What the heck?
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Joined: Oct 2000
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What the heck?
I'm having some trouble figuring out my car. Here's the story! While cruisin on the highway at 60 mph's, my car is reving at 3100 rpm(tire size is 255-60R-15). About 26 inches in height.
I've been racing my car a bit and although my L48 automatic has been running 14.0's. My 60 foot times are crap (2.13). And my mph is only 97-98.
I'm crossing the finishing line at almost 5500 rpm.
With these numbers, I was thinking that I must have had too much gear in the car. Because I'm almost revved out at the finish line. Like could they be 4:11's . But then with 4:11's wouldn't I have a better 60 foot time?
Tonight I was under the car, looking for a rear end code. No sign of any code. So I did the wheel turn and count the revs of the driveshaft. Looks like 3:55's back there.
Now, do I have (a) a trans problem, (b) inaccurate tach, (c) bad torque convertor, or what...........?
I'm running street tires at the track, great burn outs, no spinning on launch (19 psi) in rear. 45 psi front.
Can someone advise me so I can dip the 60 foot times and push my car into the 13's.
Thanks for any advice you can pass along!
indynut
I've been racing my car a bit and although my L48 automatic has been running 14.0's. My 60 foot times are crap (2.13). And my mph is only 97-98.
I'm crossing the finishing line at almost 5500 rpm.
With these numbers, I was thinking that I must have had too much gear in the car. Because I'm almost revved out at the finish line. Like could they be 4:11's . But then with 4:11's wouldn't I have a better 60 foot time?
Tonight I was under the car, looking for a rear end code. No sign of any code. So I did the wheel turn and count the revs of the driveshaft. Looks like 3:55's back there.
Now, do I have (a) a trans problem, (b) inaccurate tach, (c) bad torque convertor, or what...........?
I'm running street tires at the track, great burn outs, no spinning on launch (19 psi) in rear. 45 psi front.
Can someone advise me so I can dip the 60 foot times and push my car into the 13's.
Thanks for any advice you can pass along!
indynut
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Joined: Oct 2001
Posts: 19,653
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From: Melbourne Florida
Cruise-In IV Veteran
Re: What the heck? (Indynut)
I'll let the experts chime in further but 19 lbs in the rears is pretty darn low for street tires...could be actually hurting you...I'm with you on the rear end...something seems fishy...3100 @ say 65 mph ?...I have 3:73's and I turning 2700 @ 75 mph...I do have 17" tires though....
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: What the heck? (Indynut)
Those rpm/mph numbers sound more like 4.11s. You might try the driveline revolution count again. Make sure BOTH rear wheels make a full revolution. Your 60's should be much better. My Crossfire 60s at about 2.00-2.05 with 3.08 gears and a 700R4 trans, which has a 3.06 1st gear. I DO have a stall speed converter, though. Your 60s are much better than I could do with the stock stall. What year car and/or trans model? Good luck, and...
RACE ON!!!
RACE ON!!!
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Joined: Oct 2000
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Re: What the heck? (Indynut)
OK, here's more info on my car. Since I posted I've been under the car and changed the rear diff fluid and check out the numbers. I've spun the tires and counted the revs of the driveshaft and also decoded the rear end. My car has 3:55's in it. It is a 1979, L-48 with an automatic. I have added headers, and an Edelbrock Performer Cam and Intake. I've recurved the distributor. Timing is set at 36 degrees total, like Lars advised with the recurve. Is the stock convertor the problem or is my tach not accurate. A review of the details goes like this.
60 mph's is 3100 rpm
60 foot times 2.13 is the best
almost 5500 rpm at the end of the 1/4, @ 98 mph
car weighs 3640 with me in it
rear end is 3:55
trans is a TH350 and is my next thing to tweak. I'm planning on a trouble rebuild and also a shift kit and was planning on a new convertor (B&M Holeshot 2400) to help my 60 foots and also my ETs.
Could my tach be messin me up a bit here or what?
With those gears should I have a better mph than I have?
Thanks as always
60 mph's is 3100 rpm
60 foot times 2.13 is the best
almost 5500 rpm at the end of the 1/4, @ 98 mph
car weighs 3640 with me in it
rear end is 3:55
trans is a TH350 and is my next thing to tweak. I'm planning on a trouble rebuild and also a shift kit and was planning on a new convertor (B&M Holeshot 2400) to help my 60 foots and also my ETs.
Could my tach be messin me up a bit here or what?
With those gears should I have a better mph than I have?
Thanks as always
Race Director
Joined: Feb 2000
Posts: 12,431
Likes: 1
From: CT
Re: What the heck? (Indynut)
I read all you posted so far and cant figure this out. My car is also a 79 with an L48 auto T350. I have 4.11s and i am at about 3000 at 60 and 3500 at 70. Everything seems about right for your car considering weight, stall. Perhaps you could open the rear and check out the numbers on the gears. Sounds like 4.11s to me.
BTW, i wouldnt buy a B&M converter. They are pretty cheap and dont last long. Look for a more expensive converter that wont break that easy.
BTW, i wouldnt buy a B&M converter. They are pretty cheap and dont last long. Look for a more expensive converter that wont break that easy.
