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Old 07-06-2012, 12:25 AM
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350 carb question

im new to the forums, this is my first post.
but anyway, me and my dad have been building a 350. its bored .60 over, edelbrock performer intake, lunati retrofit roller .492.492 lift 062 vortec heads.

ive ben having issues since ive built the motor when i rev it up then let off, the truck hardly wants to run, i have to keep the throttle pressed a bit till it builds for fuel up, the throttle response it ****ty from idle (750rpm) to around 1500, but after that its very fast and responsive, im guessing the motor is pushing around 375 horse and about 350 ft lbs, it has a few more goodies on it tho. but what im trying to get at it what carb should i upgrade to if the carb is too small.
the current fuel system consists of, an holley blue electric fuel pump and a regulator. along with the stock sending unit. the carb is an edelbrock 1406 (600cfm if im correct) ive been told to upgrade to a 670 to a 700 cfm carb. but i dont want to go out spending money on a carb thats too big.
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Old 07-06-2012, 12:55 AM
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I have a 750 CFM edelbrock on my 350. Its bored 80 over and has a mild cam.
It does sound like your engine needs a little more fuel...that is if everything is done correctly.
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Old 07-06-2012, 05:31 AM
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You may want to eventually use a bigger carb, but the problem you described is not because the current carb is too small. You have a problem with the idle circuits and/or the transition from idle to the main jets, and that should be fixable without swapping the carburetor.

Does it idle okay, but not want to transition from idle to a higher rpm when you slowly press down the accelerator?

Bruce
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Old 07-06-2012, 06:46 AM
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Quote:
Originally Posted by eturner View Post
im new to the forums, this is my first post.
but anyway, me and my dad have been building a 350. its bored .60 over, edelbrock performer intake, lunati retrofit roller .492.492 lift 062 vortec heads.

ive ben having issues since ive built the motor when i rev it up then let off, the truck hardly wants to run, i have to keep the throttle pressed a bit till it builds for fuel up, the throttle response it ****ty from idle (750rpm) to around 1500, but after that its very fast and responsive, im guessing the motor is pushing around 375 horse and about 350 ft lbs, it has a few more goodies on it tho. but what im trying to get at it what carb should i upgrade to if the carb is too small.
the current fuel system consists of, an holley blue electric fuel pump and a regulator. along with the stock sending unit. the carb is an edelbrock 1406 (600cfm if im correct) ive been told to upgrade to a 670 to a 700 cfm carb. but i dont want to go out spending money on a carb thats too big.
Ayuh,... You don't need a Bigger carb,....

You just need to make the carb you've got, to Work,.. Right...

Yer motor can't move much more than 550cfms, anyways.... Do the math...
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Old 07-06-2012, 01:04 PM
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when i slowly push the throttle it revs fine and is real responsive, but when i mash on the gas its almost like the carb cant keep up then when the secondaries hit it picks back up. it acts like the motor cant get enough fuel. i have tuned my regulator up as far as it will go and as low as i can go. still no change i even tried to tune it mess w the choke and all, but could it be a jet issue? im leaning towards getting a holley 670 to throw on it, ive seen to many people down-grading edelbrock's that they dont flow what they claim out of the box
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Old 07-06-2012, 06:49 PM
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search miy posts about recurving the distributor for the cam.

more initial timing at idle.

18-22 at idle 34-36 @max advance.
Use ported vacuum.
The edlebrock carbs tend to like a generous idle timing.
get the tuning manual and read it.

change the carb jetting to .098 pri jet .068x.047 rod 5# spring.
from that point use the #1409 chart to tune further.

.101 sec jets ... move the accelerator pump linkage to the inner hole.
increase the accel shooters to .028 .031

The 750 edelbrock makes more power than the 600.
and the oput of the box jetting is very close.
A afr meter helps a lot.
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Old 07-06-2012, 11:07 PM
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Quote:
Originally Posted by eturner View Post
when i slowly push the throttle it revs fine and is real responsive, but when i mash on the gas its almost like the carb cant keep up then when the secondaries hit it picks back up. it acts like the motor cant get enough fuel. i have tuned my regulator up as far as it will go and as low as i can go. still no change i even tried to tune it mess w the choke and all, but could it be a jet issue? im leaning towards getting a holley 670 to throw on it, ive seen to many people down-grading edelbrock's that they dont flow what they claim out of the box
If the carb is working normally and doesn't need rebuilding or cleaning, it will work fine on your engine.

It sounds to me like either the accelerator pump circuit is not supplying enough fuel at the hit of the throttle, and/or the timing curve needs sorted out.

More on tuning the carb here. More on timing here. Read it then ask any questions you have- and you will have some, we all did at first.

Note- it's best to see that the accelerator pump is working first, THEN do the timing curve, THEN the rest of the carb tuning, if needed. Now, if you believe the carb needs to be rebuilt or it has been tampered with by someone else and may be out of calibration, your best bet is to baseline it back to how it was stock, then using the charts in the manual, tune it from there.

Edelbrock recalibration kits, your 1406 carb (you are correct, it is a 600 cfm) uses the p/n 1487 kit.
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Old 07-07-2012, 01:32 AM
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I have a mildly built vortec 350 with decent size can an edelbrock I take...to be honest depending on what can specs are an compression ratio,an intake....I would suggest 650 Holley double Pumper WITH vacuum secondaries....that should be fine...I run a 600 electric choke,an vacuum secondaries an believe it or not had to jet down two sizes on primary an secondary jets....my engine runs like top...
Big misconception that need huge Carb....I would say 650 would be just fine.
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Old 07-07-2012, 01:41 AM
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Oh an not knocking edelbrocks products....I have used there stuff alot in the past...but I'm sorry there carbs are nothing but fancy Door stops....metering rods instead of jets...for daily driver maybe but performance no way.the tunability of the carbs are dang near don't exist....id suggest looking into summit racings carbs. I recently purchased one for myself...and I'm huge Holley fan an can tune one to run like its injected...but I was pleasantly surprised when I put the 600 electric choke Carb on my truck...other then a little fast idle adjustment an curb idle adjustment truck runs outstanding....they have 3 carbs...one is 600 electric choke vacuum secondaries..another is 750 electric choke an such..an third is 750 mechanical everything with duel accelerator pumps....bang for the Buck an for performance in my opinion they can't be beat
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Old 07-07-2012, 02:09 AM
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If it was mine i would go for the mec 3310 holley, use them on several engine and they really do a good job, either way you may have to do some re-jetting maybe not alway's. and re-curving the distributer can really make a difference.JMO


Cole
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Old 07-07-2012, 03:24 PM
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Quote:
Originally Posted by eloc431962 View Post
If it was mine i would go for the mec 3310 holley, use them on several engine and they really do a good job, either way you may have to do some re-jetting maybe not alway's. and re-curving the distributer can really make a difference.JMO


Cole
The 3310 holley is not a "mech" carb. It has vacuum secondaries.
They do work well with some tuning and upgrades.
Proform has a cool HP style carb body for this carb.
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