Easy C3 power upgrades
Thread Starter
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
Easy C3 power upgrades
I'm sure it's been posted before, but I've got a 1981, and I'm looking to get just a little bit more power and torque out of my motor. 190 horse and 280 torque just isn't cutting it. I already put a K&N air filter and am about to put a new undercar chambered exhaust on in the next few days (waiting on the FedEx man). But without any major surgery or big $$$, is there any way to squeeze some more power out of my car?
Race Director
Joined: Jan 2003
Posts: 15,175
Likes: 86
From: State of Confusion
I'm sure it's been posted before, but I've got a 1981, and I'm looking to get just a little bit more power and torque out of my motor. 190 horse and 280 torque just isn't cutting it. I already put a K&N air filter and am about to put a new undercar chambered exhaust on in the next few days (waiting on the FedEx man). But without any major surgery or big $$$, is there any way to squeeze some more power out of my car?
Thread Starter
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
In response to Glengages, I should say that all computer controlled anything on my car is disconnected. I'm running a 1980 carb, as opposed to the 1981, since it would not work without the computer. So basically, it's a 1980 motor.
Race Director
Joined: Jan 2003
Posts: 15,175
Likes: 86
From: State of Confusion
somebody who's built an '81 can probably offer correct information.
Assuming I'm wrong (again ), what works on any SBC will work for your '81..... using GM-parts, the old #151 cam with better induction & exhaust should result in better performance, while retaining streetability on pump-gas:
I'd think your rear-gearing is very-tall, and killing off-the-line acceleration.
Thread Starter
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
Based on the general principles of how a smog pump works, I'm guessing that's probably killing some power. I'm thinking about just cutting the belt to free up some load on the motor, as well as not injecting exhaust gasses into my intake. Anything I should be worried about with that?
Pro
Joined: Oct 2006
Posts: 545
Likes: 2
From: Peoplez Republik (communist portland) Orygun
I have an 80.
Before these mods I could barely squeek the tires.
1. Stans Tri-Y Headers
2. Cut & got rid of the AC
3. Cut & got rid of the AIR pump
4. MagnaFlow 40's
The engine was bored 30 over & a street cam was installed. Then, the edelbrock hi-rise intake & edelbrock performer 600 carb were installed.
Now, the car can leave two handsome black peelies wherever needed
Oh...The 80 has 3:55 rear. I think the 81 is taller (3:09???).
Definitely get headers before buying a chambered exhaust.
A chambered exhaust is more $ than the other mods listed.
AP
Before these mods I could barely squeek the tires.
1. Stans Tri-Y Headers
2. Cut & got rid of the AC
3. Cut & got rid of the AIR pump
4. MagnaFlow 40's
The engine was bored 30 over & a street cam was installed. Then, the edelbrock hi-rise intake & edelbrock performer 600 carb were installed.
Now, the car can leave two handsome black peelies wherever needed
Oh...The 80 has 3:55 rear. I think the 81 is taller (3:09???).
Definitely get headers before buying a chambered exhaust.
A chambered exhaust is more $ than the other mods listed.
AP
Melting Slicks
Joined: Apr 1999
Posts: 2,010
Likes: 3
From: Moon Twp. PA USA
I'm sure it's been posted before, but I've got a 1981, and I'm looking to get just a little bit more power and torque out of my motor. 190 horse and 280 torque just isn't cutting it. I already put a K&N air filter and am about to put a new undercar chambered exhaust on in the next few days (waiting on the FedEx man). But without any major surgery or big $$$, is there any way to squeeze some more power out of my car?
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Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
the biggest killer on the 81 model is the gearing on the diff. it came with either 2.74 in the autos and possibly 3.07 in the manual . these gears are yuck !! get them replaced with some 3.55 gears and you car will boogey a little bit better . secondly put a 2500 stall in it and you wont believe the difference. its not all about the motor . you can run a 425 hp motor for example with the stock 2.74 and it will still bog down of the line. but a WARNING ..anything you do with DIFF,STALL and ENGINE = bye bye fuel economy !!!
Last edited by gingerbreadman1977; Jun 25, 2007 at 06:48 AM.
Thread Starter
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
There was a little bit of improvement from what I can tell. I mean, it was only around $20, but ya, there was a tiny little bit. Not the same difference you'd get from a cam and a set of heads, but it's somewhat noticable. But hey, now when I give the car some gas, it whistles a little!
Drifting
Joined: Jul 2005
Posts: 1,891
Likes: 2
From: Baltimore MD
I'm not being a smart a** here on this point, I'm dealing with an ECM issue and my horns blowing and I need a new/rebuilt module, Zip says they rebuild and Corvette Central says they have the ECM, what they really have is the CCC for sale. So all you 81 owner be darn sure of what you order. I think Dr. Rebuild is the only one that knows the difference between ECM and CCC on the 81
Drifting
Joined: Jul 2005
Posts: 1,891
Likes: 2
From: Baltimore MD
the biggest killer on the 81 model is the gearing on the diff. it came with either 2.74 in the autos and possibly 3.07 in the manual . these gears are yuck !! get them replaced with some 3.55 gears and you car will boogey a little bit better . secondly put a 2500 stall in it and you wont believe the difference. its not all about the motor . you can run a 425 hp motor for example with the stock 2.74 and it will still bog down of the line. but a WARNING ..anything you do with DIFF,STALL and ENGINE = bye bye fuel economy !!!
Actually the diff is 2.73 with the manual tranny option.
Thread Starter
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
That's sorta close and a common mistake since all later computer controlled Corvettes (C4-through C6) call the computer the ECM. On 1981 "ECM" is the Electronic theft deterrent Control Module and the Computer that controls the distributor advance and the carberator is called teh "CCC", for Computer Control Computer.
I'm not being a smart a** here on this point, I'm dealing with an ECM issue and my horns blowing and I need a new/rebuilt module, Zip says they rebuild and Corvette Central says they have the ECM, what they really have is the CCC for sale. So all you 81 owner be darn sure of what you order. I think Dr. Rebuild is the only one that knows the difference between ECM and CCC on the 81
I'm not being a smart a** here on this point, I'm dealing with an ECM issue and my horns blowing and I need a new/rebuilt module, Zip says they rebuild and Corvette Central says they have the ECM, what they really have is the CCC for sale. So all you 81 owner be darn sure of what you order. I think Dr. Rebuild is the only one that knows the difference between ECM and CCC on the 81
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
What woke mine up before doing all the other stuff is, A new $50 distributar from Whiteperformance on E-bay,wires.
Set your idle timing at 11 and total at 36@2500 RPM.
Theres no use doing anything until you max out the basics.
(PS) also set your carb idle air mixures screws with a vacuum gauge until you get the highest reading on the gauge, which should be about 1.5 more turns out.
Set your idle timing at 11 and total at 36@2500 RPM.
Theres no use doing anything until you max out the basics.
(PS) also set your carb idle air mixures screws with a vacuum gauge until you get the highest reading on the gauge, which should be about 1.5 more turns out.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
You seem to be a pretty knowledgable person. Any idea on what the wires coming out of my smog pump are? Like I said, my computer is disconnected, but I'd rather be a little over-cautious and make sure I'm not hurting anything by cutting the belt on the pump to free up some power.
So, if your looking for cheap or easy hp, start with the exhaust, open it up to breathe. Stick a better cam in there, then maybe better heads.
Thread Starter
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
Safety Car
Joined: May 2001
Posts: 3,758
Likes: 3
From: Surrey
Stock rear on an auto '81 is 2.87:1 (2.72:1 for manaul?). This is great for economy but bad for performance.
The smog pump can removed with no problems (if it's legal to do so).
You say that you've got an '80 carb, but have you also changed the dist? If the stock dist is still in place, and the computer has been disconnected, there won't be any spark advance & it'll be like driving a slug.
The problems, for performance, with an L81 are that it's got low CR & can't breath (just like any smog model). Changing the stock Y pipes to duals (or chambered), makes a big difference. The next bung in the system is the heads & cam. The intake side isn't so bad & I'm not convinced that swapping out the stock manifold on mine was worth the $'s.
Headers will help, but nowhere near like duals/chambered will do. The stock manifolds are restrictive, but I found that they only start being a problem at higher rpms. At low/mid-range I didn't notice any difference between headers & stock manifolds. If you change to headers make sure that you check the carburation afterwards - I had to change the secondary rods to DA (from CH) but I don't know if mods will be needed on the primary side (I've still got a computer taking care of all that).
The smog pump can removed with no problems (if it's legal to do so).
You say that you've got an '80 carb, but have you also changed the dist? If the stock dist is still in place, and the computer has been disconnected, there won't be any spark advance & it'll be like driving a slug.
The problems, for performance, with an L81 are that it's got low CR & can't breath (just like any smog model). Changing the stock Y pipes to duals (or chambered), makes a big difference. The next bung in the system is the heads & cam. The intake side isn't so bad & I'm not convinced that swapping out the stock manifold on mine was worth the $'s.
Headers will help, but nowhere near like duals/chambered will do. The stock manifolds are restrictive, but I found that they only start being a problem at higher rpms. At low/mid-range I didn't notice any difference between headers & stock manifolds. If you change to headers make sure that you check the carburation afterwards - I had to change the secondary rods to DA (from CH) but I don't know if mods will be needed on the primary side (I've still got a computer taking care of all that).
Race Director
Joined: Jan 2003
Posts: 15,175
Likes: 86
From: State of Confusion
That's sorta close and a common mistake since all later computer controlled Corvettes (C4-through C6) call the computer the ECM. On 1981 "ECM" is the Electronic theft deterrent Control Module and the Computer that controls the distributor advance and the carberator is called teh "CCC", for Computer Control Computer.
I'm not being a smart a** here on this point, I'm dealing with an ECM issue and my horns blowing and I need a new/rebuilt module, Zip says they rebuild and Corvette Central says they have the ECM, what they really have is the CCC for sale. So all you 81 owner be darn sure of what you order. I think Dr. Rebuild is the only one that knows the difference between ECM and CCC on the 81
I'm not being a smart a** here on this point, I'm dealing with an ECM issue and my horns blowing and I need a new/rebuilt module, Zip says they rebuild and Corvette Central says they have the ECM, what they really have is the CCC for sale. So all you 81 owner be darn sure of what you order. I think Dr. Rebuild is the only one that knows the difference between ECM and CCC on the 81
I hate ALL that ****, and can't wait to remove it from my '82 Cease-Fire.
Instructor
Joined: Jul 2006
Posts: 206
Likes: 0
From: Washington DC
do the basic stuff... (in order)
1. Full tuneup (spark plugs, wires and dizzy cap)
2. replace filters (fuel, air)
3. advance timing (someone else mentioned this)
4. Rear end gearing
If you need more power than that and you gotta start buying real parts. Be aware that almost anything that gets you more power eats more gas.
1. Full tuneup (spark plugs, wires and dizzy cap)
2. replace filters (fuel, air)
3. advance timing (someone else mentioned this)
4. Rear end gearing
If you need more power than that and you gotta start buying real parts. Be aware that almost anything that gets you more power eats more gas.
Drifting
Joined: Jul 2005
Posts: 1,891
Likes: 2
From: Baltimore MD
You seem to be a pretty knowledgable person. Any idea on what the wires coming out of my smog pump are? Like I said, my computer is disconnected, but I'd rather be a little over-cautious and make sure I'm not hurting anything by cutting the belt on the pump to free up some power.