Need help on PTV clearnce issue- 402 LS2

[Z06vet]

This was a complete pullout from 05 C6. I pulled the motor apart to put all new gaskets and inspect it. #5 piston had a very light mark where ex valve touched piston at one time. No evidence on the valve though. This led me to check ptv. I used the putty method with 2 solid lifters, adj pushrod, & checking springs. The intake valve makes no impression, the exh leaves the putty paper thin, not even measurable. No one local is interested. Few people I have talked to said this cam should not be a problem. AES built LS2 402 short block w/flycut pistons. PRC 243 heads 2.1 intake/1.6 exh. There are no #'s so I cant find exact specs on heads. I used a set of stock 799 heads for comparison with same results. Stock GM head gasket. Comp HUC cam 239/247 621/632 114. Pushrods are 7.4 I have done about 10 cam swaps on LS motors, but this is my first stroker. I don't have a degree wheel, nor have I ever used one. I'm not looking for free advise, and I'd be willing to ship the motor if needed. I know this can get technical, and I'm willing to do the legwork. Scott

[71RS/SS396]

Opening the notch in the pistons is probably the easiest solution. Are the pushrods the right length?

[Z06vet]

Hey Tim. Talked to comp yesterday. Since the issue is only w exh valve, they felt like the cam timing was retarded. Its set up at 0 now. I found it odd the intake valve made no impression in the clay, as all the non-stroker cam installs I have done left impressions by both valves when checking ptv. I may try stock cam gear just to make sure there is nothing going on w the aftermarket gear. Going to try to find someone to degree the cam. Thanks for your help. Scott

[71RS/SS396]

I thought about it and thought the cam timing had to be off. I would highly recommend that you replace that valve that touched the piston, if it's bent even .001" it will eventually break and destroy the engine. I personally would change all of the exhaust valves if there's any doubt there may have been contact.

[Mike Norris]

Is it touching inside the valve relief or on the edge? If on the edge the relief is not a big enough diameter for the valve. If it is in a "proper spot" inside the valve relief then a cam timing issue as talked about. For what it is worth, I have run cams that spec and larger with stock flat top (non-valve relief) pistons without an issue.

Mike