Air:Fuel Help. Cannot Get it Rich

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Good point... the OP has changed pumps, and checked pressure, but that pressure check is likely at idle and that does not say anything whatsover about that pressure being maintained at the top end under max flow conditions.. And, the OP checked open pump flow into a container, BUT, that says nothing about flow into back pressure; pumps with poorly functioning check valves with have their flow drop radically or to nothing when back pressure is applied.

So, while those are good checks to do, they are not 100% conclusive checks that the pump & fuel system are delivering fuel properly at max flow conditions.

The easiest way to know is the rig up a fuel pressure gauge that can be observed when running hard. Just be safe when doing this.

OP, I see you put in a new pump of adequate specifications. Did you change the regulator? And while the free flow test says the pickup is good, any way the cell pickup, or any foam blocks, are moving around and getting masked under acceleration?

You are correct, all pressure tests are at idle. I hoped that going with this specific pump, and increasing supply lines to 10AN from cell all the way through the pump, and 8AN out of pump to carb and return I would be "good" with respect to flow when accelerating or WOT for a 1/4 mile. Maybe not. When I upgraded and installed with return line in lieu of dead-head, I did install with a return regulator, although not new out of the box. It's a Mallory 4309.
Foam was pulled out of the cell a while ago while I've been a chasing this.
 
You know I'd like to say I have something to bang mine off to test it? I mean all I can do is really calibrate it and hope that it's working? And of course you drag race so you know watching the plugs is the biggest thing. The two should go hand-in-hand.
I don't like changing a part before I verified that it's the problem. I find this costly.

The original sending unit lasted a few years, and was pretty fouled. I used to do a ton of street driving and was always rich. It stopped sending a signal, therefore it was replaced. The previous sender when working seemed to match that of the plugs and the dyno testing prior to the engine being installed (+- 12.2:1 - 13.2:1).
 
Like I said and post 25.
a lot of times I come out here and say what I'm doing also and kind of check my thinking and from what I see you doing your trying the right stuff.
 
They should put those stickers on nitromethane too......

Have you taken a vacuum reading yet; Are you low? bolt a lift plate up on top a carb gasket (or a piece of sheet metal to seal carb pad) and pull the rocker shafts to close all the valves. plug all but one vacuum locations and chuck it to some compressed air. give it a shot and listen with a stethescope for any hissing or bubbles from a light soapy mix in a squirt bottle. A sprayed leak will cause bubbles. We 'flash test' airtight splice cases with same procedure and can find any pressure leak on the seams down to 2 psi. should find any vacuum leak with this method too, but ones under the intake will be audible only.

Just did this last night. Flat plate and welded an air hose fitting to the center, and mounted onto the manifold. Soapy water with air pressure at 20 psi, then 30, 40, 45, and no bubbles. Should be good here.
Thanks for mentioning this.
 
You are correct, all pressure tests are at idle. I hoped that going with this specific pump, and increasing supply lines to 10AN from cell all the way through the pump, and 8AN out of pump to carb and return I would be "good" with respect to flow when accelerating or WOT for a 1/4 mile. Maybe not. When I upgraded and installed with return line in lieu of dead-head, I did install with a return regulator, although not new out of the box. It's a Mallory 4309.
Foam was pulled out of the cell a while ago while I've been a chasing this.
Yeah, idle and other 'static' tests show up most problems but not some of the more esoteric ones. The line sizes seem adequate to me... I assume you are not running at 1000 HP? So that seems to go back to pump, regulator and restrictions as needing more checks, since all the attempts to enrich at the carb have been futile.....
 
Like I said and post 25.
a lot of times I come out here and say what I'm doing also and kind of check my thinking and from what I see you doing your trying the right stuff.

Thanks! I'm trying. I am always trying to learn. When I sometimes feel like I'm getting a handle on things, it can be the simplest thing that reminds me I don't really know much about these things.
Since i just pumped up the manifold with air last night, I've gotta reset valves, and put it all back together. I've ordered another fuel pressure gauge as a just in case. I will check timing, vacuum again, even more soapy water spray. I just hope for sun next next weekend, as I am not one for getting after it on the street. Especially since all windy roads around me.
 
Yeah, idle and other 'static' tests show up most problems but not some of the more esoteric ones. The line sizes seem adequate to me... I assume you are not running at 1000 HP? So that seems to go back to pump, regulator and restrictions as needing more checks, since all the attempts to enrich at the carb have been futile.....

I'm guessing 525ish HP, so I too think I'm adequate on the lines and parts. The car was running great with a cheaper less flowing pump, and 6AN supply line dead-headed at the regulator.
Prior to running the Mallory return regulator, I even used a (new out of the box) Holley dead-head regulator and ran this new pump with 8AN from cell to regulator since I was in a hurry to make a track event. Same issue.
 
I’m humbly throwing in the towel and asking for some opinions/guesses on this one.
Sorry a little long - but hopefully covering the details...
I had been running the same fuel set-up for 4 years with no troubles. It was probably a bit undersized, but never had any issues. Fuel cell to Mallory fuel filter to Summit electric fuel pump, to Aeromotive dead head regulator. Regulated to 6psi, all 6AN line.

The car has a 408, 10.3:1 pump gas, 850 Quickfuel carb. I shift between 6k – 6.5k. The car has been primarily more track than street over the last few years. Just a couple months ago, I’ve all of a sudden gone from always being a bit rich on the A:F to really lean. One event all is great, and the next event the car falls off about 3 tenths and a couple miles an hour. I check plugs and really lean, and now I cannot get the car rich. All plugs look uniformly lean.

After cleaning the heck out of the carb, cleaning the fuel filter, cleaning the fuel cell, and blowing the fuel line clean, I decided to start with carb jetting ~ knowing it shouldn’t be the culprit since it has been fine for the last 4 years. I kept my 4.5 power valve in (but replaced with new), dropped the high-speed bleeds to .027 (reduction of .006), increased the PVRC jets to .057 (small increase of .002), increased the primary jets to 84 (up 8 sizes), increased the secondary jets to 92 (up 8 sizes). Performing these changes incrementally made no changes to the plugs or performance, and having ALL these changes at once also made no changes to the plugs or performance. Also new bowl and metering plate gaskets, and new gasket between carb and manifold, no cracked or missing vacuum port plugs/caps.

With no change to anything with attempted carb tuning, I started changing fuel delivery ~ which I assumed was my problem all along. Started with checking flow of my electric pump. The pump was getting old, and sounding a little different than typical, and checking flow into a fuel jug appeared a bit slow. So out with the old and in with the new. New 10AN supply from cell to new fuel filter, 10AN from filter to new Aeromotive 11203 pump, with 8AN from pump to Mallory regulator, and 8AN return all the way back to the cell. Fuel regulated to 6psi, fuel level is middle (or slightly above) carb view window. Figured that would do it. No change to plugs or performance. I did another test of running the regulated fuel supply line into a fuel jug, and it appeared to flow fine (I think 5 gallons in 1:36). Since it is uniform across all cylinders, I really did think it is/was a supply problem.
I thought maybe a leak below the carb like intake gasket, but it would have to be both gaskets, and leak to all cylinders. Seems unlikely. All seems normal when engine is running and I spray carb cleaner all around (where I can reach) around the manifold.

I’m a bit stumped. Perhaps I am missing something super simple. Anyone have any experiences or words of wisdom on this? I feel like I’ve been chasing my own tail on this one.

Thanks for any help or comments!
I had this same problem many years ago.
You did not mention what heads on the engine.
15 years ago I built a 340 with w2 heads.750cfm Holley
First few runs on new motor I had backfiring and poor performance.
Plugs were white. I kept increasing jet size and got all the way to 99 jets all four and plugs still white.
A good friend of mine told me to take my carb to a carb specialist in Hamburg New York.
The guy asked me my whole car combination.
When he gave me back my carb the car ran its best ever.
I checked the bowls and he had 68,and 69 jets and plugs had perfect color. The car b guy told me that a stock street Holley 4150 carb does not have a proper fuel curve for a cylinder head that can flow that much air. He drilled passages and all that in the metering plates as that is where the fuel flow restriction was.
The only a/f ratio reading I would trust at the track on your gauge is the wide open throttle one because that is when your likely able to hurt the motor if it's lean. Today you can buy hp4150 etc that have a proper or closer to proper fuel curve. I would try another carb to see what you get. Imho.
 
I had this same problem many years ago.
You did not mention what heads on the engine.
15 years ago I built a 340 with w2 heads.750cfm Holley
First few runs on new motor I had backfiring and poor performance.
Plugs were white. I kept increasing jet size and got all the way to 99 jets all four and plugs still white.
A good friend of mine told me to take my carb to a carb specialist in Hamburg New York.
The guy asked me my whole car combination.
When he gave me back my carb the car ran its best ever.
I checked the bowls and he had 68,and 69 jets and plugs had perfect color. The car b guy told me that a stock street Holley 4150 carb does not have a proper fuel curve for a cylinder head that can flow that much air. He drilled passages and all that in the metering plates as that is where the fuel flow restriction was.
The only a/f ratio reading I would trust at the track on your gauge is the wide open throttle one because that is when your likely able to hurt the motor if it's lean. Today you can buy hp4150 etc that have a proper or closer to proper fuel curve. I would try another carb to see what you get. Imho.

I've got a pair of Eddy heads with hand work, and Quickfuel Q850 carb which has been great for 4 years right out of the box with minimal adjustments. Prior to all this I had actually been working to lean things up a bit as it had always been a touch on the rich side. Ironically, I had larger high-speed air bleeds, and smaller PRVC jets in the mail when all this started in effort to lean things up. I've got another carb to try as a test mule. If the weather holds I was planning to give it a go and see if a difference.
 
I'm guessing 525ish HP, so I too think I'm adequate on the lines and parts. The car was running great with a cheaper less flowing pump, and 6AN supply line dead-headed at the regulator.
Prior to running the Mallory return regulator, I even used a (new out of the box) Holley dead-head regulator and ran this new pump with 8AN from cell to regulator since I was in a hurry to make a track event. Same issue.
Maybe something stuck in the pickup tube? If you get a pressure gauge in place and run it once-twice hard while observing for any pressure drops, you will know right away if something in the delivery system before that point is amiss. You never know how a couple of things can add up and confuse matters: maybe the old pump was giving out and the new one is not up to snuff.... You just gotta get a direct reading on the pressure to the carb under load IMHO. At least the intake seem sounds after your testing there; those were good suggestions to find intake leaks.
 
Thanks! I'm trying. I am always trying to learn. When I sometimes feel like I'm getting a handle on things, it can be the simplest thing that reminds me I don't really know much about these things.
Since i just pumped up the manifold with air last night, I've gotta reset valves, and put it all back together. I've ordered another fuel pressure gauge as a just in case. I will check timing, vacuum again, even more soapy water spray. I just hope for sun next next weekend, as I am not one for getting after it on the street. Especially since all windy roads around me.

well doubled checked no vent tube (at cell) blockages, clean and clear fuel pump. I put things back together and idled in the garage to check for fuel leaks, then checked vacuum leaks again with soapy water, checked timing, installed another fuel pressure gauge as a double-check.
While running, no change in idle with water sprayed around the intake, carb to manifold or carb body to throttle plate.
Fuel pressure checks out. At least it does with my Summit gauge. I had to deduct 2.5lbs from my new Holley gauge that showed up showing 2.5lbs in the package...
Vaccum at idle is a steady needle fluctuation between 7-8psi. When revved to (guessing) approx 3-3.5k it fluctuated between 17-18psi. Blips of the throttle it went to 21psi, then returned to 7-8 at idle.
Timing, appears to have moved. Last time it was set at 35 degree advanced, but somehow it was at 40-42ish. I set it back down to 35.
 
well doubled checked no vent tube (at cell) blockages, clean and clear fuel pump. I put things back together and idled in the garage to check for fuel leaks, then checked vacuum leaks again with soapy water, checked timing, installed another fuel pressure gauge as a double-check.
While running, no change in idle with water sprayed around the intake, carb to manifold or carb body to throttle plate.
Fuel pressure checks out. At least it does with my Summit gauge. I had to deduct 2.5lbs from my new Holley gauge that showed up showing 2.5lbs in the package...
Vaccum at idle is a steady needle fluctuation between 7-8psi. When revved to (guessing) approx 3-3.5k it fluctuated between 17-18psi. Blips of the throttle it went to 21psi, then returned to 7-8 at idle.
Timing, appears to have moved. Last time it was set at 35 degree advanced, but somehow it was at 40-42ish. I set it back down to 35.
I wonder if that was it? If your timing creeped up on you?
 
Ugh. That would be great, and equally embarrassing!
From the get-go this just seemed like something went out of adjustment or a leak or a plug. I was really hoping it was something simple and just being over thought.
 
From the get-go this just seemed like something went out of adjustment or a leak or a plug. I was really hoping it was something simple and just being over thought.

Even if that’s not it, crazy it would be fine one weekend, the car gets parked for a week, and all of a sudden it’s off.
 
Even if that’s not it, crazy it would be fine one weekend, the car gets parked for a week, and all of a sudden it’s off.
Yeah that seems like a one thing got out of adjustment kind of thing not a whole bunch of stuff?
 
Yeah that seems like a one thing got out of adjustment kind of thing not a whole bunch of stuff?

Hey, I didn`t read all these posts, but I`ve had that trouble of not being able to get rich for 72 yrs now!! Seems these dam mopars have had a big part in it !!
 
Hey, I didn`t read all these posts, but I`ve had that trouble of not being able to get rich for 72 yrs now!! Seems these dam mopars have had a big part in it !!
You don't have to read all the post to join the thread. You just have to have 40 years experience and not much time to answer questions. Then if anybody question you you can say they're chasing you all over the forum and get mad at you even though you don't know who they are. Then the fun police tell you to stop chasing this person still leaving you wondering who the f*** they are?
 
Yeah that seems like a one thing got out of adjustment kind of thing not a whole bunch of stuff?

After all the checks, cleaning, and cleaning again, and timing adjusted, I hope to make it out this next weekend for a couple passes!
 
it's a street car that has become less fun on the street. progressively over the years it has become more strip than street.
I was just wondering if you had some street tires to do a little test driving on. And if it was still illegal enough?
 
I was just wondering if you had some street tires to do a little test driving on. And if it was still illegal enough?

Completely street legal. I don’t have street tires. I just roll on the Hoosier quick time pros and whatever the skinny Hoosiers are up front.
 
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