Please.
There are more center console owners here now than anything.
Also, read these performance threads, most say to leave engines stock.

Lol.
#smallboatsgetnorespect
#itsasmallblocknation
#osohasgonewayofcenterconsonsolesonly

OP - the comp cam XM270HR has been used in more 350/383 builds than any other. Many 383’s have used next bigger xM274hr too . Both usually requires longer inner pipe so that water mixes with exhaust further back. Do a search and you’ll see several people who explain how to do mod to stock and aftmkt exhaust.

Thanks everyone for the replies. I got the Scat 9000 series rotating assembly with 6" rods and 19cc dish hypereutectic pistons. I am only going for 400-450 HP and TQ so my machine shop said this is perfect and I did not need forged.
I am pretty sure I have decided on the 270 cam. Now I just have to figure out the heads. Shooting for around 76cc to keep me around 9 to 1. Again thanks for the help and suggestions.

I have searched and searched for longer inner pipes and can not seem to find it. I went to advanced search and searched just Do It yourself and technical. Mind sharing link if you know off hand?

You may want to check this out, https://diamondracing.net/p-10-compr...alculator.html

Do a search under member Ryan00TJ

Pretty sure he had done it and coached many over the years when he ran nesr 80mph single small block boat.

I am waiting for rotating assembly to get it to the machine shop. Then once he is finished he will suggest the heads volumes and whatnot. I am just trying to do my research and learn as this is my first engine build ever.

I look forward to seeing the results of this, the first build is always the most tedious with a lot of options and unknowns. I can't give any recommendations on the exact components but do keep in mind two things that I have learned over the years, be sure to use marine components and marine builder advice - those two things are priceless if you want a turn-key engine when you're done. Other options are marine crate engines which can net you turn key reliability, purpose built, and warranties for nearly the same overall cost. You may want to start looking at props as well with the increase in power.

Good Luck and Welcome to OSO!

i like a lot of your design but I do have a suggestion. I'd recommend bigger intake runners. I'd do 195s to 215s. Your boat will take off fine even with the lessened low end of the big runner heads. it's a lighter 20 footer. A 383 will spin up so far you won't be able to keep it wide open. You are going to have to learn to drive it at scary fast speeds
I think you ought to look into external hydraulic steering.

I'll 2nd or 3rd that XM 270 HR cam as it is very nice grind indeed. It's good for avoiding reversion, has lots of torque and idles extremely well. Go with the roller, you won't be sorry. I've used it in a small block stroker 383 and big block stroker 496 with great results. The lifters get a little pricey but you can't go wrong. If you need good cam recommendations ask for Gabby at Comp and he'll take care of you.