I'm thinking about adding HVH super sucker carb spacers but not sure which one, open or 4 hole? I have 496s with 850 Quick Fuel carbs sitting on Victor jr intakes,305 AFR heads and Bob M cams. I'm just not sure which one would work best for set up.

you'll never notice the difference in your boat.I'd go w/ the 4 hole if your buying one.

it really depends on what the engine wants. so just choose you wont notice the difference either way. id go with a phenolic material vs the metal just to keep the carb cooler.

I tested with a very similar setup. The engine did pick up power with the spacers. There was no difference from open to 4 hole, I checked both. I made about 15 hp and 10 lbs more with a 2 in spacer over no spacer.

No difference hp wise from pro comp spacer to hvh other than price tag. HRE makes the best spacers if your trying to get everything out of the combination however as said in a marine application it's not really worth the added expense... Sad to say but chinese is the way to go.

Some like both. 1" 4 hole with another 1" open sandwiched together. Can be trail and error. Given your close to bck's build I'd probably use what he did to his for starters. Then again two identacle engines may like something entirely different.

4 hole improves carb signal; open adds plenum volume. I would agree with 4 hole on your engine.

We made the best power with a 4 hole stacked on top of an open.

Any reason you didnt go with a tunnel ram vs aggressive intake w spacers? On paper (ie dyno simulations) the tunnel rams yield signifigant hp gains on these bigger motors when winding them up like yours with compression in the 10+range?

whichever you try, really need to ck AFR with a 02 after, they change the signal to carb and therefore re-jetting may be needed