What in a head can effect the static compression of an engine?
Second block, and the same compression numbers, not sure why, but the only constant is the head and its contents. Seems ironic to me to have two blocks back to back that make the same wacky compression. (B18C5 with Spoon ITR pistons and Spoon 2 layer gasket, 150, 140, 205, 170) (B18C1 with Endyn 12.5:1 pistons, stock gasket, 130, 120, 210, 170). I am out of ideas, I did a valve adjustment today, and no luck. Maybe I suck at valve jobs, but we will see on Sunday at the dyno when a leak down test is done. Despite all of this wacky compression, car still makes 194 hp and 130 ft-lbs at the wheels with a full exhaust.
Any ideas gang? 'Cuase I am fresh out...

Jason

 

When I had a CR problem.... it was because I managed to bend a couple of valves in my cyl. head.

It read from Cyl. 1-4 185, 183, 180, 80.....!!

You should check for that. My CR right now is 200, 200, 200, 205 across the board after I freshed everything up with a 2 layer gasket.

 

If the head is the only constant I would definitely say the valves/valve seats would be the culprit. But if you are making that much power and the car runs good , I wouldn't bother taking it apart unless you really have the time or desire. Secondly I think the cams and cam gear settings would affect the readings a bit also, they are most likely a constant also. I was thinking maybe bad valve guides, but I don't think that will affect compression all that much if anything, more like the valves and seats than anything. This is all assuming that the block, pistons and rings were all installed properly. My compression readings changed on my engine when I just pulled the pistons and re-installed them - same pistons, same rings, same block and head, I am thinking maybe one set of rings weren't lined up properly once I put them into the ring compressor, they do shift around.
hth.

Joey


[Modified by JSIR, 7:13 AM 8/25/2001]

 

your valves definitely aren't seating right. Pull the head off and take it to a machine shop. More than likely you have bent valves or something. Just think if you had even compresson all the way across.

 

The only alteration to the head has been replacement of the valve stem seals. Nothing else. I wonder if those could have any play in this.
Yes, I cannot wait to see what the correct compression will result in.

Jason