1995 lt1 fresh rebuild starts up and idles nice at closed loop the engine will pop at the intake and at about 2,500 rpm the headers turn cherry red . Had tuner come out and tune the car . He says his end is fine but car still has the issue . Please pm me or email me with ant ideas .. Thanks jetmech09@msn.com

 

So were your headers glowing red as he is tuning it? He was measuring the A/F ratio and it was fine as your headers are glowing? Glowing red headers is lean condition. Did he have a wideband O2 to measure A/F?

 

Valves adjusted too tight?

 

Yes , headers are red at the collector , they are shorties . Then all pipes glow red at 2500 Rpm . Re adjusted valves Hyd . Valve at round of lobe, tightened rocker till almost no movement the 1/4 turn .

 

Are you running a cat? Possibly plugged?

 

No wide band used Cats removed

 

How does it idle and run? What modifications have been made to the engine? The fact that you appear to have combustion in the collectors at low RPM, and the combustion moves to the primaries at 2,500 RPM may be indicating a spark timing issue. Are you sure the Opti is correctly indexed to the cam dowel pin?

Valve adjustment sounds OK, but read this to see if it matches what you did:

Courtesy of Shoebox

4th Gen LT1 F-body Tech Articles

 

No mods except headers with no cats . Engine starts right up and idles nice . I would think the opti is installed correctly since engine starts right up and idles good . Going crazy with this . Lol

 

Just throwing this out there....vacuum leak maybe?

 

Are the headers new ? Or used ?

 

It couple only be a couple of things like a burnt exh valve or timing is so retarded that the fuel mixture is finishing it's burn outside the combustion chamber and into the header. or something is blocking the the exhaust from leaving the car

 

No vacuums leaks, headers are new Hookers , valves were just done with overhaul . I have the tuner coming back next weekend . I am also thinking timing , but the engine starts so easy and idles nice. Might take the opti spark back off to double check timing alignment . Will keep you guys posted. Thank for the help.

 

Suggested scenario:

You've got intake valves open when the plug fires, allowing popping on the intake manifold. You've got exhaust valve open when the mixture's burning, putting combustion in the headers. Either the spark timing is wrong, or the valves are not closing.

Just a suggestion.

 

You didn't adjust the valves by just tightening them down, did you? When the exhaust valve is about to open, set the intake valve. When the intake is about to close, adjust the exhaust valve. That ensures that the lifters are on the opposite end of the lobe.

 

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