The stock 900sc carbs, 1050 doms. The only way it works is at that high rpm the amount of fuel being pulled from the carb can offset the pressure. Your right about the cavitation issuse. With the electric pumps off I can watch the fuel pressure gauge begin to drop and it'll start to flutter a bit. Only on hard wot pulls. Other than that no issuses.

Fuel psi with carbs is a funny thing. We all panic when we see fuel psi fall below say 7psi. What we are looking for is volume of fuel though. For example. 7psi of fuel psi thru a standard .097 Will not move as much fuel as say 5psi thru a .130 Needle and seat. Also, too much fuel psi can cause aeration issues within the fuel bowls of the carb.

As far as the mercury 900sc, I know of more than a few boats equipped with them ran extremely well as far as power goes and long high speed poker run scenerios. Back in the day when a guy was dropping ridiculous money to have the 900sc dry sump 6 package, he wouldn't be very happy if on his first wot boat ride the engines torched holes in the pistons from lack of fuel when running his brand new 42 Fountain at 115mph in a poker run.

The six valve mechanical pumps been around a long time. Many have made big power with them on gas, alky, etc. Baker, clay smith, and c&s carbs stock these pumps . I know Roger at c&s has made some big power with these pumps as well. It was very common back in the day to see these pumps on big marine roots blown engines from Gellner, zul, teague, etc. The coolest thing about them was the simplicity and the price.

I am very happy with my Clay Smith pump. I have it plumed with a bypass regulator back to the tank with 1/2 " lines. It holds 8lbs. of pressure and does not drop off. The only problem is the wear on the push rod. I think I will try the Crane push rod that Bob talked about.

Yes they do and it is the pushrod that Clay Smith recommends, called em this morning, ordered 2 , its made out of Chromoly with a hollow center i.e. light weight.

Specifically recommended to run with a billet cam? Might have to check it out, what was the cost?

This thread prompted me to do some searching. Plenty of people having issues with bronze tipped push rods, but hard to determine if those failures could have been from some other condition contributing to it. Also did a search trying to find long term results with the composite rod, but not much there. Saw several that reported good results, but have not seen anyone posting pictures of one that was run with a high pressure pump and a billet cam over thousands of miles. Saw someone saying that they had "heard of" several failures of the composite rods, but he did not post any pictures or specific instances.

The last thing I want to do is go through the trouble of switching over to a mechanical pump only to have my bronze tip pushrod mushroom out and strand me on the water. Worse than that would be for it to get stuck in the block and then have to pull the engine to get it out. :eek:

Brain Teazer: Has anyone ever thought if the cam manufacturers use the exact same opening and closing ramps, seat, .050", .100", .200" and etc duration figures + net lift on their fuel pump lobes.

LOL.....but makes you wonder !

Edit in: maybe these should be Cam Doctor'd and Spintron'd too. Double LOL.

ICD, is it this one?

http://www.allensfasteners.com/detai...ID=ARP135-8701

PN ARP135-8701

The site selling it has a specific recommendation AGAINST using it with a roller cam.

It would be nice if they made a roller tip rod for a big block like they did for a small block.

I agree. I looked at the one for small blocks, and it makes use of the bolt hole on the front of the block (that is used to hold the pushrod in place for pump installation) to hold a guide. I always wondered why Chevrolet didn't do the same thing for the big block engines. Someone who knows what they are doing could probably drill and tap a block to retrofit.

Bud,

The Crane number is the correct part for and 8620/9310 billet Roller camshaft. It is all a matter of core material compatibility, which varies greatly between, cast, SADI, steel, and steel billet.

Please note the disclaimer at the bottom of both pages. The difference in getting it right or wrong in regards to materials compatibility is; best case an expensive parts failure; worst case significant collateral damage.

Bob