Clay PigeonI'm having a problem finding the proper information on valve clearances for my B20-VTEC. I have a stock B20B bottom end with a Golden Eagle block guard, VTEC oil pump, and water pump, and GS-R timing belt. I'm using a B16A head out of a '99 civic Si, with Type R cams, Skunk2 titanium retainers and springs. I also have a Skunk2 Pro intake, AEM high-volume fuel rail and regulator, AEM V2 cold-air intake, and an MSD ignition. Please help me figure this thing out. I have been reading and hearing so many different measurements. I have spent a lot of money on this motor and I don't want to screw it all up over a few millimeters. Thanks.JonnyVia the Internet
You need at least 0.1 of an inch of clearance between the piston and the valve. You can get away with less if you're building a competition race motor, but on the street, you don't want to miss a shift at 9000 rpm, float your valves, and destroy a whole motor just because you were looking for that extra 0.01 on your compression ratio.
First, I'm going to tell you from experience that you'll be just fine. We've seen this build done before and it works great. Unfortunately, this is not always the case. What is an engine builder to do when he can't fall back on other people's experience to make sure his pistons don't get friendly with his valves? He "clays" the motor.
All you need is about a buck worth of modeling clay and an extra head gasket. Here's what you do. Clean the piston top with lacquer thinner or acetone to provide a clean surface for the clay to stick to. Cut a couple of 0.25-inch thick strips of clay and put them on the piston where you think the valves might hit. Put some oil on the valves so they don't stick to the clay. Put an old head gasket on and install the head like normal, then adjust the valve lash. Once your lash has been adjusted you're ready to rotate the motor.
Spin the crank two full rotations just as you would after installing a timing belt. If it gets hard to turn, don't force it; pull the head off and see what's stopping it. After you've rotated the motor, pull the head off and take a look at your clay. The valves should have made some fairly large impression in the clay. If there are any parts where the piston is visible through the clay, you may have a problem. Measure the deepest part of the impression made by the valve in the clay using a set of dial calipers or whatever your preferred measuring tool is. Make sure and measure any parts that might get close, i.e. high parts of a dome piston or the outside of a dish piston. If any of your measurements are out of spec, you'll need to address the problem accordingly.- DB
Poor Man's RI have a 1992 Honda Civic VX hatch. It has a B16A swap with some other goodies. I wanted some advice on a plan I've been thinking up. I wanted to swap out my lower end for a GS-R. I tried researching it but all I found were LS/VTEC builds. What's your advice? Will it work? Good idea or a waste of effort?Tom WellerVia the Internet
What you're describing is known as a poor man's Type R. The B18C1 has identical rotating assembly geometry to the B18C5. Also, the B18C5's PR3-4 head is the same PR3 casting as a B16 head but it has been reworked a bit from the factory. A GS-R bottom end with a B16 top end is a great motor. If you want more, though, swapping in ITR cams and pistons will leave you with an ITR motor that is stamped B18C1 for the sleeper effect-awesome. - DB