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What impeller

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    Default What impeller

    I heard all this talk about What impeller so i thought i would ask.
    I have a 16ft semi v (with gas tank in the bow) with a 468. the motor is stock crank, stock rods 4 bolt main. the heads are stock with a 500 lift cam with a lobe center of 108. Dual plane intake with a 750 dual feed vac sec. over the tran water cooled headers. The pump i just got back from CP PERFORMANCE. they put in a AA impeller. after all that took the book out and only turned 4000-4100 at 58mph on gps. so should I change my impeller or what.

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    Sit N' Spin Jetaholic's Avatar
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    Quote Originally Posted by jetboatkid View Post
    I heard all this talk about What impeller so i thought i would ask.
    I have a 16ft semi v (with gas tank in the bow) with a 468. the motor is stock crank, stock rods 4 bolt main. the heads are stock with a 500 lift cam with a lobe center of 108. Dual plane intake with a 750 dual feed vac sec. over the tran water cooled headers. The pump i just got back from CP PERFORMANCE. they put in a AA impeller. after all that took the book out and only turned 4000-4100 at 58mph on gps. so should I change my impeller or what.
    AA is too big of an impeller for your motor combo. However, instead of replacing it, you can get the AA that you have machined down. I'd get it cut down to an AB or a B cut for your combo.



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    Same here

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    Quote Originally Posted by Jetaholic View Post
    AA is too big of an impeller for your motor combo. However, instead of replacing it, you can get the AA that you have machined down. I'd get it cut down to an AB or a B cut for your combo.
    Would my Rpm's go out the roof or just a little higher

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    Resident Ford Nut Sleeper CP's Avatar
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    Quote Originally Posted by jetboatkid View Post
    Would my Rpm's go out the roof or just a little higher
    This might help:



    Plot where it now turns with the AA and go from there.

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    Quote Originally Posted by jetboatkid View Post
    Would my Rpm's go out the roof or just a little higher
    I would expect a 200-400 RPM increase. The fact that your motor is only turning an AA to 4100 tells me that you're only making about 260hp at 4100 RPM.

    Ignition timing is one thing I'd look into to milk some more power out of that mill. It should be hitting about 34-36* total advance and it should be at full advance by 3000 RPM.

    I would also look into which stock heads you have. If they're the small oval port type (i.e. "peanut ports"), I would consider upgrading to a set of large oval port heads like an '049' or a '781' casting (those are the last 3 numbers of the casting number). If they're the small oval port heads, those are considered a "truck" head and are better suited for a low RPM torque motor. Above 4500 they don't breathe very well, whereas the large oval port heads are better for mid-range RPM, which is where a jet runs at.

    Pull your valve covers off and get the casting number from them. Post it up and I'll look it up to see what you currently have.
    Last edited by Jetaholic; 06-30-2009 at 10:18 PM.



    Quote Originally Posted by HammerDown
    Kendall L-427 Super Blu...extreme-pressure (ep) lithium complex keeps my thrusting balls happy
    Quote Originally Posted by back2k5 View Post
    Well I am putting in a nice stereo system in the Carrera...maybe Ill put on some rap and turn the scoop sideways

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    Senior Member jetboatperformance's Avatar
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    Take it out (the Impeller) (call if you need tech help ) I'll cut it for free (you pay the frieght ) , Little boat, big power can't really understand why the AA ?? but then different concepts , differerent ideas and opinions , Where this motor make power ?(I'm guessin' 5k whats the actual Cam ##s whats the static compresion ratio and what are you doing with the boat ? Tom

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    That's a pretty mild motor. I don't think you are going to gain alot cutting down the imp. One might get a few more mph. at the cost of fuel mileage. It comes down to how your planning on using it.

    My only concern at this point would be if I was lugging the motor down which may create some issues. Maybe someone could add to that thought. I think 4100 is just above that threshold though.
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    Quote Originally Posted by jetboatperformance View Post
    Take it out (the Impeller) (call if you need tech help ) I'll cut it for free (you pay the frieght ) , Little boat, big power can't really understand why the AA ?? but then different concepts , differerent ideas and opinions , Where this motor make power ?(I'm guessin' 5k whats the actual Cam ##s whats the static compresion ratio and what are you doing with the boat ? Tom
    Tom, i gave the motor to a guy here in the city (Oklahoma) to rebuild. told him to put hypertech pistons .060 over and had a 685 lift cam to put in it. was told the motor would be around 10.5 to 1. after i got the motor back it only ran for about 30 min while breckin in. Had three lobes go down. took back and he told me it was my falt. so i had to put new cam in and new brg in the whole motor. after this time i pulled the vales covers off and checked the vales and all was way to tight. so now i ony have a 500 lift cam and a 10.5 to 1 motor. I would like the motor to turn 5k at lease.
    Last edited by jetboatkid; 07-01-2009 at 07:05 PM.

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    Quote Originally Posted by Jetaholic View Post
    I would expect a 200-400 RPM increase. The fact that your motor is only turning an AA to 4100 tells me that you're only making about 260hp at 4100 RPM.

    Ignition timing is one thing I'd look into to milk some more power out of that mill. It should be hitting about 34-36* total advance and it should be at full advance by 3000 RPM.

    I would also look into which stock heads you have. If they're the small oval port type (i.e. "peanut ports"), I would consider upgrading to a set of large oval port heads like an '049' or a '781' casting (those are the last 3 numbers of the casting number). If they're the small oval port heads, those are considered a "truck" head and are better suited for a low RPM torque motor. Above 4500 they don't breathe very well, whereas the large oval port heads are better for mid-range RPM, which is where a jet runs at.

    Pull your valve covers off and get the casting number from them. Post it up and I'll look it up to see what you currently have.

    I am running the MSD 6AL and the advance it locked out and my tmie is set to 32. I tried turn it up to 34 36 and there was no diff so i sett it at 32. thanks for all the help guys.

  13. #11
    Senior Member H20MOFO's Avatar
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    Quote Originally Posted by jetboatkid View Post
    Tom, i gave the motor to a guy here in the city (Oklahoma) to rebuild. told him to put hypertech pistons .060 over and had a 685 lift cam to put in it. was told the motor would be around 10.5 to 1. after i got the motor back it only ran for about 30 min while breckin in. Had three lobes go down. took back and he told me it was my falt. so i had to put new cam in and new brg in the whole motor. after this time i pulled the vales covers off and checked the vales and all was way to tight. so now i ony have a 500 lift cam and a 10.5 to 1 motor. I would like the motor to turn 5k at lease.
    Lost 3 lobes....wow. Maybe have your lifter bore alignment checked, or ????? When I lost 1 lobe it took out every bore and piston skirt, I'm done with flat tappets, the money you save isn't worth the $ it will cost ya, IMO. Good luck btw.
    Another Hot Boat refugee

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    Not sure why it seems that people have had issues with flat tappet cams as of late. Last 2 motors I built had flat tappets and haven't lost a cam yet.



    Quote Originally Posted by HammerDown
    Kendall L-427 Super Blu...extreme-pressure (ep) lithium complex keeps my thrusting balls happy
    Quote Originally Posted by back2k5 View Post
    Well I am putting in a nice stereo system in the Carrera...maybe Ill put on some rap and turn the scoop sideways

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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by jetboatkid View Post
    I am running the MSD 6AL and the advance it locked out and my tmie is set to 32. I tried turn it up to 34 36 and there was no diff so i sett it at 32. thanks for all the help guys.
    Just as a wild a$$ Guess that motor should likley turn an AA impeller around 4500 to 4600 , Still sounds like your down on power a "smidge" Tom

    re the Cam IMO I hope your builder takes care of you , I can recall two cam failure in the last "several dozen motors" and we stepped up on both , Comp replaced the cams and lifters without a question Tom

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    Quote Originally Posted by jetboatkid View Post
    Would my Rpm's go out the roof or just a little higher
    They should typically go up 200 to 300 RPM per full cut (AA to "A", "A" to "B", etc).

    AA to B is 2 full cuts, and there is a "middle ground", you could refer to as a "half-cut", which is (depending on who you ask) A+ or A1.5 between an A and a AA, AB between A and B, BC, between B & C, etc.

    Much depends on the HP your engine makes, how and where in the RPM range it makes it.
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