Hi Guys,

Some of you may have read my previous posts about converting to a new style opti and having a lack of power...well i swapped the used opti i had in the car with a new one, and it still has no power off the line and all the same problems.

My symptoms are:
No power off the line/low rpms
High RPM backfiring at WOT, if i ease to high rpms at light throttle it doesn't seem to backfire
Poor gas mileage
General loss of power

I was trying to look for anything i could see in the dark, like sparking wires or something, and noticed the headers were glowing dimly, not very bright but noticable. Is this normal? I am wondering if after all this time i still have my chain a half tooth off (retarded timing causes glowing headers right?) I already tore it back apart once, and redid the timing chain, and it seemed perfect, but what else would cause my symptoms? :smash:

 

Glowing headers isn't normal. The headers on my IROC LB9 are almost cool enough to touch.

Sounds like you're burning fuel in the header tubes, like either too rich or the exhaust valve is opening too soon.

 

Those symptoms sound very fimilar. My headers were a glow as well,
I had to tear it all back down and reinstall the timing set as I was a little off.


I knows its no fun to redo but That sounds like what it is.

 

I thought that glowing headers meant you were runnin lean. :confused:

 

You are right, unless you had her WOT all the way home. :D but that might not be so slight a glow

 

Not an expert on Vettes, but every 4 stroke I have ever seen heat up the exhaust like that was running lean (or sucking air if carbed). If that is the case you could be dangerously close to a piston seizure.

Disclaimer; I am not a licensed mechanic nor have I played one on TV and I have not stayed at a Holiday Inn. :) Just my non-expert opinion. FWIW


[Modified by LaVidaLoca, 9:56 PM 9/26/2002]

 

Glowing headers is almost always due to either lean mixture or retarded timing or a combination of both.

Jake

 

i was afraid the timing set might be off...this will be the second time i am re-doing it :mad this time i will post some pictures before i put it back together so you guys can tell me if i have it right, after last time i thought i had it perfect.

anyone have a good way to make sure it is lined up :confused: do you have to pull all the slack out of the chain on one side or the other? when i lined it up, i tried to have the chain at even tightness on both sides...

oh well, thanks for the help!!
:cheers:

 

You're still running your stock cam right? I was gonna say if you put in a different cam it would be possible that it was just ground wrong. In which case if you put it perfectly in time according to the gears it could still be wrong.

It just doesn't make any sense man. My cam was out of time and it was obvious. I'm pretty sure mine was actually advanced. At least that's what my good friend and excellent mechanic thought the car sounded like. I believe ya, you've already had it apart twice. But I just don't know what else to tell you. What did you end up putting on there as a timing chain? If it's the stock one maybe it's stretched?

 

Hey Nathan,

Yeah, i still have the stock cam, i ended up picking up a standard SBC timing set to use the upper gear, and i went ahead and used the new chain that came with it. I verified the upper gear was identical except for the size of the hole in the center and it doesn't have the water pump drive gear.

I want to check a few other things before i take it back apart, but most likely i think i just misaligned it twice, this time it stays apart until i am 100% sure it is right!!

 

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

 

I'm referring to ignition timing, not valve/cam timing.

Sorry if I wasn't more specific.

Jake

 

As far as valve/cam timing goes, over the years I've run into all sorts of problems.

I've bought brand new Cloyes timing chain sets - chain and both gears - and found that the crank gear, on one occasion and the cam gear on another, was stamped one tooth off.

I discovered this in degreeing in the cams.

On other occasions, I've found that no matter what I did when I was beginning the installation, I couldn't get the "dots" to align. The cam gear dot would either be on the "5 o'clock" side or the "7 o'clock" side - never 6 o'clock as you would expect.

Installing and degreeing in the cam in those cases proved that when confronted with that situation, the "5 o'clock" side was ALWAYS the correct choice.

Using the "7 o'clock" side always put the cam so far off that no single bushing could correct it.

Remember, too, that aligning the dots is only one step in the cam installation process. Aligning the dots only tells you that the dots are aligned, nothing more. It doesn't mean that the cam is installed "straight-up" as many believe.

The cam is straight up only when it's degreed and verified to be straight-up according to the camshaft card. Sometimes the cam has to be offset in the advanced position to make it "straight-up" and other times the cam has to be offset in the retarded position to achieve "straight-up"

Wish I had a dollar to every time I've tried to make guys understand this.

Just some more stuff to think about.

Jake

 

Could it be clogged cats? Saw lots of glowing exhausts a night time racing at Sebring :cool: . Only thing glowing on the vettes was the rotors. :cheers:

 

I checked the timing marks on the old cam gear vs. the new one when i swapped gears, so i think they should be right and i should be able to just line up the dots...

 

i think if it was clogged cats i wouldn't get my power back as it revs higher...it is weak off the line until about 3k rpms, then has good power, but starts backfiring at around 5k+ rpms...

i think i am going to tear it back down to verify timing either tonight or tomorrow night. Thanks for all the suggestions!!

 

At what point did all of this start happening? After the chain change?

 

yup...i modified my car to use the new style opti, and part of that was changing out the upper timing gear...i am about 90% sure that is the problem :mad oh well, i will post some pictures of my timing set to make sure it looks right before i re-assemble...
:cheers:

 

well, i got the car apart...and the chain looks fine as far as i can tell

i am running out of ideas as to what's wrong with my car.

where should i get a fuel pressure guage? what's the best diagnostic cable to buy to hook up to a laptop?

thanks
:cheers:

 

does it use a cam button to keep it from walking forward?
I don't see one in the pic (I'm not real sure about LT1 motors though), if the cam is walking that may effect the spark timing.

while you have it apart you might as well degree the cam, just to check it.