Dart swinger slowing down???

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Jarod340

Jarod340

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Petaluma, ca
Hello, I'm trying to figure out what's wrong with my dart swinger it has a mild 408 with 727 manual valvebody 4,000 stall 8.75 391. The car ran its best of 11.97 @ 113.95. I ran this pass 3 weeks ago and came back the following and ran 11.97 again, then 2nd pass 12.1 then 3rd 12.50 @ 107 Since then I knew something is jacked up. I checked spark, compression test and timing, all are good. No visible damage to valve train, car starts Every time. I just went back 1 day ago and first pass it ran 12.45 @ 107 Then 2nd pass 12.80! Wtf The car feels like it just not accelerating, loseing hp or something slipping? Please help me, thanks everyone!
 
Are you sure your rocker arms haven't come out of adjustment? Do you have a collection of cinder block in the trunk?
 
What has the 60' and 1/8 mile times been. If your slowing down on the big end 3rd gear could be slipping. Slowing everywhere could be converter. I would drop the trans pan and see if you have debris. Band adjustment while you are in there.
 
mderoy340 said:
What has the 60' and 1/8 mile times been. If your slowing down on the big end 3rd gear could be slipping. Slowing everywhere could be converter. I would drop the trans pan and see if you have debris. Band adjustment while you are in there.
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60 ft have best been 1.68. On my best pass slowest 1.92
 
Willyrd said:
Are you sure your rocker arms haven't come out of adjustment? Do you have a collection of cinder block in the trunk?
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I checked them they appear to be fine visually but I have not taken them all off to inspect pushrods or lifters
 
mderoy340 said:
What has the 60' and 1/8 mile times been. If your slowing down on the big end 3rd gear could be slipping. Slowing everywhere could be converter. I would drop the trans pan and see if you have debris. Band adjustment while you are in there.
Click to expand...
And my mph are slower at every distance. The whole time after I launch it feels slow and not pulling or accelerating. Feels like engine is working but car not moving
 
No pop,stumble or hesitation? No symptoms at all? Whatever it is it's going away fast and shouldn't be to hard to find. Slowing throughout the run I will go with the torque converter.
 
hangn0ut said:
No pop,stumble or hesitation? No symptoms at all? Whatever it is it's going away fast and shouldn't be to hard to find. Slowing throughout the run I will go with the torque converter.
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Yep. With no missing, banging, popping or anything else it sounds like the converter. When the car starts acting like its eating all the power and doing nothing it's usually the converter.
 
hangn0ut said:
No pop,stumble or hesitation? No symptoms at all? Whatever it is it's going away fast and shouldn't be to hard to find. Slowing throughout the run I will go with the torque converter.
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No pop or stumble at all or backfire
 
Sounds like could be a bad battery. Check it closely, along with the alternator.
Not getting good juice kills ET and MPH
Been there done that.
 
B3422w5 said:
Sounds like could be a bad battery. Check it closely, along with the alternator.
Not getting good juice kills ET and MPH
Been there done that.
Click to expand...


That's true also. You can have low battery voltage and it affects ignition out put. Although they all say their **** boxes will run below 11 volts it's pretty easy to see that once you get down around 125 volts you start getting issues. Under 12 volts and it's a problem.

Sometimes they will lay down and act like valve springs.
 
Good thinking on the low voltage. Sometimes its the oddball things you usually dont think about.
 
Pull the transmission dip stick and smell it. If it smells burnt (i.e. stinks big time) then you burned up the clutches and its time to rebuild the trans.

I had this happen the last race before the division finals a few years back (probably due to me launching the car in second gear all season...long story...). I had a friend rebuild it in a week, just in time for the race....good times.
 
Jarod340 said:
Hello, I'm trying to figure out what's wrong with my dart swinger it has a mild 408 with 727 manual valvebody 4,000 stall 8.75 391. The car ran its best of 11.97 @ 113.95. I ran this pass 3 weeks ago and came back the following and ran 11.97 again, then 2nd pass 12.1 then 3rd 12.50 @ 107 Since then I knew something is jacked up. I checked spark, compression test and timing, all are good. No visible damage to valve train, car starts Every time. I just went back 1 day ago and first pass it ran 12.45 @ 107 Then 2nd pass 12.80! Wtf The car feels like it just not accelerating, loseing hp or something slipping? Please help me, thanks everyone!
Click to expand...
Could be Valve springs, if engine runs good but less power.
 
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