Looking down into the spark plug hole. What you see is the top of the piston at TDC.



Seeing this, I put a section of vacuum hose onto a pick and rested the hose against the top of the shelf that the spark plug would sit on and inserted the pick until it bottomed out against the top of the piston. I placed the pick next to the spark plug and as you can see, there's not a whole lot of room between the top of the piston and the sparkplug.


Is this possibly correct? I know there are a couple other people out there with CTR pistons in a B17. Can you shed some light?

B17a crank and rods with oversized PCT pistons and OEM head gasket.

 

bump

 

yeah its that close..
pct's have negative (0.010) deck height on a b16/17 block.12.4 compression...
are you using stock hd?

 

thats about how close mine is......runs fine but was worried at first as you were so i turned the motor over manually at the crank about 4 full rotations then looked to find the plugs ok.

 

Have the decks been milled any?

You should clay the motor and shoot for 1.5mm to 2mm (no less than 1mm) of plug-to-piston dome clearance with the plugs you plan on using and at the maximum amount of gap you plan on using.

And, if need be, use a thicker head gasket.

 

The CTR pistons also have a smaller compression height, so they sit closer to the deck, it not just more domeage. good luck though.