Nice numbers!!!! I would like to see the what the AFR's are. They definitely don't need 1100cfm carbs. A well tuned 850cfm should be plenty.
I would prop for around 5600WOT. Fully dressed in the boat with wet exhaust they will prob be in 580-600hp range.

100% agree! I’m leaving them alone and just gonna go enjoy this dumb thing for once lol!

Are those exhaust risers flipped? Looks like the mounts for your shifter quadrants and throttles should be towards the insides.

Probably should be but these weren’t for this boat originally and they aren’t used for my set up. Pulled these risers out of some old formula

What do the numbers below 4800 look like?

+1 for the red bilge. Doesn't show the blood from the fight and the clamps!

Those ProMaxx heads look like the 317s? Raised exh ports 3/8". These flow really well on the exh.

Griff is spot on. A worked over 850 would be your best bet if you wanted more. But the 800s are working for you, and can get worked over a bit to help some flow if you want.

Interesting to see the correction factor for the dyno runs.

Nice to see where the cam peaks and how it runs on a 460. Also good to see how the 2.25 or 2.30 In valves breathe on the 4.280" bore.

I may go NA if this works out for you.

It's going to feel pretty good installing these mills into the Cig.

Looking forward to some photos on the water and hearing how she runs.

Thank you for the thread and updates. Dyno sheets of good heads etc with cam for marine are a great to see real world engine combos.

yes sir 317’s promaxxs my builder has had absolute great success with them and swears by them and even runs them on his personal builds / drag cars etc.

he has seen numbers on a flow machine up close to 400 according to him right out of the box.

im feeling pretty good about these hunks of iron for now considering where I started. As for the carbs and such probably just gonna leave them alone and let them ride as they will do be mine for my Situation and lake I believe.


soon as I get the time I’ll get the correction factor and i will post here asap!


I believe they are going to be fun engines and have good manners for my old cafe. Trying to stay “ 80’s” as I can for the most part. It was kinda sad putting all the accessories on and not getting to see my cool to me aluminum heads hardly anymore lol!

I’ll be updating a lot and hope to have one engine in tomorrow or Thursday night we will see! Fingers crossed!

thank you for the kind words as well!

Just want to say that my asking was not a dig on your builds, not in the least! They just made a ton of power for the size and rpm range.

Glad you’re getting her buttoned up!

Eric Weingartner YT Channel has some great vids on the 317 Promaxx heads. He's a head porter and flows them etc. He does dyno testing and puts the 290 and 317 head to head. Pun intended.

540 dyno mule the 317s were getting more power down low than the 290s @ WOT. The caveat is he runs drag sized cams.