Brian Austin Green Sued Over $330,000 Porsche Sale

Brian Austin Green sold a classic Porsche to a guy overseas, but the buyer claims the car's engine wasn't what Brian advertised it to be ... and now he wants his money back.

According to a new lawsuit, obtained by TMZ ... Gonzalo da Silva Pinto says Brian was trying to sell a 1955 Porsche Speedster back in May 2017, and when Pinto saw the online ad, he did his due diligence to make sure the Porsche was the real deal.

After all, the asking price was $385k -- makes sense he'd wanna kick the tires.

Pinto claims he hired a couple Porsche experts to inspect the car and make sure the engine matched the certificate of authenticity -- by verifying a stamp on the motor. He says everything looked up to snuff, so he bought the car from Brian for $330,000 and shipped it to Germany.

Problem is ... Pinto says when the Porsche got to the motherland, he tried to get his own certificate of authenticity and found out the engine was NOT authentic. Pinto claims the engine stamp was forged.

Now, Pinto wants to cancel the sale and get back his $330k ... plus all the costs and fees he racked up during the purchase, authentication and delivery. Although he's clearly pissed about the alleged forgery ... Pinto is not accusing Brian of fraud in the lawsuit.

We reached out to Brian's camp ... so far, radio silence.

No word if Pinto checked the Carfax.