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Old 02-09-2009, 07:17 AM   #1 (permalink)
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Default 750cfm too much for a 351W?

I have a brand new edelbrock 750cfm carb that came with a low mileage 460 I bought for my truck. I've been told that my plans for the truck dont really call for a carb this big and that something in the 650 range would be better. It currently has a 600cfm edelbrock carb. I'm thinking of putting the 750 on my mustang and the holley 650dp(currently on the stang) on my truck. Would this still be too big for my 351W? It has a stage 2 cam, ported heads, airgap intake. I'm not sure what else would dictate the need for a bigger carb.
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Old 02-09-2009, 11:04 AM   #2 (permalink)
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Default 750cfm too much for a 351W?

You can tune a carb to run on pretty much anything..However the swap you are doing seems backwards to me..460s love big carbs if your after power so the 650 will hurt it.If your just after mileage the DP is not the way to go either...The 750 will work on the 351 but you probably don't need it..
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Old 02-09-2009, 12:30 PM   #3 (permalink)
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I'm running a Demon 750 DP on my 351w. It didn't run well out of the box, but runs great after some tuning.
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Old 02-09-2009, 06:09 PM   #4 (permalink)
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I ran a Edel 750 on my old built 289 and it ran great. Remember edelbrocks are vacuum secondaries so the back barrels only open up as needed.
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Old 02-09-2009, 06:26 PM   #5 (permalink)
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The formula to calc CFM is...

CID times max rpm times volumetric efficiency (.80 for street/.90 for track) divided by 3456

For the 351, assuming a max rpm of 5800 that's 530 cfm
For the truck 460, assuming a max rpm of 5500 that's 585 cfm.

Now if you have header's, cam etc, you can increase this by 20%. To find the correct jetting, take the % of excess cfm, divide by 2 and change your jet size to that calc...

Example... if your carb had jet size 73, in the case of the 351, the 750 is 165 cfm too big or 22% - so reduce the jet size by 11% ie run 65's (the extra air won't bother the engine because it will only take in sooo much but the fuel will kill it)-
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Old 02-09-2009, 08:25 PM   #6 (permalink)
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if your running a dual plane intake you can use a bigger carb, a 750 edel will work and I have ran one on a 351w, vac sec is fine but a DP might be too much. I took off my edel 750 and installed a speed demon 650 VS and the car was much faster. It had hy roller, TW heads, 1 3/4 headers etc....

the edel I spent hrs tuning an the demon was pefect out of the box.

I run a 750 mighty demon annular on my 408.
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Old 02-09-2009, 08:33 PM   #7 (permalink)
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Quote:
Originally Posted by coolblue65
I ran a Edel 750 on my old built 289 and it ran great. Remember edelbrocks are vacuum secondaries so the back barrels only open up as needed.
Edelbrocks are mechanical secondaries, however they do have an air valve located in the secondaries.
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Old 02-09-2009, 10:05 PM   #8 (permalink)
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Yea I would leave the 650dp on the stang and run the 750 edelbrock on the truck. The edelbrock is more streetable and if the stang is set up more for performance im sure it runs good if the dp is tuned.
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Old 02-09-2009, 11:19 PM   #9 (permalink)
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I'd throw the edel 600 on the truck for MPG's and low end TQ,sell the edel 750 and the holley dp, buy a reman speed demon 650 preferably with annular boosters, Theres an article out there where they compared a reg demon and a demon annular carb on a 350 or 383 chev the annular carb produced like 100 ft lbs of tq more below 2500 rpm and about 25hp an beat the downleg booster carb all the way around in power and BSFC.I think it was on the super chevy website.

Autolite 4100's they say are some of the best carbs made, why? annular boosters, BTW summit has re-introuced the summit version of the holley 4010, which is much like the autolite but the holley version for a pretty decent price but I still love demon carbs.

I bought a custom made prosystems 950 hp for my 408 built to my exact combo,it cost me 600.00, I bought a reman 750 annular mighty demon for about 400.00 off ebay and my car runs way better (idle,part throttle, warm up and WOT) and it is out of the box untouched.
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Old 02-10-2009, 03:05 PM   #10 (permalink)
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The 460 in my truck is so tired right now, there's no point in spinning it any faster than 3500rpm as it wont go any faster, it just uses more gas. I suppose that will change once I get the rebuilt 460 put in there. I guess I will leave the stang alone right now and try both of the edelbrock carbs on the 460 and see which I like better.
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1993 F-250HD SC 4X4 7.3TD/5spd
2012 Jeep Wrangler Sahara 3.6/5spd-auto
1979 Mercury Capri 302/5spd-Sold(found and being restored), Ran 12.47 @ 110mph
http://forums.vintage-mustang.com/si...ypCSLHv_kx.jpg
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