1989 SBC 5.7 (TBI) Problem with rebuild. - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-05-2007, 07:34 AM
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1989 SBC 5.7 (TBI) Problem with rebuild.

Hello everyone and thanks in advance for you help on this matter.

My son who is 17 wrecked his Mitsubishi Eclipse and we got him an 89 Silverado and went totally through it.

We had the block (5.7) dipped and cam bearings inserted. The block was bored to .040 over and a towing cam (or so they said) was installed for more torque or whatever the guy said...

Now I have an engine that has been totally rebuilt with new pistons, rings, rods, cam, lifters the whole works.

The thing has trouble idling right and while it is idling sits there and black smoke comes out at times but barely visible. Goose the throttle and it will shoot out a faint puff of black smoke.

Performance is awesome and extremly responsive. Can blip the throttle and the tires spin like on ice. Put her to the floor and she is gone like a scalded dog. However, at the stop lights it seems like she may stall. Here is what I have found so far...

We discovered that the EGR switch that is controlled by a vacum line from the front of the throttle body was causing the EGR to open at around 1500 rpms. You could sit there and watch as the throttle (neutral) was moved from 700 rpms to 1200-1500 rpms that the egr would just open wide open and she would be stumbling like an old man with a crutch. We disconnected the electrical supply to this switch and she runs MUCH better at partial throttle but is still throwing a couple of codes.

I'm getting a 41 and a 43 the last time and I think it said something about a bad connection at the CPU and that there was a lean code detected by the O2 sensor or something...I understand this lean code as the cam may be drawing in more air then the injectors are programed to inject. But, I don't at the same time understand a lean code with black (unburned fuel) smoke???

Now, I realize that this engine is controlled by a computer and I pulled a ******* move by putting a cam in there and the specs on the cam are causing more fuel / air mixture to be drawn in and the sensors are probably having a problem with this. What is my recousre:

1. Take it to a chevy dealership
2. Buy a perfomance chip for this engine (which will still act as though it has a std cam???)

3. Torch it..ha!

4. Other options..???

Thanks for your help.

Mr. Tripp
Augusta, GA

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Old 06-05-2007, 08:51 AM
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Is the cam computer compatible? if not it can cause havoc on the computer. It`s size also plays a big role. You will need a after market chip that`s programmed to your engine. Since my 92 chevy truck has a 4.3 and tbi, I had to learn a few things myself. I just did a rebuild on it, added flat top pistons, isky roller cam, and many other goodies, when I reinstalled it in the truck the biggest issue I ran into was the egr, the code would read EGR failure. Since I`ve just disconnected it and plugged the vacuum line, now it runs good but it running rich has been a side effect. Since you added a bigger cam you`ll also need a adjustable fuel pressure regulator with a vacuum compensator. When I order my chip I`m going to have the EGR bypassed so it can`t throw a code. the only time it throws a code is when it`s at steady cruise speed for more than 10 minutes. The egr is designed to not operate at idle, anything off idle and it will operate.
I can`t find a code 41, but, code 43 comes up as: Electronic spark control is not recieveing a knock signal from the knock sensor. Check the knock system sensor or the ESC module. Have the module checked by a dealer service department.
Did you reinstall the knock sensor after the rebuild? Is it connected? is it getting any power? As for the idle I would check it very carefully for vacuum leaks. If there are none, check over the valves, make sure there in proper adjustment.
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Old 06-05-2007, 10:45 AM
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Just curious - have you pulled a spark plug to see what they look like after running under these conditions?

Does anyone know if running a higher heat range plug would help?
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Old 06-05-2007, 01:24 PM
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Thanks for the help

Not real sure on the codes but will run down and do a diag on it again. My EGR is disconnected. The cam (I'm not sure if it is computer compatible).

Knock Sensor, I remember hooking that up and I will check the curcuit.

It idles like a car with a full race cam in it. Sounds good and when you blip the throttle the tires spin...the spring on the throttle is a bit strong and it is hard not to turn the tires when you take off. I'm going to call and get the specs on the cam and will post them with the diag results later.

Greg
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Old 06-06-2007, 02:39 PM
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Machine shop answer...

Just called and visited the machine shop that sold me the cam. They said to come on down and pick up another...the cam they sold me was NOT Computer Compatible.

So I walked in and they had another cam with lifters on the counter and handed them to me at no charge....they must have made a mistake...!!!

The specs on the computer cam I just got are as follows:

Melling Select: Model 22111

Cam Spec's
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Old 06-06-2007, 02:44 PM
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Machine Shop Answer (cont.)

The cam they gave me that is susposed to be computer compatble is a Melling 22111 cam. It has a valve lift of .398 (int) and .421 (exh), while the camshaft that is in it has a valve lift of .447 (int) and .447 (exh).

Wonder how much power I will loose with this cam...or will I gain power through a better mixture ratio and cleaner burn?

Thanks!

Last edited by gandl2123; 06-06-2007 at 03:05 PM.
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Old 06-06-2007, 05:04 PM
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it sounds like the cam that`s in there is the old L79 350 horsepower 327 cam, and it`s far from computer compatible, it`s a old design and there`s far better cams out there now, the L79 cam is forgotten technology. The new cam should give it alot of low end torque and drivibility that should help get your combo back in line.
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Old 06-06-2007, 07:14 PM
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I'd see if I could get them to spring for a set of intake gaskets and a timing cover set, too.

tom
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Old 06-06-2007, 08:51 PM
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I will try that...

Sounds like a good idea on the gaskets. You are right there. This place is a place I do a lot of business with and they wanted 1100.00 to build i for me and I told them I could get a long block from Autozone with a 1 year waranty and they would only give 30 days.

So after that conversation I just told them to clean the block and bore it for the .040 over pistons and they put them on the rods and charged me a few hundred for that....then when I got her home noticed they didn't even installthe cam bearings and I bought the entire set of rods, mains and gaskets form them.

I was so pissed I just ordered a cam bearing installation tool and learned how to do it on this site. I had done it years before in auto mechanics and a refresher course, and teaching my 17year old how, was good medicine. I wasn't about to take it back there.

Seems they like the customer who drops their stuff off and don't care about the price as long as it is race ready on Friday. Well, I'm the budget guy who is hypersensitive to being fu#%@$ ed and won't let it happend if I can help it.

Thanks for your help guys.

Mr. Tripp
Augusta, GA

PS I will call them and enquire about the gaskets in the morning.
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