For those curious about simple bolt ons for your engine, there is a good article in CHP about various bolt on upgrades for BB & SB chevys, here are some dyno results they posted.....


Electric Water Recirc Pump: +23hp, 335hp to 358hp on a 383ci.
Underdrive pulleys & serp belt: +25hp, 335 to 360hp on a 383ci
Exhaust Headers: +8hp, 473hp to 481hp on a stock LS7
Roller Rocker upgrade: +22hp, 344 to 366 hp on a 350ci
K&N air filter: -1hp, 583hp to 582hp on a 406ci
Nitrous kit: +211hp, 602 to 813hp on a 588ci
Blower: +116hp, 390 to 506 hp on a 355ci.


So the smallest, simplest things like electric water pump, pulleys, and roller rockers added decent gains, 20+hp each, while exhaust did very little. I am sure exhaust would add more in a marine setup. The K&N did nothing of course. Blowers and nitrous for big time gains. Others that did little; carb swap +10hp, intake change +11, mass airflow sensor +12, new chip +2. They did heads too, factory iron to Holley aluminum, with +68hp (307 to 375hp on a 355ci) but that would vary so much between apps. Nitrous +211hp!! Wow, (but for how long until the meltdown) Great article.

Several years ago while we were dyno testing one of my 540's we were doing dyno pulls with an open carb (no spark arrestor/air filter, etc) then added a K&N air filter and picked up 3+hp------that's not much, but I actually was expecting that we would LOSE at least 5hp!!! I really thought nothing could/would flow better than an open carb and was surprised to find out the opposite.

Anyone ever tried an electric water recirc pump?? Lots on bolt ons talked about here often but not electric water recirculators. Small pulleys??Never heard of those here either.

Lots of auto-related stuff not talked about in the marine world.
That exhaust data is from a LS7; probably one of the best "OEM production" exhaust manifolds as stock.
The water pump issue gets fixed with a crossover. What would be more intersting is to consider an electric power steering pump. Get it off the engine and run it at a constant 1500-2000rpm.
"underdrive" pulleys are typically a smaller crank pulley, and/or larger alt/h2o pump pullies. Probably not a good thing for idle-speed zones.
Seeing as how most of these results are on small blocks, I'd expect less improvement on a big block because of engine torque.

friction and drag.... they never sleep

KAAMA:

Have seen this many times...yes, the filter adds resistance, but a well designed air filter base will reduce the entry loss of the bare carb (or centrifugal compressor inlet) so no net loss and sometimes a gain depending on how bad the entry loss was to begin with.

I would think an electric recirc pump would not change the cooling parameters like a crossover does and would therefore be a better answer. I think I am most impressed by the roller rocker switch. Simple, effective and a superior valvetrain in the end.

The numbers don't lie, but keep in mind that the roller rockers really make their living (gains) at high RPM's, 6-7K and up and on real big cams. The gains won't be as big in a 5-6K motor. If I had to guess, those figures were from a higher RPM than we will see. I still like' em though.

Makes sense. Before was 344hp at 5200 and 366hp at 5400 after on a ZZ4 350ci with 10:1CR and a "mild cam" whatever that means. Probably hotter than most marine cams.

My understanding is that while the friction reduction itself gains some power, the "real" benefit of a good full roller is the accuracy/response of the valve action due to both the precision and reduction in friction.