Yellow Bullet Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
1,319 Posts
Discussion Starter #1
Just looking for opinions on what might be causing a slight stumble on power in first gear and suggestions on what to do about it.

The car weighs 2650 and the best run Sunday was 8.09 at 166 in NA trim. Five speed Liberty, 500inch "small" block AMC. Sheet metal intake with two 1050 Doms.

The issue is that the engine stops accelerating for about 1/4 second around .65 seconds into the run. I think it may be related to the car coming down from the wheelie although it doesn't come down hard at all.

Here's a couple data plots. You can see the flat spot in the middle of first gear. At first I thought it was clutch related but you can see in the one graph I had it set tight and it still went flat. I don't see anything weird in the EGTs.

Any suggestions?



 

·
Registered
Joined
·
1,248 Posts
Check fuel pressure(7.5), float levels( Even 1 low one will do it), and make sure your regulator, if not secured, is not banging on something to disrupt it.
 

·
Registered
Joined
·
65 Posts
I agree check the float levels. We were having the same issue this weekend on our 2x4 set up. We were uncovering the jets at the peak of the launch. Raised the floats and no more issue.
 

·
Registered
Joined
·
1,319 Posts
Discussion Starter #4
Thanks.
The car has an Aeromotive A1000 pump with the by-pass regulator in the front. The current pressure is set at 6.75psi. I will bump that up and double check the float settings.

Here's a picture of the engine. You can see how the carbs are mounted and the way the fuel lines are run to the carbs from the regulator.
 

·
Registered
Joined
·
3,673 Posts
I wonder if it could be valve spring surge, it only happens on the first ramp up and then it never really has a chance to come down in rpm enough to show itself again.
 

·
Registered
Joined
·
1,319 Posts
Discussion Starter #6
Tony, can you explain?
I do notice that it happens at 7000 RPM each time. Not sure if that is just a coincidence or a symptom.
Doctor, is there a cure?
Thanks!
 

·
Registered
Joined
·
1,319 Posts
Discussion Starter #9
Interesting for sure. I remember reading that thread but never made the connection to my current situation. I will double check my numbers later. Easy enough to change the bind clearance and see what happens.
Thanks.
 

·
Registered
Joined
·
794 Posts
maybe its fuel slosh? I had a similar problem, my carb is sideways just like a dual set up. I just ran a hose from vent tube to vent tube on each carb, be sure to cut a slit in the top to let it vent. its worth a shot.
 

·
Registered
Joined
·
2 Posts
Did you cure the problem, I have similar situation at start, I put the vent tube and cure the problem , but if I launch at higher rpm and stay little more time wheeling in the air it boggs again, I dont know if I need to lower more the fuel pressure or the float, right now is 7 psi and level of the float is 25% over the plugs sight, any recommendations?
 
1 - 16 of 16 Posts
Top