Hesitation after landing of wheel stand

Z28-69 · 05-17-2009, 12:15 PM

Hi guys could use some help with hesitation after a wheel stand. The car is carrying the wheels out about 50-55 feet and the hesitation is accuring when the cars front suspension is below static, not in the air. We have tube running from vent tube to vent tube, fuel pressure is at 7, flout levels are good. We tried raising them a touch and lowering them. Oh and yes we have bowl extentions. Pretty sure its a fuel problem, but maybe you guys can give me suggestions. Thanks Eric

Dave Ficacci · 05-17-2009, 01:05 PM

Quote:

Originally Posted by Z28-69

Hi guys could use some help with hesitation after a wheel stand. The car is carrying the wheels out about 50-55 feet and the hesitation is accuring when the cars front suspension is below static, not in the air. We have tube running from vent tube to vent tube, fuel pressure is at 7, flout levels are good. We tried raising them a touch and lowering them. Oh and yes we have bowl extentions. Pretty sure its a fuel problem, but maybe you guys can give me suggestions. Thanks Eric

Fuel pump or ignition box. I chased this exact problem for several races and after changing carbs, jets and playing with fuel pressure, I replaced the igniton box and fuel pump and the problem went away. Neither parts have been back in the car since so I cant tell you which one fixed it.

Alan Roehrich · 05-17-2009, 01:28 PM

Also, check your battery (or batteries) and cables VERY closely. If a battery has a loose plate, the "bounce" will cause it to short out or open intermittently. The "bounce" on landing is also likely to make every connection in the car try to move, so if one is weak, it will move.

By the way, if the battery has dual connections (top and side posts) be aware that those connections should be checked carefully as problems will hide there. Check ALL of your ground connections.

Jim Cimarolli · 05-17-2009, 02:56 PM

Z-28

I'm sure you have jet extensions on the rear, but do you think the bowl extensions could be allowing them enough room to uncover? Just a thought.

Z28-69 · 05-17-2009, 03:59 PM

Quote:

Originally Posted by Jim Cimarolli

Z-28

I'm sure you have jet extensions on the rear, but do you think the bowl extensions could be allowing them enough room to uncover? Just a thought.

Sorry, I have jet extensions not bowl extentions. Miss print

Jim Cimarolli · 05-17-2009, 05:54 PM

Can you describe the hesitation? Does it bang, pop, or miss, or does the engine just loose power without any other sound? Does the symptom occur after the rebound/bounce or before?
I am thinking that if the ignition is crapping out you would experience a bang or pop when the engine comes back to life? Maybe Dave can further describe his situation to shed more light.

Z28-69 · 05-17-2009, 06:30 PM

Hi Jim,

It's not a pop or bang....It's more a flutter that is short and then motor picks back up and runs strong through out rest of run. It does it when car has landed and at the bottom of suspension travel. When the car was 60' footing low 40's it didn't do it. Now we found power and it's 60's are 36-38's. and it's doing it. It does it when it really carries the wheels out. Thanks Eric

Jim Cimarolli · 05-17-2009, 06:54 PM

Just trying to help determine if you have a momentary fuel starvation problem or an ignition malfunction.
Dave and Alan both mentioned some very strong possibilities of the cause if it is ignition related.
Can you swap carbs to at least eliminate that as one of the possible causes?
I would say that a car would not suffer from fuel starvation that early in the run unless you are uncovering the jets.

Steve Cozakos · 05-19-2009, 03:09 PM

I had a similar situation. A hesitaion when the car landed. It didn't do every run. It did it on harder launchs only. I later figured out that when the suspension bottomed out the inner fenders and the tops of the tires would make contact. I put slightly longer bumpers on the lower control arms and it has never happened again.

Steve

Adger Smith · 05-19-2009, 04:49 PM

If you don't suspect fuel then it has to be ignition. I Like the idea it could be battery plates bouncing around & shorting out. Put a Battery Volt gauge where you can read it during the landing. If it doesn't drop then start looking for grounds or connections pulling apart or anything that could be causing high resistance during the crash back to earth. I found a rotor/cap in my V-6 causing problems similar to yours. The cap fit too loose & was shaking around causing spark scatter. Look for the simple things. It will always be the last thing you look at that fixes the problem... :~)

05-17-2009, 12:15 PM	#1
Z28-69 Junior Member Join Date: Dec 2007 Location: Grand Rapids MI Posts: 66 Likes: 0 Liked 0 Times in 0 Posts	Hesitation after landing of wheel stand Hi guys could use some help with hesitation after a wheel stand. The car is carrying the wheels out about 50-55 feet and the hesitation is accuring when the cars front suspension is below static, not in the air. We have tube running from vent tube to vent tube, fuel pressure is at 7, flout levels are good. We tried raising them a touch and lowering them. Oh and yes we have bowl extentions. Pretty sure its a fuel problem, but maybe you guys can give me suggestions. Thanks Eric

05-17-2009, 01:28 PM	#3
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,104 Likes: 1,560 Liked 1,784 Times in 407 Posts	Re: Hesitation after landing of wheel stand Also, check your battery (or batteries) and cables VERY closely. If a battery has a loose plate, the "bounce" will cause it to short out or open intermittently. The "bounce" on landing is also likely to make every connection in the car try to move, so if one is weak, it will move. By the way, if the battery has dual connections (top and side posts) be aware that those connections should be checked carefully as problems will hide there. Check ALL of your ground connections. __________________ Alan Roehrich 212A G/S

05-17-2009, 02:56 PM	#4
Jim Cimarolli Senior Member Join Date: Mar 2002 Location: Sulphur Springs Texas Posts: 742 Likes: 146 Liked 166 Times in 46 Posts	Re: Hesitation after landing of wheel stand Z-28 I'm sure you have jet extensions on the rear, but do you think the bowl extensions could be allowing them enough room to uncover? Just a thought.

05-17-2009, 05:54 PM	#6
Jim Cimarolli Senior Member Join Date: Mar 2002 Location: Sulphur Springs Texas Posts: 742 Likes: 146 Liked 166 Times in 46 Posts	Re: Hesitation after landing of wheel stand Can you describe the hesitation? Does it bang, pop, or miss, or does the engine just loose power without any other sound? Does the symptom occur after the rebound/bounce or before? I am thinking that if the ignition is crapping out you would experience a bang or pop when the engine comes back to life? Maybe Dave can further describe his situation to shed more light.

05-17-2009, 06:30 PM	#7
Z28-69 Junior Member Join Date: Dec 2007 Location: Grand Rapids MI Posts: 66 Likes: 0 Liked 0 Times in 0 Posts	Re: Hesitation after landing of wheel stand Hi Jim, It's not a pop or bang....It's more a flutter that is short and then motor picks back up and runs strong through out rest of run. It does it when car has landed and at the bottom of suspension travel. When the car was 60' footing low 40's it didn't do it. Now we found power and it's 60's are 36-38's. and it's doing it. It does it when it really carries the wheels out. Thanks Eric

05-17-2009, 06:54 PM	#8
Jim Cimarolli Senior Member Join Date: Mar 2002 Location: Sulphur Springs Texas Posts: 742 Likes: 146 Liked 166 Times in 46 Posts	Re: Hesitation after landing of wheel stand Just trying to help determine if you have a momentary fuel starvation problem or an ignition malfunction. Dave and Alan both mentioned some very strong possibilities of the cause if it is ignition related. Can you swap carbs to at least eliminate that as one of the possible causes? I would say that a car would not suffer from fuel starvation that early in the run unless you are uncovering the jets.

05-19-2009, 03:09 PM	#9
Steve Cozakos Junior Member Join Date: Aug 2003 Posts: 51 Likes: 0 Liked 0 Times in 0 Posts	Re: Hesitation after landing of wheel stand I had a similar situation. A hesitaion when the car landed. It didn't do every run. It did it on harder launchs only. I later figured out that when the suspension bottomed out the inner fenders and the tops of the tires would make contact. I put slightly longer bumpers on the lower control arms and it has never happened again. Steve

05-19-2009, 04:49 PM	#10
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Hesitation after landing of wheel stand If you don't suspect fuel then it has to be ignition. I Like the idea it could be battery plates bouncing around & shorting out. Put a Battery Volt gauge where you can read it during the landing. If it doesn't drop then start looking for grounds or connections pulling apart or anything that could be causing high resistance during the crash back to earth. I found a rotor/cap in my V-6 causing problems similar to yours. The cap fit too loose & was shaking around causing spark scatter. Look for the simple things. It will always be the last thing you look at that fixes the problem... :~) __________________ Adger Smith (Former SS) Last edited by Adger Smith; 05-19-2009 at 04:51 PM. Reason: SP