A-A2 impeller differences what are they???
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A-A2 impeller differences what are they???

  1. #1
    Senior Member matt1840's Avatar
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    Default A-A2 impeller differences what are they???

    I purchesed an impeller under the impression it was an A cut and when i recieved it today A2 is stamped on the impeller... Im running a built olds 455 and worried about rpms... What kind of difference is there between the A and A2 cut??? example holeshots and top speeds and rpm.....?

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    Super Moderator HammerDown's Avatar
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    The difference could be a couple hundred RPM's and mph.
    I run a full Aggressor A which is equal to a 2A Berk etc.
    My hole shot and midrange pull is strong but, I would be going a tad faster at the top via more engine rpm's if the impeller was a (A).
    However, I like to cruise at 28-3000 rpm and with a smaller cut imp I'd be giving up a bit on that side.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Senior Member matt1840's Avatar
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    is your boat pretty responsive in the mid rpm range??? i wanted the most top speed possible out my boat and i was 65 with my A while cavitating badly... My holeshot should be better with the A2 then huh at the cost of a few mph

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    Resident Ford Nut Sleeper CP's Avatar
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    You may want to check this out. Read the entire thread:

    http://www.performanceboats.com//sho...Impeller+chart

    How high did it rev and how high do you want to rev it ?

    Sleeper CP

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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by matt1840 View Post
    is your boat pretty responsive in the mid rpm range??? i wanted the most top speed possible out my boat and i was 65 with my A while cavitating badly... My holeshot should be better with the A2 then huh at the cost of a few mph
    "midrange" by boat hits hard and I'm sure the Aggressor has something to do with it....but keep in mind the loader, shoe etc and general set up is helping everything.
    Cavitating "badly" badly sounds like you're starving the pump for water.

    *One other thing you must be cautious of is, the 455 is known for holding oil up in the heads and running the lower end/pump dry. There are some other things about a "stock" 455 you may want to read up on before you go spinning the snot out of it.
    My brother had one...he put external oil drains in the back of the heads and beat the life out of his...he couldn't kill it. 455 is a torque strong engine, it just may need some simple modifications before you'll want to run it hard and long at upper rpm's.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Senior Member matt1840's Avatar
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    Quote Originally Posted by HammerDown View Post
    "midrange" by boat hits hard and I'm sure the Aggressor has something to do with it....but keep in mind the loader, shoe etc and general set up is helping everything.
    Cavitating "badly" badly sounds like you're starving the pump for water.

    *One other thing you must be cautious of is, the 455 is known for holding oil up in the heads and running the lower end/pump dry. There are some other things about a "stock" 455 you may want to read up on before you go spinning the snot out of it.
    My brother had one...he put external oil drains in the back of the heads and beat the life out of his...he couldn't kill it. 455 is a torque strong engine, it just may need some simple modifications before you'll want to run it hard and long at upper rpm's.
    My 455 is higly modified and ive done everything possible to the motor including the head drainbacks to help the oiling problems.. Its a nasty build and should be up near the high 400's hp range.. Ill tryin this impeller out and see how i like it. The A impeller had me in the 5200 range at top speed with a SHIT holeshot. The impeller looked like it had cobble stones ran through it. Fully rebuilt pump and motor id like to see 70 considering i had 65 before. But if this impeller is gonna keep me in the 46-4800 range ill glady miss a few mph for reliablilty.

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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by matt1840 View Post
    My 455 is higly modified and ive done everything possible to the motor including the head drainbacks to help the oiling problems.. Its a nasty build and should be up near the high 400's hp range.. Ill tryin this impeller out and see how i like it. The A impeller had me in the 5200 range at top speed with a SHIT holeshot. The impeller looked like it had cobble stones ran through it. Fully rebuilt pump and motor id like to see 70 considering i had 65 before. But if this impeller is gonna keep me in the 46-4800 range ill glady miss a few mph for reliablilty.
    A chewed up Impeller will kill it's bite and efficiency for sure.
    I would try the 2A and the good thing is (if) you're not digging it you can always cut it down.
    Record RPM/MPH readings at different areas.
    Keep us posted of the results.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Senior Member matt1840's Avatar
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    Quote Originally Posted by HammerDown View Post
    A chewed up Impeller will kill it's bite and efficiency for sure.
    I would try the 2A and the good thing is (if) you're not digging it you can always cut it down.
    Record RPM/MPH readings at different areas.
    Keep us posted of the results.
    im guessing it can be turned down to an A??
    Last edited by HammerDown; 05-23-2008 at 04:34 PM.

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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by matt1840 View Post
    im guessing it can be turned down to an A??
    It can be cut down to a "D" if you wanted...but you DON'T want that!
    They cut material off the back of the blades thus making them shorter.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Senior Member matt1840's Avatar
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    Quote Originally Posted by HammerDown View Post
    It can be cut down to a "D" if you wanted...but you DON'T want that!
    They cut material off the back of the blades thus making them shorter.

    Now if they are cut down are they restamped???

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    smoknoldy smoknoldy's Avatar
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    Default oldsmobile's and Impellars

    A Built Olds should run great on a "A" cut Impeller. A built Oldsmobile should run 5200-5400 rpm on an "A" cut Berkley or similar like American Turbine. When you Bought the Impeller did you measure it to see if it was a "A2" or an "A". It might have been cut down! There's other issues here does the bowl have a stuffer, is grate a speed grate that loads the Impeller, etc?

    Engine wise Mellings High flow oil pump with the Mondello relief spring kit, and oil galley restrictor kit. The Cam shaft oil galley plug that oils you timing chain needs to be soldered up. With roller rockers I would not be afraid of 5400 rpm just watch you oil pressure, oil pressure tells you everything. Joe Mondello also has a chromemoly strap kit for your Main Bearing Caps also! Joe Mondello is in Paso Robles, Ca.

    Smoknoldy - 468 inch Oldsmopile turns 6100 rpm with a "B" cut American turbine Hi Helix in a Berkley Pump. The Boat Placecraft Tunnel!

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    RAT PATROL rich s's Avatar
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    Default cut impeller

    Quote Originally Posted by matt1840 View Post
    Now if they are cut down are they restamped???
    not always. measure it and it will tell you exacly what you have.
    quote from (seloc publications marine jet drive) book
    berkely impeller specification
    berk (a2) large dia. 9" small dia. 7 7/16" machined angle 57.5
    berk (a) large dia. 9" small dia 7 1/4 " machined angle 60
    hope this helps
    Last edited by rich s; 05-23-2008 at 07:38 PM. Reason: more info

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    Senior Member matt1840's Avatar
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    Quote Originally Posted by rich s View Post
    not always. measure it and it will tell you exacly what you have.
    quote from (seloc publications marine jet drive) book
    berkely impeller specification
    berk (a2) large dia. 9" small dia. 7 7/16" machined angle 57.5
    berk (a) large dia. 9" small dia 7 1/4 " machined angle 60
    hope this helps
    How do i go about measuring??? im guessing a dial caliper??? and as for the angle im guessing its the angle from the flat surface of the small diameter to the large diameter across the fins??? Shit id reall like to know what i have haha either way i am sending it to HTP to have a ultimate wear ring made to fit and a rebuild kit maybe they can double check the cut for me.. I had a rebuild kit from Cp but htp is much cheaper



    Last edited by matt1840; 05-23-2008 at 08:24 PM.

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Duane should have no trouble telling you what cut it is and marking it as such if it isn't already.

    If the impeller is all rough/beat-up looking/feeling, it needs some smoothing. All that "damage" will just tend to increase cavitation problems, which it sounds like you have plenty of as is.

    I run an Aggressor B cut, in a heavy old Taylor SS, her holeshot is very strong, and no cavitation problems UNLESS I flat-foot it from idle, which causes me to blow the pump dry.
    5400 RPM off the nitrous.
    I love the UWR setup. Running my seccond. First ran tight for 16 years, till I changed impellers, changed UWR's with the rebuild.
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