Hole Shot Sucks
Thread Starter
Instructor
Joined: Oct 2009
Posts: 165
Likes: 1
From: Stanley NC
Hole Shot Sucks
1981 vette, stock 350, still running all ECM parts. Hole shot from dead stop is sluggish, but once takes off she runs fine, will set you back if punch the gas once on the street. Run 93 octain gas only.
New carb, Q-jet installed, new fuel pump, gas tank cleaned out, all lines blown out or replaced on fuel system.
Any comments will be great if can help solve this terrible hole shot/take off problem.
New carb, Q-jet installed, new fuel pump, gas tank cleaned out, all lines blown out or replaced on fuel system.
Any comments will be great if can help solve this terrible hole shot/take off problem.
Instructor
Joined: Sep 2007
Posts: 218
Likes: 7
From: Tonbridge, Kent
i take it you are running a auto box ? What is she like if you hold her on the brake, increase the revs to say 1200 to 1500 rpm and then floor it if she takes off really well i would think that a higher stall converter would work a treat. 
Drifting
Joined: Jul 2004
Posts: 1,695
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From: Kissimmee fl
Finalist 2021 C3 of the Year - Modified
2017 C3 of Year Finalist
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St. Jude Donor '07
Where did you get the Q-jet? Who rebuilt it? There is a post currently running here started by Lars on the quality of the accelerator pumps made for the Q-jet. Find it and read up, you may find that is your problem. 
Race Director
Joined: Oct 2000
Posts: 12,684
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From: Shamong, NJ
The 81 Corvette came with either a 2:72 with a 4 speed or 2:87 rear gear ratio, with the automatic. These kind of gear ratios are not designed for drag racing or strong launches. The gears in the 81 were used to improve fuel mileage and not for ultimate acceration. I think what your experiencing is typical for 81's. If you want stronger launches, or more buttom end acceration, you may want to concider a switch to a shorter (higher numerical) rear gear ratio.
Thread Starter
Instructor
Joined: Oct 2009
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From: Stanley NC
Thread Starter
Instructor
Joined: Oct 2009
Posts: 165
Likes: 1
From: Stanley NC
The 81 Corvette came with either a 2:72 with a 4 speed or 2:87 rear gear ratio, with the automatic. These kind of gear ratios are not designed for drag racing or strong launches. The gears in the 81 were used to improve fuel mileage and not for ultimate acceration. I think what your experiencing is typical for 81's. If you want stronger launches, or more buttom end acceration, you may want to concider a switch to a shorter (higher numerical) rear gear ratio.
Going to replace ERG valve tomorrow for it is hard to push in and see if that helps.
Drifting
Joined: Jul 2004
Posts: 1,695
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From: Kissimmee fl
Finalist 2021 C3 of the Year - Modified
2017 C3 of Year Finalist
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St. Jude Donor '07
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Drifting
Joined: Apr 2006
Posts: 1,911
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From: gold coast queensland
welcome to the world of a stock 81 . Gbvettesaid it all. you have a weak motor with highway rear gears with a stock stall . you can change your gears to 355 for example and have much better launch and reduce fuel economy . then you can take the next step and go to a 2500 stall for example and lose more fuel economy. then you can go the next step and bomb the motor...end result you have launch and no fuel economy .
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
welcome to the world of a stock 81 .
you have a weak motor with highway rear gears with a stock stall .
you can change your gears to 355 for example and have much better launch
then you can take the next step and go to a 2500 stall for example
then you can go the next step and upgrade the motor
you have a weak motor with highway rear gears with a stock stall .
you can change your gears to 355 for example and have much better launch
then you can take the next step and go to a 2500 stall for example
then you can go the next step and upgrade the motor
While those will help, it sounds to me like you have more of an issue with engine tune - could be carb or ignition related. Make sure your timing is set right and the advance mechanisms are working well. Make sure your vacuum advance is set up properly.
Then go on to the carb and check accel pump actuation, check for vacuum leaks, etc.
Drifting
Joined: Apr 2008
Posts: 1,992
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From: Antioch IL
I agree with gingerbread man. I changed the gear in the rear diff from the stock to a 3:54, big difference. Also went with true dual exhaust also improved.....but I am considering changing the heads and a cam this winter. in addition of a 200R with overdrive. Fun on the launch and economy on the highway with the overdrive.
Race Director
Joined: Jan 2003
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From: State of Confusion
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
One *can* build a relatively good launching car while maintaining decent, but not great fuel economy. These cars were pigs from the factory with poor breathing motors that really weren't good at anything.
I don't think someone who is worried about having a 1.5s or faster hole-shot is going to be worrying about fuel economy. (If they do, they're nuts. The money they're spending to get that car hooking could easily cover a 15 year old Honda that would get better economy than any V8 powered Corvette could dream of getting.)
I don't think someone who is worried about having a 1.5s or faster hole-shot is going to be worrying about fuel economy. (If they do, they're nuts. The money they're spending to get that car hooking could easily cover a 15 year old Honda that would get better economy than any V8 powered Corvette could dream of getting.)
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
One *can* build a relatively good launching car while maintaining decent, but not great fuel economy. These cars were pigs from the factory with poor breathing motors that really weren't good at anything.
I don't think someone who is worried about having a 1.5s or faster hole-shot is going to be worrying about fuel economy. (If they do, they're nuts. The money they're spending to get that car hooking could easily cover a 15 year old Honda that would get better economy than any V8 powered Corvette could dream of getting.)
I don't think someone who is worried about having a 1.5s or faster hole-shot is going to be worrying about fuel economy. (If they do, they're nuts. The money they're spending to get that car hooking could easily cover a 15 year old Honda that would get better economy than any V8 powered Corvette could dream of getting.)
were you picking at something i said or agreeing with something. im just a little lost to where drivel comes into it ?
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Didn't read the whole post but what you have engine wise from the factory is POS. Auto makes 2x as bad as far as hole shot goes. My 215HP 245TQ stock Pt Cruiser would make you look silly at the dragstrip.
Don't get me worng here I am not putting you down, I stated with a stock L48 '80 and was handed my azz by a 1993 Cavalier. Motor came out the next day.
Only this worth playing with now are litre bikes and the guy better know how to drive, nothing like looking it the rear veiw mirror and see him hunch over then sit up and take a look at the back of my Vette and say what f was that
Don't lose the faith, its a sexy machine now and potential for more power when the time and money comes along
Don't get me worng here I am not putting you down, I stated with a stock L48 '80 and was handed my azz by a 1993 Cavalier. Motor came out the next day.
Only this worth playing with now are litre bikes and the guy better know how to drive, nothing like looking it the rear veiw mirror and see him hunch over then sit up and take a look at the back of my Vette and say what f was that
Don't lose the faith, its a sexy machine now and potential for more power when the time and money comes along
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
Of course, when building an all-out dragster, one plans on running a fixed distance at a time.
Drifting
Joined: Apr 2006
Posts: 1,911
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From: gold coast queensland
I agreed with the bulk of it, didn't see the point(or total accuracy) of adding all the fuel economy comments. I think fuel economy can actually be improved during the progress of upgrading the car (while adding power), to a point.
Of course, when building an all-out dragster, one plans on running a fixed distance at a time.
Of course, when building an all-out dragster, one plans on running a fixed distance at a time.
maybe it was just my jealous side coming out because as far as fuel economy goes i generally have none.