1972 Demon 340 engine mods

nm9stheham said

These have an offset in the pin, hence the 4 eyebrows. IIRC, the late 340 pistons had 4 valve eyebrows but were about .080" below deck.

If those pistons above truly are at 0 deck, then they may be the Silvolite cast ones; they look right per all the pix I have ever found. The Silvolite number is 1267 and have a CH of 1.824" which would put them around .002" above a stock LA deck. (That Silvolite number crosses to Federal Mogul/Sealed Power 428P, per the Silvolite catalog, which have a .005" higher CH.)

Click to expand...

Photo is off internet, I did not take it. Also I did not do detailed measurement. At TDC I put transparent plexi to measure cc over the piston and saw contact with it along with contact to the block. Seemed flat but 0.002" is something I wont deny. I'm sure even thick plexi will adjust to this. Frankly when I saw these pistons I was disappointed... To the point I did not bother taking a nice photo. Those valve eyebrows have more volume than I would like to see, but it could have been worse I guess?

Car runs much better with these heads, more power everywhere. When the owner gets some more money to spend I am sure right cam + carb will make this Demon run really nice.
I will measure cylinder pressure tomorrow just to see what it shows.

For now it is what it is. I don't like hydraulic cams, Never saw a car with all lifters to be hard as they should be. In this case 4 lifters were soft so I am not fully happy with end result.

Cant wait for next step to finish this one up.