What impeller

2735 Views 25 Replies 10 Participants Last post by jetboatkid, Jul 7, 2009

jetboatkid

Discussion Starter · Jul 1, 2009

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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Jetaholic

· #2 · Jul 1, 2009

jetboatkid said:
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.

pisston in the wind

· #3 · Jul 1, 2009

Same here

jetboatkid

Discussion Starter · #4 · Jul 1, 2009

Jetaholic said:
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

Sleeper CP

· #5 · Jul 1, 2009

jetboatkid said:
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.

S CP

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Jetaholic

· #6 · Jul 1, 2009 (Edited)

jetboatkid said:
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.

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jetboatperformance

· #7 · Jul 1, 2009

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 ?

hand Tom

Carlson-jet

· #8 · Jul 1, 2009

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.

jetboatkid

Discussion Starter · #9 · Jul 2, 2009 (Edited)

jetboatperformance said:
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 ? hand 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.

jetboatkid

Discussion Starter · #10 · Jul 2, 2009

Jetaholic said:
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.

H20MOFO

· #11 · Jul 2, 2009

jetboatkid said:
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.

Jetaholic

· #12 · Jul 2, 2009

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.

jetboatperformance

· #13 · Jul 2, 2009

jetboatkid said:
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

SmokinLowriderSS

· #14 · Jul 2, 2009

jetboatkid said:
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.

konajet74

· #15 · Jul 2, 2009

Jetaholic said:
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.

I think it depends if your lifter bores are not true, which is what i've
been told haunts 454's??

Jetaholic

· #16 · Jul 2, 2009

konajet74 said:
I think it depends if your lifter bores are not true, which is what i've
been told haunts 454's??

That or the lobe spacing/alignment itself.

One thing my machinist taught me was to install the cam and lifters, then rotate the cam by hand and make sure all of the lifters are spinning. If they are and you set the valve train up right (adjustments, etc etc), use the right oil (something with ZDDP) and run it through the 20 minute break-in, then you should be good.

SmokinLowriderSS

· #17 · Jul 2, 2009

konajet74 said:
I think it depends if your lifter bores are not true, which is what i've
been told haunts 454's??

I wonder at times how true this is.

Not that it does not happen, but, to hear some people, it happens more often than not, and seems to only happen to Chevy's.

Both of which I serriously doubt to be true.

I don't think ANY oil additives will save a cam from a fast death if the bores are not properly aimed, and, especially since I keep running a hyd. cam without adding anything to the synthetic oil I run, with a pretty aggressive hydraulic setup, if they ARE straight, pointed where they should be, just about any oil would do just fine.
My stock cam only ran 25 years straight, without annual or weekly pre-oiling efforts of any kind, on standard auto-parts-shop oils (Mobil, Texaco Havoline, Castrol GTX).

I had far worse trouble from rockers as I progressively pushed my 454 harder and harder, wound it higher and higher, than I had out of anything else.
That problem stopped when I finally scraped up cash to go roller rockers.

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jetboatkid

Discussion Starter · #18 · Jul 2, 2009

jetboatperformance said:
Take it out (the Impeller) (call if you need tech help ) I'll cut it for free (you pay the frieght ) hand Tom

I have the motor out right now, trying to find out what happen to the timming chain. ill be going back together with is in a few weeks andthen i might have to pull that Impeller out and just let you do that. if i take the impeller off will it just go right back on after you cut it or will i have to sett it back up. thanks Tom

you da man

Jetaholic

· #19 · Jul 2, 2009

jetboatkid said:
I have the motor out right now, trying to find out what happen to the timming chain. ill be going back together with is in a few weeks andthen i might have to pull that Impeller out and just let you do that. if i take the impeller off will it just go right back on after you cut it or will i have to sett it back up. thanks Tom you da man

No it should go right back on. If there's any shims installed in front of the impeller, leave them in place so they don't get lost.

jetboatkid

Discussion Starter · #20 · Jul 2, 2009

Jetaholic said:
No it should go right back on. If there's any shims installed in front of the impeller, leave them in place so they don't get lost.

can I leave the tran plate on there and just take the bowl off or do you have to take the tran plate off to.

Did you get the Videos and pic I sent to you jon

Does anyone have any idaes for a impeller nut tool. head it is a bear to get off

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