bbc ab impeller Q&A

[robsquezn]

have a 468 BBC ram 2 750 carbs had oval port heads & a solid cam 630 lift
max rpm was 5000 now i have dart steel heads & a 690 lift cam solid roller
any buddy know what the rpm change should be

[sanger rat]

Are you saying you only spun a AB to 5000?

[Squirtin Thunder]

Too much cam for that impeller.
Too much carb for that impeller at that rpm !!

[sanger rat]

Let's get all the facts before you jump the gun Jim. :)

[robsquezn]

yes the old combo ran 80 mph at 4900 to 5000

[RCB19]

have a 468 BBC ram 2 750 carbs had oval port heads & a solid cam 630 lift
max rpm was 5000 now i have dart steel heads & a 690 lift cam solid roller
any buddy know what the rpm change should be
You should be seeing more than 5K out of the oval setup for starts. What's the CR of the motor?

[robsquezn]

more details- 19 foot pioneer river racer 468 BBC edelbrock rec port tunnel ram with 2 750 edelbrock carbs 11.5 t1 comp isky z89 solid cam 630/630 304/264 @50 with 108 lc ran 4 deg adv..oval port heads with big valves
berc jg pump with A/B impeller
loder grate
shoe
ride plate
3.025 nozzle
& a droop snoot
ran 78.6 to 80.5 all day long
now im going to a set off box stock rec port dart 320s with 2.300 / 1.88 valves $ a solid roller cam 695/661 lift 278/279 @50 109 lc

[YeLLowBoaT]

1500 cfm is ALOT of air.... a 468 ci with 100% VE @5k rpms is only going to use 677.08 CFM thats barly over a 3rd of what his carbs are puting out.

[robsquezn]

the boat ran real good last year i have yet to be beaten out off the gate
it ran real hard to the 1/8th but seemed to even out on the top end

[malcolm]

Yeah, that doesn't sound right... Sure that's not another A instead of that B? :)

[396_WAYS_TO_SPIT]

Yeah, that doesn't sound right... Sure that's not another A instead of that B? :)
that or the tune up is not right....

[SmokinLowriderSS]

Something funny going on, and it ain't funny.
I'm spinning 4800 against a Berk "A" in a good pump with a 454, single 700 CFM Holley, performer manifold, stock oval port heads, .565" lift cam, 8.5:1 compression. Not nearly the rpm setup he had, and now is even more so.
I'm afraid you're gonna go backwards with those rect-ports, especially only making 5-grand now. I think the pump/impeller is ahead of ya, preventing you from getting to the power band of the motor.

[sleekcrafter]

have a 468 BBC ram 2 750 carbs had oval port heads & a solid cam 630 lift
max rpm was 5000 now i have dart steel heads & a 690 lift cam solid roller
any buddy know what the rpm change should be
Any idea on compression ratio? And you have an oval port T-ram, on oval heads, with two 750's. The mis match on the intake maybe a factor, in combo with the 750's. Are you running power valves in the carbs?
Sleek

[IMPATIENT 1]

It Does Sound Like He's Runnin Alittle "fat" With To Much Carb. I'd Switch It Up For A Single Plane With A 850 Or A Dominator If Ya Want. 1500cfm Is Way!!too Much Carb For Your Setup. Leaning It Out Alittle Will Give You Alot More Power.tunnel Rams Are Mostly Ran For The Bling.i Want To Be Fast, Not Pretty.

[sanger rat]

Either that's a AA impeller or your tach is junk.

[PC Rat]

It Does Sound Like He's Runnin Alittle "fat" With To Much Carb. I'd Switch It Up For A Single Plane With A 850 Or A Dominator If Ya Want. 1500cfm Is Way!!too Much Carb For Your Setup. Leaning It Out Alittle Will Give You Alot More Power.tunnel Rams Are Mostly Ran For The Bling.i Want To Be Fast, Not Pretty.
A big carb does not necessarily make it fat.

[HaulinAss]

I dont see how dude could be going backwards by going to a set of Rect port (better flowing heads)
Heres a lil scenario for you all the doubters
Last year I removed my OVER CARBED Tunnel with 2 yes 2 750 CFM carbs and my "GOING BACKWARDS set of Rect Port 990 heads" and threw a set of NEW redone set of Oval Port 049 heads with a single plane intake a 870cfm Holley HP carb.Keep in mind the rect port to big of a set of heads and the to big of intake/carb setup netted me 81.7mph.In search for more efficient power to turn my 100% stock pump "A Impellar" I decided to go the ***boat JETS ONLY COMBO netted me a BLISTERING,EYEWATERING,STEERING WHEEL GRABBING<HANGING ON FOR DEAR SPEED 72.9 MPH Although I didnt acheive the speed I was searching for my girl now feels comfortable piloting the badddude.Now I see why I see so many 70mph jetboats.I am now going back to the old combo so I can go back to chopping everyone of with my OVERCARBED OVER HEADED "JET" Boat................
Point being horsepower EQUALS Speed............In other words for the 70mph crew HORSEPOWER means not being stuck in the 70mph crew........
Oh and I forgot to mention my cam combo,but I think by now youve been taken to school enough,well save that for next weeks lesson
Oh and this was in a full interiored,stock pumped,non ride plated,non drooped,heavy ass boat...............

[QuickJet]

You guys hear crickets????

[MikeF]

You guys hear crickets????
Yeah, that and a vdrive hull sittin on a trailer. :mix:

[MikeF]

81.7mph to 72.9 MPH
What was the rpm change between the 2 top speeds? :boxed:

[QuickJet]

Yeah, that and a vdrive hull sittin on a trailer. :mix:
Well if it's just a hull then that would explain why it's sittin on the trailer. Not too many people this side of the Rockies launch boats without motors in them. :cool:

[Rondane]

Either that's a AA impeller or your tach is junk.
I was thinkin the same thing. It's definatley not overcarberated. Maybe in a ford application but not a chevy. :D
Whats the duration and it a solid lifter or solid roller?
ron

[garret]

Are you sure it is not an Aggressor Ab which would be like a Berkley aa?

[robsquezn]

its a solid roller it was a solid

[robsquezn]

its a AB

[robsquezn]

its far from over carbed im going to put 2 850s

[Oldsquirt]

its a AB
What BRAND AB? They aren't all the same.......