201_174033.jpg
 
Hard to believe it is rich with the 62 jets and 6.5 PV's. The a/f screws are a question at this point, but, and not knowing the engine combo, i have to think your initial timing is way retarded from where it needs to be. Let us know the combo and where you are with the timing please.
 
You have to correct the T slot exposure first. That means probably drilling some small holes in the primary butterflies so you can close the throttle. You’ll need to reduce the Idle Feed Restriction and maybe go bigger on the Idle Air Bleed. And you’ll need T slot restricters.

Search this forum. How to do all that has already been posted.
 
Rick, thanks for reply.
360 with stroker kit, .030 over, 10.5-1 comp cam 575 both valve solid roller cam 308 duration 262@.050, slightly ported 915j heads large valves. Roller rockers, TTI headers, 4k converter, built 904 trans, 4:56 mini spool rear. Of course the intake is an old school TR5 Edelbrock with new style shorter top section.
I didn't bother checking timing as I didn't pull distributor out when I did the intake but I believe I am around 20* initial with about 32* total all in.
I will have to throw the light on it again.
I'm just trying to get a good start on setup and I don't think I can be that far off. But never doing a 2x4 setup before tell me where I start first to get my best setup.
Including some carb pics as well. I did have the choke tops milled off both carbs as well and pics are with carbs just sitting on nuts.
I still don't understand why carbs don't have quick float adjustment bowls. The pic of bowl is very close to where I have floats set.
Thanks, Rod
20210611_161815.jpg
20210725_213422.jpg
 
Rat, thanks for your response. I do believe the primary butterflies are totally closed on both carbs. I did verify that as I rebuilt both carbs. I have read some of those posts. Is that the starting point I should start setup or one that as I find a problem I move to. I don't want to make a change that I can't go back and redo.
Thanks Rod
 
I like running an AF gauge.. it's not an end-all but it is a good tool for tuning dual carbs.. you'll know more exactly how it's running as far as their fuel mixture as opposed to just smelling gassy... I used the AF cage to get it pretty close during idle cruise and full throttle but reading the plugs is the ultimate... I use completely different carbs and had to drill holes in the secondaries but not before I ordered new secondary flaps just in case I screwed up...
 
Also you'll notice that dual carb setups aren't necessarily set up exactly the same... I have slightly different primary setups from front to back carb...
Dozens of summertime warm the car up making adjustment take it for a test drive experiences before I got it to where I was happy with it... It can be very trial and error as any carburetor is adjusted different for any different motor let alone two...
 
One thing that should be highlighted is you're mounting them sideways.

I did a TR with those same "basic" 600's for a buds sm blk Camaro. They were mounted inline and came from a 428 Ford low rise already set up. Other than some squirter experimentation, the transition was pretty seamless. Long way around to say i think you'll get there, but i'd prefer to use Double pumpers in that application.
 
rod7515 said:
Rat, thanks for your response. I do believe the primary butterflies are totally closed on both carbs. I did verify that as I rebuilt both carbs. I have read some of those posts. Is that the starting point I should start setup or one that as I find a problem I move to. I don't want to make a change that I can't go back and redo.
Thanks Rod
Click to expand...


If the T slots have the correct exposure and it’s still fat at idle you’ll need to measure the idle feed restriction and see what it is. And measure the idle air bleed to see what it is. Then make a decision on what to change to get the idle cleaned up.

I went back and read your OP again. If the air/fuel mixture screws are not functioning it means it’s getting fuel and air from somewhere. Make sure the secondaries are open the same amount and not open too far.

If the T slots are correct and the secondaries aren’t open too much, the next step is to open up the idle air bleed by .006-.008 and see what you get. I say start there because you don’t have to pull the float bowl off to do that. If it gets better then you can take a look at the idle feed restriction.

The IAB and IFR work together. You may have to increase the IAB some and restrict the IFR some to get what you need rather than try and get it all done with the air bleed or the IFR.

At this point you most likely will need to drill and tap the IFR and IAB so you can replace the brass easier.
 
As I mentioned earlier I think the timing is at 20* and all in at 32*. I didn't remove the distributor when I swapped intakes so it shouldn't have changed but I will verify this weekend.
J-Par, I am assuming you are speaking of something like this-
20220210_073046.jpg

20220210_073246.jpg

I bought this about 4 or 5 years ago but haven't added it to the car yet. Guess its time to learn how it works and what I should or want to see.
Again a big problem is that its winter here so I won't take it out on the road as they have them covered in de-ice chemicals. So clean roads are probably not going to happen until early April. And I'm sure setting up car just sitting idling and reving won't be a good method.
Like I said it fired right up and idles at lower rpm then the single 4 and ran smoother quicker while warming up. My concern was how rich the exhaust seemed to be. But maybe that was from sitting so long and first startup.
Thanks Rod

20220210_073046.jpg
 
Last edited:
I tried to work those 600 cfm 1850s on my 440. Mounted straight. I was told about changing bleeds which unfortunately those carbs will require disassembling drilling and tapping . The metering blocks will need to be changed and then set up properly. I gave up and bought 2 450 Quick Fuel carbs. Dedicated dual quad carbs. Needed to jet up and change the power valves because I have like 15 inches at idle and 21 at cruise. Now I don't have extra money a d this was a bitter pill to swallow after I had spent so much time and money on 2 1850s. Fat at idle. Couldn't make them work. Tried tried tried. Street car.....makes a big difference. Race? Street? I can tell you what worked for me.
 
Rat Bastid, I've gotta get some additional information such as verify my timing and my vacuum at idle which I hope to do tomorrow. But reading your post about idle air bleed I wanna make sure I but the correct parts. Here's an address to some on eBay I can purchase if there correct. ( (10 Pk) Blank Drill To Size Holley Carburetor 10-32 UNF Air Bleed Screw In Style | eBay )
Also what drill bits will I need and should I look into a pin kit to be able to check sizing.
Thanks for your help as this will be all new to me and I'm sure ill have a ton more Questions.
Rod
 
rod7515 said:
Rat Bastid, I've gotta get some additional information such as verify my timing and my vacuum at idle which I hope to do tomorrow. But reading your post about idle air bleed I wanna make sure I but the correct parts. Here's an address to some on eBay I can purchase if there correct. ( (10 Pk) Blank Drill To Size Holley Carburetor 10-32 UNF Air Bleed Screw In Style | eBay )
Also what drill bits will I need and should I look into a pin kit to be able to check sizing.
Thanks for your help as this will be all new to me and I'm sure ill have a ton more Questions.
Rod
Click to expand...


What carb do you have? If the bleeds are changeable from the factory those work nice. If your carb had press in bleeds from the factory you’re better off getting some 6-32, 8-32 and 10-32 brass set screws from McMaster-Carr and using them.

For what you are doing you will need an .011-.060 pin gauge set. It would be better if you had one that went up to .125 or so, but you can get around that.

Then you need those frustrating drill bit that go from some really small size like .014 (maybe smaller, I’d have to go out and look at mine) up to .039 or something like that. You can get that little kit at any good hardware store.

And 2 GOOD pin vises. When you start drilling brass it’s a PITA to keep changing drill bits out. At least to me it is.

Then you can get a pretty decent number drill kit from Harbor Freight.

And then you need 6-32, 8-32 and 10-32 taps.

Then it’s a pretty simple task to pin everything, write it down and the make your tuning decisions. Then you drill your brass and screw it back together.

BTW, on TR stuff you can use an 8-32 set screw for the T-slot restrictors. On single 4 stuff you’ll need to use a 10-32 set screw because you you may need the restricter to be big enough that it gets into the hex on an 8-32 screw. Unless you are using E85 or methanol fuel. Then that’s a whole nuther situation.

On a TR you can squeeze the T-slots down pretty good on gas and really clean up the cruise.

Don’t forget to pin the power valve channel restricters too and make them changeable if they aren’t already.
 
So I got some needed data tonight with my engine. I started it up and left it warm up real good. Once it was at normal operating temp I checked the timing and I am at 14* base and all in at 34*@3300 rpm. Then I checked vacuum at idle and I am at 8.5 at idle or 975 rpm. I kept the backend of the car sticking outside the garage door so I couldn't really tell if it was as rich as last week. probably had it idling 20 minutes or so and it didn't load up and its very responsive to acceleration. Now a couple more things that have been ask, the idle air bleeds appear to be changeable which is a good thing. I am attaching a few pics to show that and carb # and also a pic of the secondary plate even tho I'm not anywhere close to secondary yet but this way I have the pic posted for later. Ill order a pin set as I couldn't find one anywhere today or a small drill set. So let me know what other info I need to grab to get help moving foreard. Also I'm not in a big hurry as it was only 18* tonight when I got this info.
Thanks Rod
20210610_220240.jpg
10-adjusting-holley-carburetor-vacuum-secondaries-2.jpg
20210610_213906.jpg
 
rod7515 said:
So I got some needed data tonight with my engine. I started it up and left it warm up real good. Once it was at normal operating temp I checked the timing and I am at 14* base and all in at 34*@3300 rpm. Then I checked vacuum at idle and I am at 8.5 at idle or 975 rpm. I kept the backend of the car sticking outside the garage door so I couldn't really tell if it was as rich as last week. probably had it idling 20 minutes or so and it didn't load up and its very responsive to acceleration. Now a couple more things that have been ask, the idle air bleeds appear to be changeable which is a good thing. I am attaching a few pics to show that and carb # and also a pic of the secondary plate even tho I'm not anywhere close to secondary yet but this way I have the pic posted for later. Ill order a pin set as I couldn't find one anywhere today or a small drill set. So let me know what other info I need to grab to get help moving foreard. Also I'm not in a big hurry as it was only 18* tonight when I got this info.
Thanks Rod
View attachment 1715870104 View attachment 1715870105 View attachment 1715870106
Click to expand...


There are two ways to change those bleeds. Pull them out and replace them with bleeds just like that. I think you can buy them from BLP. Or you have to drill them out and use set screws.


You need to be 22 or so initial at idle. A little more won’t hurt but it’s hard to get the curve right when it’s that short and you don’t have a machine to play with it on.
 
Rat, a few more questions. When you say 22 are you referring to my timing? if you are referring to timing, isnt that a lot? Ive never run anything that far advanced so will i run into cranking/starting hard when hot? And what type of machine are you referring to?
I've ordered my pin set and drill set along with a few pin vices. A question I have is once I start playing with the circuits do I do one carb at a time or do both carbs at the same time.
Anything else I need to do before starting this?
This will be a long process. I hope you are around until the end. Lol
Thanks Rod
 
rod7515 said:
Rat, a few more questions. When you say 22 are you referring to my timing? if you are referring to timing, isnt that a lot? Ive never run anything that far advanced so will i run into cranking/starting hard when hot? And what type of machine are you referring to?
I've ordered my pin set and drill set along with a few pin vices. A question I have is once I start playing with the circuits do I do one carb at a time or do both carbs at the same time.
Anything else I need to do before starting this?
This will be a long process. I hope you are around until the end. Lol
Thanks Rod
Click to expand...


Yes, I’m talking about 22 initial timing. You can maybe squeeze some more out of it if it needs it. At 14 you just don’t have enough initial timing.

In order to get 22-24 initial and still keep the total where you want it, you have to shorten up the mechanical advance.

Looking at your 14/34 numbers tells us you have 10 degrees mechanical advance in the distributor (which is 20 on the crank) and you have 14 initial. If you want to get to 22 initial you only need 6 degrees of mechanical advance in the distributor.

The math is 6 degrees in the distributor, which you double for timing at the crank for 12 degrees of mechanical advance. To get to your 34 degrees of total advance you’ll need 22 initial timing.

That will lean up the idle a bunch. What distributor do you have?

I do both carbs at the same time. So get your bleeds and T slot restrictors done on both carbs at the same time. Any changes you make you do the same to th carbs.

Make sure you don’t have one carb “leading” the other. The best was to do it is with a Unisyn. Edelbrock makes it and it’s part number 4025. Then you need a 4150 carb cover. It can be plastic or aluminum. You drill a hole in the middle of that cover and glue the unisyn to it. Once you do that, you can get the carbs “sync’d” up.

The unisyn is just a simple manometer. What I do is get the timing set and everything else as close as I can and get up to operating temp. Then I disconnect the front carb because it’s easier to get to.

Then stick the unisyn on the back carb and see what the unisyn says. It’s adjustable so I make the meter read in the middle. Once I see where that back carb is, I put the unisyn on the front carb and take a reading. No matter how close you might think you are with your initial idle settings with the idle screws, you won’t be real close and one carb will be leading (flowing more air at the same idle speed) as the other.

If you have that, you’ll get all kinds of weird issues, like tip in stumbles that you can’t tune out and all kinds of things.

Once you see the difference between the 2 carbs you use the idle screws to make both carbs flow the same air. It doesn’t matter if one carb is open a bit further than the other as long as both flow the same amount of air.

You might be a bit surprised of how things like firing order, carb placement on the plenum, header length, runner length and shape and such can affect how much each carb needs to flow. And that’s the end goal. Getting both carbs to FLOW the same at idle. You can’t (or you shouldn’t) just close the throttles to zero and then say open each carb 1.5 turns and then adjust it from there with equal turns on each screw. Both carbs may be open the same but they may not be flowing the same, and probably are not. That’s why the unisyn is so important.
 
Rat, thanks for the info. As you may have figured out by now these changes you recommend are more involved then I have ever gone and I'm a slow learner. As for my distributor and my entire ignition I am using a system called procomp. im sure its a cheaper system but it works good. Im hoping i can change the mechanical advance in it. When I ran into the person that I bought my intake and the original carbs that were with it he also threw in this ignition system. I gave $250 for all of it. I probably should have sold the ignition and went with a Mallory or MSD ignition. I am including pics of the system. I will start by making changes to the timing before I move to carbs.
Thanks again for good direction.
Rod
DSCN0080.JPG
DSCN0076.JPG
DSCN0079.JPG
 
With a 262 @ 050 cam, you are going to need a LOT more than 22* at idle for best idle quality/performance/off idle tip in. More like 40-50*. The large plenum volume of a TR intake is another reason that more timing is needed.
Don't believe me? Do this 5 min test: engine idling at about 22*, rotate dist slowly to advance timing. Idle rpm will increase & idle will be smoother. Both are indicators of more efficient use of the A/F mixture [ rpm increase is actually the engine making more HP ].
 
I've contacted a person in my area that has a sun distributor machine and can change the advance in my distributor if this distributor allows for it. I didn't pull it out yet however is there something I can do myself or does it need to be done on the machine? He said my cost would be about $85. Is this a reasonable price? I have no issues if its fair and its something I can't do. Thanks for your help.
Rod
 
rod7515 said:
I've contacted a person in my area that has a sun distributor machine and can change the advance in my distributor if this distributor allows for it. I didn't pull it out yet however is there something I can do myself or does it need to be done on the machine? He said my cost would be about $85. Is this a reasonable price? I have no issues if its fair and its something I can't do. Thanks for your help.
Rod
Click to expand...


That’s DIRT cheap. I’d do that so fast I’d have to wait for my shorts to show up.
 
Last edited:
Ok, ill get it to him in the next week or so. Ill have him shorten it up about 6 degrees as you spoke of earlier to get me to 22*. I already let him know where I was looking to get to in base timing, the only problem would be if this distributor is not capable of being changed. Hopefully it will all work out. I really appreciate all the help and guidance. As I move forward there will be many more questions. Lol.
Thanks,
Rod
 
You must log in or register to reply here.
-

Back
Top