question about loud knocking phase 1 DOHC engine when cold

[996TT]

Hi and thanks for looking.....Just a question with regards to engine knock....

I have a 98 LGT and just had the heads rebuilt and everything else replaced. My questions is, I know that some Subarus in general have a slight knock when cold...but quite down when warm.........After my heads were rebuilt,, and everything put back together,..my engine sounds like a diesel when cold......but when it warms up to full operating temp, the engine is nice and quiet,.........The story behind the engine, is the car sat around for about 5 months while things were getting done as this car was being built for a daily driver(the car had a minor front accident).....so since the engine had only 80k miles, I figured the block would still be fine, but when everything went back together, no I am faced with this awful noise when the engine is cold. I never owned the car in running form and wasn't sure how it sounded when it was in working order......
I did some searches and found some articles, but not similar to this........I'm just wondering if the engine is a ticking time bomb or not? Or is anyone going through something similar......

any knowledgeable input would be appreciated...

thanks again for reading

[Huffer]

Piston slap. The older DOHC engines were built with bigger tolerances in the cylinder, and the pistons expand when they are hot to fill the gap.