[motormonkey]

Hi everyone, I would like to know if anybody here has tried c or d cut imp. and with what results. I looking for top end and launch experiances and what kind of bowl pressures did or want to see. Thanks.

 

[DuaneHTP]

You're going to have to give a lot more information than you did to get an intelligent answer to your question.

 

[unblown fool jet]

I run an f- in my southwind tunnel. its about the size of an inducer

thanks

 

[motormonkey]

Duane, What info do you want? Motor to make high rpm hp lower tq N/A. Looked at impellar chart and it looks like something in the upper imp ranges.thanks.

 

[motormonkey]

Will a c or d cut launch.I also wanted the loading info as a ballpark for that rpm.thanks

 

[DuaneHTP]

Are you running a small block or a big block? Ford or Chevy?
How much HP is it making, and at what RPM? Is it normally aspirated or blown?
Vee-Bottom or Tunnel boat? How much does it weigh?
What impeller are you runing now, and what rpm is it turning it?
Are you running an inducer? Are you after MPH or ET? (yeah I know, both). Which? Are you running an open or blocker loader?
Is the boat red or blue?
Just kidding on that one.

 

[W.O.T]

i have a b/c in my challenger with a 468bbc. it was cut down from a a/b. lost holeshot but upper rpms my stuff screams and hauls. an inducer would really help me out but im not a racer just like to go fast every once and a while when im running light on the river.

 

[motormonkey]

Duane, Want to try a small 400 chevy in the 550 range normaly aspirated. Its a v bottom 18' rogers with a set back pump,I dont know what the weight is but its not family rigged. It has a berkely with a "b" impellar, no inducer. Trying to get an idea. Thanks.

 

[motormonkey]

WOT, How much hole shot do youthink you lost and does it pick up in the mid range. Also do you find that you have to load the pump more for the rpm.

 

[SmokinLowriderSS]

Duane, Want to try a small 400 chevy in the 550 range normaly aspirated. Its a v bottom 18' rogers with a set back pump,I dont know what the weight is but its not family rigged. It has a berkely with a "b" impellar, no inducer. Trying to get an idea. Thanks.

All things being equal, you will loose some holeshot acceleration running a smaller impeller, and generally gain a few mph on the top end.
Since I pull tubes and skiers, I have never cut below an A, I need the holeshot, but then I am running a 454 also.
550HP on a Berk B should spin arround 5800+ rpm. Cut it to a C increase RPM to arround 6200+ A "D" I am estimating arround 6500-6600 RPM. I don't have a D on a chart handy.

You need to plan to get that HP at or before the RPM you expect to spin. You do need a decent torque curve.

 

[DuaneHTP]

I'd start with a "C" cut impeller with that motor.

 

[W.O.T]

WOT, How much hole shot do youthink you lost and does it pick up in the mid range. Also do you find that you have to load the pump more for the rpm.

The boat cavitates a little more on takeoff. Once im on plane it hauls ass. I have a Berkely Extreme loader. Im running a 468 BBC about 600 Hp.

 

[bp298]

All things being equal, you will loose some holeshot acceleration running a smaller impeller, and generally gain a few mph on the top end.

what is "all things being equal" supposed to mean? and how do you come to this conclusion if your total experience is with an A impeller???

 

[bp298]

The boat cavitates a little more on takeoff. Once im on plane it hauls ass. I have a Berkely Extreme loader. Im running a 468 BBC about 600 Hp.

what size nozzle insert do you run, and have you tried any other sizes?

 

[W.O.T]

i have never tried a nozzel insert before. should i? A shoe and rideplate are in my plans.

 

[motormonkey]

Bp, What size inserts have you had any luck with. Would you want to go bigger in nozle size.

 

[scott foxwell]

You're trying to get a definative answer to a general qestion that really can't be answered. I'm not near as knowledgable as some of these other guys, but it's my experience that there are too many variables to suggest or advise the best set up right off the bat. Impeller choice usually has to do with how much power your engine's making ans where it's making it. How well it works is all togeter another story. That usually has to do more with the boat than the impeller. In the end, it's all about a combination of many things, and deciding on what you want to accomplish. If you're starting with a small block, you're going to be limited, so depending on your goals, you'll have to be willing to accept certain compromises. There aren't a ton of small blocks out there, so not a ton of info. The white water guys may be able to help you more, but they're running with much more effecient hull and pump designs so their info may oir may not be useful. Bottom line is, you're going to have to do a lot of testing and data comparison...just like most anyone else trying to get more out of their set up. Trial and error.
For example: You can't automatically say a smaller impeller will give you less of a hole shot. That depends on how well the impeller loads, which has a lot to do with the bottom of the boat and hardware. The sooner the boat is moving forward, the sooner the impeller is being fed. The faster it moves forward, the better the loading. The more effecient the bottom of the boat is, and the entry into the pump is, the faster and more effeciently this all takes place, and it all happens at the same time.
In general, nozzle dia. can effect loading and hole shot. Smaller dia. nozzle will hold more water in the pump and allow loading and pressure to build quicker. Smaller nozzle will also tend to decrease top end slightly, due to reduced volume out of the pump. Larger nozzle the opposite...again, in general.

 

[motormonkey]

Steelcomp,originaly I was just trying to get peoples experiances of running small impellars. Ive always hear that they wont launch and their not effeciant. As far as the loading questions, I was fishing for info, like does it need to be loaded more, does the volume x rpm make up for any losses, larger nozzle for volume. Just data.

 

[scott foxwell]

Steelcomp,originaly I was just trying to get peoples experiances of running small impellars. Ive always hear that they wont launch and their not effeciant. As far as the loading questions, I was fishing for info, like does it need to be loaded more, does the volume x rpm make up for any losses, larger nozzle for volume. Just data.

I ran a BC with about 770 actual hp in a Bahner tunnel with extensive bottom work and a modified intake. If I flat footed it, it just went to the rev limiter. I never took time to sort it out, but there were many things I could have tried, including going to a B impeller. There are others who have a similar setup that can flat foot their deal and never look back. Similar power, similar hull design, etc. My BC was a race prepped stainless and turned 6400-6500. Boat has run 114mph (in 1/4) according to new owner with no changes. One thing I was considering was changing to a slightly smaller nozzle. I was losing at least 3-4 tenths, probably more, on the start.

 

[motormonkey]

Steelcomp, Thanks. Thats the kind of info that I was looking for. Ive been wanting to try a small chevy jet thing for a while and might persue it. Some time ago I remember a tunnell at the drags that was running a small 400 with squeeze and did good with it. I have some take off parts and could chuck something together for fun.