Re: Inconsistency
 

With only RPM to read it's hard to telling. I would say more input is needed. I would expect a convertor problem to swing that graph wider.

Re: Inconsistency
 

Is there anything in the fuel system that you believe could be causing this? The fuel pressure seems to remain consistent throughout the run but the gauge is hard to read accurately with so much vibration. Fuel pressure definitely doesn't move more than a half of pound or so. We are getting desperate for answers.

Re: Inconsistency
 

Well, I'll go this route.
.
First I would want weather station input to see if it's changing & then how much. Then see how it follows how the car is running. Next, besides an RPM sensor I would want an output shaft sensor. With these you could see if there was a traction or transmission problem. Next I would want either a pyrometer or O2 sensor. With these you can see where your fuel metering is @ & if it fell over the edge on the bad run.

Without the sensors,

There are many things that can go wrong inside a carb. Do you have a known good piece that you can swap onto the car ?

Re: Inconsistency
 

"While I was researching this site for possible answers to my problem, I came across your post and the graph (and inconsistancy) is similar to what I am experiencing. It started after I repalced the torque converter to a 9" unit that was made for my combination. I blamed it on the new converter but they told me it is spragless so that ruled out a rolled sprag. When I told them that I did not see this problem with the 8" (loose) convert, I was tolded the looseness masked the true problem. I have been going through everything trying to find what is causing this intermittent loss of power.
Did you find what was your issue?

2500# door car
565 CI w/TH400 and Transbrake

Bob

Re: Inconsistency
 

I can't say for sure that we found our issue. However this past weekend I borrowed a converter off of a buddy to try. The converter that i swapped to, we found out after swapping was way to tight for my car. But other than the car running really slow and laboring to bring up the RPMs with the tight converter, the car ran consistent. Not as consistent as i would like but I am blaming the little inconsistency on the tight converter. I will be sending mine away to be cut open and inspected.

Another racer at the track was looking at my car and brought to my attention that I have a majority of my ground wires running to an aluminum grounding block and the grounding block straight to the frame and that could cause an issue. I will be running a ground wire directly to the battery. Something to think about.

Re: Inconsistency
 

Convertor is good test.

Re: Inconsistency
 

Do you have a trans temp gauge? Sounds to me like your trans might be getting a bit too hot in the later rounds. I use to have that issue but since I have been putting a small carpet drying fan on my trans between rounds, that has gone away. I try to leave the line at 160 to 180 trans temp. It is usually 200 to 220 when I get back to the pits. I believe this helps with reaction time consistency also. Just my humble opinion based on trying a few different things.

Re: Inconsistency
 

On your "bad runs", how much is the 60 ft off??

Re: Inconsistency
 

you may need to check rear end. I had a bearing going bad that caused similar

Re: Inconsistency
 

Exactly