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Air Pump...I'd like to leave it off !

HammerDown

Well-known member
Joined
Jan 23, 2003
Messages
470
Location
Glenolden Pa
Corvette
1981 White/ Red int.
Air Pump/Related Items,I'd like to leave Them off !

As some here know I just did the Timing set change in my 81.

While my Air Pump is hanging in the breeze, I've always wanted to eliminate the computer controlled carb, distributor etc.

Install a vacuum HEI and maybe Eldbrock Carb and remove all the smog stuff.

Does the computer control the tranny on a 81?

Will the computer toss up any codes if I pull all the emission stuff off?

Anyone done what I'm looking to do...sure could use some guidance.

Thanks...

PS not worried about emission testing as I'm well under the 5000 mile per year cut-off.
 

Yoda

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Administrator
Joined
Oct 12, 2000
Messages
4,885
Location
Amarillo, TX
Corvette
1981 UL5
Install a vacuum HEI and maybe Eldbrock Carb and remove all that crap.
Good Luck. Some conversions go without problems some have gone back to the ECM. (GerryLP)
Does the computer control the tranny on a 81?
Automatics ONLY it monitors enough items to try to control the Torque Converter. Some folk have installed a toggle switch to engage or disengage the Torque Converter. (NUT)
Will the computer toss up any codes if I pull all the emission stuff off?
YES, you need to disconnect all computer monitoring points and them probably remove the console idiot light. The computer monitors:
  • Exhaust Oxygen Concentration (O2 Sensor)
  • Engine Coolant Temp.
  • Throttle position
  • Distributor Reference Pulse
  • and a few other items
Anyone done what I'm looking to do...sure could use some guidance.
Contact GerryLP or Peer81 both have extensive knowledge (Hands ON) about the workings of the engine and ECM system ;) And there are other 81 owners that have first hand knowledge that hopefully will chime in..

Rare is an 4-Speed and fairly stock ;)

Bud
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Hammer,

As Bud stated above, a lot of that stuff can be done. To go "computer-less" you'll need:

a non-computer distributor (HEI or module with divorced coil). I used a Accel distributor HEI.

Carburetor must be disconnected as well. There are a ton of choices out there.

With stock intake manifold: non-computer Q-jets, Holley Model 4011's, Edelbrock model ????

Intake manifold change: standard a Holley 4150 or square-bore Edelbrocks. Holley has a quarter-mile closed-loop carb that will at least give you control on WOT fuel mixture...like I said...extensive selection on carbs.

The wiring diagram for maintaining the use of the lock-up converter feature I seem to have displaced it, but Nut should still have it.

That smog stuff put aside and save it in case you change your mind later (I did). Try to keep your fumes evaporative cannister hooked-up. It is useful in the elimination of fumes in the garage and while driving.

I used to get an occasional flashing of the "check engine light", but like Bud said, that is easily solved by pulling the light bulb from the light location at the cluster.

You can p.m. me if you want more information. I got my car to run pretty good once I removed the bad MSD box I had installed, but it sent me on a wild goose chase, and wasted my time for a while. I went back to ECM, for I got my fill on tweaking my other motor and racing at the track with this Vette.

Now I am wiser and see the ways of my pal Bud...he's a Jedi, you know?;)

GerryLP:cool
 

HammerDown

Well-known member
Joined
Jan 23, 2003
Messages
470
Location
Glenolden Pa
Corvette
1981 White/ Red int.
Thanks for the feedback...Gerry I will PM you for some info !
I'm NOT looking to turn this car into a hot rod. I cant help but think without all the emissions crap, I'll pick up a few HP and have a much better running engine with some added fuel mileage.
The 350 small block is a great engine...sensors and relays, EGR's and computers tend to F-things up.

I get tired of hearing the OE Carb click and clacking trying to adjust the mixture at idle and sometimes having a miss or engine stumble here and there until it smooths out.:eyerole
Not to mention these engines run way to lean (know wonder it pings)...I even have 5 turns out on the adjustment screws.
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Not to mention these engines run way to lean (know wonder it pings)...I even have 5 turns out on the adjustment screws.

The A.I.R. pump absorbs maybe 0.1 horsepower; what kills the power is the slow/inadequate distributor centrifugal advance curve, retarded initial timing, not having the distributor vacuum advance connected to full manifold vacuum, and lean carb calibration.

The idle mixture screws only control IDLE mixture - they have nothing to do with off-idle or cruise mixture - that's a function of jets and metering rods; simply adjust them (using a vacuum gauge) for highest steady vacuum at normal idle.

:beer
 

HammerDown

Well-known member
Joined
Jan 23, 2003
Messages
470
Location
Glenolden Pa
Corvette
1981 White/ Red int.
The A.I.R. pump absorbs maybe 0.1 horsepower; what kills the power is the slow/inadequate distributor centrifugal advance curve, retarded initial timing, not having the distributor vacuum advance connected to full manifold vacuum, and lean carb calibration.

The idle mixture screws only control IDLE mixture - they have nothing to do with off-idle or cruise mixture - that's a function of jets and metering rods; simply adjust them (using a vacuum gauge) for highest steady vacuum at normal idle.

:beer
I fully understand the mixture screws only work for Idle, I'm not as savy with the Quad vs Holley so, how does one adjust metering rods on a computer controlled carb?
Thanks....
 

Sensei

Well-known member
Joined
Apr 5, 2004
Messages
393
Location
Jacksonville, Fl
Corvette
'81 dark blue
I've done it all with the '81 CCC system and humbly submit my findings. This is all from personal hands on experience, not hearsay.

The Carb and distributor are first rate units. If you replace them, you are downgrading. (The Edelbrock Performer carb will be a real disappointment).

The computer keeps your A/F ratio at 14.7:1 during normal operation (ideal efficiency) and lets the carb flow all the fuel the engine will take at WOT (depending on how you have the carb set up). It will advance your timing and if for any reason you have detonation, it will back the advance off 2 degrees and save your engine! For $120, you can buy a chip with a more aggressive, performance curve that requires premium fuel, but you don't really need it. When you do performance upgrades on the engine, the computer will automatically adjust for it, all you may need to do is change out secondary rods, which can be done without even removing the entire air cleaner housing. The only reason people get rid of these systems is out of an unjustified fear of the unknown. I've seen people throw away hundreds of dollars (not even counting resale value) on inferior stuff because they were too scared or lazy to find out why their check engine light was on. Good grief, the computer itself can be purchased for about the price of a distributor! What are they thinking?

You can ditch the emmissions stuff (EGR, AIR, Cat/ Exhaust system etc.) and the computer will never notice; no codes, no problems. But as mentioned earlier, getting rid of the EGR and AIR will not make a noticable performance difference. The exhaust will, but if you are just looking at getting rid of the AIR pump, don't bother. The only difference you will notice is the drop in resale value.

God bless, Sensei

P.S. My '81 has about 350-400 HP and is FAST! It also gets 18 MPG in town and still has original computer, carb and distributor!
 

HammerDown

Well-known member
Joined
Jan 23, 2003
Messages
470
Location
Glenolden Pa
Corvette
1981 White/ Red int.
I've done it all with the '81 CCC system and humbly submit my findings. This is all from personal hands on experience, not hearsay.

The Carb and distributor are first rate units. If you replace them, you are downgrading. (The Edelbrock Performer carb will be a real disappointment).

The computer keeps your A/F ratio at 14.7:1 during normal operation (ideal efficiency) and lets the carb flow all the fuel the engine will take at WOT (depending on how you have the carb set up). It will advance your timing and if for any reason you have detonation, it will back the advance off 2 degrees and save your engine! For $120, you can buy a chip with a more aggressive, performance curve that requires premium fuel, but you don't really need it. When you do performance upgrades on the engine, the computer will automatically adjust for it, all you may need to do is change out secondary rods, which can be done without even removing the entire air cleaner housing. The only reason people get rid of these systems is out of an unjustified fear of the unknown. I've seen people throw away hundreds of dollars (not even counting resale value) on inferior stuff because they were too scared or lazy to find out why their check engine light was on. Good grief, the computer itself can be purchased for about the price of a distributor! What are they thinking?

You can ditch the emmissions stuff (EGR, AIR, Cat/ Exhaust system etc.) and the computer will never notice; no codes, no problems. But as mentioned earlier, getting rid of the EGR and AIR will not make a noticable performance difference. The exhaust will, but if you are just looking at getting rid of the AIR pump, don't bother. The only difference you will notice is the drop in resale value.

God bless, Sensei

P.S. My '81 has about 350-400 HP and is FAST! It also gets 18 MPG in town and still has original computer, carb and distributor!

Thanks for the feedback...but here's the thing.
For years and years I've had issues with engine ping...even using Premium fuel for the past 20+ years! No carbon on the pistons, the plugs are a bit clean for me but that's how HEI's burn them. I've moved the timing around a bit...no help. Then there's the occasional rough idle then it smoothes out...no vacuum leaks found. I blocked off the EGR, got tired of purchasing them. As far as being lazy I'm far from it, few years back I pulled both heads, cam, lifters and replaced with all new. And just did the timing gear set again because i didn't have any prior records for it.
Simply put, for me chasing wires, sensors, relays etc ain't my cup of tea. Now I'll happily tear into the guts of an engine. Done it several times on my Drag Boat.

Oh and not to mention the horrible fuel mileage my car gets...and it's only rated @ 190 HP! This and the above is why I would like to open the hood, see and work on a simple small block. Maybe I'm stuck in the 70's :eyerole


Maybe @124,000 miles the OE Cad-Converter is somewhat blocked, I could punch it out, remove the EGR fully and block w/a plate, dump the air pump and...fool around with the carb > maybe fatten it up some. I can't imagine the fuel mileage getting any worse. :crazy


Ps. there was some idea of me wanting to install a 4 speed manual trans...NO WAY. Someone miss understood my words. My gear shifting/Hot Rod days are long gone.

I do want the 3 speed Auto to work properly (if) I do the project I hope to.

Thanks for the feedback, kindest regards... Ray
 

Sensei

Well-known member
Joined
Apr 5, 2004
Messages
393
Location
Jacksonville, Fl
Corvette
'81 dark blue
Dear Hammerdown, First off let me say I did not mean to infer you were lazy, thank you for not taking offense. But I have tried to help people with simple problems and instead of going through a few diagnostic steps, they said, "screw this, I'm getting a regular carb and distributor and getting rid of this computer."

Now, on to your problems:
1. The pinging is a head scratcher. The car only has 8.25:1 compression. You say you replaced the heads. What did you use? Also, what have you tried with the timing?

2. With 125k miles, I'd say the stock exhaust is a prime candidate for replacement. My stainless headers were rotted out and leaking right where the primary tubes come together and I'm sure the cat was clogged when I got the car several years ago at 85k miles. With your poor milage, I bet the exhaust is your main culprit.

3. You can go agead and get rid of the EGR and AIR if it will make you feel better. It won't cause you any problems (except possibly with the state).

4. The TH350C is a good transmission. As others have said, the computer controls the lock up but it is a simple thing to control it manually. The only problem with that is that you have to remember to turn the lock off when you are stopping!

God bless, Sensei
 

HammerDown

Well-known member
Joined
Jan 23, 2003
Messages
470
Location
Glenolden Pa
Corvette
1981 White/ Red int.
Dear Hammerdown, First off let me say I did not mean to infer you were lazy, thank you for not taking offense. But I have tried to help people with simple problems and instead of going through a few diagnostic steps, they said, "screw this, I'm getting a regular carb and distributor and getting rid of this computer."

Now, on to your problems:
1. The pinging is a head scratcher. The car only has 8.25:1 compression. You say you replaced the heads. What did you use? Also, what have you tried with the timing?

2. With 125k miles, I'd say the stock exhaust is a prime candidate for replacement. My stainless headers were rotted out and leaking right where the primary tubes come together and I'm sure the cat was clogged when I got the car several years ago at 85k miles. With your poor milage, I bet the exhaust is your main culprit.

3. You can go agead and get rid of the EGR and AIR if it will make you feel better. It won't cause you any problems (except possibly with the state).

4. The TH350C is a good transmission. As others have said, the computer controls the lock up but it is a simple thing to control it manually. The only problem with that is that you have to remember to turn the lock off when you are stopping!

God bless, Sensei

#1 With the low compression of the engine it should take 87 octane easily, but it won't! And still at times pings on Premium, especially if it turn on the AC in the Summer months.
About the heads, what I meant was... I had the originals totally rebuilt, valves, guides, springs etc I also installed another OE profile cam and lifters. When the heads were off I noticed little to no carbon build up on the pistons. And as clean as the spark plugs are now I can be assured there's very little build up so that eliminates the ping is coming from carbon.

#2. I did weld up one small spot on the OE header, where the primary tubes come together. I must get the CAT off the car and knock the inners out, THIS could very well be an issues with some blockage/flow and not letting the hot exhaust gas out.

#3. The air pump and EGR are coming off for sure. No worries with the state as it's always well under the 5000 mile limit for emissions per year. I'm just not sure if the two plugs going to the air pump send info to the computer > (CEL coming on).

#4. The 3-speed auto is fine, not sure I like the idea about manually controlling the lock-up. > I have no problem leaving the computer in the car, I just don't want it to control the carb or distributor/timing...so would it still properly controll the tranny if I installed a non computer carb and HEI?

* I'll be the first to admit I'm not one to fully understand the operations of this system and, I know it's simple compared to todays standards but...could some component of the system be sending a (rich) condition to the carb leaning it out, making the combustion temps hotter then usual and also maybe advancing the timing causing the ping issue?

Since new and all the years owning my car, it only tossed up a CEL 3-times. Two times for an O2 sensor I happily replaced. And once for the TPS in the carb I also replaced. I've also replaced the EGR-twice. This never helped the ping issues or the occasional rough idle OR bad fuel mileage.

Thanks for any further feedback...Ray
 

Bullshark

Active member
Joined
Jun 19, 2004
Messages
28
Location
St. Charles Mo
Corvette
69 BB vert, 70 LT-1, 70 454.72 LT-1
Hammer, Instead of taking a step backward in time and technology why don't you consider upgrading to FI? There are many good options out there depending on your requirments, i.e. MPFI, TBI, hood clearance, etc. IMHO the only reason for keeping a carb is if you want to keep it original. I reluctantly keep the LT-1's carbureted for only that reason.

Bullshark
 

HammerDown

Well-known member
Joined
Jan 23, 2003
Messages
470
Location
Glenolden Pa
Corvette
1981 White/ Red int.
Hammer, Instead of taking a step backward in time and technology why don't you consider upgrading to FI? There are many good options out there depending on your requirments, i.e. MPFI, TBI, hood clearance, etc. IMHO the only reason for keeping a carb is if you want to keep it original. I reluctantly keep the LT-1's carbureted for only that reason.

Bullshark

Sometimes technology can really confuse the simple things in life. When they're dead on it's great but, when they're not right....ohhhh brother look out. :crazy

For me your suggestion could be like jumping from the pan into the fire. :D

Keeping it 100% original or lack there of doesn't really bother me too much. These 81's aren't bringing any big cash numbers and never really will, not like a 1967 427 etc. I've owned it since new, don't have any plans on selling it...yet.
 

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