Okay I want to remove my computer next summer, but Im going to start buying parts now. What all will I need? Also, how do I make my engine run without a computer? Also, how will I control the TC lockup? I have been thinking about parts like the EGR valve and fuel vapor canister and stuff, too. Will I need a different style EGR valve? Also, when should it get vacuum, full time, idle, etc.?
And can I just remove the vapor canister? If so, what do I do with the vapor line from the tank? Sorry about all the questions, but removing the ECM is a big job!

------------------
1983 Pontiac Firebird SE
LG4-Based Chevy 400
700R4 Tansmission
Modified 4 Barrel Q-Jet Carb
Accel Super Stock 8mm Wires
Edelbrock Pro-Flo Air Cleaner
3.23 Posi Rear
14X7" Cragar SS/T Wheels
35X4 CD/AM/FM Head Unit
100WX2 Amp
2 Pioneer 12" Subs in Custom Box
http://fbody.cjb.net/

 

You are in luck, I am doing this more or less right now. Check out my woes on the Carb board!

More or less, you will need a new carb and vacuum HEI. I hooked up the vacuum lines to everything again, but you may not want to. I have to keep the EGR and some things for the e-check, so it may not be the same.

The biggest PITA is the fuel fittings. The dual bowl fuel line that came with my Holley 750vac didn't clear the ERG valve and the end was right behind where the heater hose goes into the intake manifold!

I also needed a special bracket that Holley sells for $15 to hold the throttle cable and TV cable. I had to drill a hole in it myself for the throttle return spring, I am not 100% sure the TV cable is long enough (will see today), and I still had to buy two $7 studs to install onto the throttle bracket to mount the two cables (they didn't come with the carb!).

No matter what you do and how many people you talk to who have done this exact same swap... you will be waiting for the mailman to deliver parts from Jegs at least once... maybe twice! Good luck.

------------------
1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

-=ICON Motorsports=-

 

And, in my opinion, a stupid thing to do for a street driven car. But, I'm opinionated, which, by defination, means that I hold unreasonably or obstinately to my own opinions.

------------------
82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

I'm glad you hold that to being your own opinion. I too am going to get rid of my TPI. Reasons are: I know carbs and how to adjust them, don't know computers; it's a lot cheaper to upgrade without having to buy expensive FI stuff and a new prom; I have a MAF, so that limits me there. Carbs are just an easier and cheaper way for me to go.

I know B&M make a torque converter lockup switch that we will need for this conversion.

What about the fuel pump? Do we need to go to manual and unplug the electric, or will a pressure regulator hold back the electric's 40+psi?

------------------
Rob
'86 TA 305 TPI

 

I have to disagree about de-computerizing a carb car. While the idea may have merit, the execution was absolutely awful. The computer doesn't have enough "authority" to control the carb very much, only within a very narrow range that is easily exceeded by any serious modifications to the engine. The passages in it (especially the idle circuit) are too small to flow enough fuel for a larger motor. There are more problems with it than I can begin to count.

I did the same thing myself after spending a couple of years fighting the L69 Q-jet that I thought I could re-use on my 400. While it wasn't too hard to get it to do OK at WOT, it was miserable the other 99.5% of the time. Cold driving, stop-&-go situations, idling with the A/C on, etc. were all things I could not get it to do gracefully.

I used a Holley 6211 carb and a Performance Distributors DUI. Another carb and dist of your choice would no doubt also be suitable. I did not hook the EGR back up; of all the emissions devices on a carbed car, that one is the least effective and most harmful to the cars overall (not WOT) performance and fuel economy. However, if I had wanted to, I would have simply gotten the temp sensor for it for an older car, and plumbed like it was done in the late 70s: ported vacuum to the sensor, from there to the valve. I entirely removed the ECM wiring harness, intact - no cutting of ANYTHING!! - and plugged up the hole in the kick panel area where it goes through. I removed the whole air mgmt valve thing for the AIR system, and hooked up the pump so that it works full-time. I am still using a catalytic converter; I have a 3" Dynomax on there, and I can't tell any difference between it and a piece of same-size pipe. The car passes TN emissions: no visual, sniffer at idle, must meet OE specs for the year of the chassis. It passes easily.

The fuel vapor canister does not require the computer. I left mine intact and operating.

------------------
"So many Mustangs, so little time..."

 

Oh yes, lets keep my car with the LG4 $hit on there five7, and maybe i can hang with you in those awesome 15s. No offense, but I didnt ask for opinions, I asked for help. BTW, i mnot ditching fuel injection, im ditching the LG4 computerized cabr setup. If I had TBI or TPI I would keep it.

------------------
1983 Pontiac Firebird SE
LG4-Based Chevy 400
700R4 Tansmission
Modified 4 Barrel Q-Jet Carb
Accel Super Stock 8mm Wires
Edelbrock Pro-Flo Air Cleaner
3.23 Posi Rear
14X7" Cragar SS/T Wheels
35X4 CD/AM/FM Head Unit
100WX2 Amp
2 Pioneer 12" Subs in Custom Box
Third Gen Performance

[This message has been edited by Ward (edited November 30, 2000).]

 

Computerizing integrates everything so if you mess with one thing, it sometimes screws up the whole system.

The no-brainer bolt-in solution would be to simply build your 400 just like an early 1970's stock GM engine. It had a Q-Jet and an HEI distributor. All the rest of the emissions stuff were add-ons back then. The EGR could be there for appearances but not work. The charcoal can doesn't hurt anyting. It's just there to collect gas fumes from the tank and float bowl and feed them back in to the engine, just like the PCV valve.

Just keep it simple and just remember that your 400 has a pedigree that goes back to a simpler day when all you needed was a carb and a distributor. Then you can rip out the ECM like a Luddite and fling it into the trash!

 

I admitted to being opinionated, but I have those opinions for a reason.

Everything you're talking about is important for a street-driven, emissions-checked vehicle. The question to ask is, which is easier: to make the computer do the job with the modifications you've done, or replace all the functions it provides with mechanical devices?

In some locales, it isn't even a question, because emissions laws dictate that you keep the factory-type or otherwise certified equipment. But, you seem to be looking to keep emissions functions, just not necessarily the "legal" methods for an '83.

So, "in my opinion", you're looking at more work to remove the computer than you'd have to do to make the computer equipment work, what RB said not withstanding.

Perhaps this doesn't apply to you, but if your job transfers you to an area that has strict inspection and testing requirements, you're looking at either re-installing all that stuff, taking your car off the street, or selling it. If you're retired or independently wealthy, then you probably don't have to worry about that. I haven't gotten the impression that most people on these boards fit into one of those two catagories.

 

Hey, 5-7!

I'm retarded - and "independently wealthy! I have so little wealth, nobody wants to have anything to do with me, leaving me independent.

I'd have to agree with your "opinion" about a lightly-modded street engine. Maintaining is always a lot less trouble than redesigning. Not that it can't be done successfully, but it requires a lot more effort. On the other side of the coin, the old 8-bit processor ECMs aren't really anything to get a stiffie over, especially on a carbed engine. Your point about modifying beyond factory design is correct if the emissions cops are patrolling in your area. Just for grins, I'd save everything that was taken off the engine just in case. Inspections are eventually going to be required everywhere - even sooner if our buddy "Algore" (Frankenstein's assitant) manages to steal the election.

Inasmuch as the ECM route might be easier, if you do decide to remove it, removing the EVAP will have zero net positive effect on performance. If you need the space, that is a different issue. Since the same size block is going back in the engine bay, it shouldn't be a problem.

The distributor will have to be a centrifugal/vacuum HEI, and the carburetor will require a timed EGR provision. You'll have to install a TVS in the water jacket to hold off the EGR when the engine is cold. As long as this control scheme is used, you might as well just connect the purge control valve on the EVAP to the same vacuum line from the TVS so you can keep the EVAP and avoid f'ing up your fuel tank pressure control valve.

Your oxygen sensor will be no more than a decoration, so it might as well come off, too. You can still use the EFE system if your air cleaner setup will allow it, but it can be operated by local control of vacuum circuits rather than the ECM (probably just like it is now).

The PCV should stay unless you want to change your oil every weekend. The rest is toast, since you probably don't have a VSS or electric speedo head. The tach can connect just like it is now, and since it's not taking any useful space, you can "store" the ECM right where it is in case you have to use it later.

On the other side of the coin, you could repair the ECM-controlled system, and learn something along the way, so that you'll be ready for your next car that has no option for a carburetor or non-ECM system.



------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0