I have a set of 5.3 heads I am going to use on my car. I was told that I only needed the seats ground instead of new seats to install the 2.00 LS1 valves. To me that doesn't make any sense, sounds like covering up a small hole with a bigger valve. That just sounds like it would flow worse than if I just left the 1.89 valves in them. Am I right about needing new seats?????

 

All the 5.3 heads we have seen have the same seat sive in them as the 5.7 heads. This will allow you to install the 2.02 valves with appro. machine work to the heads. Those castings will require a bit of hand porting below the seat after they are machined out for the bigger valves.

 

I agree, the seats are the same...

But , if the intake ports are the same , why would you need the porting below the seat...

Dave

 

The area just below the seat is cast about the same but when the heads are machined for the bigger valves (@ GM) they also have a small cut below the seat to make the transition from the valve job to the bowl area.