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Author
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Topic: Slipping sprag
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kid vishus
Gearhead Posts: 7251
From: middle of NC
Registered: Oct 2000
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posted 11-19-2006 07:06 PM
 
I took the car to the track yesterday. The car was terribly inconsistant. The sixty foot times were bouncing around, the half track times were inconsistant, the incremental times were all over the place, the et varied a tenth in 4 passes, and the mph varied over 2 mph. When I got home, I called a fairly respected trans/convertor guy and told him what the car was doing. He asked a couple of questions, and after I responded to them, he told me everything I said pointed to the sprag slipping. I firmly beleive he is correct. I knew it needed the convertor tweeked for this combo, but now there is no doubt it has to come out this winter.Here's what it did. First pass times were, 1.437 , 4.112, 6.395 @ 108.3 mph. Next pass less than an hour later, same weather conditions,(didnt change a thing on the car either) it went 1.426, 4.090, 6.343 @ 110. 2 mph. First round, I dailed 6.32, and it went 1.451, 4.119, 6.383 @ 109.4 mph. Needless to say, I lost. But like a moron, I bought back and stuck a 6.37 on the window. Went back up, had a good light, (.003) and it went 1.400, 4.051, 6.321 @ 106.4 mph (on the brakes hard at the mph cone.) Based the half track time, it would have gone 6.29 if I had run it out the other end. It goes without saying, it wasnt a very fun day at the track. Nevermind the fact when I got there the spark plug in the generator was broke and I had to buy a plug from a racer to stick in it. I will say this, even though it's a cold plug, an Autolite AR3933 will work in my generator. 
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Buster
Gearhead Posts: 1821
From: Hurricane alley
Registered: May 2002
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posted 11-19-2006 07:21 PM
quote:
Originally posted by kid vishus:
I took the car to the track yesterday. The car was terribly inconsistant. The sixty foot times were bouncing around, the half track times were inconsistant, the incremental times were all over the place, the et varied a tenth in 4 passes, and the mph varied over 2 mph. When I got home, I called a fairly respected trans/convertor guy and told him what the car was doing. He asked a couple of questions, and after I responded to them, he told me everything I said pointed to the sprag slipping. I firmly beleive he is correct. I knew it needed the convertor tweeked for this combo, but now there is no doubt it has to come out this winter.Here's what it did. First pass times were, 1.437 , 4.112, 6.395 @ 108.3 mph. Next pass less than an hour later, same weather conditions,(didnt change a thing on the car either) it went 1.426, 4.090, 6.343 @ 110. 2 mph. First round, I dailed 6.32, and it went 1.451, 4.119, 6.383 @ 109.4 mph. Needless to say, I lost. But like a moron, I bought back and stuck a 6.37 on the window. Went back up, had a good light, (.003) and it went 1.400, 4.051, 6.321 @ 106.4 mph (on the brakes hard at the mph cone.) Based the half track time, it would have gone 6.29 if I had run it out the other end. It goes without saying, it wasnt a very fun day at the track. Nevermind the fact when I got there the spark plug in the generator was broke and I had to buy a plug from a racer to stick in it. I will say this, even though it's a cold plug, an Autolite AR3933 will work in my generator.
I have a 5500 stall Yank converter in the 68 and when the converter sprag failed it was like someone grabbed the rear bumper right off the line and the car really struggled to make it down the track. It kept getting worst throughout the day, only able to make three passes before loading it on the trailer. This was at Bradenton which is a great hooking track. I don?t know sprags can fail in different ways, but this is what happened to me.
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kid vishus
Gearhead Posts: 7251
From: middle of NC
Registered: Oct 2000
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posted 11-19-2006 07:37 PM
Thats the way most sprags fail. But he explained it to me that mine hasnt completely failed, but it is slipping, or as he liked to call it, skipping. The sprag is supposed to hold the stator in place so it can multiply torque. Mine isnt staying in place, and is allowing the stator to move ever so briefly. I wish it would have just failed. I would have known what was wrong with it right away, instead of constantly fooling with things that weren't related at all to the problem I was experiancing.
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Buster
Gearhead Posts: 1821
From: Hurricane alley
Registered: May 2002
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posted 11-19-2006 08:49 PM
quote:
Originally posted by kid vishus:
I wish it would have just failed. I would have known what was wrong with it right away, instead of constantly fooling with things that weren't related at all to the problem I was experiancing.
Don't we all, lol.....
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cookie_monster
Journeyman Posts: 70
From: south, central, us
Registered: Nov 2005
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posted 11-19-2006 09:43 PM
Mine did the exact same thing, for most of a full season. Would make a good pass and good mph, then next pass it would fall off, fall off again the next and randomly pick up ET/mph...usually in the final or semi-final rounds with my luck!Anyway, I called my converter guy. He said the same thing, probably slipping sprag. I didn't have time to pull it & send it in, so I made the next race. First TT it ran great. 6.11/113. Ran 6.15/108 next time, then 6.09/115 next run. Broke out with a 6.06/99 (on the brakes) the very next run with a 1.29 60'. 60's were 1.31-1.37 all day and track conditions did not change one bit. I bought back & won the next round, though the ET was down to 6.13. Next pass, ran 6.13...in fact...It ran 6.13 the rest of the day & took the money & trophy, but I knew the converter was gone! Took the car home & immediately noticed while it was still on the trailer that something was not right. The black paint on the converter looked like someone had torched it...literally. The paint on the transmission was also turning colors. I pulled it, sent the converter to my converter guy...and he told me that the sprag was slipping. WOrse, the thrust bearings had given way...and let the aluminum stator get into the vanes. He tells me to pull the pan and inspect it. Good thing I had an extra transmission....I have never in my entire life seen SO much metal in a transmission! I could have sold the shavings for scrap metal and made enough to pay for a decent lunch. Yours sounds like a sprag issue as well. Depending on what you're going to be doing and if you're willing to sacrifice a few mph for consistency, it might be a good idea to look into spragless. I borrowed a spragless while mine was out. Consistency was excellent. 60' times were 1.30 and within ten thousandths (.0001) all day. But, MPH was down by 3. RPM did not drop much at the shift either. But, it did what it was supposed to...repeat ET's. Got mine back the next Monday and put it in, car is back to where it should be...maybe even a lil better. 1.33 60' times all day and it picked up some 1/8 ET...ran a 5.94 on a 5.98 dial at 116 (weather change big time!) for my personal best ET. I went back with a traditional sprag-type converter as I'm generally not hard on sprags and I just felt that those 3 mph I lost with the borrowed converter were detrimental. Lots of us all run the same ETs but my mph is higher than most of those guys...and it makes it harder to judge the stripe.
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Buster
Gearhead Posts: 1821
From: Hurricane alley
Registered: May 2002
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posted 11-20-2006 12:18 AM
quote:
Originally posted by cookie_monster:
\it might be a good idea to look into spragless. I borrowed a spragless while mine was out. Consistency was excellent. 60' times were 1.30 and within ten thousandths (.0001) all day.
That's something I would like to try... I would love to get into the 1.30 60' times. My best 60' now is in the 1.43 and it runs 10.16's in the 1/4. cookie_monster, do you know what your car run in the 1/4?
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cookie_monster
Journeyman Posts: 70
From: south, central, us
Registered: Nov 2005
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posted 11-20-2006 03:58 PM
I've never run 1/4 mile. I run mostly 1000'. Best time in the 1000' is 7.74/131 with a 1.32 in the 60' (with the new converter). That was one of the 5.95 passes I made at 116. What does that equal out to in the 1/4? About 9.70?No doubt in my mind that it'd go a full 1/4 mile set up like it is. The converter is just locking up right about the 1000' finish and only turning 6900 RPM. [This message has been edited by cookie_monster (edited 11-20-2006).]
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clevelandstyle
Gearhead Posts: 1558
From: central Indiana
Registered: Jul 2001
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posted 11-20-2006 05:24 PM
When my sprag failed it went all at once and felt like Buster discribed. It just wouldn't get off the line. The engine wanted to rev but the car wouldn't launch. It gained 2 tenths in 60'. Down track was lazy. ------------------
Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 408C 4V, 10.50 127 MPH
Prowler Purple '87 T'bird Turbo Coupe
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kid vishus
Gearhead Posts: 7251
From: middle of NC
Registered: Oct 2000
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posted 11-20-2006 06:44 PM
This is the first time I have ever hurt a sprag. And since I really dont know the history of this convertor, it may have over a thousand passes on it for all I know. I really like the mph the car runs, and I'm not willing to lose any of it, so I will be going with another ~sprag~ type convertor. Not many 6.30 cars run 110 mph, and as you all know, that makes judging the stripe harder for the other guy. And actually, the guy I ran in the second round was a c4 car. He was dialed 6.31 and had a 1.300 60' time, but only ran 106.5 mph (I had the same mph while standing on the brakes  .)I really think with a good convertor, the car would cut mid 1.30 sixties now, which of course would make it et substantially quicker.
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