I have a motor problem that has me a little stumped. Here's the background info. The motor is a D15a3 1986 Civic Si motor, built for SCCA EP autocross. It's 12:1, big cam, SS valves, big springs, etc. I just started the motor for the first time today. It fired right up and sounded good. I didn't notice any unusual smoking. I let it idle for 5-10min to check for leaks, then drove around the neighborhood a few times, getting on it a little.

After running it, I noticed some oil on the underside of the exhaust flange at the head where the 1-2 pistons are. I took the header off and found that there was a coating of black oil and actually some pooled oil on the exhaust ports for 1&2. 3&4 looked great, light tan with no oil. I pulled the plugs and 3&4 look great, 1&2 were oily. I pulled the head to see what was wrong and this is where I'm having trouble figuring it out.

The head gasket was wet with oil, particularly around 1&2. The cylinder walls and tops of the pistons were wet with oil on 1&2. There is no oil in the coolant, and no coolant in the oil. Oil on the dipstick looks brand new.

I checked the valve seals and checked the valve to guide clearance (by feel). There is nothing different about the valves on 1&2 vs 3&4.

I was using an 86 Integra headgasket because my motor is .040" over and that's the same bore as the Integra, but the gaskets don't exactly match up. I had to open up some of the coolant holes, and there was a spot where one of the oil drain passages didn't line up right and I used Hondabond. I was worried about that spot leaking out the back of the block, I didn't think it would leak into the chamber.

Because of the bearing clearances and rpms I'm planning, I did shim the oil pump spring with two small washers totalling about 1/8".

The head gasket seems like the obvious culpret to me, but I want to make sure I'm not missing something while I have it apart. I've just never seen a head gasket fail in this way before.

Any help would be appreciated.

Thanks - Chris

 

When I used to run this engine with 75mm pistons I used the 1st gen head gasket also, but I didn't like to mod the gasket and the block between #2 and #4 (I think it was), so I just used the stock gasket and there was still enough room for the larger pistons and never once in 10 years did I blow a head gasket with either gasket.

I think your oil may be a stem seal issue, maybe a small cut or groove in the actual stem????

 

Any way to check the stem seal, other than visual inspection? The shop that did the valve job replaced all of the exhaust guides, because they were out of spec. Everything was checked with the valves that are in it now.

The intake ports looked dry and clean when I took it apart. The exhaust ports were covered in oil, but I didn't see any wet oil on the top of the valves. My first thought was a stem seal too, but I can't see any problem with them.

-Chris