I recently replaced my intake valves, valve stem seals, milled my slightly warped head, and a new valve job. The car was smoking before all this on heavy loads.

I put the fresh head back on and some CTR cams and the car just doesn't make as much power. The compression is still 230-235 across the board and less than 4% leakdown on every cylinder. Previously it was 7, 12, 7, 9 percent. On the dyno, it just doesn't make the power it used to. Everything is good, timing, compression, electronics, it just won't make power. I keep losing power, even after a new clutch.

So, I'm thinking that the oil control rings are shot and allowing a lot of blowby into the system and causing me to lose power. Does this sound resonable? My next step is to open the motor back up and try to just hone and re-ring the motor with new bearings. My questions are, do you guys think I can get away with just rehoning and re-ringing or should I go with a 25 over piston and bore/hone it?

The motor is a B18C1 bottom end with B16a head. The bottom end, since I've had it, has at least 35000 miles, daily/race driven miles, many at 9000rpms. Thanks for any input

 

I wouldn't think the rings are bad because of the good leakdown readings.

 

The reason I think its the rings is that you can still have good compression (compression rings) and have bad oil comsumption problems (oil control rings). The last time I looked at the cylinder walls too, they were pretty shiny and no crosshatch marks could be seen.

 

Is it using oil? Still a little oil won't effect power much. The only way to tell if an overbore is needed is to inspect the cylinder bore. Do they measure within spec? Are they round? Any deep scratches? One possibility for a slight loss of power could be the cam timeing being slightly retarded from the head being milled. (Though I don't know how much effect that would have.)

 

Yeah, its still using oil, but not as much since I changed to Castrol. I was going through at least 2 quarts of Mobil 1 Supersyn 10w30. I am only a little low now ith the Castrol, but its only been 2 weeks since I changed last.

The last time I checked, they weren't any scratches or anything I could see in the cylinder walls. I have cam gears and have adjusted on the dyno. I have picked up a little bit of power, but nowhere near what I was putting down a few weeks before. The temps have actually been lower when I've put less power down too. The car smokes under WOT acceration, especially on the top end, but its ok when normal driving.

 

Any specific numbers from the dyno?

 

When my car was running its best with GSR cams, the car put down 182 HP and 134 torque at a slightly lower elevation. Where I live is about 2000 ft higher than where I dynoed those numbers. The best here I have done is 179 and 132 torque. I did those things in the first post recently, CTR cams, along with a new clutch and put down close to the same numbers, but LESS midrange. Every time I dyno, the car gets worse. The best I've been able to pull is 170hp and 128 torque. I'm at the point where I'm ready to just tear it apart again.