Im porting and polishing my heads and ive come to the cumbustion chambers. There is a bump in front of the spark plug hole in the chambers. Should I remove this bump and then polish the chambers or leave this bump? I tried to search for it but could not find anything on it so i figured I better ask. Thanks , Jason
That is a casting pad. It is not necessary to remove it. I did remove mine when polishing up my combustion chambers. It will add slightly to the chamber volume. But you will end up with a totally smooth chamber and no areas to develop hot spots. I polished mine up with a dye grinder and finished off with an 80-grit flapper wheel from Dremel tool. They came out great and I have 10.13 compression and run 92/93 octance fuel all the time with no detonation problems. I had also taken the sharp edge off of the area around the spark plug. I also put a gasket on the heads and drew a line with a fat felt tip marker. I used the narrower part (maybe 1/8") as my limit and ground/polished out to that. I had zero-decked my block and was actually trying to lower my compression to not have detonation problems. It does take about an hour each chamber and I highly recommend putting an old valve in each valve pocket to procect the new valve job. Good luck.
combustion chamber work I can second Phillip's comments. I'm running just under 10.5:1 with the chambers polished (casting bump removed) on pump gas. The polish I did included all the surfaces inside the chamber exposed to combustion. I polished the dished pistons as well and knocked the sharp edges off the valve relief notches. Sorry for the poor picture, but maybe it can help: Devon
Thanks Phill and devon. On my way to the garage to grind and polish. Maybe between this and my new x pipe I can hit those elusive 11's.
:grin: :grin: I'm sure glad you asked this question as I have also wondered the same thing. I was always concerned the "bump" was for coolant flow. Its good to know I can grind that sucker off from now on. :TU:
