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Converting back before Computer Control

  
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Converting back before Computer Control

 
cam91go cam91go
New User | Posts: 11 | Joined: 07/13
Posted: 07/19/13
10:20 AM

Who or what would be the best source for converting a 1991 Camaro RS back to 1970's style ignition, carb etc operation.  

waynep712222 waynep712222
User | Posts: 103 | Joined: 03/13
Posted: 07/19/13
07:36 PM

1991 Chevrolet Camaro RS:
Available engines
6 Cylinders T 3.1L MFI OHV
8 Cylinders E 5.0L TBI OHV

there are several vendors... who sell carb , manifolds.. distributers..


i would like to know.. unless you are building an all out drag race car..

why would you want to remove all the electronic fuel injection and controls..  they really do work well when they are properly adjusted and not messed with...


i am not trying to chase you off.. as there are upgrades and improvements to either the 3.1 multi point fuel injection system  or 5.0 Throttle Body Fuel injection system..


since you are probably talking about the 5.0 TBI engine..  there are new throttle bodies from holley and a few other companies that actually flow more air and have injectors with more fuel flow capabilities.

its hard to beat an ignition system that changes the amount of advance dozens of times a second depending on the throttle position.. RPM.. manifold vacuum reading.. coolant temp.. vehicle speed.. what position the gear shift is in and what gear the transmission is in...  and when it pings.. it backs off on the timing...

5.0 TBI systems have a few issues that are normally handled..

bad coolant temp sensors.. these are under 20 bucks with a new pigtail connector..

improper thermostats... it should have a 192F thermostat.. unless you are going to have the computer reprogrammed.

worn throttle shaft bores.. engine off.. open the throttle part way and wiggle the throttle lever.. does it have play between the shaft and the housing.. this causes idle issues..  easily fixed by having the throttle body shaft rebushed.

leaking air injection systems.. allowing uncommanded air into the upstream exhaust system causing dilution of the exhaust with atmosphere.. that throws off the percentage of oxygen in the exhaust and the computer cannot handle it.. makes the car really hard to drive..

cracked distributer reluctor magnets..  causing ghost patterns in the seine wave from the pickup coil to the module and ECM.. this messes with the electronic spark control. ..

leaking ignition coils...  where the high voltage has burned thru the sides of the winding insulation to take a short cut to ground .. robbing the spark plugs of some of the voltage needed to jump the gaps..

this takes about an hour to diagnose one item at a time..


describe you issues with the current systems..

describe your WANTS .. and the reason behind them..

or buy an intake.. a 500 or 600CFM carb and a vacuum advance distributer..

you will also need a return style fuel pressure regulator..

need to figure out a way to operate the fuel pump relay .. not hard to do.. leaving the 3 wire oil pressure switch intact as that runs the oil gauge/light and the electric fuel pump also..

you will need an electric fan controller.. as the electric radiator fans were controlled by the ECM..

you will need to examine how to wire up the Torque converter clutch circuit so it still disconnects when you step on the brake.. but also does not turn on till the car is moving..

you will also need a throttle valve cable adaptor for the carb lever as almost all are the wrong length for the 200-4R or 700R4 transmission throttle valve cable unless you want the transmission to last only 2 or 3 blocks. .

you will need to modify or change the throttle linkage bracket  ...

there are a few more things..   before we get into tuning the carb and adjusting the advance curves of the distributer.


one last thing.. do you need to have your car smog tested.???  are you planning on selling it where it might need to be smog tested??

please reply.. as there are a bunch of us here to help you with questions you have...  

cam91go cam91go
New User | Posts: 11 | Joined: 07/13
Posted: 07/20/13
04:18 AM

Right now, the car runs smoothly.Being a 305, it not a great performer. I wanted to replace it with a 350 or 383. While I had the engine out I figured it was the best time to do the rewiring. Dist,coil,starter,etc to by pass the anti theft controls. I didn't know what had to be done with the 700R4, and if anything had to be done with the wiring for all the gauges. I much prefer the way an engine looks with out all the electronics and fuel injection, so does the factories or they wouldn't cover the top of the engines with plastic shields to hide everything.Smog testing is not a concern. Actually being able to work, performance tune and modify cars, with out the aid of a lap top, may not be 21st Century,but it's a lot more fun

Dave  

redneckjoe69 redneckjoe69
Enthusiast | Posts: 388 | Joined: 04/10
Posted: 07/20/13
06:46 AM

i got rid of all the computer/TPI stuff on my 87 iroc for about the same reasons you mentioned.    Waynes right though, its a bit more invloved than most think.    heres a good link and site for info on these cars.
http://www.thirdgen.org/carbswap

Pinger 1518164238 Zpsa9df0f8f  

redneckjoe69 redneckjoe69
Enthusiast | Posts: 388 | Joined: 04/10
Posted: 07/20/13
06:46 AM

double post.  

waynep712222 waynep712222
User | Posts: 103 | Joined: 03/13
Posted: 07/20/13
10:45 AM

I wanted to replace it with a 350 or 383.

easily done.. and still keeping the Throttle body fuel injection..

only needing an increase in injector flow rates to keep up with the 350 or 383 sizing..

TBI injectors can be had for conventional 350 needs. or even better the 350 police 9c3 cars with an injector flow rate between the 350 and 454 injector..

there are also 2 flow rates for 454 injectors that will work.. larger bore throttle body will really help and you can get a holley flange to TBI adaptor plate..  so you can use a better flowing intake..

hint.. you can also get a set of vortec heads .. and either a vortec TBI intake or a  vortec 4 bbl intake and then the TBI adaptor..

~~~~~~~~~~~~~~~~~~

by pass the anti theft controls  well.. thats not hard to accomplish.. if you are having issues with the VATS ignition switch ... you have several options...

one is to replace the vats lock cylinder..  take the original ignition key with you to the parts store.. buy a replacement vats ignition lock cylinder with the orange wiring harness. take that and the original vats key to the locksmith shop.. have them measure the resistance of the original vats key.. they will select the proper blank with the same resistance.. then have them cut the new locks key pattern into that blank..  when you install the new lock you will already have the proper vats key to start the engine and this will save you a LOT of money in a locksmith visit..

~~
the other is to bypass the vats circuitry..   this can be done for about 10 bucks worth of stuff at radio shack... a 15 turn 10K Ohm trimmer pot.. and the smallest size of european style terminal block.. this does require the original key to be present.. and a digital ohm meter to set the trimmer pot adjustment..  use the first and second or second and third lead from the side of the pot..  not the first and third.. radioshack 15 turn 10K ohm Trimmer Model: 271-343  | Catalog #: 271-343

the vats system not only prevents the engine from cranking.. via a hidden relay.. but it turns off the fuel injector pulses from the computer..

lastly.. you will want to also think about improvements to the 700R4.. as a stock rebuild is not enough for most higher powered 350/383 applications..  additional clutches in the 3/4 clutch pack. and a bunch of other stuff..  

cam91go cam91go
New User | Posts: 11 | Joined: 07/13
Posted: 07/20/13
12:14 PM

Will the stock ecm computer work with the increased engine size and flow from the injectors and vortec heads  

cam91go cam91go
New User | Posts: 11 | Joined: 07/13
Posted: 07/20/13
12:18 PM

Will the stock computer work with the increased size of the motor, injectors, and cylinder head flow  

cam91go cam91go
New User | Posts: 11 | Joined: 07/13
Posted: 07/20/13
12:19 PM

Thank you I saved the article for reference  

waynep712222 waynep712222
User | Posts: 103 | Joined: 03/13
Posted: 07/20/13
08:04 PM

Icon Quotecam91go:
Will the stock computer work with the increased size of the motor, injectors, and cylinder head flow

YES.....

only issue is the increased displacement when the computer drops into open loop when the fuel is not being controlled by the feed back reading from the oxygen sensor..

thats why just going to larger flow fuel injectors is the big part of the swap...

back in the early thru mid 90s.. when the transverse caddy 4100 motors were failing all over the place.. dealers stocked them by the dozens..  yep.. brand new all aluminum tiny caddy v8's..

then caddy updated it with the 4500.. then the 4900 both of which were far superior motors.

we dropped the 4500's and 4900s in by the dozens.. only swap was the larger injectors..

some of the 4500s came with throttle body fuel injection already.. so we just moved the injectors over to the 4100 throttle body if it was different..  4900s.. we use 305 chevy injectors. i even had a good friend who used some 5.7 injectors..

the only issue was really a flat spot on moderate to hard acceleration.. the injector swap fixed it.. make them wonderful cars ...

just like going from a 305 to a 350/355 or even a 383 stroker..

the big issue is the TBI heads are kinda restrictive..  some years if i am not mistaken are swirl port.. with a ramp in the intake to cause the incoming air charge to start spinning the air in the chamber and cylinder..

thats why there are so many vortec head swaps and vortec intake manifolds..


if you stick to a 350 /355.. you can just swap on a 5.7 throttle body.. and perhaps a 5.7 chip and wake up the car. there are JUST SO MANY WAYS to build a better Mouse trap.  

cam91go cam91go
New User | Posts: 11 | Joined: 07/13
Posted: 07/21/13
05:26 PM

I have worked very hard not to deal with EFI,computer controlled performance cars, and Blogging. looks like I might have to store my accumulated carb and points knowledge and learn some new things. Thanks for the info
Dave  

waynep712222 waynep712222
User | Posts: 103 | Joined: 03/13
Posted: 07/22/13
08:06 AM

depending on what your purpose is for the car..  you still might end up with a carb and vacuum advance distributer..

perhaps redneckjoe will post more pictures of his conversion...

i am not trying to scare you away from going to carb and HEI.. only that there are a lot of other things to consider to make the car really drivable..

this is totally your decision on what to change or not..

if you decide to stay with fuel injection you will want to search around for info in print.... or take a subscription to an online service info..

hint.. at autozone dot com.. when you are registered and logged in.. there is a decent amount of repair info.. not every page you need but AZ owns a company called alldatadiy dot com who does have it.. i like it in print..

you will want to perhaps search out a decent used OBD1 scan tool... with the proper cables and cartridges for your year of GM..  craigs list has them once in a while..  an OTC monitor 2000 will only work with models up to 89..  but the 4000 and other models will do newer.. this way.. you can monitor what the fuel injection system is doing.. so will know what to change or adjust..