Hello to any experts or shade tree mechanics,
I posted a thread a few weeks ago ("Just got heads off, need help") after tearing the heads off my 5.7L L-98, '88 GTA. All back together but something still not right. My brazing seems to be holding good. 130+ in all cylinders.

Now, I had mentioned in the first thread that I am no expert, but I think I need one now.

Car fired up and could tell it was firing on all 8 cylinders. Would not idle though. Grabbed timing light and started to tinker. When I had the car in time (seeing the painted line hitting the degree tab on engine), it ran like crap. Would not even remotely close to idle. When I turned dist. counterclockwise, to the point of not being able to even see the line, would run alot better. Line was so far, it was hidden by air pump. Still wouldn't idle. Maybe for 10 or so seconds, then falls fast and dies.

A friend had mentioned that I was off a tooth on the dizzy, but its not that I couldn't get the painted line on the mark, its that it ran like crap when on there. I should mention, I had borrowed the timing light and after it had left, I realized I hadn't disconnected the tan/black stripe wire before trying to set time, like book says.

I also should mention, the previous owner (or someone) had cut the catalytic converter off, putting in a hollow 3" diameter straight pipe. Entire exhaust consists of Eldebrock shorty headers, 3" "y" pipe, to 3" straight, to small muffler with one in and one out. Loud as hell. And I like it!

On the pollution control black thingy (black box with like 10 hoses, directly behind air conditioning compressor), were the catalytic (I assume) went to, he put a rubber hose with a one way diaphragm that allows air out but not in. Don't know if this could be the culprit. There is a couple two wire plugs that go to the inside of that box.

Don't know what to try next. Is it, forget about setting time without a catalytic? Or, would not disconnecting that wire really throw off timing that much? Could really use some help on this one. Car is on premises and could get any info or pictures.

Thank you to whoever responds with some of that sweet, sweet knowledge.

 

well, I am no expert here either, but I have read threads where other people have had the balancer slip so the timing mark is no longer accurate at all.

Also, when the distributor cap is in the right location, and you are standing looking from the front of the car, the flat of the ign module plugs should be at a 1:30 clock postion (about a 45* to the firewall on the driver side). If the plugs going to the ign module were like facing the front of the car or something, I would say you dropped the dizzy in wrong.

Another thing **some** people will do is pull all the wires off the cap and move them each clockwise or counter-clockwise untill the timing mark lines up and the cap is where you want it. But that will add to the confusion.

 

Thats why. Its going to read about 20 advanced +/- with it connected.

 

What about the catalytic converter? Hypothetically, lets say you had a car sitting there running/idling flawlessly. You cut catalytic off. What would happen? Mine don't have it, nor do I really want/need it unless its part of my problem. Live in Illinois with no vehicle emissions inspections. Getting timing light tomorrow and trying again. Thanks...

 

Having the cat gone shouldnt hurt a thing. Especially since you have a heads back aftermarket exhaust.

 

just a thought, but did you check the vacuum hoses? And you might want to recheck that timing with the tan wire disconnected.

 

Yes, did a quick inspection on all hoses (vacuum and coolant) as I reassembled. I'm sure nothing was forgotten. Getting timing light today and trying again after work. Making sure wire is disconnected. Guy also has a vacuum tester I will also grab. Just to be on safe side. Will try timing again and post results. Thanx...

 

A "friend" (<--- no expert here either) tried to say there was such a thing as breathing TOO easy. Said catalytic holds back pressure. I don't know. Like you said before, just adding to the confusion...

 

The cat being gone is a non issue. The backpressure argument gets into a lot of superstition, (Check the stickies in the exhaust boards) but even if your friend were right, it wouldn't make a big enough different to hurt anything.

 

Without the backpressure, there is a smaller amount of CO2 concentration, before the cat because pressure has dropped. The sensor near the cat will read something other than normal readings, and will adjust fuel mixture accordingly.

Im getting mixed up here, but if the sensor detect O2, it means there is an excess of fresh air, meaning there isnt enough fuel reacting. Lack of O2 is the opposite. (hope i got those right)

In any case, such is the case with my freind's 92 F-150 with straight exhaust.

HOWEVER: The difference is very minute. You have to be a real good listener to notice its idling ever so slightly different, and it makes absolutely no difference in driving, except for slightly poorer gas mileage. He drives in the winter, so cold weather starting is no issue at all.

Would you mind posting a link to your last thread? Id like to know what you braised for repair.

 

Except our o2 is nowhere near the cat. The backpressure argument is worthless as well, headers and catbacks make significant backpressure changes and you dont see people complaining about those mods aside of a few TBI guys with EGR issues due to the design of the valve. More than anything a change like removing or hollowing the cat is a tuning issue as it would be with any other change to the engine. I'd assume this same friend that commented about backpressure also said off a tooth right? Those are old wives tales that have no basis in reality.

I agree its a non-issue. Its not the problem at hand. Set the timing correctly, then see how the car is before you second guess more things that might be the cause.

 

https://www.thirdgen.org/forums/tech...heads-off.html

Here is my old thread. I know its not a fix that will last, but should hold for a mellow test drive. Will not be driven but only for test. If deemed worthy, will park till spring and save for new engine or one to rebuild. If its a turd, I will trade in on something alike. Hardly worth anything not running, worth maybe 3ooo or so giving the condition, miles, and that you haven't been reading my threads...

 

Okay, did I just read your original post right? You didn't disconnect the tan wire before setting the timing? If that is the case, disconnect it and reset the timing. If that isn't the case, I apologize for jumping to the wrong conclusion.