Engine dieseling on shut down

I have a friend's GTO that will diesel a little once in a while when we shut it down. Every few shut downs, the car with huff a couple of times when the key is turned off.

The basic setup is 235/240 cam with trickflow heads and a vic jr. Assuming everything mechanical is good, is there something in the tables that would cause this. TIA

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Originally Posted by angrygoat

I have a friend's GTO that will diesel a little once in a while when we shut it down. Every few shut downs, the car with huff a couple of times when the key is turned off.

The basic setup is 235/240 cam with trickflow heads and a vic jr. Assuming everything mechanical is good, is there something in the tables that would cause this. TIA

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Yes too much timing or too much fuel at idle.

what he said..

Too rich at idle will leave fuel in the cylinders at shutdown and help cause this. Too rich also leads to carbon coating the pistons and combustion chambers, which increases compression.

I would recommend seafoam the top end and then do a closed loop STFT VE/MAF tune session to dial in AFR.