85 TPI Throttle Body Ques
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
85 TPI Throttle Body Ques
I've had my 85 C4 for 15 years now and it has been really fun. About 7 years ago, I bought an 85 Trans Am with TPI to compliment it (lost that car in a nasty divorce). Anyway, I preferred the throttle response of the T/A to the C4, it seemed smoother and took less effort on the pedal at lower speeds. My C4 seems to take a little more effort at the pedal at the lower speeds, it's really stiff (it's a stock TB btw). Like other things, do these TB's wear out, like maybe the bore where the butterfly rotates is out of round and hanging up? I keep the TB clean and the IAC and TPS are within spec. I've heard the throttle body used on the TPI Camaros and T/As were a little different, any truth to that? Basically, I'd like to give my C4 the same feel at the pedal like my T/A had. Any input is greatly appreciated.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Tpi
There are a number of reasons why the corvette is not like the pontiac.
1. You have a 2:56 rear gear ratio.
chevy advertised the car when it was new as a true 150 mph car.
cant get there with low gears.
pontiac has 3.07 rear gears
2. Your car has a separate mass air module that feeds your computer.
unclear if it’s job is just to change signal
to one the computer reads or it just controls mass air burnoff. Its the only year that has that.
3. different computer
4. Different programming
5. different heads
6. different cam
so you have work to do.
1. You have a 2:56 rear gear ratio.
chevy advertised the car when it was new as a true 150 mph car.
cant get there with low gears.
pontiac has 3.07 rear gears
2. Your car has a separate mass air module that feeds your computer.
unclear if it’s job is just to change signal
to one the computer reads or it just controls mass air burnoff. Its the only year that has that.
3. different computer
4. Different programming
5. different heads
6. different cam
so you have work to do.
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
There are a number of reasons why the corvette is not like the pontiac.
1. You have a 2:56 rear gear ratio.
chevy advertised the car when it was new as a true 150 mph car.
cant get there with low gears.
pontiac has 3.07 rear gears
2. Your car has a separate mass air module that feeds your computer.
unclear if it’s job is just to change signal
to one the computer reads or it just controls mass air burnoff. Its the only year that has that.
3. different computer
4. Different programming
5. different heads
6. different cam
so you have work to do.
1. You have a 2:56 rear gear ratio.
chevy advertised the car when it was new as a true 150 mph car.
cant get there with low gears.
pontiac has 3.07 rear gears
2. Your car has a separate mass air module that feeds your computer.
unclear if it’s job is just to change signal
to one the computer reads or it just controls mass air burnoff. Its the only year that has that.
3. different computer
4. Different programming
5. different heads
6. different cam
so you have work to do.
Advanced
Joined: Feb 2019
Posts: 73
Likes: 4
From: Connecticut
I am having the same issue as you with my 85. Currently, I have the stock throttle body on it and it is very stiff, close to being as stiff as the clutch. My father has an 87 iroc lb9 5 speed car and his throttle pedal is a lot lighter. I am also wondering about the differences between the two throttle bodies. Is my throttle body on the 85 supposed to feel that stiff or is it worn?
