i'm pulling the engine, mainly to detail the engine bay, and add long branches, didn't plan on going into the bottom end (10000 or less miles on rebuild)but want to get this right the first time so i'm open to anything. this deck hight issue! i have read that zeroing it out is better, because there is nothing above the piston to heat up and you get a better quench (what ever that is, please tell me) but it also increases compression. can this be over come by dishing the pistons and enlarging the camber on the heads. and is there anything to be gained by porting of the heads +/- 240 cfm. it's a driver, 5000 rpm is about it for me and not that much of it. do any of you know of an early q-jet for an auto.
Having an average compression reading of 186 psi is very high for pump gas.
If you don't want to get into the short block, you're pretty much limited to opening up the chambers or getting different heads. If you want to open up the chambers, do so by unshrouding the valves and rounding the machined edges, but try not to reduce the flat quench areas. That will retain the "squish" effect when the piston is at TDC. This essentially squirts the air caught between the head and the piston into the rest of the combustion chamber, stirring up the mixture and speeding up the burn. Since this accelerates the burn after TDC, the engine is more efficient and makes more power with less ignition timing. The slight compression increase that accompanies decking is greatly outweighed by the benefit of the squish effect.
If you are thinking about getting the block decked, remember that piston to head clearance is the key to attaining the proper squish effect and is set by the combination of deck height and head gasket thickness. Know which gaskets you're going to use before setting the deck height.
Porting the head to bring up the flow is always beneficial as long as the port isn't "hogged". A reputable shop that has and knows how to use a flow bench is usually your best bet. I wouldn't go much beyond bowl porting for street use.
