For some reason I have lost a tenth and a half. However the car runs down the track, no miss, just slow. Have you ever seen this with ignition, or with oil?

What are the incrementals compared to how it ran .... “ before” where is it slower?

Ot could be tires or compression. Mine slowed down a tenth after 8 years with over 1,000 quarter mile hits. No miss , seemed to run fine but slower. Low on compression from worn out rings. Re ringed came right back. Do a compression check.

As already ask, where did it slow down the most?
Is it and ET and MPH or just ET?

According to the Racepack, everything is fine, and incrementals are comparable through the run. The horsepower from the dyno does not translate to track. More ET, than mph.

So, what are you comparing the loss to? Dyno numbers or actual et loss? If the car is losing .15 seconds, it should show up in your 60, 330, 660 to give you an idea of traction, engine power loss, top end charge. If you are just looking at dyno numbers and predicted et compared to actual et, sometimes dyno numbers aren't always accurate, or the car needs some work.

It is a historical comparison. The engine is the same, actually everything is the same. I freshened the motor, consisted dyno figures, but a loss of
performance through all of the incrementals. The car needs work, I am trying find where. I was hoping that some other racers may have run into this, and could make suggestions. For example, ignition, oils, gasoline. For example, the impulse in the MSD may need replacement, (done that), odd things on that nature.

Years ago I had a 340 that I had beat like a rented mule. It ran its best ET(11.98) then a few weeks later it slowed about .1-.2. I assumed it was tired and it needed to be refreshed, then it broke the crankshaft. Everything else inside the motor looked fantastic, even the bearings. The crank was just broken behind the last rod journal. Next time my car slows that much for no apparent reason it will be inspected more.

So you don't think it tyres?....how hard do you beat on them, how old are they, my mate runs a 540 Cuda over here and his 60's/ET went away some, down to 1.34's, tyres looked all ok, plenty of meat on them, put some new tyres on and his 60's came back to 1.23's and it picked back up into the 8.70's.

Over what period of time did it loose this..
a day or weeks or what

Converter

I rolled a sprag in my converter and lost a second a few years ago. It will show up in the 60 ft.

If the MPH is down, something is eating the power. Like mentioned above, sounds like a converter.

This has been going on for about 2-3 years. I had a great performance level, but lost my way and I have not been able to isolate it. The dyno hp number are consistent, if not a little more, but do not reflect on the track. According to the graphing in the Racepack the torque converter is functioning correctly, as with fuel pressure, voltage, drive shaft speed, O2 would suggest a little fat. I even had the front end aligned.

I feel like I have done something not knowing that I have done something to upset the balance and performance. The combination is this, 1971 Dodge Demon340 D/SA. Weight 3215 with driver, Sunoco 110, Amsoil 5-20 race,MSD7Al Gold box, 1971
Carter Thermoquad, ATI 5600 converter, 4.86 gear, Hoosier 9" radial. Performance 10:79 @ 121.00 mph, needs to be 10:55.

Fat motors are lazy, can you post a picture of #7 spark plug? Please do that

Send me your racepak data history when it ran good and current. I'll take a look at it, hopefully I can find something
jkcomp5957@yahoo.com

Just a few ideas I thought I'd throw out:

* I recently found the coil wire/rotor contact inside my distributor cap badly chipped and possibly causing arcing/spark scatter inside the cap. Rotor top had burn marks. But I haven't run it yet to confirm.
* Reluctor gap change?
* Old plug wires?
* Choke pull-off/hose leaking?
* From what I've read about the sensitive Thermoquads, expect the unexpected. (Still learning.) Do you have a good, spare carb to try?
* Any unusual wear indicators on oil pan magnet or in trans pan?

I guess if it's been gradual over a few years, it's not any weather anomalies.

Between breaking down your timeslip Increments and RacePak info that’s a lot of good info. Now double check your chassis for changes. Shocks, pinion angle changes, dragging brakes, etc.

Using the same dyno? Same engine/head person? Same trans guy? MPH down? 60s? Incrementals? All of a sudden or over a period of time? Have you look at things like the rear, brakes, fuel volume, tried different fuels? Has the carb been looked at by someone? I know a guy had a fast E car till he started "tuning" the TQ and the car slowed significantly.

Agree with all the suggestions. Plug wires, ignition boxes, master switches, grounds, are all things that can cause issues without being obviously broken.