Is 850 cfm too much for warmed over 440?

[djais1801]

Main jets only affect the fuel mixture, and unless you are getting black smoke or the spark plugs are black I'd say don't go there yet. What's more likely in your case is a power valve that's too high since your cam is healthy and intake vacuum may be low at idle.

Warm it up with a vacuum gauge on an intake manifold vacuum port and read the vacuum at idle. Divide by two to find the correct power valve. The Brawler comes stock with a 65 (which means 6.5" vacuum) so if you have anything less than 13" vac. at idle a change might be in order.

There's lots of knobs to twist and buttons to push on a Holley and many give up and bolt on an Eddy, but my 2 cents is once the Holley is dialed in it will be a great carb. There's lots of great carb tuning info on the Holley site.

I am curious about your answer to Mastertech's question about use.... what percent street and what percent track? Because if it's never - or very rarely - going to the track perhaps a carb change might be in order.

As long as I own it...there will be no track time...cruise nights and the occasional laying rubber on the streets

 

[djais1801]

The big question is this for mainly street or track. If for street always go with vacuum secondary's. You can then fine tune the opening to prevent any bog. With mechanical secondary's you are pretty much flushing a toilet with gallons of unused fuel to cover a bog on the street. This will wash down the cylinder walls and thin out your oil. The key to the Carter T-Q was the ability to adjust the rate of the air valve opening so that the engine could draw only as much air and fuel as it needed.
Also the little 340 cylinder heads way outflowed the 350 chevy and mopar rated the horse power at 5000 rpm to keep the insurance companies happy but neglected to mention that at 6000 rpm it was actually about 30 hp higher. The Camaro guys never did figure this out!

it is a mechanical secondary...As long as I own it...there will be no track time...cruise nights and the occasional laying rubber on the streets

 

[djais1801]

it also has an edelbrock torker II intake. Am I better off changing to a spread bore/dual plane intake and smaller carb for low end torque and strictly street use or will that not be effective with the cam I have?

 

[fasjac]

As Racer Dave states, when you get the holley dialed in, it doesn't get any better. I've heard your car and it's sound very healthy. Use patience, it's not rocket science, just trial and error. I once built a stock 440 4 speed, 906 heads, MP 509 purple shaft, headers, dual plane eddy, and put a 600 eddy carb on it. I could only get 4-5" of vac. The initial timing was 12 degrees and total at 35 @ 2800 rpm. The motor ran ok....with the eddy carb as not to rich, plugs looked good etc. Good drivability but, WOT something was just lacking. I changed to an old 750 holley with vac sec, electric choke. Whole different car after the carb change. Still had the drivability and WOT was tremendously increased with no bogging or hesitation whatso ever. IMO, if you frequent the track, I don't think you'll like an eddy carbs vs holleys.

 

[Racer Dave]

The car really wants that 850 double pumper, but for your intended use you might be happier with a vacuum secondary carb - but the 4-speed covers a multitude of tuning sins. Stick with the Torker II, it's one of the best for street performance. A dual plane will only gain marginal torque and sacrifice top end power. The spread bore idea is really more for under-cammed and poor breathing engines. Yours has neither of those problems.

 

[12sandwich]

How you drive it will make a difference, especially if it never sees any RPM, in which case smaller will be more responsive (due to greater air speed through smaller venturiis though - not because of less max. CFM) . My experience has been a lot like Chryco's - no problem with an 850 on a healthy 440, and running a 1050 Dominator on a 440+.030 (not stroked) as well. After all, Chrysler didn't feel shy about 1,200 CFM on a 6-pack Of course around town the 500 CFM center carb does all the work....but when you stand on it, hold on! And those motors didn't have anywhere near the cam or breathing you do.

Anyway, your richness problem is most likely carb tuning (those needle/seats sound suspect to me as well). Sort that stuff and happiness will follow.

The Mopar six packs flowed 1350cfm and the center carb was 350cfm not 500.
The outboard carbs were 500cfm
An 850 double pumper is a great carb with a 4 speed car, and a 440

 

[Mastertech]

The 6 pack set up uses vac operated outboard carbs. Also most 2bbl carbs are flow rated with a different vac draw than four barrel carbs and are not directly comparable. The 1350 sounds awesome but is actually not a lot more than an 850 four. When setting up a carb I always use a four or five gas analyzer to determine mixture at idle, cruise, accelerator pump shot, and a vac gauge both at idle and under part throttle load to determine power valve required. I started my career as a tune-up and diagnostic specialist back in the mid 70's and have worked on just about every make and model of carb and engines from around the world that you could name. One of the most important things that I learned from my mentor was Test, Verify, Repair, Retest and this is what I have always taught my apprentices.

Test to find what the problem is. Verify by approaching your test results from a different perspective. Repair what you found was the problem. Retest to make sure that what you did cured the problem.

I know that having a garage full of tools and test equipment (especially my Sun 500E analyzer and Allen synchrograph) gives me a different perspective. As you can gather from this I don't like guessing or throwing parts at a problem in the hope that it goes away. To fix your problem may require a bit more knowledge, experience, tools and reference information than you currently have. I would suggest that you find a shop that is equipped and experienced to help you out.

My final bit of advice goes back to the debate on vac or mechanical secondaries. When you have a car that is for street use you want the correct amount of fuel and air going into the engine at all times. When you stomp on the gas pedal with your double pumper it will squirt both accelerator pumps at the same time no matter what the engine load or rpm is. (Just look down into your carb and push the throttle wide open) The vac secondary or air valve carb only puts in the amount of fuel and air that is required for that given load and rpm avoiding fuel wash and skyrocketing emissions.

 

[djais1801]

The 6 pack set up uses vac operated outboard carbs. Also most 2bbl carbs are flow rated with a different vac draw than four barrel carbs and are not directly comparable. The 1350 sounds awesome but is actually not a lot more than an 850 four. When setting up a carb I always use a four or five gas analyzer to determine mixture at idle, cruise, accelerator pump shot, and a vac gauge both at idle and under part throttle load to determine power valve required. I started my career as a tune-up and diagnostic specialist back in the mid 70's and have worked on just about every make and model of carb and engines from around the world that you could name. One of the most important things that I learned from my mentor was Test, Verify, Repair, Retest and this is what I have always taught my apprentices.

Test to find what the problem is. Verify by approaching your test results from a different perspective. Repair what you found was the problem. Retest to make sure that what you did cured the problem.

I know that having a garage full of tools and test equipment (especially my Sun 500E analyzer and Allen synchrograph) gives me a different perspective. As you can gather from this I don't like guessing or throwing parts at a problem in the hope that it goes away. To fix your problem may require a bit more knowledge, experience, tools and reference information than you currently have. I would suggest that you find a shop that is equipped and experienced to help you out.

My final bit of advice goes back to the debate on vac or mechanical secondaries. When you have a car that is for street use you want the correct amount of fuel and air going into the engine at all times. When you stomp on the gas pedal with your double pumper it will squirt both accelerator pumps at the same time no matter what the engine load or rpm is. (Just look down into your carb and push the throttle wide open) The vac secondary or air valve carb only puts in the amount of fuel and air that is required for that given load and rpm avoiding fuel wash and skyrocketing emissions.

so for my use are you suggesting i move away from the mechanical and go for a vacuum secondary carb?

 

[fasjac]

IMO, From what I have read about how you use your car. It would suit your better. DO you have a buddy that would let you barrow one. just a thought

 

[djais1801]

IMO, From what I have read about how you use your car. It would suit your better. DO you have a buddy that would let you barrow one. just a thought

i don't think so...i'm gonna replace the front float, needle and seat and see how it goes.

 

[fasjac]

You'll get it dialed in. And you definitely have a good carb. Please keep us posted on the tune.

 

[Dodgeboy]

I have always been told to use a vac. advance dist. and a vac. secondary carb for street use, this way the engine decides what it wants/needs. Dial it all in and you'll be happy. I don't listen to my own advice so i have a mechanical dist. & carb. Works good. I have 5.5 inchs of vacuum at idle and run a 6.5 power valve, I have no issues/extra fuel dumping down the carb. At 60mph I have 10 inchs of vacuum. As long as the power valve is not defective, There is not enough preasure/draw thru the pvrc circuit too pull fuel thru the power valve at idle.

 

[12sandwich]

I had some Ansen ball bearing progressive mechanical linkage on my wife’s 440 six pack car.
it was flawless as long as you didn’t kick it from a idle. As long as you brought the rpms up a little over a 1,000-1100 rpms zero hesitation. So a 4 speed car would be a moot issue.

 

[Chryco Psycho]

You will not see me recommending vacuum secondary ever , I prefer to have control & learn how to pedal it , the vacuum will never match the performance of mech secondary carbs , I would recommend a 1200 CFM multiport EFI over any carb though

 

[Mastertech]

1. Vacuum advance does respond to engine demand and will give you better drivability and much better fuel economy.
2. A 65 power valve opens at 6.5 inches of vacuum. If you are running a cam on the street that only has 5 inches of vacuum you probably don't need a power valve just very rich jetting. Holley makes a plug that replaces the valve in racing applications. If you drive with a portable gas analyzer hooked up to your exhaust you will see exactly when the valve opens. For example take a Ford truck with a 351W and a four barrel. Engine idles at 15 - 17 inches of vacuum. It comes with a 10.5 power valve from the factory. You are cruising down the road and hit a slight grade the vacuum under load drops to 9 inches and the power valve pops open even though you don' need the extra fuel. Solution is to change to 75 or 65 valve. Gain of almost 5 miles to the gallon in fuel economy with no loss of performance. This is what I mean about testing to determine what the problem really is and correcting what is actually wrong. Often by throwing a bunch of maybe it's or it might be that you end up digging yourself a bigger hole.

3. As far as the bog with the 6 pack this was quite common with the factory setting for the vacuum end carbs . They actually opened up a little too soon and the engine wasn't ready for it. A slight change of the diaphragm springs to the next heavier will cure this. The factory setting for the air valve on the carter T-Q was also to loose and would bog. It required a little more tension plus a little bit of an increase of the height of the metering rods to increase fuel flow a bit and you have an instant response to the go pedal and those great big 2 1/4 inch secondary throttle plates and unlike a Holley there is no venturie to restrict air flow. Great fun and the most incredible roar of all that air going into the engine.

4. And yes I still maintain that for street driving with only an occasional trip to the track that the only way to go is with a vacuum secondary or an air valve to control air flow like the T-Q or Quadrajet. It has been mentioned here that with the double pumper and the 4spd will hide a lot of tuning sins, and it will. But how it hides these sins is by dumping a whole bunch of fuel in to cover for the lack of air flow until the engine can catch up. In a race car you essentially have to throttle positions, idle and wide open, there is really no in-between and you also have a rear end geared for race not the street. 5.16 is great if you want to go through all for gears and hit your rev limit and max speed by the other side of the intersection. I had a friend who built a 65 mustang as stop light racer and could outrun anything on wheels at the light but gas was 45 cents a gallon and the top speed was a whole 60mph. Lots of fun but not very practical as a driver.

5. Bog and an intake backfire is possibly a) accelerator pump timing and shot. The duration and volume are adjusted by the squirter. It's too lean or not long enough.
b) Engine not ready for the airflow from the secondaries. c) crossed plug wires or plug wires running parallel causing an inductive misfire under load.
A backfire in the exhaust is from unburned fuel in the hot muffler or pipes. Running over rich, ignition misfire resulting in unburned fuel going out into the exhaust, A very lean mixture causes the flame to go out before all the fuel is consumed resulting unburned fuel and extra air going into the exhaust, air leaks in the exhaust system as a leak has exhauist gases going out when the exhaust valve is open but actually has a low pressure pulse that draws fresh air in when it closes and before the next one opens.
Enough for tonight. Happy motoring to everone.
Terry

 

[Chryco Psycho]

The car will run far better with the Holley once you get it dialed in , so stick with it , we can help with tuning issues , You need to confirm the float level first , if it is high it will run rich , low can cause a bog . The power valve adds extra fuel under heavy load / low vacuum , you need a vacuum reading to determine where you are . Jet ust provide fuel under steady cruise situations the power valve & accelerator pump adds fuel under varying situations .
Personally I find vacuum secondaries are slow to respond & hit too soft , learning how to drive the car is more effective , you can get a lot of power using 1/2 throttle without wasting the extra fuel opening the secondaries but when you ator above the right rpm & floor it the car will respond much harder which is why I never recommend vacuum secondary carbs .
I have a 6 pack on my 512 CI Challenger , it has 3 full mechanical carbs on it it is amazing when you jump on it

 

[Midnight340]

I’m told the big Thermoquad from 440’s flow 850+ if needed. 910 on a bench with choke removed. My 340 with ported iron heads and healthy cam ran great with a well tuned 750, but really woke up with the big Thermoquad jetted up and without choke. Feels like a whole different motor on the street. Nobody will ever convince me big carbs don’t work well if tuned. I think those formulas are so very misleading if you care at all about performance!

 

[Mastertech]

The 30 came with the 800 TQ while the 440 had the 850. Properly set up the TQ gives instant throttle response at any RPM with no bog or lag. Even better when the distributor curve is also tweaked as the factory springs are way to strong. Mopar had a quick curve spring kit that worked really well but I don't know if it's still available.

 

[Midnight340]

I’ve got an MSD and am working on the curve now. One heavy, one lighter, both stretched just a bit to come in earlier.

 

[craigbred]

I installed a Wide Band air/fuel meter, AEM, and for now the O2 sensor is in the pass side collector.

I recently built a new 505 engine with a new 870 vac 2nd Holley. ​

I also bought a Holley tuning book by David Vizard. The A/F gauge is GREAT for setting up the carb. With my limited Holley tuning experience, this is the only way I can tune the carb with it's multiple circuits. (I have tuned 2-cycle carbs, but usually with Exh. Temp. gauges) Even if you are having someone else tune your carb, it will make their job much much easier and more accurate. The big question "is that bog lean or rich?" is instantly answered. 2 cautions, no header or collector gasket leaks allowed, and a lean misfire will make it momentarily read rich.
I will give an example, before changing any jetting, the engine just seemed not as responsive as I though it should be, I called it "flat". I had 16 deg initial, 32 deg all in by 2000rpm, and the vac advance adding another 22 deg when it came in. It didn't misfire or smoke. At 30-40mph steady, I was pretty sure I was still on the transfer slot, and the A/F was around 10.9:1.
I started playing with the low speed jetting. 1st I drilled out the Idle air bleeds some (I don't have my notes here, so I don't know how much, also my carb did not have "changeable" air bleeds). But that didn't seem to do much. Next I removed the fixed brass idle circuit jets from the metering block (they were .036"), tapped threads in those holes, and drilled smaller holes in brass set screws to "jet down" the fuel in the low speed circuit. That was the answer! Dropping to .033" gave it noticeably better throttle response, .030" was better, .027" caused a lean misfire. So I settled on the .030", that gave me around 13.0:1 A/F. Not as lean as I though I could get it, but I guess that's what this engine wants. Keep in mind, when driving and testing throttle response, I'm only using the 1st 1/4 of the throttle for this circuit. To get the A/F reading, I go steady state at about 30 or 40 mph with very light throttle - you have stay on the transfer slot, with no main booster fuel.
The idle mixture screws changed this some, but they must be optimized for idle mixture. I discovered by accident that they can be used to test idle circuit jetting, I accidently had them screwed in too far, I think 1/2 turn. While test driving, I had to keep bumping the acc. pump to keep it idling, BUT it gave it improved response in the 1/4 throttle area. That was a big tip - I had to go leaner!
I have a few more details in my last post of my "440 to 505 Build".