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Author Topic: 750 CFM Edlebrock  (Read 3956 times)
chevysscamaro68
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« on: October 01, 2006, 07:36:39 PM »

I have a 350 in my Camaro, it is pushing close to 350 hp. I have a 600cfm edlebrock sitting on top right now, but would like to try a 750. I have heard it will be to much carb., but I've seen a 750 on a stock 350 do just fine. what are your opinions??
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chevysscamaro68
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« Reply #1 on: October 02, 2006, 04:56:16 PM »

Come on guys, opinions.....
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Ed Bertrand
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« Reply #2 on: October 02, 2006, 05:43:57 PM »

Well... I've always read that you really don't need more than 650 CFM on any small block unless you plan on racing it. Heck, I have a 650 CFM on my 396 and it works just fine! (Of course, I rarely go past 3500 RPM, so the engine doesn't require anything more than that.)

That said, the original Rochester Q-Jet installed on the 327/275 and 350/295 was rated at 780 CFM, so I don't see why the Edelbrock won't work. However, the 600 you already have is just fine for the street.

One thing I've always believed in is never go too big with regards to carburetion. You'll get crap for mileage and the engine will be a pig at the low RPM's.

Ed
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lakeholme
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« Reply #3 on: October 02, 2006, 07:19:36 PM »

Well... I've always read that you really don't need more than 650 CFM on any small block unless you plan on racing it... However, the 600 you already have is just fine for the street.
I agree with Ed.
But let me also say:
What are your goals for your 68?
If it is a driver, Ed is certainly right.  Too big justs costs money.
If it is to show and originality counts, you've already done too much.
If you want someone to look under the hood and say, "Looks sweet!", then the bigger the better and do it in chrome.
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Phillip
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chevysscamaro68
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« Reply #4 on: October 02, 2006, 08:27:17 PM »

Thanks for the replies.
I am just looking for a little bit more ummmph! I drive it very little, maybe 1000 miles a year, if that.
I like people seeing under the hood and commenting like that.
thanks guys
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hotrod68
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« Reply #5 on: October 02, 2006, 09:49:57 PM »

For me, nothing makes a better statement than a dual-line Holley! They just LOOK mean. But that's my preference and an Edelbrock is a good carburetor as long as you don't have to work on it. I vote to keep the 600--it's plenty for your engine.
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dab67
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« Reply #6 on: November 06, 2006, 01:31:52 PM »

The 600 is more than enough. If you are looking for more ooph as you state, then I would guess pushing almost 350hp, there is something else wrong!!!!!!!!! 350 hp should be more than enough to put you in the back seat and then some! Just a guess, the engine is not stock to the 68 correct?
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jdv69z
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« Reply #7 on: November 06, 2006, 04:14:17 PM »

What are the throttle bore diameters for the 600 and the 750? The larger the bore, the more air which the carb can flow. The trade off is that that same larger diameter bore will result in slower air velocity (speed). Thus it takes more time for the mixture to go from carb to cylinder. This is where throttle response can suffer. Air speed is why a carb is a 4 small barrels, not 1 large barrel. If your house has a ceiling fan in the attic, you can demonstrate to yourself the air speed effect of different size openings. Close all the windows in the house except one, and open this window slightly while turning on the ceiling fan. Feel the incoming air moving thru the opening and then open the window further and feel the speed of the incoming air decrease as the opening size increases.

Jimmy V.
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Jimmy V.
JohnZ
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« Reply #8 on: November 07, 2006, 11:22:56 AM »

What are the throttle bore diameters for the 600 and the 750? The larger the bore, the more air which the carb can flow. The trade off is that that same larger diameter bore will result in slower air velocity (speed). Thus it takes more time for the mixture to go from carb to cylinder.

What really matters between larger and smaller venturi diameters (not throttle bore diameter) is the strength of the metering signal at the boosters; smaller venturi diameter means higher velocity airflow at the boosters, which generates a stronger signal and crisper throttle response. Over-carbureted engines (which are a disease that originates at Jeg's and Summit) have lower air velocity at the boosters and poor part-throttle response. Carburetors don't make horsepower - they just meter fuel based on engine demand; total airflow makes horsepower, which is a function of intake manifold design, camshaft design, valve layout, port sizing and airflow velocity, and exhaust system restriction.
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