Replaced header gasket now loss of power

[clayton]

I need some help. Recently replaced a header gasket, I had a small leak where header bolted to cylinder head. Fixed the leak no problem. But now the car runs with low vacuum ( bounces between 5 and 10). Also it's running a lot leaner than normal. My car always ran kinda rich but now runs between lean and stoich area on my air and fuel gauge. Also at idle it surges on and off from 800 to 1200 rom. End result is now loss of my low end power. The car RIPPED off the line before, you couldn't keep the tires from shredding asphalt. Now they just chirp and slowly climbs in rpm until you get to around 4k then the engine will come alive. Same with down shifting for example ; cruising in 5th gear around 3k on the tach, throwing it down in 4th and smashing on the gas it takes off like a boat anchor. I can't find any vacuum leaks and literally all I did was replace a header gasket. Please help...I want my 331 to feel like the snappy little stroker beast she once was.

 

[cobrajeff96]

Sounds like air is slipping in and affecting the O2 sensor(s).

 

[clayton]

Sounds like air is slipping in and affecting the O2 sensor(s).

 

[clayton]

Yea man I don't know how that would be, the header gasket seems to have sealed up real nice and all the bolts are tight. Where the exhaust pipe meets the header is also bolted up tight, you can't feel any exhaust leak pushing out at all ( I just put my hand up to the header collector area while it's running).

 

[ttocs]

maybe ya didn't get a plug wire all the way on or it is shorting out now? Just close enough that sometimes when ya floor it, it makes contact and you have all 8 firing but the rest of the time it is either not firing or not completely firing. Also if you do not know, a bad plug wire can make an arking/clicking sound when they go bad