427w carbed: done
- Thread starter cody50
- Start date
Tanus
New Member
BlackVert
15 Year Member
it all depends. on a 427, 750 is good for up to about 6000 rpm. and as you probably know, with carbs the air velocity is a much bigger deal, so an oversized carb is much worse than an oversized throttle body.
so if it is a street car, then the 750 is probably better. if he is winding it above 6000 on a regular basis, then an 850 might be called for.
for support, read this:
Technical FAQ
quickfuel makes some great carbs with lots of adjustment for idle, part throttle and WOT operation
Tanus
New Member
well I think the biggest increase would be from switching to the holley set-up opposed to the quadrajunk. that thing would rip with a mechanical secondary double pumper, 750 or 850. but yeah gas milage would be.... bad. I had a 67 camaro with 383 and 750DP, it seriously got about 2-3 miles a gallon when ripping on it, where as my mustang, which it almost as fast gets +15mpg, rompping it at every light.
99FiveOh
15 Year Member
Is that what we're calling Edelbrock carbs these days? I thought quadrajunk was what we called GM Quadrajet 4 barrel carbs...
BlackVert
15 Year Member
how is the hood clearance? i can see you have a cowl hood, but how much rise does it have? did you lower the engine at the k-member at all? and how much extra room do you have?
i'm just trying to get a feel for how tall a carb setup is compared to an efi setup ...
i'm just trying to get a feel for how tall a carb setup is compared to an efi setup ...
Tanus
New Member
thats what I call um, haha, go to the track, bet you see a 100 holley style carbs to every 1 quadrajunk style carbs.Is that what we're calling Edelbrock carbs these days? I thought quadrajunk was what we called GM Quadrajet 4 barrel carbs...
Joe 5.0
Founding Member
Nice, I'm sure it runs nice.
I almost went carb when I needed a rebuild on my 347, but ended up going soller roller and staying EFI instead.
In hind sight I probably could have put in a carb'd windsor for the same $$ and make a bunch more hp/tq.
How's the driveability of the carb?
I almost went carb when I needed a rebuild on my 347, but ended up going soller roller and staying EFI instead.
In hind sight I probably could have put in a carb'd windsor for the same $$ and make a bunch more hp/tq.
How's the driveability of the carb?
carb
The biggest problem with the edelbrock was the choke horn, and choke parts that really eat up a lot of the quoted 750cfm. Plus the horn went a good way into my air cleaner really restricting air flow into the carb. This 850 I have now was worked over by the carb shop, it is supposed to flow 930cfm. I do think I was missing gobs of hp with the eddy. I have done the cfm calculation, but I have heard that there are a lot of real-world factors that aren't considered, such as valve overlap.
With the carb and the .620 cam it is a little fussy off its 800RPM idle. All in all with the big cam, single runner intake, 215cc heads, and such I think its drives really well. I have Nitto 275s in the rear and they are hopeless with the 4.10 gears and monster torque. With the slicks it really beats your head into the headrest. I really like the look, feel, and sound of the carb. I had an EFI 347 in here before and it was nothing compared to this. No matter which way you go, I am now a firm believer that widebands are worth the money. Makes driveability and race tuning so much easier.
The hood is pretty tall, but I really like it. It is cut open so air goes straight to the filter. I did not use drop mounts or anything, and with about 3" of air cleaner height I have about 1/3" of space to the hood. I am considering getting the drop mounts and a taller cleaner.
The biggest problem with the edelbrock was the choke horn, and choke parts that really eat up a lot of the quoted 750cfm. Plus the horn went a good way into my air cleaner really restricting air flow into the carb. This 850 I have now was worked over by the carb shop, it is supposed to flow 930cfm. I do think I was missing gobs of hp with the eddy. I have done the cfm calculation, but I have heard that there are a lot of real-world factors that aren't considered, such as valve overlap.
With the carb and the .620 cam it is a little fussy off its 800RPM idle. All in all with the big cam, single runner intake, 215cc heads, and such I think its drives really well. I have Nitto 275s in the rear and they are hopeless with the 4.10 gears and monster torque. With the slicks it really beats your head into the headrest. I really like the look, feel, and sound of the carb. I had an EFI 347 in here before and it was nothing compared to this. No matter which way you go, I am now a firm believer that widebands are worth the money. Makes driveability and race tuning so much easier.
The hood is pretty tall, but I really like it. It is cut open so air goes straight to the filter. I did not use drop mounts or anything, and with about 3" of air cleaner height I have about 1/3" of space to the hood. I am considering getting the drop mounts and a taller cleaner.
More Carb info
I researched carbs a little more to back-up what I am saying. An Edelbrock 750cfm carb actually flows around 680cfm, and Holley 750 flow a little over 750, and a holley 850 flows under 850cfm. Now I know mine has been milled and smoothed to about 900. That is pretty stout, and a big difference from 680. Knowing this, it appears the Edelbrock shoud run out of flow at 5,500rpm. Add in the turbulance from the choke horn and maxing out the air flow, you can see why this is the WRONG carb. Also cfm changes with vacuum across the venturies. If you have a high performance engine with little vacuum, you need a higher cfm rating because you won't actually GET that cfm through it. It is true that if you want to make horsepower you need to oversize your carburetor.
I researched carbs a little more to back-up what I am saying. An Edelbrock 750cfm carb actually flows around 680cfm, and Holley 750 flow a little over 750, and a holley 850 flows under 850cfm. Now I know mine has been milled and smoothed to about 900. That is pretty stout, and a big difference from 680. Knowing this, it appears the Edelbrock shoud run out of flow at 5,500rpm. Add in the turbulance from the choke horn and maxing out the air flow, you can see why this is the WRONG carb. Also cfm changes with vacuum across the venturies. If you have a high performance engine with little vacuum, you need a higher cfm rating because you won't actually GET that cfm through it. It is true that if you want to make horsepower you need to oversize your carburetor.
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