What are these Pistons and what's up with my block
I have Mr. Gasket head gaskets on my 318, bored .030 over. Part number 1121G, compress to around .028. My engine is stock. Do not believe you can get much thinner than that, at least I couldn't find any.
Thanks all plan is the do the aluminum heads, xe268h cam, air gap, and 750 Holley. Just wanted to make sure there were no abnormalities
Where are the "clean" spots on the pistons? All by the intake valve, so one cylinder it is on the left and the next on the right?
If you are running an AirGap intake, there is little heat to aid fuel vapourization. This lets fuel droplets from a standard booster carb get into the cylinder. This is wasted fuel, higher emissions and the fuel on the cylinder wall washes the oil off and into the oil pan. Cylinder wall and ring wear go up. Look for a carb with annular boosters in the primary side, for the much better atomization characteristic. On a Holley the boosters may be replaceable, but require knocking the originals out and staking the annular in. There is a company that manufactures a variety they call shear boosters. The new Edelbrock AVS2 carbs have annular primary boosters.
If that "clean spot" went all around the piston it would indicate oil coming up past rings not doing their job. Concentrated where it is, I concur with the other guys on fuel. Between the AirGap, standard boosters and possibly a bit rich fuel mixture explains that.
For a 318 that is mostly street driven, I would recommend changing to an Edelbrock AVS2 650 cfm carb. If you are used to tuning a Holley the Carter/Edelbrock and Rochester carbs take a bit of getting used to. A new carb will come with a tuning manual with a jet/metering rod chart. Once you get it tuned, for serious racing, to adjust for weather conditions you generally just change the metering rods. No spilled fuel.
For head gaskets, Cometic and probably some others, you can get thin MLS gaskets that will aid getting some more static compression. Block deck and head surface finish is critical. I want to use thin MLS gaskets for my Ford 289. The machinist that hot tanked them said the heads had been milled with old technology, probably in the mid to late '70's when the engine was rebuilt to put in the 40 Fordor. To run MLS he will need to skim the heads and possibly the block.