I have a 1996 GSR motor with the 11.8-12.x Wiseco pistons and Alaniz Street Master head work done along with stock GSR cams. After putting the head back on and driving the car for 5 miles, I barely went into Vtec (revved out 3rd gear to 4500rpm) and a noise started immediately (knocking noise thats speeds up with increasing RPM). I immediately suspected a valve smacking a piston. I did a compression test and found all cylinders at 260-275 psi (WOT, warm motor). I then couldn't figure out what the problem was but knew it was coming from cylinder #1 by using a stethoscope.

Took the head off and found indents on the top of the piston and in the head (about 5-6 that were small but enough to create a positive on the forged piston). Had the rod mic'd, bearings checked = everything perfect on the bottom end. Concluded something must have got sucked into the motor to cause the slight piston damage and then the positive alloy on the piston. This positive was then causing the noise by making contact with the head.

Cleaned up the piston, put everything back together with a new head gasket, started up the car and the noise was gone and the engine running good. Took it back out, drove about 5 miles again, went into vtec and exact same thing: Motor is again making knocking noise that increases with RPM and it doesn't matter if the motor or is hot or cold.

What could be causing this? Easy suggestion is valve to piston contact but:
1. Why would have my compression not been affected?
2. Wouldn't the valve be damaged and not the forged piston?

Please help, I am ready to just part out the whole car in frustration.

 

did you ever clay the motor

 

No I did not clay the motor because the motor was running fine with these pistons prior to the head work. Elias only 'cleaned up' the head and said he didn't take enough material off to make a CR difference. Because of that, I didn't worry about claying the motor because I didn't have a clearance problem before.

If there is a clearance problem, wouldn't I have noticed a reduced compression # on that cylinder and why would the piston show indent damage but not a sign of a valve hitting it?

 

Common thing hear is both times the engine ran good it was below VTEC..after you went into VTEC the noise occured and stayed there till you took it apart.., maybe you have a VTEC pin stuck in the on position on one cylinder? Dirt in the oil causing it to stick? just some ideas. As far as compression goes may be the piston is tapping the valve just enough to make a noise but not bend it, valves are slightly forgiving but not much.