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Discussion Starter · #1 · (Edited)
95 Impala ss with 503cc, roller rockers,373 gears, cold air, no cats, no smog tubes

I saw my manifolds glowing red the other night after put a tranny in the ss. Im thinking the car has been like this for a long time and I just happened to run into it because it was dark. The 503 cc has been in the car for 2 years now with no problems. I have checked for vac leaks fuel pressure is 38psi on crank up and 42 wot. new egr, new AC delco opti, no pcm codes, plugs and wires are good. I went back to my tuner and put it back on the dyno, and played with the air fuel ratio and timming but no change. Air fuel ratio was 13.5 at wot and 16 idle. Timming is adv 30 wot and 18 at idle. I checked the temp of the manifolds after driving few miles and they were 650 deg. I can hear a backfire sometimes if i romp on the gas or just tap it sometimes.

I will be thankful for any help on this
 

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clogged cats?

any other restriction other than the manifolds themselves?
 

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Can you datalog, and do you know what your BLM's are running? Could be that you're lean in open loop, and that's why unplugging the O2's made no difference.

Bosch O2 sensors are known trouble-causers on these cars. I'd say swap them out for Delco's and see if things get better.
 

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Discussion Starter · #9 ·
Can you datalog, and do you know what your BLM's are running? Could be that you're lean in open loop, and that's why unplugging the O2's made no difference.

Bosch O2 sensors are known trouble-causers on these cars. I'd say swap them out for Delco's and see if things get better.
No datalog yet, what is BLM's? What's the difference in open and closed loop
 

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Could be that you're lean .

Bosch O2 sensors are known trouble-causers on these cars. I'd say swap them out for Delco's and see if things get better.
Glowing red manifolds = Lean fuel condition or a timing condition. Possibly both as 1 is a direct result of the other condition and being controlled by the PCM.

Bosch O2 Sensors are Junk! Replace them with the OEM AC-Delco's.
 

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Glowing red manifolds = Lean fuel condition or a timing condition. Possibly both as 1 is a direct result of the other condition and being controlled by the PCM.
I agree but I would add that the PCM is probably stuck in open loop mode because it's not getting good data from the O2 sensors.

Sharkx
 

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You should put some headers on that car and let it breathe.
 
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