Preferred Head Gaskets for 408 LQ4 w/ FI?
 

Ok like the title states im at the point where i need to get some good head gaskets for my motor, its a 408 LQ4 pt88 build thats 4.030 bore and want some head gasket recommendations thanks!

If everything is new and you can control the Ra (roughness average) of the deck and cylinder head surfaces, then I say Cometic. If the surface finishes are already beyond your control or you’re using used components, I would recommend GM MLS gaskets. Some people have experienced sealing issues when installing Cometic head gaskets dry on blocks without a proper finish surface. While you can clean and prep the surface with 3M pads, you destroy the finish surface. People do it everyday and you can get away with it in most instances, it just doesn’t make it the correct thing to do and when someone is trying to clean up the surfaces in the vehicle, they sometimes have to do what they can.

According to surfacing experts, the recommended surface finish for a traditional composite-style soft-face head gasket in an engine with cast iron heads and block is 60-120 micro-inches Ra (roughness average). The recommended finish for the same head gasket with an aluminum head on a cast iron block is typically 20-50 micro-inches Ra. For engines with MLS gaskets, the OEM surface finish recommendations are even smoother, perhaps 20-30 or even 7-15 Ra.

According to Cometic:
Cometic recommends a surface finish of 50 RA (roughness average) or finer for a proper gasket seal. Anything rougher may conflict with the gasket design. Cometic also recommends their Multi-Layer Steel (MLS) head gaskets go on dry because they are coated with a sealant. Each MLS head gasket is coated with a .001" thick viton rubber that is bonded to the outer stainless steel layers. Adding an additional sealer can hinder the performance of an MLS head gasket.

The heads on his motor are brand new Trick Flow but the block was not decked. I vote for LS9 gaskets.

2nd that LQ9 recomendation. I did a lot of research and found a lot of high HP turbos applications running them.

You can install them dry or with copper. Seems to be a personal preference. I found 20+ lbs builds doing it either way with excellent results. I have always used copper in the past so I sprayed my LS9's.

Rick

Cool thanks guys ls9 gaskets it is! Now most reasonable place to buy!?

gm parts direct and here is the part number.
12622033

I used the ls9s on both of my engines

thanks guys ordered em 89$ with shipping not bad