Author Topic: Carb size 750 or 850?  (Read 2241 times)

gt350son

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Carb size 750 or 850?
« on: October 10, 2010, 05:41:19 PM »
I'm building a 347 stroker with
225cc AFR Heads
Lunati Cam retrofit - Duration 300 int / 310 exh, Lift .560 int /.576 exh
Edelbrock Performer Air-Gap

And would like to know what size holley carb you guys suggest.
Its going to be a street/heavy strip car
Thank you in advanced

ol dirty doug

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Re: Carb size 750 or 850?
« Reply #1 on: October 10, 2010, 07:25:26 PM »
whats the rpm range you will be driving and shifting at?

gt350son

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Re: Carb size 750 or 850?
« Reply #2 on: October 10, 2010, 07:37:05 PM »
Rpm range from 1500 to about 7000. With shifting around 4-5k

ol dirty doug

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Re: Carb size 750 or 850?
« Reply #3 on: October 10, 2010, 07:48:45 PM »
a good 650 double pumper is really all you would need because at 6500 rpm your engine will be consuming 652.633 cubic feet or air. but if you are going for all out drag racing then i might do a 750 or possibly a dominator for a high reving engine.

66GTKFB

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Re: Carb size 750 or 850?
« Reply #4 on: October 10, 2010, 09:43:10 PM »
Rpm range from 1500 to about 7000. With shifting around 4-5k
Seems to be a dissagrement here. If you are on the strip, shifting at 7.0K to 7.2K RPM would be a better range. I would recomend you invest in a crank and set of rods other than stock.
Jim

gt350son

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Re: Carb size 750 or 850?
« Reply #5 on: October 10, 2010, 10:18:37 PM »
I probably should change my wording. 4-5k  is on the streets, and I would go to about 7k on the strip. And since I'm stroking it I'm using a scat rotation assembly. Forged pistons and forged i-beam rods with a cast iron crank.

66GTKFB

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Re: Carb size 750 or 850?
« Reply #6 on: October 10, 2010, 10:52:06 PM »
A couple of Rat Racers I know routinely get 7.5K to 8.0K with 347CID engines at Laguna Seca in Fox body cars, but they are injected. If you are looking for mostly strip, start with 850 but be prepared to drop back to 750 if you run rotten. For reference, a Boss 351 ran with a 715CFM carb.
Jim

Jeff73Mach1

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Re: Carb size 750 or 850?
« Reply #7 on: October 11, 2010, 06:44:19 AM »
my reference was that a Boss 351 ran a 780 cfm carb

I would recommend going with vacuum secondaries which are more forgiving of overcarburation.

ol dirty doug

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Re: Carb size 750 or 850?
« Reply #8 on: October 11, 2010, 11:27:45 AM »
all you have to do is the math.  it will you exactly what you need.

gt350son

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Re: Carb size 750 or 850?
« Reply #9 on: October 11, 2010, 01:51:02 PM »
I've read about the differences in Down-leg and annular boosters, and I read that annular boosters allow for a little more CFM, mainly because the size of the booster restricts the air flow. And the annular also increased throttle response and low-end torque. Is this all true?

 

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