406 Build!

[70c10guy]

Hi guys, I have a 400 small block that I acquired on a per day “trade.”

It’s at the machine shop as of now. Having him disassemble the short block and hot tank it.

I am getting the short block built for my boat. It’s a 17’ ski boat.

Here’s the story, I couldn’t pass up a deal on a set of NEW vortec heads. So I bought them. Unfortunately the chamber size is a bit on the small end for the 400.

I’m wanting to get the short block built to a 406. I found pistons on summit that have a 14cc dish to them. With the block being 0 decked, .040 head gaskets, and the vortec heads, my compression ratio is at around 10.6:1

Wanted to stay around 9.5-10:1 but I can’t find pistons that fit my application. I will be using the stock rods and I mostly see piston applications for the 5.7 rods.

So my question to everyone here is will I be safe with a 10.6:1 compression in the boat?

Does anyone have any experience using a bigger dish piston for a 5.565 rod? (More than 14cc dish, if so please Inform me)

Don’t really want to get other heads as well.

The boat will see a max rpm of possibly 5000? Not all day long though. Just occasional. Hoping to hear from someone here as this has been bugging me.. I was just going to bite the bullet and keep my timing on the conservative side but I had to ask!!! Thanks everyone in advance.