Best Carb Spacer 4 hole or Open?
 

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

How much benefit is realized just by getting the carb up and away from the heat of the engine?

Hatch Clearance

I have only twisted my 572's to 5700 so far in the boat, and they peaked at 6000 on the dyno with 9.95:1 compression. But I do agree tunnel rams are SWEEET and would love to have them! It would be very fun to do some back to back testing on your dyno :-) Originally we didn't plan on running both spacers but there was another one laying around so we tried it.

Almost same result here. Still a cheap 15-20hp!

Tunnel ram vs single plane 572 on smittys dyno? I like where this is going .

Jesel setup, why not throw in a cam swap while there too!

Maybe smitty could turn his dyno into the oso mythbuster. I would tune in for that show.

Just my .02, I did notice an overall difference (seat of pants) with the addition of the HVH Street Sweeper on my setup. Off idle stumble went away, smoother mid range power. Top end is crisp. I did back to back testing on the water one day between no spacer, mr. gasket $20 open spacer, and the HVH. The HVH performed well. I am running a Gen VI 454 .030 over, 088 Heads, +23 CC Domed Pistons, 9.6 CR, Stainless Marine full exhaust, Performer RPM, Holley DP, Comp Cams cam and valvetrain.

I wanted to do a test on the difference between SS and standard spacers.
Used 1" 4 hole spacers on my 540 builds super sucker on one, plain 4 hole on the other. On the dyno SS made about 6hp/12ft/lbs, in the boat shows up as 50-75rpm.
Not a huge difference but it's there.