The V8 Owners Forum -

Just a quicky here guys,

I'm just removing/blending the lip in the combustion chambers from the valve seat inserts and just wondered if its worth polishing the chambers to remove possible hotspots and to help reduce carbon build up as I'm half way there anyway now?

Brian

6 of my combustion chambers are stock 4.6 with no polishing. Two of them are modified though?

These two sufferd severe shrapnel damage last year from piston debris. One had a chunk of piston ring embedded in it.

I just dug out the ring fragment and smoothed out the damaged areas so no sharp edges were prominent. She still runs fine nasp. And I have not had any issues with running gas on these cylinders. My last outing with a big shot of gas lifted both heads and blew both gaskets. But there was no sign of any melting on the edges of these smoothed out areas in the combustion chambers.

So for your application I would not worry about hot spots to be honest.

Regards
Perry

Hi
It is generally recommended for surface finnish of ports to use 120 grit emery to give a slightly rough finnish, this is related to boundry layer flow that requires the air molacules against the chamber wall to tumble across the surface. For combustion chamber you can use the same or finnish with 300 or 360 grit, the finer finnish is generally held to delay the build up of carbon in the chamber, however a better way to delay carbon build up is to avoid an over rich mixture.
Best regards
Mike

kiwicar wrote:Hi
It is generally recommended for surface finnish of ports to use 120 grit emery to give a slightly rough finnish, this is related to boundry layer flow that requires the air molacules against the chamber wall to tumble across the surface. For combustion chamber you can use the same or finnish with 300 or 360 grit, the finer finnish is generally held to delay the build up of carbon in the chamber, however a better way to delay carbon build up is to avoid an over rich mixture.
Best regards
Mike

thanks guys

was pretty much as I thought, I always leave a non polished finnish on ports and had never worried about polishing combustion chambers unless I had modified the shape. I will just give em a clean up once I have finnished the blending then.

As always, thanks for the info