hey i'm 17 and i have a 81 corvette it is basically stock, i wanted to know what i would need to do to convert it to non computerized. Because i want to buy some headers, get rid of that smog pump emissions thing, probly a holley double pumper carb and a new intake manifold, and i don't know were to start if someone could show me some steps, and what to do it would be greatly appreciated!

 

you will need a new distributor and a new carb, both are computer controlled. if you dont need smog testing all the smog stuff can come off.

 

Gator speaks the basics of it. Learn how to time because new distributor = new timing. Look on ebay for a pro-comp HEI for ~$80, that'll be your best bet. They're excellent HEIs in my opinion.

You'll gain a few extra ponies pretty easily with exhaust and deleting that computer BS. If you know how to work on the engine deeper, get a new cam in there ASAP. The original cam will go flat after about 80k miles.

 

Forget the ancient dino-tech and install a real EFI system.

 

He's 17, you think he has the resources to do that? Let him learn how to tinker with a carburetor first.

 

I think I've spent more trying to keep carburetors tuned than I have on FI parts...

Anyway, it's a computer-carb car. It's already about halfway to FI.

 

So was mine... Dunno, my preference is that a computer should be on the floor or desk of my home, not behind the seat of my car messing with my engine settings. I like my standard q-jet and vaccume advance HEI distributor without all of those damn extra wires hanging everywhere. Although vaccume tubes get sorta ugly, too.

 

Before you start ripping out all the emission crap, you might want to consider the laws where you live. Do you need that stuff to pass inspection? Even a visual?

 

After you have removed eveything it will be dificult to put back

 

Save it in a box and give it to the next owner.

 

I agree with everyone here but before giving any adivice how much $ do you have for the project it is beter to work slowy and buy the right stuff the first time then jumping out of the gate and just having to do over later also before increasing horsepower look at brakes and suspension going fast is great but you must be able to keep the car on the road and not kill your self!

 

Amen,,,,,Peace,,,Moosie

 

I live in a state with no emission testing, so everything was taken off my 81. new distributer (HEI).. edelbrock preformer manifold and edelbrock carb. one thing if you disconnect the computer and you have an automatic tranny it won't lock up the coverter, unless you install a lock up kit from bowtie or b&m. you can also lock it by grounding the plug on the left side of the console near the lighter.

 

Keep one thing in mind if you remove the the computer and related hardware, regardless if your community has testing or not....it is a Federal Crime to tamper with the emissions equipment and subject to 6 figure fine and/or time spent in a concrete room with bars in windows. Course they have to catch you and when they do......

 

Or..... assuming that at 17 you're not exactly dripping spare cash, I'd suggest doing it one step at a time (sort of). The first thing to do on an '81 is to sort out the stock exhaust system as it's a big hindrance to performance that can be kicked into touch fairly easily. I fitted Dynomax ceramic coated Headers on mine, which fit perfectly, still look good 4 years later & am very happy with (1 5/8" primaries, 3" collectors ruduced to 2 1/2" exhaust pipes). Doing that will allow/force you to scrap the AIR injection system (careful that you don't leave any vacuum pipes "connected" to the atmosphere) & EGR system. This is where I get flamed(!): you don't need to junk the computer. If it's behaving itself then why shell out cash to replace it? You'll need to modify the mixture to compensate for headers but this is simple. As the computer is controlling the carbs' primaries then you haven't got to worry about adjusting them to compensate for the Headers as the computer will sort it all out automatically. What the computer won't do is the secondary mixture (as the secondaries behave in the traditional way - they just open up & lots of free air & expensive fuel is fed into the engine). All you need to do is to swap out the stock CH secondary needles for a pair of DA ones & the mixture will then be pretty close to bang on. And it'll be a lot cheaper than buying another carb.
Next thing to do is to hook the Headers into the exhaust pipes. Don't even consider hooking them to the stock system as it's junk. That "Y" pipe is a huge bottleneck in the system & replacing those pipes with a set of 2 1/2" dual pipes will really let the motor breath & give a real seat of the pants improvement in power (far more than you'll no9tice by fitting Headers). You can buy an off the shelf system (eg from Mid America) or you can do what I did & make your own. I've got a custom trans x-member that let me run a pipe down the drivers side, but the same advantage can be had by modifying the stock x-member. Know anybody that can weld? What you need to do is unbolt the x-member (making sure that you've put a support inder the trans!) & cut an arch out of it in the area where you want the pipe to run (a mirror image of the p.side will be fine). Then weld a curved piece of steel over the part that you've cut out, slap some paint on & bolt it back in. You've then got the room to run a pipe under the d.side of the car, so haven't got to mess about routing it & getting lots of bends done. All my system required was a 15* bend just after the Header collectors to bring the pipes up level (the collectors point down slightly), then I ran the pipes to the back aiming at the gap either side of the diff. Just after there I put an 85* bend in & cut them so that the mufflers hooked up OK. I also fitted an "H" pipe (a piece of pipe joining the 2 sides) just behind the trans x-member. The "H" pipe makes the engine run sweeter (balances out the pressures between the 2 banks, blah, blah, blah), stops the annoying popping at idle you can get with unbalanced duals, takes the edge off of the sound (if you run loud mufflers this is really important!) & holds the system rigidly in place. An exhaust shop should be able to make up a system easily enough (it's just a few cuts, some expanding of pipe ends & a total of 4 bends). IM me your email address if you want any pics. Also needed will be a Header collector that's got provision for fitting the O2 sensor (in the stock d.side pipe just down from the manifold). Summit sell these &, even though the sensor has been moved further downstream than stock, I've not had any problems with it cooling down at idle & giving false readings (though it's something to be aware of after you do it. If it gives problems then just fit an electrically heated one). Having sorted out the exhaust system you'll get a much stronger running car. You'll soon get used to it & want more power though Something that's worth doing is to advance the ignition timing from the stock 6*BTDC (remembering to disconnect one of the connectors fromn the dist. while checking it). I went to 11*BTDC & it felt much nicer for it (cleaner pick up , better throttle response) & it costs nothing to do.
Anyway, that's the exhaust system covered, you can scrap the computer & do it, or you can keep the computer & do it. I took the cheapest option All the emissions eqpt on mine has long gone & the computer is fine about it. When you scrap the EGR system take particular care with some sort of solenoid thingy on the p.side of the engine bay. Whoever did mine didn't plug a tiny hole in the underside of it (some sort of square ended connector used to fit in it) & it literally took me weeks of searching before I found why the check engine light occasionally flashed at low rpms & why the idle was never quite right.
The biggest difference I ever felt was when I swapped out the stock exhausts for duals. Even then I was still running the stock manifolds & mufflers. What was interesting is that the cat had previously been replace by a length of "test pipe", so the restriction due to the cat had been removed - but the "Y" still put a big restriction in there. Swapping out the mufflers may have improved it, but I couldn't tell just by driving (a dyno might show some improvement), though it sure sounded better The Headers made no difference at low speeds that I noticed. What I did notice was at high revs there was more power as the stock manifolds were strangling it at those speeds. Headers freed it up, but I've still got some restriction due to the stock heads. The exhaust system is probably the best place to start when modifying these things & I'd recommend doing that before anything else. Something strange I noticed was that cabin temps have been reduced since changing the system. The ceramic coated Headers "trap" the heat in the exhaust gas & st/st (which I made the system out of) doensn't conduct heat as well as steel, but the drop in temps was surprising (having removed the aircon it's a real bonus!). Sig attached for mods.

 

UKPaul - as the post directly above you stated: Removing the SMOG system is a Federal Offense subject to huge fines if they catch you and "catch you" are the operative words I know. Say the kid wants to sell the car later - during transfer of ownership it goes through a vehicle inspection - guess what unless you cheat and pay under the table to Bubba - it isn't gonna pass.

What I plan on doing is the following - the stock exhaust manifolds are not available any more from any where except junk yards. YOU CAN install headers that retain the A.I.R tubes, YOU CAN open the exhaust up to dual with two cats if you can get it to burn hot enough for the ECM system to regulate air/fuel mixture. YOU CAN install some good sounding mufflers.

or you can do as you did retaining the ECM system and by trashing the EGR/SMOG system.

Let's face it with the stock engine in the 81 it would never be a racer, they are cruisers, I choose to keep mine as close to stock as I can, but like I said the exhaust manifolds are no longer available, I got an exhaust leak at the moment and if it's in the Drivers side exhaust manifold, I'll go the route I laid out above and see what happens.

 

[QUOTE=IrishJoker]UKPaul - as the post directly above you stated: Removing the SMOG system is a Federal Offense subject to huge fines if they catch you and "catch you" are the operative words I know. Say the kid wants to sell the car later - during transfer of ownership it goes through a vehicle inspection - guess what unless you cheat and pay under the table to Bubba - it isn't gonna pass.
[QUOTE]
So why are so many people on here removing it all?!!!! What I suggested was the exhaust system & associated smog systems (AIR/EGR) as, unlike junking the entire computer system, it's not a difficult job to change back to stock if you ever need to.
While I had my stock manifolds I had them repaired a couple of times to fix leaks due to cracks (TIG welded I think?). What I noticed about the AIR system (or what was left of it on mine) was that the manifolds just consisted of small metal tubes welded into them through holes. Surely it wouldn't be difficult to fit the tubes to Headers if an AIR system is needed? Or could you get some of the earlier rams horns from the company that makes them flow really well?
The ECM only monitors the exhaust on the d.side so isn't very accurate regarding emissions (just need the carb to be set up badly for the p.side bank, as mine was, for dire emissions). Any cats are fitted downstream of the O2 sensor so how hot they burn at wouldn't matter for closed loop operation (they're after the sensor so whatever they do is of no consequence to the computer). Have you any idea of the general CO & HC limits for an '81 in the US? From memory, mine gave a CO reading of 0.14 (ppm?) & the HC reading was a little higher than the ideal, but still within limits (I haven't accurately set the idle mixture yet). Both readings were in the pass range (here) for smaller cars fitted with cats & the testers said that they test 3 year old small cars with much worse readings than mine was giving with no emissions systems in place. Hence my keeness to keep the computer. If the govt (in their quest to get old cars off the road) bring in retrospective legislation regarding pollution then at least I'm in with a fighting chance of passing any tests

Or, lets face it, for the cost of a late C3 in decent condition you could buy something like a 928S which is a LOT quicker as stock The late C3 is a cruiser/GT BUT, lets face it, they're strangled by the exhaust/CR/heads & cams used. The performance got from a 5.7L engine is grim. Off the line starts well with most of the torque being at low revs, but it feels really strange to me to drive a car that leaves the line really strong & then rapidly loses power. Letting it breath more like the original design intended won't turn it into a racer, but it'll give a much better performance & be far more enjoyable to drive. I don't want 500hp, I just want it to perform as it should.
Good luck with the leak (any possibility that it could be welded up?).

 

Being that I've pretty much removed nearly all of my emissions equipment, I think I've broken many federal laws already hah. However, my vette isn't registered as a standard use vehicle and is no longer required to keep the emissions equipment. Granted the federal law thing is hefty, what are the chances of being caught? However, if you get a jerk of a cop looking for a reason to bust ya, that's something to consider. Removing the cats on a daily driver is probably not a good idea. Gutting them... probably safer than removing.

Just be careful and know what you're getting in to before you do it.

 

<---no federal emissions laws broken here.
all my smog equipment just seemed to fall off
i'm with batman though, save your pennies and go with a projection system or the like. the only serious race car builders that still use carburation are the ones that have to because the rules say so.

 

actually, the computer stuff is not the reason the '81 makes no power (really, ask me, i'll tell you). it makes no power because of the weak-a$$ed cam, compression and exhaust.
i can tell you that with the computer hooked up, you can make an honest 250hp with a new cam, slight increase in compression and an exhaust system. although it may not be smog legal.
you want an additional 15hp right now? put electric fans on it.
there is an article in a recent corvette fever (february, i think) telling how to adapt factory salvage yard TBI to a carburated car. you should really think that one over. (i know i am)