Bad Launch with 572 ! up -down up -down !

Hi Guys .. yesterday tried first time my new 572 .. but some problem with or without nitrous ... at Launch engine go up down... up down ... RPM ! look like bad converter stall ... any idea ?

https://youtu.be/Ldq5viB9gFQ

If carbureted check float levels, or rear jets getting uncovered. If EFI and stock tank, possibly fuel pickup in tank getting uncovered?

Sounds like a fuel delivery issue to me.

Sounds like fuel, but I'd like to see a side shot of the run to check for any wheel hop.

Sounded like fuel issue to me too.

SEEMS MORE LIKE CHASSIS IS LOADING AND UNLOADING?????

yep is 1050 Dominator ! when i have checked bowl level and was ok but after pass the rear bowl was low .. but after 5 minute when come back at my box was ok ... very strange ....Fuel Pump is Aeromotive A2000 all 10AN Fuel Line ... im also think the problem is possible on furl line issue

im working for put a video from Side

hi ! im Race with Old 496 Combo from 10 years ... never problem .. 9.2@150 ... with new 572 .. the ET drop to 9.6 9.8 with this problem

https://youtu.be/dX4EcS8Jewk

Are you hitting the NOS on that run with that surging?
How about a piece of fuel line on the front fuel bowl vent to route any splashed or sloshed fuel away from the carb opening?
Do you have jet extensions on the rear jets?

You have a chassis issue. It's not out of fuel. It's loading and unloading the rear tires.

i had this suspension setting from many years .. Caltracs, Dana 60,monoleaf ..i have onky swap the engibe from 496 to 572 .. same transmission same axle ... same tires only change Engine .. the only difference is the weight .. 572 weight is 80 lb more than 440 block .. i think ..you think this can cause unloading rear tires?

Hi ! i dont understand how put a piece of fuel line .. from bowl vent to ?? i don't have Fuel Jet extension..

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So everything stayed the same from your 496 to the 572? whats your idle fuel pressure set to? I hear engine surge... timing or fuel. rear tire is planted pretty good in your video. Almost sounds like the converter is too tight??

Put jet extensions in the rear jets

You gained 76 cubic inches and are probably making more power. You need to tune the chassis.

Get some video of the tires. Bet you it's beating the hell out of the tire.

Take a piece of soft fuel line that will fit snugly over the vent tube sticking up in the front of your carb squirters and route it back towards the rear of the carbs so if any fuel sloshes up into the fuel bowl vent it won't spray or spew into the carb.
Your probably okay with those stock white vent tubes on the metering blocks though
You need jet extensions in the rear
Are you spraying the NOS?

As said get some jet extensions

Put a piece of rubber hose in a high arch between front and rear bowl vents. Cut a notch out at the top of the arch. You can zip tie it to the air cleaner stud to secure it. And jet extensions on the secondary jets.

And I still feel there is something else going on in the suspension. The increase in torque from the new motor is causing rear suspension issues.

Looks to me like the shocks could be topping out, pulling the tires off the track.

Yes Everything the same except engine from 496 to 572 with new camshaft and torque converter from 5500 on 496 to 5000 on 572 , the rest is the same , also change the headers with 496 was 2" , now is 2 1/8 same brand TTI ceramic

ohh i see this in some car at mopar nats OHIO , need connect the two hose of bowl vent and make a hole ??

Yep 400 shot of nitrous !

Chassis have Dana 60 , caltracs , monoleaf , connecting frame , double adj qa1 shock , never problem in many years , hook very good 1.40 60 ft with 3900 lb

At this point the cause of surging could be :

1) fuel issue but yesterday i have checked filters pump all hose and carb , no restriction

2) fuel jet extension ?

3) fuel pressure is at 7 psi , is better at 9 psi ?

4) carburetor too small ? from calculator 572x7500 / 3456 would be 1250cfm , i have 1050 .. can cause this surging ???

4) rear tires unloading ? shock ? mmmmmm very strange

5) tight converter ? is 5000 RPM

I have never heard that a to small carb. will make the motor surge
They usually will run better with a bigger carb
Surging, running out of fuel, and hopping are two completely different issues Figuring out what the car is doing is the key to fixing it
I would try and have someone video a run from the side at a 90 degree angle on the starting line as close as they can get to see what the chassis is doing the first 50 to 100 Ft.

As mentioned, put two jet extensions for the rear jets.

https://www.summitracing.com/int/search/...et%20Extensions

Guys ... i zoommed the video from inside and found the problem...at launch the fuel pressure gauge drop from 8 to 2-3 Psi ..the safety switch of fuel line of nitrous when go down switch off the nitrous ... this up and down ... cyclyc ... , i think this is caused from bad pump A2000 ? low tank vwnt ? i have factory tank with big 5/8" tank sender ... i think is time of Fuel Cell ...

OK but you still need the Jet extensions for rear bowl
Im sure 1250 would work better on your engine.

yes Sure !! how many HP more with 1250 ???

my Pump A2000 Flow is 350 GPH , this is good for 900 HP +400 of nitrous ?? i see when fogger is actived the pressure go down from 8 to 3 PSI , i dont know is is only caused from tank or also from opening fuel solenoids

8-9 psi fuel pressure is higher than necessary, but dropping to 2-3 psi will cause a problem. You need constant pressure going down the track. The rubber tube will make sure that you aren't pulling fuel out of the vents and dumping it into the venturi's. The jet extensions will make sure that the secondary jets stay covered with fuel. Putting a bigger carb on will probably help make more power, but will not change anything with the surging.

I would be surprised if it is that. you could shut your fuel pump off at the line and still have enough fuel in bowl to make it threw first gear. If you have qa1 shocks in back I doubt they have enough valving to control caltrac.

yes drop at 2-3 psi ..understand the problem of bowl ...but also the stock tank can cause this ??

over-all when fuel pressure drop down ... the fuel safety switch switch off the nitrous !!!! intermittently !!!this is the surging

this problem of the vents , will solve with the tube .. but can't cause a drop pressure ... i think

You need jet extensions and need to solve that pressure drop issue.
Too small a carb won't cause your problem. Neither will too tight of a converter.

The car is still surging down the track...by then the suspension has settled. I still say this is a fuel delivery issue.
You do need to do some suspension tuning, but that isn't the cause of your immediate problem. I fought the bouncing 60' w/ Cal-Tracs years ago too.

The A2000 should be plenty of pump as long as everything else is up to par. You could have a bad piece of fuel line...the AN braided line can deteriorate and come apart inside causing restrictions.

hello New hose with no restriction , ok i can put jet extension , the last year no problem of sunspension with same setting , and factory tank can cause this ??? all fuel line is 10 AN

On your pickup on the tank, how is it made? Sump at rear or internal #10 ?
Lots of ways for Murphy to mess with us drag racers
Your on the correct tract, keep fighting the Gremlins until there all fixed

I think he said he has a low fuel pressure safety shutoff switch on his Nitrous . This could be his problem with surging on/off. Maybe it is set too high and causing the problem. I think Monte said those cause more problems than they are worth.
Mike

Factory tank with 10AN sending removed .. fuel cell with double 8 AN line installed

sump was not at rear but at half tank .. not good ..

yep could be this.. i think now the pressure will be more consistently... switch is adjustable ? i think

Yep, Monte hated those things. I've seen guys at the track have issues w/ them too. Don't run one myself.

the problem is you don't put it after the regulator. you put it before so it doesn't have that problem. unless the pump dies. have used them over 30 years never had an issue.

Guys ... problem solved .. was low fuel flow .. that caused fuel safety nitrous switch off..

So...Let's here some new results, with video and lots of sound.

Good luck

Glad you found it! Now, go run an 8.xx!

You do need extensions, but that's not causing that much surge, and neither is the chassis, carb, or converter. Check your WOT switch. To see if it's not staying engaged.
If you have a grid, download the run and look at the step switch for timing, I bet it's on and off.


I just read the part about a fuel pressure switch, and that would for sure do it. Just a thought though, if your primary pressure drops that much, I wonder what the nitrous fuel pressure is doing. 400 is a good size shot to have the pressure fluctuating more than a quarter of a pound.