I 98% sure whats causing the car to run so rich, its the fact that I have a pretty serious camshaft on a stock plenum, tb and intake but ill go ahead and list the resy of my mods too maybe you guys can point out a confliction I overlooked. It runs really rich if ou stand at the exhaust even non-car people can smell the gas.

86 IROC TPI .040 305
*Casting # 186 heads (or so the machine shop guy told me) shaved (.040 in I believe)
*Lunati 259/271 deg lift .500 .515 duration Cam and hi perform Hydrolic lifters
Shorty Headers 3in exhaust and flowmaster
I have other mods like built transmission but I wont list them since they arent the problem.

I just got the car put back together and Im not really ready to tear the intake back apart and put it in the machine shop hten have to wait for it to be ported and put it back on but I will if necessary. What I was wondering is if a aftermarket tb will make a substantial difference if only temporary until I have the time to get the whole intake system done. If so can my set up take the 58mm one or would I be better off sticking to the 52mm body.


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I find your lack of faith disturbing

 

Did you change the injectors, fuel pressure or computer chip along with all this?

An 86 TPI setup uses a mass air flow meter and doesn't take kindly to large changes in injectors or fuel pressure unless the chip is also reprogrammed (for one, the injector constant must match with the flow of what is actually installed on the engine).

Do you have O2 readings? A lean misfire can cause a gas smell that will make you think it's running rich, but isn't.

 

Everything points to it running leaner but it does the opposite. I mean, opening it up with the cam should allow more air in it. Are you sure that it is really running rich WRT the O2 sensor? I ran pig rich to the point of flooding the engine yet the O2 sensor said lean. This was because I had a bad injector fuse and the entire driver side bank shut down. The O2 sensor was on the driver side so it kept saying lean when it was rich. What tipped us off was the fact that idling Fuel Injector Pulse Width should be around 1.4-1.7 ms when in reality it was running at 3.6. Besides that, the driver side exhaust was stone cold and when running, we took a hose and stuck it in the O2 sensor hole and found that it was just air. Connected a new fuse, found the short and all was well.

Your intakes should increase the air going in and as such, the MAS should read that as running lean and in conjunction with the O2 should try to richen it up. What kind of fuel pressure are you running and what kind of injectors? When I had stock calibration on my 383 with 30 pph injectors it would run pig rich too. Are the injectors any good? If they are bad, they might be stuck open. I think the problem lies with the fuel system.

 

I'll throw my $.02 in and see if it makes any sense.

#1 is that you are not positive of your combination, so any theory any of us come up with is just speculative until we find out for sure what you have.

With that said, I think for the combination you've explained that the cam is too big for a 305 TPI with stock intake pieces. Even if you did get better intake flow capacity you would then have a bottleneck when the air reaches the heads. With the work done to the heads as you've explained, you have raised the compression ratio, however even in doing so the stock ports and small 1.88 intake valves are too restrictive to move the air into the cylinders.

So in theory the cam is too big. At this point also custom PROM burning is necessary. You may be able to stay with the current combination with a custom PROM, but it still won't be operating to full capacity.



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Mike L.

1987 IROC Z 5.7 TPI A4 3.27 Borg-Warner four wheel disc
Mods: 2300-2500 Stall Converter, Shift Kit(GM parts), TPI Specialties Stage 3 PROM, Modified airbox w/ K&N's, Relocated MAT sensor, Gutted MAF, 160* thermostat, MSD 6A, Accel 8mm Wires, bypassed TB coolant, 3" Flowmaster 3 chamber single outlet, custom adjustable cutout, 3" MAC mandrel intermediate, airfoil, ported plenum. !smog, Crane AFPR, Accel rail mounted FP gauge, Harlan shiftlite, 24lb. injectors, Hedman headers, a few others I forgot...??? FINALLY GOT PAINT!!

Check out my IROC webpage!

 

Dammit you guys want O2 readings but when I put my Headers on I eleminated the O2 sensor along with all the stock Pollution control deals (in Florida we dont have emmiisons anymore). The hole where the sensor would have went in was plugged anyway rirght from Summit so I thought maybe they know somehting I dont and left it be.
By the way the valves arent 1.88 in. In the heads. This is gonna sound stupid but when I inquired about there size to several different people I got just about all different answers. The machine shop guy said they were #186 heads. But the guy I bought them from said they were 1.98 in. THe only hard evidense I have is I put them up a set of what I know was chevy 1.94 valves and they were slightly larger.

Im running stock fuel pressure I dont have a pressure regulator and the injectors are bone stock I mean factory 1986. I was planning on somebody doing the injectors and tb next but Im not sure now someone gave me the idea of suspension work and he backed up his argument well so I may do that.

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I find your lack of faith disturbing

[This message has been edited by DarthIROC (edited August 25, 2002).]

[This message has been edited by DarthIROC (edited August 25, 2002).]

 

Ok i can see where your coming from but if I had the intake system done would that solve the huge cam problem. Also I dont understand what you mean when you say even if I got a bigger tb I would have a bottleneck when I got to the heads could you explain that termanology because I dont understand.

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I find your lack of faith disturbing

 

DING! DING! DING!

I think we have a winner. When the O2 sensor reads that the exhaust is lean, a LOW voltage is sent to the ECM to inform it to richen up the mixture. HIGH voltage signals a rich condition to lean the mixture. 0-0.5V tells the ECM to richen the mixture and say 0.8-1.-V tells the ECM to lean out the mixture. Since you removed the O2 sensor, it will always run in open loop and try to richen the mixture. O2 sensor tells the car what the fuel mix should be. Your ECM thinks it is really lean so it needs to richen the mix up and that contributes to your problem.

 

Look at the Rice cars out there. 4 in exhaust tip. If your exhaust pipe is 1 in, even a 10 inch tip doesn't help. You can enlarge your TB and even port the heads. However, you are only sending it down a narrow chamber aka, your intakes. The stock intakes are horrible as far as restrictions go.

Take a huge hose connected to a garden hose and at the other end another huge hose. If you drop a golf ball into the large hose, it will stop at the garden hose. The air is like your golf ball, it will go thru the large hose and up to the garden hose but will not go thru and reach the other large hose. You have a 1000 cfm TB and a set of larger heads. Your garden hose in this case is the plenum, runners and the intake manifold.

[This message has been edited by aklim (edited August 25, 2002).]

 

Thanks for clarifying that for him Aklim...

As far as taking off emmissions components... Yes it saves you horsepower, but before you go and take things off make sure its not a critical component that the ECM relies on for information. Removing the smog pump, the smog tubes and the cat converter are fine for performance, but eliminating the O2 is the root of your problem.

Even after you correct that problem your engine is not running anywhere near its' peak efficiency. Look at our other suggestions and take them into consideration as well.

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Mike L.

1987 IROC Z 5.7 TPI A4 3.27 Borg-Warner four wheel disc
Mods: 2300-2500 Stall Converter, Shift Kit(GM parts), TPI Specialties Stage 3 PROM, Modified airbox w/ K&N's, Relocated MAT sensor, Gutted MAF, 160* thermostat, MSD 6A, Accel 8mm Wires, bypassed TB coolant, 3" Flowmaster 3 chamber single outlet, custom adjustable cutout, 3" MAC mandrel intermediate, airfoil, ported plenum. !smog, Crane AFPR, Accel rail mounted FP gauge, Harlan shiftlite, 24lb. injectors, Hedman headers, a few others I forgot...??? FINALLY GOT PAINT!!

Check out my IROC webpage!

 

You need to get a scanner to monitor your BLMs. Your o2 voltage varies way to much to really get anything out of it. 128 is the ideal BLM number while less than 128 means the car is rich and ECM is taking fuel and greater than 128 means car is lean, ECM giving extra fuel.

 

No it will not. He removed it so the O2 will be 0 V all day long.

 

Um... Right well obviously you didnt see this car when I got it it was nearly a total restore none of those emissions things worked anyway most of it was just dead aluminum that made it harder to change spark plugs.

As for the O2 sensor the headers when I got them for some reason had the hole for it plugged up. The housing for it was there I guess if you wanted to drill it out but at the time after struggling with those things (which were probably harder to put on than any other upgrade ive made.) I was alot more interested in just making sure that the exhaust was on right.

It seems to me that all the problems are tied in with the computer If I was to get a custom computer module burned cuold it solve alot of the problems. By the was its not like the car runs bad I mean the damn thing rattles windows going down the street and snaps your neck if you gas it at 80mph I just noticed I could smell gas while the thing idles and wondered how I could make that more efficient. LOL gas is expensive enough without letting it just not burn.

 

your right, all your problems are related to the computer, and the problem with the computer is that its missing one of it's two most important sensors. You NEED to have an o2 sensor for the computer to function properly. Just take the car to an exhaust shop and have them weld in a new bung for the sensor, and then put one in. Getting a costom chip burned will help in no way shape or form until you get that O2 sensor back in...

Eric

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86 camaro Z28, way too much sh*t done to list...

 

I don't have my papers here but I think the computer gives a voltage of about XXX ( guessing at .54 volts ) for the O2 until it sees a fluctuation and that gives a rich mixture thinking the car is cold. Combined with the CTS the car will still run strong but will never use the variable ability of the computer for fuel control. Until you put the O2 back you might as well not have EFI.
Bob

 

AFAIK, the closer to 0 it gets, the leaner and the closer to 1 it gets, he richer. When it is not under WOT, it fluctuates between rich and lean.