Hi I would like to ask you, I changed the lexus gs430 year 2005, the head gasket, I was also taking out the motor, after installation, I can not start the engine only start | to 3 seconds and turns off when you hold the gas pedal when starting the engine and nastaruje but it intermittently as a bad valve timing, but everything I checked about 5X the timing belt is on the marks, and sprockets on the camshafts are one dot, no fault diagnostics, please help

 

Run a compression test, see if there is a problem with the cam install. Were the cams removed? Could they have been installed wrong (aka, intake cam swapped with exhaust)?

 

I dont think you can accidentally get the cam gears mixed, most only go one way and usually would have a rear sprocket, a tab or similar(on one of the camshafts for each bank) for one of the CPS sensors to read. If the motor build and timing was successful, check compression like what he said, then check all the electronics and vacuum lines.