Incredible Performance

thanks


I'll have to compare with my buddies boat and see how close it is.

BC,
I am not familar with Acme props, sorry.

The formula is correct, depending on how severs the cup.In some cases it can add to the pitch a extra pich. Ex a prop with a 15 cup pitch could be in theory a 16.
Stock 81 CC
13 X 13 X .009469 = 59.0340 -20% = 47 MPH
as I said you have to rate your hull, Bass boats or flatbottom are 10%. Rermember if you havea 123 tranny you subtract 23 % from the engine RPM.

bill is the formula correct? it seems to be off when I plug in the numbers it comes up 5 mph lower than what I would expect. What effect would cup have on the calculation?

The power valve is a key component of the power enrichment system of Holley
performance carburetors. The power enrichment system supplies additional
fuel to the main system during heavy load or full power situations. Holley
utilizes a vacuum operated power enrichment system and a selection of power
valves is available to "time" this system's operation to your
specific requirements.


Each Holley power valve is stamped with a number to indicate its vacuum
opening point. For example, the number "65" indicates that the power valve
will open when the engine vacuum drops to 6.5" Hg, or below.


An accurate vacuum gauge, such as Holley P/N 26-501, should be used when
determining the correct power valve to use.


A competition or race engine which has installed a long duration, high overlap
cam will have low manifold vacuum at idle speeds. If the vehicle has a
manual transmission, take the vacuum reading with the engine thoroughly
warmed up and at idle. If the vehicle is equipped with an automatic
transmission, take the vacuum reading with the engine thoroughly warmed
up and idling in gear. In either case, the power valve selected should have
a vacuum opening point about 2" Hg below the intake manifold
vacuum reading taken.

to figure speed.
RPM X prop pitch X .00946 then divide that by the prop diameter that gives you the speed at 100% then subtract at least 10 - 20 % it gives the speed. However most CC subtract 15 - 18%.

ex. 4800 rpm X 14 = 67200 X .00946 = 6357 minus 18% 521.26834 or 52 MPH.

I got mine in the water this week-end and tried out the new prop and did a little stopwatch test as well. It was a little tricky doing it myself with the cell phone, not enought hands to hold the trottle, phone and wheel all at once. But I timed mine a little differently as well, I went from a dead stop to top RPM (5K) or WOT or top speed what ever you want to call it and it took just under 8 seconds on last years gas as well. My speedo's never read over 40-45 mph and need adjusted. But I figure the first time I peg the speedo they'll have to be re-adjusted again anyway so I haven't done it.

SS201....about 6 months ago you helped me fix my carb problems...she's still running great.

Jim,

I recall you putting a HP cam in that rebuild...you may want to get a vacuum gauge and measure your engine vacuum from idle to Max RPM...dead starts with a skier etc and then talk to Holley before you buy.

I can't remember and maybe one of you guy's know, but under a hard start you may not want the secondaries flooding in more fuel to quickly so a lower # power valve may be better???

Isn't there some type of rule of thumb for the vacuum and RPM you want the power valve to unload more fuel???

If they are the blue holley gaskets you should be able to remove them without damage just be carefull. I pulled mine off about four or five times with no problem when I was change the jets last year.

Yes, the bowl and primary metering block has to come off, for a 4160 model. New gaskets are required.

Yah, I think you're right I described it backwards, and probably experienced the same symtoms as you guys before I sorted it out..

Gotta Ski, that sounds backwards, the higher your power valve number, the earlier (and more often) it opens and enriches your mixture. You have high vacuum when you are idleing or holding steady RPM, but when you open your throttle plates and put your engine under load, your vacuum drops and your power valve opens. If you have a low number power valve, it will not open unless you put a HUGE load on your engine (like wide-open-throttle from stop) and your vacuum drops WAY down. If your have a high number power valve, it will open more often and under less load.

for those that want to replace your prop overtons has a prop puller 99.99 its well worth it to have if you ever ding your prop or need to change a friends.

Jegs lists the trick kit on their website still. I got my kit from rex marine. I used holley's website to get the correct kit number first. I don't remember if the kit had the diaphram for the secondaries or not, my dad did the overhaul at his shop, he did have to get something that wasn't in the kit and maybe it was the diaphram. On me carb it doesn't have all of the interchangable cams for the accel pump and all of the other goodies that the double pumper models have. I have thought about getting one but what I have has worked well. I had to re-jet it after all of the engine mods I did so it wouldn't run lean. I just put on my new ACME prop and a shaft seal yesterday and should be able to take it for a spin this week-end to see if I got the right pitch and dia to bring back the RPM's to 5k-5.5k and I'm looking to top out around 65mph on smooth water. My buddy is bring up his bass boat this week-end so I can find out what the top end is. I killed him out of the hole last year and hope to still be able to with the new prop.