Saturday, March 19, 2011

Engine Rebuild - Measuring Combustion Chambers

Finally found the time to measure the combustion chamber volume of the head.  The B20F head that I've got used a pretty low compression ratio stock, somewhere in the mid-8 range.  I'd like that to be a lot closer to 10:1 once everything is done.  That'll happen through a combination of shaving the head down to reduce the combustion chamber volume, and milling the block to get more "squish" in conjunction with a thinner head gasket.

The head has already been skimmed to clean it up, but no significant material was removed, so it should be pretty close to stock.  My first attempt I used water with a couple drops of dish soap to break surface tension, and blue food coloring for viability.  The water got way too "foamy" when injected with the syringe, making it hard to get a good measurement.  I switched to isopropyl alcohol with blue food coloring, and had much more repeatable results.  All the combustion chambers ended up right around 56-57 cc's, which is about what I was expecting.

Next step will be getting the block and head taken to the machine shop for the last time (hopefully).

Also got the starter taken apart in preparation to freshen it up.

Wednesday, March 2, 2011

Engine Rebuild - New Pistons II

Got the pistons loaded into the block this evening (no rings).  The fit is smoother than I figured it'd be without rings keeping everything squared up.  Just a good coat of teflon-based lubricant on the cylinder bores and healthy amounts of assembly lube on all the bearings.

At TDC the pistons are still visibly below the deck surface.

I did some pretty crude measuring with a caliper near the edges of the bores.  Seemed to be pretty consistently reading .026"-.030" down in the bores at TDC, regardless of location or cylinder I'm measuring at.  The technique wasn't particularly confidence inspiring, but it's good to see the numbers are fairly consistent.  I have a nice deck bridge to check the measurements in the center of the bores, just need to bring home a nice calibrated dial indicator from work to stick in it.