[the70OOJudge]

Hi everyone.... Took the Judge out this year and she runs fantastic till I push her at WOT and at around 4200 to 4500 She craps out like no gas....

I built the Original Ram Air III back in 1994, running around 425 hp, I put in a 69 fuel pump 5 years after that and rebuilt the carb... Its been running fantastic till now...

I did change the wires ( running 8mm ) with GM HEI this spring and figured it might be the new wires so went back to the old ones and its still there....???

I am using the original Ram AIr Carb and she idles and I can play up till 4200 and no problems... I am thinking its my pump? Getting old so I did order a new one from Ames .

[Dave M]

Maybe needle and seat too small? Does it feel like it's running out of gas?


Sent from my iPhone using Tapatalk

[steve25]

Did this issue start from the get go when you took it out of hibernation?

[pfilean]

Fuel filter?? Had similar problem a while back and finally chased it to a fuel filter that I didn't think should be bad.

[Tom Vaught]

Are you starting to get Corn in your gas out in BC?

Sounds like the fuel sock might be fused up somewhat.

Tom V.

[the70OOJudge]

Yes, It feels like its running out of gas...

[the70OOJudge]

I changed the tank and sending unit 10 years or so ago,

[the70OOJudge]

Originally Posted by pfilean

Fuel filter?? Had similar problem a while back and finally chased it to a fuel filter that I didn't think should be bad.

Changed the fuel filter in the carb.. Thats the only one I have..

[the70OOJudge]

Originally Posted by steve25

Did this issue start from the get go when you took it out of hibernation?

Yes , but I have run a couple tanks of gas through her and I had gas stabilizer in the tank.. Put it away October and had her out in April... Nice weather here lol

[the70OOJudge]

Originally Posted by Dave M

Maybe needle and seat too small? Does it feel like it's running out of gas?


Sent from my iPhone using Tapatalk

It just started this year... it was good last year... same needle and seat from resto

[Dave M]

Originally Posted by the70OOJudge

Yes, It feels like its running out of gas...

Sounds like the same problem that I had. Mine was doing it with different engines in the same car. Same carburetor too, which was rebuild by Cliff. I thought it was the filter, so I changed it. Didn't fix it. A friend told me to change the sock. Not only did I do that, but I changed the tank, sending unit, fuel lines, and pump. Still didn't fix it. So I called Cliff. He told me that I needed a bigger needle and seat. Because, the ethanol in the fuel. Engine burns the fuel faster. So I changed (going off memory here, which isn't very good) from a .125 to a .135. Haven't had the problem since.


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[the70OOJudge]

Originally Posted by Dave M

Sounds like the same problem that I had. Mine was doing it with different engines in the same car. Same carburetor too, which was rebuild by Cliff. I thought it was the filter, so I changed it. Didn't fix it. A friend told me to change the sock. Not only did I do that, but I changed the tank, sending unit, fuel lines, and pump. Still didn't fix it. So I called Cliff. He told me that I needed a bigger needle and seat. Because, the ethanol in the fuel. Engine burns the fuel faster. So I changed (going off memory here, which isn't very good) from a .125 to a .135. Haven't had the problem since.


Sent from my iPad using Tapatalk

That could be part of it... I use 94 octane up here in Canada.. And Chevron says it has no ethanol but who can believe them now a days..... the only time I have ended up with a lower octane is when I head down to the States and the chevrons I get only have 92 octane and it apparently states it has ethanol.. I will check what size seats I have... I thought they were a .135 but my memory is like yours Thanks

[HO Kenny]

I had a weird similar problem but it started a little earlier in the rpms. A baffle in a muffler must have come come loose. It ran great as long as I didn't floor it. I unbolted the header flanges and my power came back. Lots of noise as well.

[steve25]

If the motor will rev up passed 4500 out of gear then it's 90 % certain you have a Carb / fuel delivery issue.
Does the Carbs secondary diaphragm work?

[Cliff R]

Here's my lengthy response to a similar question from a few days ago on my Website. Long reading but worth it if you have the time, and should clear up a few things when it comes to this topic:

Stock fuel pumps and fuel systems were NOT designed for 500hp, or anywhere close to that.

The truth is that most stock systems are hard pressed to keep up with much past about 350hp and we start to see all sorts of issues depending on the vehicle, tank location, routing of the factory lines, etc when folks install powerful engines and start taxing the fuel system harder. Heat can be a player here as well as lines often run too close to exhaust pipes and pick up too much heat on the suction side of the mechanical pump.

I went thru this with my own vehicle over 20 years ago and quickly learned that a stock fuel system on a 1973 Ventura is good for about 350hp with no issues anyplace.

When I installed my first 428 engine making about 400hp I didn't have any issues at all until I took steps to improve traction (DOT tires or slicks) and installed 3.42 gears and a good aftermarket converter to get the car to leave harder. The car ran fine in all scenarios until I found good traction and left hard, then it would start to loose power right up near the shift point (5500rpms). I could actually "feel" the engines power falling off around 5000rpms but it never ran completely out of fuel, most likely just sucking the fuel bowl pretty low.

I tried an HP Carter mechanical pump, pusher electric pump, and they really didn't correct the issues, the car still felt like it was loosing power past 5000rpms but only at the track or on the street when it hooked up really hard.

Next move was to install a more powerful 455 engine which INSTANTLY resulted in fuel delivery issues much more pronounced than with the 428 engine. The engine would pull like a freight train in low gear to about 4500-4800rpm's then nose over, quickly recover and pull right on up to the shift point.

It ONLY did this on hard runs with good traction. I could do "John Force" burnouts with zero issues, or blast thru the gears without any problems, etc. Any attempts to heat up the tires and launch hard and it would nose right over.

At this point I was perplexed by the problem and had tried several different things to correct it and each time I thought I had it beat then did a hard run with traction and the problems came right back.

The last attempt I did was to remove the gas tank and install a larger line and relocate the pick-up more to the rear of the tank as it was right in the front. I put a Holley Blue pump just outside the tank, and 3/8" steel lines to a regulator in front of the carb dead headed. Low and behold the problems still existed and I was completely stumped at this point. I even tried pushing to the Carter HP mechanical pump which wasn't quite as good as just re-routing around it.

The car by now was being drag raced couple of times a week weather permitting and running solid mid 12's with best ET of 12.43 at 109MPH. I settled on just short shifting the engine at 5000rpms for all runs right before where it would suck the fuel bowl low and start loosing power. At the suggestion of several well meaning folks I even built and installed a Holley 4781-2 850 DP carb and it didn't do much better, power still fell off at high rpm's. I would have thought that the much larger fuel bowls and 2 N/S assemblies would have certainly helped, but really no improvement as the car still ran mid 12's at 109mph.

So I just dealt with this problem for several years and enjoyed the car on the street and track, and logged over 1000 track runs with it without any noticeable problems. Over one Winter I decided to upgrade the fuel system one last time and pulled the tank and welded on a CE rear sump, upgraded to a Comp 140GPH pump, and 8AN lines/fittings everyplace.

First track outings the next Spring resulted in 12.0's at 112mph!!!!!!! I was simply amazed with the improvements and the engine pulled so hard past 5500rpms on the first two runs that I didn't get it shifted quick enough and actually ran a little slower than the runs to follow shifting at 5500rpm's. I ended up with a best run for the car that day of 12.02 at just under 113mph!

I would also mention here that I carried the big Holley 850 to the track that day and it also ran 12.0's at 112mph, showing that it was also not staying full on hard runs with the previous fuel delivery system.

Lessons learned in fuel delivery with these cars for sure. I went on to install a bypass system back to the tank to take some load off of the electric pump as I "fried" the brushes in the first one in about 2 months running it "dead head".

All of this happened in 1999-2000 and to date the current system has been FLAWLESs clear down to 7.18 @ 96mph in the 1/8th mile and nearly into the 10's in the 1/4 mile with a newer and more powerful 455 engine.

By this point in the long response folks have probably figured out that the pick-up location in the factory tank was the culprit and I was uncovering it on really hard runs. Installing a rear sump and moving the 140GPH pump behind the tank, and larger 8an lines everyplace also works for us on hard launches as fuel rushes back to the pump not being sucked away from it.

With this topic you will see a wide variety of threads on different websites where some folks run deep into the 10's with "stock" fuel systems where others can't get out of the 14's trying to do the same thing.

All I can say about all of that is that we have learned here to make sure the fuel system is more than adequate for the power level and vehicle performance and since those lessons nearly 20 years ago have had zero issues in that area.

One thing that I'll point out here is that folks are quick to toss out their Q-jet and go to some sort of aftermarket "high performance" carburetor thinking the Q-jet is simply not capable of keeping up with these powerful engines.

Folks quickly blame the small fuel bowl but in reality it simply let's you know that fuel delivery is inadequate for the power level much sooner than a carb with more fuel capacity.

I even see folks "chopping" up the insides of the q-jets fuel bowl, splash guard, etc in order to increase fuel bowl capacity when the real cure is to increase fuel delivery so it simply stays full on hard runs.

Of course you have to keep in mind that you only have ONE needle/seat assembly, so in addition to fuel delivery being adequate the size of the N/S plays a big role here as well.

What I've found over the years is that the myth of the q-jet not wanting or liking high fuel pressure has folks setting their regulators WAY too low. The only q-jets that gave issues with high pressure were the early designs with the short hinge pin and huge float. They can still be made to work for HP use but a later model is much more desirable.

Anyhow, what I've found is that a .135" seat is fine to at least 550hp and cars running well into the 10's IF you have adequate uninterrupted fuel delivery and at least 6lbs fuel pressure.

Of course that is just a blanket statement based on quite a bit of drag racing with good traction on half a dozen vehicles I've owned or sponsored out of the shop.

Even for those we seldom use a .135" seat and go to .145" instead, and run around 7.5psi. This simply insures that fuel delivery is NOT an issue and if/when we have tuning issues we look someplace else.

There are also several different schools of thought on that deal. I have several customer who run really quick and prefer smaller N/S assemblies and really high pressure, like using a .125" seat and 12-13psi with HUGE fuel lines and high flow electric pumps with a full bypass system.

Others doing the same thing will go .145 or even .149" and drop the pressure back some and claim perfect results.

For myself I've settled on simply installing a fuel delivery system capable of supporting at least 700hp even though my engine is a tad under 600hp. This simply takes fuel delivery out of the equation and we have never once in nearly 2 decades now had the first hint of a problem at the track with good traction.......Cliff

[Formulajones]

Originally Posted by the70OOJudge

It just started this year... it was good last year... same needle and seat from resto

Sure sounds like a delivery issue. I'd rig a temporary cheap fuel pressure gauge taped to the windshield and go for a drive to confirm you're on the right track. If so, from there you'll have to start looking at the entire system. Check the rubber line connections at all the junctions for kinks, (tank to frame, frame to pump etc..) and even look inside the rubber lines to make sure they aren't deteriorated or collapsed. I've had the rubber lines that looked perfect on the outside, but deteriorated and looked like bubble gum inside, restricting fuel flow. If in doubt, just replace it.
Fuel sock is another area. More difficult to inspect as it requires pulling the tank, so I'd save that one for last after you've exhausted all other possibilities. Could be simple and just the pump getting weak. Not much to the fuel systems on these cars so should be pretty easy to narrow down.

[the70OOJudge]

Originally Posted by steve25

If the motor will rev up passed 4500 out of gear then it's 90 % certain you have a Carb / fuel delivery issue.
Does the Carbs secondary diaphragm work?

I have not tried that yet... Good idea... Just did it under load.. Thanks

[the70OOJudge]

Originally Posted by Formulajones

Sure sounds like a delivery issue. I'd rig a temporary cheap fuel pressure gauge taped to the windshield and go for a drive to confirm you're on the right track. If so, from there you'll have to start looking at the entire system. Check the rubber line connections at all the junctions for kinks, (tank to frame, frame to pump etc..) and even look inside the rubber lines to make sure they aren't deteriorated or collapsed. I've had the rubber lines that looked perfect on the outside, but deteriorated and looked like bubble gum inside, restricting fuel flow. If in doubt, just replace it.
Fuel sock is another area. More difficult to inspect as it requires pulling the tank, so I'd save that one for last after you've exhausted all other possibilities. Could be simple and just the pump getting weak. Not much to the fuel systems on these cars so should be pretty easy to narrow down.

Never thought of the rubber lines as they were changed back in 1994 or so .. keep forgetting I started the resto way back then... Maybe the ole goat and I should do another resto... just to tidy her up.. Thanks

[the70OOJudge]

Awesome!!! Thanks Cliff... a very good read!!! Lots of good info that should be in a book....

Pete

Originally Posted by Cliff R

Here's my lengthy response to a similar question from a few days ago on my Website. Long reading but worth it if you have the time, and should clear up a few things when it comes to this topic:

Stock fuel pumps and fuel systems were NOT designed for 500hp, or anywhere close to that.

The truth is that most stock systems are hard pressed to keep up with much past about 350hp and we start to see all sorts of issues depending on the vehicle, tank location, routing of the factory lines, etc when folks install powerful engines and start taxing the fuel system harder. Heat can be a player here as well as lines often run too close to exhaust pipes and pick up too much heat on the suction side of the mechanical pump.

I went thru this with my own vehicle over 20 years ago and quickly learned that a stock fuel system on a 1973 Ventura is good for about 350hp with no issues anyplace.

When I installed my first 428 engine making about 400hp I didn't have any issues at all until I took steps to improve traction (DOT tires or slicks) and installed 3.42 gears and a good aftermarket converter to get the car to leave harder. The car ran fine in all scenarios until I found good traction and left hard, then it would start to loose power right up near the shift point (5500rpms). I could actually "feel" the engines power falling off around 5000rpms but it never ran completely out of fuel, most likely just sucking the fuel bowl pretty low.

I tried an HP Carter mechanical pump, pusher electric pump, and they really didn't correct the issues, the car still felt like it was loosing power past 5000rpms but only at the track or on the street when it hooked up really hard.

Next move was to install a more powerful 455 engine which INSTANTLY resulted in fuel delivery issues much more pronounced than with the 428 engine. The engine would pull like a freight train in low gear to about 4500-4800rpm's then nose over, quickly recover and pull right on up to the shift point.

It ONLY did this on hard runs with good traction. I could do "John Force" burnouts with zero issues, or blast thru the gears without any problems, etc. Any attempts to heat up the tires and launch hard and it would nose right over.

At this point I was perplexed by the problem and had tried several different things to correct it and each time I thought I had it beat then did a hard run with traction and the problems came right back.

The last attempt I did was to remove the gas tank and install a larger line and relocate the pick-up more to the rear of the tank as it was right in the front. I put a Holley Blue pump just outside the tank, and 3/8" steel lines to a regulator in front of the carb dead headed. Low and behold the problems still existed and I was completely stumped at this point. I even tried pushing to the Carter HP mechanical pump which wasn't quite as good as just re-routing around it.

The car by now was being drag raced couple of times a week weather permitting and running solid mid 12's with best ET of 12.43 at 109MPH. I settled on just short shifting the engine at 5000rpms for all runs right before where it would suck the fuel bowl low and start loosing power. At the suggestion of several well meaning folks I even built and installed a Holley 4781-2 850 DP carb and it didn't do much better, power still fell off at high rpm's. I would have thought that the much larger fuel bowls and 2 N/S assemblies would have certainly helped, but really no improvement as the car still ran mid 12's at 109mph.

So I just dealt with this problem for several years and enjoyed the car on the street and track, and logged over 1000 track runs with it without any noticeable problems. Over one Winter I decided to upgrade the fuel system one last time and pulled the tank and welded on a CE rear sump, upgraded to a Comp 140GPH pump, and 8AN lines/fittings everyplace.

First track outings the next Spring resulted in 12.0's at 112mph!!!!!!! I was simply amazed with the improvements and the engine pulled so hard past 5500rpms on the first two runs that I didn't get it shifted quick enough and actually ran a little slower than the runs to follow shifting at 5500rpm's. I ended up with a best run for the car that day of 12.02 at just under 113mph!

I would also mention here that I carried the big Holley 850 to the track that day and it also ran 12.0's at 112mph, showing that it was also not staying full on hard runs with the previous fuel delivery system.

Lessons learned in fuel delivery with these cars for sure. I went on to install a bypass system back to the tank to take some load off of the electric pump as I "fried" the brushes in the first one in about 2 months running it "dead head".

All of this happened in 1999-2000 and to date the current system has been FLAWLESs clear down to 7.18 @ 96mph in the 1/8th mile and nearly into the 10's in the 1/4 mile with a newer and more powerful 455 engine.

By this point in the long response folks have probably figured out that the pick-up location in the factory tank was the culprit and I was uncovering it on really hard runs. Installing a rear sump and moving the 140GPH pump behind the tank, and larger 8an lines everyplace also works for us on hard launches as fuel rushes back to the pump not being sucked away from it.

With this topic you will see a wide variety of threads on different websites where some folks run deep into the 10's with "stock" fuel systems where others can't get out of the 14's trying to do the same thing.

All I can say about all of that is that we have learned here to make sure the fuel system is more than adequate for the power level and vehicle performance and since those lessons nearly 20 years ago have had zero issues in that area.

One thing that I'll point out here is that folks are quick to toss out their Q-jet and go to some sort of aftermarket "high performance" carburetor thinking the Q-jet is simply not capable of keeping up with these powerful engines.

Folks quickly blame the small fuel bowl but in reality it simply let's you know that fuel delivery is inadequate for the power level much sooner than a carb with more fuel capacity.

I even see folks "chopping" up the insides of the q-jets fuel bowl, splash guard, etc in order to increase fuel bowl capacity when the real cure is to increase fuel delivery so it simply stays full on hard runs.

Of course you have to keep in mind that you only have ONE needle/seat assembly, so in addition to fuel delivery being adequate the size of the N/S plays a big role here as well.

What I've found over the years is that the myth of the q-jet not wanting or liking high fuel pressure has folks setting their regulators WAY too low. The only q-jets that gave issues with high pressure were the early designs with the short hinge pin and huge float. They can still be made to work for HP use but a later model is much more desirable.

Anyhow, what I've found is that a .135" seat is fine to at least 550hp and cars running well into the 10's IF you have adequate uninterrupted fuel delivery and at least 6lbs fuel pressure.

Of course that is just a blanket statement based on quite a bit of drag racing with good traction on half a dozen vehicles I've owned or sponsored out of the shop.

Even for those we seldom use a .135" seat and go to .145" instead, and run around 7.5psi. This simply insures that fuel delivery is NOT an issue and if/when we have tuning issues we look someplace else.

There are also several different schools of thought on that deal. I have several customer who run really quick and prefer smaller N/S assemblies and really high pressure, like using a .125" seat and 12-13psi with HUGE fuel lines and high flow electric pumps with a full bypass system.

Others doing the same thing will go .145 or even .149" and drop the pressure back some and claim perfect results.

For myself I've settled on simply installing a fuel delivery system capable of supporting at least 700hp even though my engine is a tad under 600hp. This simply takes fuel delivery out of the equation and we have never once in nearly 2 decades now had the first hint of a problem at the track with good traction.......Cliff

[ta man]

When I put my current car together a few years back one of the best things I did was install an in dash fuel pressure gauge. I've seen the results of a pinched fuel line, pump not working 100% to low fuel level in the tank as the pressure would drop.
I'm still trying to get away with a stock tank with no sump..no issues yet with a Robb Mc half inch pickup and minimum half a tank of fuel. Steady
6.5 lbs at the end of the track at 125/126mph. I do run a Mallory 140 with heavy gauge wires with a relay and all 8AN lines.

Similar to Cliff's experience I found a couple mph and tenths just upgrading from a fuel system that consisted of factory 3/8 lines and a Holley Blue Pump with no other changes.