who runs b impellers.

[77charger]

Thinkin of going to a b cut was wondering what i will expect from going to an a to a b.Engine is a bbf 429 248@.50 cam 590 lift 11-1comp,750 holley,headers,performerrpm intake,will be lorting the heads soon,Currentlyruns 68mph@4800rpm.But i know the motor can rev more would like to turn around 52-5500 and get a speed increase.

[SPECTRABRENT]

I would not go to a B right away. Cut your impeller to an A-B first than see if you are satisfied. Once you cut the impeller to a B its all over. You will loose a little out of the hole, but gain it in mph.
I prefer an A impeller because you can cruise with less RPMs.
Brent
[This message has been edited by SPECTRABRENT (edited October 13, 2001).]

[LVjetboy]

You didn't mention your pump, but say it's a Berkeley. Let's see what the Jet Performance Calculator says http://free.***boat.net/ubb/smile.gif
JPC (http://www.angelfire.com/extreme2/dragnjet/JPC.xls)
First, your data point of 4800 on an "a" shows total hp of 349. Assume you cut to "b" and got no increase in hp (engine was already near top of hp curve) Your max rpm would increase to 5050...and you'd see no change in top speed. However, for your apparently well-built 429, you may be short of the peak hp curve at 4800. So any increase in rpm may give you more total hp, which in turn would spin the pump higher, until the engine/pump meet their match point. Of course you'd have to know your engine's power curve between 4800 and 5200 to know where this point is for sure. But let's consider this healthy Ford 390 with a Performer RPM intake:
Healthy 390 (http://www.edelbrock.com/automotive/7105graph.html)
The dyno shows a gain of about 20-30 hp with a 400 rpm increase. Back to the JPC, setting the rpms to 5200 on a "b" shows near 30 hp increase (to 380) is required to spin this number...a match.
Finally, entering the added 30 hp to your data point, the JPC predicts 71 mph as your new top speed.
jer
[This message has been edited by LVjetboy (edited October 14, 2001).]
[This message has been edited by LVjetboy (edited October 15, 2001).]

[77charger]

the pump is american turbine.i'm pretty sure im not at peak i would guess my peak to be around 52-5500 with my set up.

[LVjetboy]

For the AT, I got a 29 hp increase needed to turn the "B" at 5200 rpm with your engine (given you can turn the "A" at 4800 right now.) So for these impellers, the AT and Berk. manufacturers curves are very similar. This should be good for 2-3 mph in top speed assuming you're short of the peak.
Cheers!
jer

[77charger]

so let me get this right if i go to a b and dont make anymore hp then i will not gain speed just rpm(5050 but if there is more hp gained at a higher rpm then my speed will increase as my rpm also.poss higher than the 5050.

[LVjetboy]

Yep. Ultmately, you need more hp to push more thrust, not just the change in impeller rpm that comes from going smaller. More hp = more work on the flow. And if your engine specs allow you to climb the hp curve with a smaller impeller, how your boat reacts to that extra thrust will depend on the hull, weight and pump setup. The top speed of 71 at 5200 rpm is just my best guess at this point, not knowing anything else about your setup. Wish I had a dyno curve for your engine, but I couldn't find one and I don't have the DTD...yet http://free.***boat.net/ubb/smile.gif However, considering where your rpm/speed is now, those numbers will be typical for adding 30 hp to a 18-19 foot jet with no hook.
jer

[77charger]

thanks for the info i ran the boat at those readings with the baffles and normal rec weekend weight also(cooler gas radio etc)wasnt a get the highest number possible and i know i can get 100-150 more rpm w/o baffles.boat is a 19'too hope this helps.I think im going to try the b or maybe start out with an a-b to see how that works.any more info would be appreciated.thanks.

[FoMoCo]

I am running a 429 BBF in my boat! its someware in the area of 500HP at 5500+ rpm's. I had MPD do a stage 1.5 on my pump and cut my impeller to a b+ which is not quite a B. its supposed to turn close to 5500 rpms with 500HP. mY BOAT IS A 1977 Kachina 18.5ft with a Berk JG pump. SO for its only spun 5200rpms with a Lean problem and not legged out so I think it will spin to 5500 when its dialed in! I would switch to a B if I were you because the 429 BBF makes more power on the top-end & 4800 just is not enough!

[custom-cruiser]

LVJetboy
If a guy was turning an AT pump with a "AA" 5500rpm at 64.9 mph how much hp is that on the JPC and what would it take to do 70mph(probably a different hull http://free.***boat.net/ubb/biggrin.gif)
Thanx http://free.***boat.net/ubb/biggrin.gif
http://wsphotofews.excite.com/036/T2/Eb/Qf/QC20183.jpg
Thanks LV yah she's healthy!
[This message has been edited by custom-cruiser (edited October 15, 2001).]
[This message has been edited by custom-cruiser (edited October 15, 2001).]

[LVjetboy]

Wow, that must be a heavy boat! For an AT pump turning 5500 on an AA, JPC says 683 hp. That's assuming the pump isn't excessively worn or cavitating. The reason the AT AA takes more power than a Berkeley AA (for example) is the AT's 3/32 larger on the outer diameter. So you must have one healthy engine!
If you're considering pushing 70 on that hull, JPC says 757 hp. So switching to a different hull may be a good thing if that's your goal. Hope this helps.
jer

[LVjetboy]

Nice! Put that sucker in a light-weight tunnel and you're mid 90's...knocking on 100. Hmmmmm....can I borrow it? http://free.***boat.net/ubb/smile.gif
jer

[superdave013]

Originally posted by LVjetboy:
Nice! Put that sucker in a light-weight tunnel and you're mid 90's...knocking on 100. Hmmmmm....can I borrow it? http://free.***boat.net/ubb/smile.gif
jer
Put this one in your light weight tunnel and your way over 100. And no, you can't borrow it.
http://wsphotofews.excite.com/033/RY/Lh/fP/U273984.jpg

[custom-cruiser]

Fuel injection,Super Chiller,Aluminum Heads MMMMMMM!!! You got my mouth watering.... http://free.***boat.net/ubb/biggrin.gif
[This message has been edited by custom-cruiser (edited October 16, 2001).]

[superdave013]

With a big a$$ nitrous system!

[superdave013]

custom-cruiser, I have a few bottom pullies that are drilled three hole like yours. They are also resesed in the back to fit the balancer. I know I have a 63 tooth and am sure I have a few others. I'll sell them for a good price if you might need them.

[custom-cruiser]

Superdave013,
Sounds good. Figure out what you have and email the list. Right now im running 59 tooth top and 54 bottom so well under driven. I'm going to break down and put the squeeze on the old piggy bank and pop for a superchiller here soon so i'll be playn' with different boost.Currently 5lbs I think if I go 1-1 it would be about 10lbs. 70? maybe 80!!LOL http://free.***boat.net/ubb/biggrin.gif

[superdave013]

Don't go one to one. It can set up some harmonics between the blower and crank. You should go a little over or a little under.

[LVjetboy]

SuperDave...do you have a dyno sheet on that monster and have you run it in your boat? Just curious.
jer

[superdave013]

Engine never was on the dyno. Ran 127 mph @ 8.00's in my old flatbottom. Never made a pass on nitrous at the races but at the lake it did pick up a bunch. It was only 461".