OUTLAW EAGLE MANUFACTURING

Arthur · Posted: Sun Aug 02, 2009 9:39 pm Post subject: Lost some RPM.....

Why is it that I put a new shaft in and a new SS impellor and I dropped 3-400 RPM? Is this normal with a heavier impellor?

shallow draft · Posted: Sun Aug 02, 2009 10:18 pm Post subject:

Your old impellor was likey slipping to some extent due to being somewhat worn and it is possable that your new impellor also has a more "aggressive" bite.
What motor and pump combination?
What RPM before and after?
Also if you are over impellored and the motor is pulled down and it has to labor to pull normal cruise speed the secondarys may open to often and fuel consumption will suffer!!!

Arthur · Posted: Mon Aug 03, 2009 8:14 am Post subject:

I have a crate 383/425HP......with a American turbine SD-309, and alway's ran a 'A' cut. Ever since I put this motor in a couple season's ago I could see 4800ish.....installed 3-4 alum since then and never lost any rev's. Now I decided to stop wasting money on the aluminum and put in a SS and I lost some RPM?? Although I haven't GPS'd it yet, it still feel's like the top end speed is there, just missing a few rev's. I also had to do the Panic/scramble and track down a shim kit for this impellor Sat morning.....never had to shim the aluminum one's.....why is this? Thanks for the help!

Xerophobic · Posted: Mon Aug 03, 2009 1:32 pm Post subject:

yes you will lose RPM because of a heavier SS impeller most def.

SouthIdahoGary · Joined: 15 Jun 2005 Posts: 295 Location: Wilder, ID, USA

Stainless is stronger and holds its shape better. Aluminum, under pressure, distorts and will deflect slightly. Consequently the "pitch" flattens slightly at the exit. Over time the constant working of the aluminum causes fatigue and cracking. (One of the reasons that stainless is recommended once horsepower goes over 400.)

Guest · Posted: Sat Aug 15, 2009 8:15 am Post subject:

with 425 hp you should spin the steel A at 4500 to 4600, depending on your air quality, I have a very similar set up, 421 sbc 455hp / 491 tq and spin steel A at 4650 Red Deer area, 4750 to 4800 in Ft Mac. 2500 ft elevation difference between the two cities. Ft. Mac has good air.

Arthur · Posted: Mon Aug 17, 2009 9:14 am Post subject:

Hines · Joined: 05 Jul 2005 Posts: 304 Location: Red Deer

Hey Bling Bling can you check on the elavation diff. between the two cities , my math is not good but i'am about 1740ft diff. but maybe i'am missing something very possible lol.Later.

Viking502 · Joined: 23 Nov 2007 Posts: 137 Location: Alberta Beach, AB

Lost only 50 rpzooms going from aluminum to SS.
with BB502 @ 540hp