It sounds like a sewing machine i was told this was normal by my friend but i dont like the sound of it, also something different when i deccelerate my car sounds like it has dual decompression stages it almost sounds like a jake brake any info would help thanks

 

does anyone have an idea about either

 

By "Jake brake" do you mean no burble and pop on decel?

That could be turned off (pcm/tune).

Did you install headers?

 

it has headers and some valvetrain work but when i let off the gas at like 4500 rpm it will slow down like normal then at about 2500-3000 it gets louder and starts to use more compression to slow it down it seems like its really noticeable with the cutouts open cause you can hear it alot better

 

what oil are you using in the car and how cold is it where you live?

Auto or M6?

 

DFCO - Deceleration Fuel Cut Off

When the car is coasting, and certain conditions are met, the injectors turn off completely for fuel savings. I noticed it a lot more when I got my GMMG, as the exhaust sound changes when the injectors drop out, as well as when they come back on. You can tune it out somewhat, or turn it off, but expect fuel economy to drop.

As for the "valvetrain work" what has been done? Aftermarket cams with too short a pushrod is the common cause.

 

its the stock cam with a aftermarket chromoly pushrods and ls6 valve springs thats all i can think of for now i just bought the car about 2 months ago now oh yeah and its an m6' should i pull off the valve cover and check the pushrods?

 

yeah and replace them stock pushrods.......................................... .........

 

*replace with stock pushrods*

 

i thought stock pushrods were one of the first things to give on these motors excpecially with the m6, its not nececarily that i mind the noise i was just wondering if it was a problem

 

i got some stock pushrods for sale! lol

 

If they are the same length as stock, then you are fine. If they are too short, you may not have enough lifter preload, which seems to be the reason why so many have complained about the "sewing machine" noise.

The best way to know for sure is pull off a valve cover and measure how much the lifter plunger compresses when the rockers are torqued down. I believe .060" is the recommended preload on stock hydraulic lifters.