I am about to begin building a 408 to replace my stocker which has a spun bearing. I want to reuse my heads that I haveon this engine now. They are a custom ported by one of my buddies. They are 5.3's with 2.02"/1.57" and have only 207 cc runners and flow 312.2cfm int. 255.4cfm exh. My question is how much if any do you think will be left on the table by using these heads. They will be re-decked to bump up the compression a bit. We don't know what cam we will be running that will be decided later. Thanks for the input.

Drew

 

Looks like we are in the same boat my friend. Doesn't the 408 need a bigger bore head though? I'm not sure but I have a pair of 243's I would like to get ported for a 408. I bought these heads to go on my LS1 but I too have spun a bearing and probably would be doing a 408 buildup.

Good Luck to you bro!

Check my thread: Which Heads for a 408?

 

I believe it does need to be machined being that it's going on a larger bore (.130" larger).

 

From what I understand there will be a bit of bore shrouding. But I talked to my buddy yesterday and he said it would be negligable.

 

You need to make sure you get 4.060 gaskets in the appropriate thickness.