94 Blazer Backfiring

[PaulQ]

Ok here we go. Changed out my 94 fullsize Blazer 350 with Vortec heads and Vortec intake, in the process I put on new roller rockers, pushrods, and lifters along with a new crane cam(Duration 254/ 264, Lift .401/ .423). Also put on new headers.

 

Here comes the problem, I can't seem to get the timing right because at 0-6 degrees I get backfires and any hire than that I get a bad idle. I'm beginning to wonder if I'm chasing my tail and have another problem but what could cause these symptoms and not show a computer code.

 

I'm fairly confident I did my valves right. With the truck running I back off each one until it clatters and tighten down until it stops and went both a quarter and half turn and neither seemed to correct it.

 

Anyone got any ideas?

 

Thanks,

Paul Q.