Im searching LQ4s and LQ9s on junkyard inventories for a 3rd gen swap, and I see the listings are divided into engines for CNG and for gasoline.

I've never seen a compressed natural gas setup. What did they change to run it? How much of the engines themselves are the same?

Thanks

 

Of what i have read the motors are the same except the heads have different valve seats for the natural gas. I don't have any first hand knowledge.

 

That matches the only thing I've read about them too.