why did my car slow down?

Kegracing · 05-21-2014, 06:44 PM

I raced the Super Chevy show at Texas motorplex last weekend. Went a couple of rounds on Saturday, and then made it to the finals on Sunday. Lost about .12 in final.
67 Firebird convertible, zz4 IHRA crate motor stocker legal motor. 3400 lbs. Set up soft, shifting about 6800, big bias tires, leaving at 2500 footbreak. 5-30 full syn oil. Turbo350, deep pan, syn fluid, no cooler. Was about 85 degrees and sunny out.
5 round race, and car had been in the 11.58-11.60 all weekend. They were hot lapping us late Sunday. Had been running about every hour, 4th round was a 40 minute run to run per the time slips, and 5th round was at 20 minutes, per time slips.
Car lost .05 in 60' then about .02 every break rest of way down track... 60' had been within one # all weekend. Did not feel it spin. Had .023 light in finals... playback tach of run shows that converter flashed same (5200) as earler runs, shifts were on the mark and did not flash between. Lost about 3/4 mph at 8th mile mark and about same at finish I am guessing, as I tapped brakes since I was behind.
I have ran valves, and did not find any issues. Changed oil and cut filter, all looks good. Trans fluid is clean. Car does not have any miss or any noise. Everything ran fine and felt fine on the run, just slow. Everything sounds fine now. Good oil pressure, etc.
Water temperature was back within 5 degrees of other runs when I staged, and pump and fan were on and working. Staged at 155.
Was motor and trans just hot?
I cant find anything wrong with it... ?

Sorry so long, but wanted to give all data.
thanks,
Ken

Stock 412

Terry Cain · 05-21-2014, 06:57 PM

Weather/Wind ?

Kegracing · 05-21-2014, 07:43 PM

wind and weather was same...

Ken

Myron Piatek · 05-21-2014, 07:50 PM

Losing .05 in 60' is a lot! Watch the playback again. My Autometer playback has been a huge help even without using it's driveshaft or download features.
You have a PM.

mcashman · 05-22-2014, 08:15 PM

Do you have a trans temp gauge? My car would really slow down with to much trans temp.

Kegracing · 05-22-2014, 10:49 PM

I do not currently, but thinking about a gauge and cooler.

Adger Smith · 05-23-2014, 07:12 AM

I had a customer that had a similar issue in late rounds and it turned out to be the sprag in the converter liked a certain temp to be consistent. he found it by changing his warm up procedure.

Dave Ribeiro · 05-23-2014, 08:13 AM

Ken,

A deeper tranny pan will also help , do you use a fan or sprayer to cool motor & trans between rounds ??? Good Luck..

Dwight Southerland · 05-23-2014, 08:24 AM

Put a stick in it.

Kegracing · 05-23-2014, 04:15 PM

Dwight, I want to, along with a Pontiac 400... Just time and money:-)
Dave, have deep pan, adding a temp gauge.
Thanks everyone. I am planning to run it tomorrow and see what happens. Will let you all know.
Unless I got the sprag in the ATI, I can't find anything wrong but heat.

Ken
Stock 412
67 Firebird

05-21-2014, 06:44 PM	#1
Kegracing Member Join Date: Jun 2002 Location: Red Oak, TX Posts: 441 Likes: 0 Liked 0 Times in 0 Posts	why did my car slow down? I raced the Super Chevy show at Texas motorplex last weekend. Went a couple of rounds on Saturday, and then made it to the finals on Sunday. Lost about .12 in final. 67 Firebird convertible, zz4 IHRA crate motor stocker legal motor. 3400 lbs. Set up soft, shifting about 6800, big bias tires, leaving at 2500 footbreak. 5-30 full syn oil. Turbo350, deep pan, syn fluid, no cooler. Was about 85 degrees and sunny out. 5 round race, and car had been in the 11.58-11.60 all weekend. They were hot lapping us late Sunday. Had been running about every hour, 4th round was a 40 minute run to run per the time slips, and 5th round was at 20 minutes, per time slips. Car lost .05 in 60' then about .02 every break rest of way down track... 60' had been within one # all weekend. Did not feel it spin. Had .023 light in finals... playback tach of run shows that converter flashed same (5200) as earler runs, shifts were on the mark and did not flash between. Lost about 3/4 mph at 8th mile mark and about same at finish I am guessing, as I tapped brakes since I was behind. I have ran valves, and did not find any issues. Changed oil and cut filter, all looks good. Trans fluid is clean. Car does not have any miss or any noise. Everything ran fine and felt fine on the run, just slow. Everything sounds fine now. Good oil pressure, etc. Water temperature was back within 5 degrees of other runs when I staged, and pump and fan were on and working. Staged at 155. Was motor and trans just hot? I cant find anything wrong with it... ? Sorry so long, but wanted to give all data. thanks, Ken Stock 412

05-21-2014, 06:57 PM	#2
Terry Cain Senior Member Join Date: Feb 2008 Location: Georgetown, Indiana (close to Louisville, KY) Posts: 776 Likes: 530 Liked 230 Times in 106 Posts	Re: why did my car slow down? Weather/Wind ? __________________ Terry Cain ???? STK tcain19689585@gmail.com

05-21-2014, 07:43 PM	#3
Kegracing Member Join Date: Jun 2002 Location: Red Oak, TX Posts: 441 Likes: 0 Liked 0 Times in 0 Posts	Re: why did my car slow down? wind and weather was same... Ken

05-21-2014, 07:50 PM	#4
Myron Piatek VIP Member Join Date: Nov 2001 Location: Florida Posts: 1,542 Likes: 34 Liked 138 Times in 51 Posts	Re: why did my car slow down? Losing .05 in 60' is a lot! Watch the playback again. My Autometer playback has been a huge help even without using it's driveshaft or download features. You have a PM. __________________ LOCOMOTION Racing

05-22-2014, 08:15 PM	#5
mcashman Junior Member Join Date: Oct 2007 Location: Westminster MD Posts: 82 Likes: 16 Liked 6 Times in 3 Posts	Re: why did my car slow down? Do you have a trans temp gauge? My car would really slow down with to much trans temp.

05-22-2014, 10:49 PM	#6
Kegracing Member Join Date: Jun 2002 Location: Red Oak, TX Posts: 441 Likes: 0 Liked 0 Times in 0 Posts	Re: why did my car slow down? I do not currently, but thinking about a gauge and cooler.

05-23-2014, 07:12 AM	#7
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: why did my car slow down? I had a customer that had a similar issue in late rounds and it turned out to be the sprag in the converter liked a certain temp to be consistent. he found it by changing his warm up procedure. __________________ Adger Smith (Former SS)

05-23-2014, 08:13 AM	#8
Dave Ribeiro VIP Member Join Date: Sep 2002 Location: Williamsburg, Va.---USA Posts: 1,827 Likes: 1,612 Liked 56 Times in 27 Posts	Re: why did my car slow down? Ken, A deeper tranny pan will also help , do you use a fan or sprayer to cool motor & trans between rounds ??? Good Luck.. __________________ Dave Ribeiro 1033 STK

05-23-2014, 08:24 AM	#9
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 2,000 Likes: 64 Liked 777 Times in 193 Posts	Re: why did my car slow down? Put a stick in it.

05-23-2014, 04:15 PM	#10
Kegracing Member Join Date: Jun 2002 Location: Red Oak, TX Posts: 441 Likes: 0 Liked 0 Times in 0 Posts	Re: why did my car slow down? Dwight, I want to, along with a Pontiac 400... Just time and money:-) Dave, have deep pan, adding a temp gauge. Thanks everyone. I am planning to run it tomorrow and see what happens. Will let you all know. Unless I got the sprag in the ATI, I can't find anything wrong but heat. Ken Stock 412 67 Firebird