george88gta

iTrader: (3)

Purchased a used pair of 799 heads to install on my 6.0L. I had a local machine shop measure the combustion chambers so I would have a starting point to bump up the compression ratio. 7 of the chambers meaured 65 cc and one measured 65.5 cc. I believe that the factory number for these heads is 64.54 cc's. Anyone seen this before, is it normal for the chambers to be bigger than the factory spec? The interior of the chambers dont show any tool marks, etc. so I dont think they were reworked. Also, I was thinking about using Cometic gaskets at 0.030" or 0.036" compressed thickness to raise the CR. Will I run in to the same issue with the intake ( mill a lot of material from the head and the intake wont fit) if I go with the thinner gaskets?

A.R. Shale Targa

iTrader: (2)

If your heads have had a valvejob done on them and have not been resurfaced then it is possible for them to measure another cc larger as cutting the seats and grinding the valves does sink them, This is why everyone who sets up heads will tell you to measure the installed heights before installing the valvesprings in order to shim where necessary for proper pressures.
Second thing is you need to know if your pistons are down in the hole, flush, or up out. Then when you know that measurment you can pick the correct thickness head gasket to get a .035"-.040" quench.

COSPEED2

iTrader: (7)

I would stay away from anything below .040 on a stock shortblock that isnt at zero deck.

george88gta

iTrader: (3)

Yes, they had a valve job before I purchased them. That makes sense. The pistons stick above the deck 0.006" and they have a 7cc dish. Regarding the springs, it looks like they just put the old springs back. Guess I will have to do some research to verify intalled spring height.