Carb cfm with ported heads?

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KnuckleDuster

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410ci with box stock Edelbrock 63cc heads, been running a 750cfm Proform electric choke street carb.
Considering an 850cfm or even 950cfm Proform or Quickfuel RACE carb now that the heads are getting a max port job.
3.23 gears
2.5" exhaust
3500 stall converter
28" tires
241/247 5.45 lift cam.
Thoughts?
 
The carb size maybe ok, depending what you what to use the car for, drag racing bigger may help you, one thing is the 2.5 exhaust has to go.
 
Are you looking to improve 1/4 mile times?
If so, other things in the combo would help more
If a street car, i would probably keep what you have
In a “ racy” smallblock, i have never ever seen a bigger carb not ET better than a smaller carb. Never

I had a “ hot” 318 motor in another car couple of years ago. Ran 11.60’s. It was a tenth quicker with a good 950 than with a good 750. And thats just a 318.
 
So you think now the exhaust will be the choke point?
My exhaust guy won't do 3" over the axles. That and the 3.23's are pretty much non-negotiable. Mainly a street car, but would like to crack 11's at the track.
Will the 750 hold me back with the added flow? I want a bigger carb, but do I really need one?
 
I had a “ hot” 318 motor in another car couple of years ago. Ran 11.60’s. It was a tenth quicker with a good 950 than with a good 750. And thats just a 318.
OMG! I had said a few times before that and had a 850 on a 318 and the scorn was. Un-freaking-believable!!!!!
 
So you think now the exhaust will be the choke point?
My exhaust guy won't do 3" over the axles. That and the 3.23's are pretty much non-negotiable. Mainly a street car, but would like to crack 11's at the track.
Will the 750 hold me back with the added flow? I want a bigger carb, but do I really need one?
I’d just try it with what you have and go from there. 1 thing at a time.
 
On a flawed run the 750 went 12.66, with ZERO tuning other than idle mixture. I'm tired of dealing with the electric choke. I should probably just ask, 850 or 950? If I switch it won't be another 750, Lol...
 
Your in Texas, remove the choke plate and go for a run. A drop in et of .66 is a lot. Just see what you got with what you have before you spend your money.
 
I hear ya rumblefish, but curiosity is a *****. Whatever it runs, I'm gonna wonder.
950 costs the same as 850, will it be more temperamental to tune?
 
I can’t say for sure based on a few factors starting with I haven’t been there and done that.

Generally speaking, a bigger carb can be harder to tune because of the reduced signal to the carb because of the bigger throttle bores, cam size and timing events, numerically low gear ratio, etc....

Your engine has increased in size thus reducing what would be a huge carb on a 318 down to something closer to what it could use.

Depending on many factors it may very well be a non issue going to a 950. But as I said before have not been there and done that.

I hesitate to say, “Go for it!” I don’t want to suggest something that I’m not confident on.
 
The 3500 converter helps a lot.
But, even with 3.32’s?
 
yesterday at Pamona the NHRA stock class winner was a 1969 340 Dart in E/SA = 10.7 seconds with - STOCK : 625 AVS carb, intake, rockers, heads, compression ratio (blueprinted), stock cam lift, weight, 9" slick. I run 11.6 with 360 cubes and 2.5" Edelbrock mufflers. an $ 650. ? carb is worth what, .10 seconds?
 
My brother pickup 2 tenths going from 2.5 to 3 inch exhaust with a 408



So you think now the exhaust will be the choke point?
My exhaust guy won't do 3" over the axles. That and the 3.23's are pretty much non-negotiable. Mainly a street car, but would like to crack 11's at the track.
Will the 750 hold me back with the added flow? I want a bigger carb, but do I really need one?[/QUOTe
 
410ci with box stock Edelbrock 63cc heads, been running a 750cfm Proform electric choke street carb.
Considering an 850cfm or even 950cfm Proform or Quickfuel RACE carb now that the heads are getting a max port job.
3.23 gears
2.5" exhaust
3500 stall converter
28" tires
241/247 5.45 lift cam.
Thoughts?

To bad you didnt live closer. I have a complete 3 inch A body exhaust that is less than a year old, mufflers, tips.... the whole deal.... just sitting in a bay at work collecting dust.... i would sell cheap
 
Man you've got everybody chasing their tail. You want a bigger carburetor? Just go buy it. You don't need my okay to do it.
 
Man you've got everybody chasing their tail. You want a bigger carburetor? Just go buy it. You don't need my okay to do it.

;-)
Sometimes we all just want to hear somebody say, "Go for it!"
I appreciate your sense of humor, but would also I would love to hear your experience on the subject, in particular, as an engine builder.
 
Who the hell knows without the rest of your engine combo? That's like askin "hay is this hooker good for me?" "She's blonde"
 
You probably can go larger no problem. But just measure how much vacuum your engine pulls at full throttle and load. And decided from there.
 
KD, I have a 408 in my car also with 3:23 gears and 2-1/2" exh but a loser converter (4k) and for a long time I ran a 750 HP on it. Ran great but I ran across a fantastic deal on a 830 annular so I bought it and put it on. I have a wide band A/F gauge on my car so I can tune it and when tuned the 830 did out perform the 750 on the mid to top end by a little bit, but not a huge amount. Boy did it kill the fuel mileage though (mine is also mostly a street car so mpg is of somewhat importance). BTW: my car with a 727 and 3500 converter and the aforementioned 750 ran 12.24 at 112. I went back to a 750. IMO the extra .10 quicker didn't offset the big mpg drop. If mpg isn't a factor for you go for the bigger carb and get one without a choke at all and put a wide band a/f gauge on it and tune it for max perf
 
yesterday at Pamona the NHRA stock class winner was a 1969 340 Dart in E/SA = 10.7 seconds with - STOCK : 625 AVS carb, intake, rockers, heads, compression ratio (blueprinted), stock cam lift, weight, 9" slick. I run 11.6 with 360 cubes and 2.5" Edelbrock mufflers. an $ 650. ? carb is worth what, .10 seconds?

intake is a LD340....T&D roller rockers... cam lift is .480 with about 260 duration at .050.....aint much stock in a stocker....

if you buy a 950 may sure it is a real 950 ...holley made some 950s that are only about 830 cfm...
 
On a flawed run the 750 went 12.66, with ZERO tuning other than idle mixture. I'm tired of dealing with the electric choke. I should probably just ask, 850 or 950? If I switch it won't be another 750, Lol...
What did it go when you tuned it? What's the deal with the electric choke? Just wondering is all:)
 
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