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So I have been fighting a issue that is kicking my ass. No matter the weather, cool down period, fuel used, spark plug changed ect. I can pull my 69 Camaro (582, powerglide, 4 link, 4.88 gear 14x32 tire 3200 lbs.) I can unload the car, make a couple laps around the pits to warm up the car. pull into staging lanes with a coolant temp of 160 (gas car) do a decent burn out in high gear. Stage at 3500 on the brake. Launch on a 5400 stall convertor. 1.27 60 ft. 5.76 1/8 mile. cool the car with fans (one one the top of engine area and one on the convertor) for an hour. Water temp is cold enough to not show on the gauge. I know the oil temp is still warm but not hot. Make a second run with the same set up as first, now 1.36 60ft, 5.82 1/8th. the moore passes, the worse it gets. I have checked and changed plugs, Checked fuel preesure, checked all of the ignition components. changed the car to 16 volt hopeing for more spark, same issue. I have checked transmission, the rear axle, all of the brakes. all show no issues. What the hell am I missing. I have gone 4 to 5 rounds and slowed to as much as 6.12 1/8th mile. Thanks for the help
 

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So I have been fighting a issue that is kicking my ass. No matter the weather, cool down period, fuel used, spark plug changed ect. I can pull my 69 Camaro (582, powerglide, 4 link, 4.88 gear 14x32 tire 3200 lbs.) I can unload the car, make a couple laps around the pits to warm up the car. pull into staging lanes with a coolant temp of 160 (gas car) do a decent burn out in high gear. Stage at 3500 on the brake. Launch on a 5400 stall convertor. 1.27 60 ft. 5.76 1/8 mile. cool the car with fans (one one the top of engine area and one on the convertor) for an hour. Water temp is cold enough to not show on the gauge. I know the oil temp is still warm but not hot. Make a second run with the same set up as first, now 1.36 60ft, 5.82 1/8th. the moore passes, the worse it gets. I have checked and changed plugs, Checked fuel preesure, checked all of the ignition components. changed the car to 16 volt hopeing for more spark, same issue. I have checked transmission, the rear axle, all of the brakes. all show no issues. What the hell am I missing. I have gone 4 to 5 rounds and slowed to as much as 6.12 1/8th mile. Thanks for the help
Had this happen. I think your brakes are getting hot on the first run, and dragging bad after that. Just a thought. Nothing to do with the engine.
 

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You said you check out the rear axle, I assume you mean the gears? I had an issue where I was slowing every pass as the rounds went on years ago and it was the rear end and it would worsen as the gear oil gained temp. The pinion bearing was going but the gears still looked good. Way I found it was it had gotten to the point that I heard a slight whine in the shutdown that I never heard before. Rebuilt rear and new gears and the consistency came back.

Seen engines tighten up too like that but they will blow up in short order. Usually don't get many passes for it to slow up before the boom.
 

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Just curious, have you checked the rear end by jacking up the rear of the car, after your second or third pass and tried spinning it by hand?

My initial thought reading your post was the brakes but I see you checked them off the list.

Since it seems to be heat related. Something in the trans or conv ?
 

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Had a similar problem years ago, fast off the trailer would slow down as the night progressed turned out to be the valve springs, changed them and fixed the problem
 

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Do you have a temp gun to check front spindle temp of the bearings? Might be getting hot the more you run it and getting tighter. Can you push the car easily before first pass and push as easily after 3rd or 4th pass? It's either that or convertor going Kaput Fubar. Hope you find it.
 

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Discussion Starter #11
The converter is not new but was recently gone through by FTI. Not sure about the sprag. Definitely my next call though. Going to go ahead and rebuild the rear calipers anyway as they are older. Thanks so much for all of the ideas to check.
 

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If you can measure the pull to move the car with a fish scale type tool, them remove the brake pads, front, then rear, then both, you can see if brake drag is effecting your rolling resistance. Wilwood brakes will always have drag even if carefully centered. Strange can have less. JMO.
 

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Discussion Starter #13
Found the issue. pulled the drain plug on the rear axle cover to find about 6 quarts oil( should be 2.5) and the pinion bearings loose. someone built the rear witrh a crush sleeve and not a spacer :cautious:. replaced all bearings with a spacer kit and new 4.56 gear. runs within .005 now. all good.Thanks for all of the help
 

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Glad to hear you were able to find and fix the problem.
 
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