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48 poncho


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need carb advice
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im looking to buy a carb for my 454 BBC i was thinking a 750 or 780 cfm holley
some people say get vacume secondary's others say mechanical are the vacume secondarys hard to tune thats what im told your thoughts please

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48 pontiac silverstreak 454 big block
68post


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Well, the 780 vacuum secondary carb was good enough for the L78, L72 and LS6, plus with a new Holley, you can get with the quick change spring capability on the vacuum diaphragm.

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SD 396


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I find that a lot of people run too much carb. I agree with Barry about the vacuum secondaries. Get the quick change spring kit so you can tune it without removing the vacuum pod. Start with the brown (second heaviest) spring and go from there.

 A Holley may take more time to set up but nothing works better. 

 There are a lot of factors to take into account when selecting the correct carb size. Intended use, cam specs, compression ratio, exhaust, gear ratio.

 My suggestion would be dual plane intake and a 750 cfm with vacuum secondaries. 66 front and 58 rear.

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87 player bird


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I dunno, Me thinks mech secondaries. if going vacuum, a well set up quadra jet runs way better than a holley. my 2 pennies though.

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427carl


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My bad Boy runs a Holley R4770 650 cfm  double pumper wink 

will run good fuel milage and will run 13.40 @101  w/2.73 gears   We like it!!!     

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4SPEED427


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Always err on the cautious side with carbs and cams!!!

I agree with the masses----vacuum secondary.

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427carl


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Didn't the L79's have a little 585 cfm?    vacuum?

-- Edited by 427carl on Tuesday 28th of September 2010 10:18:31 PM

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65 SD L79


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87 player bird wrote:

I dunno, Me thinks mech secondaries. if going vacuum, a well set up quadra jet runs way better than a holley. my 2 pennies though.


A local speed shop called Wild Goose does a great job building Q jets. I have only run them on small blocks. Give them a call with your engine info, I`m sure they would steer you in the right direction.

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Steve C


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427carl wrote:

Didn't the L79's have a little 585 cfm?    vacuum?

-- Edited by 427carl on Tuesday 28th of September 2010 10:18:31 PM


Yes they did 585 vac secondary and this was an engine built to rev. Holley has a good cfm calculator on their site. Most people go with too much cfm.  

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4SPEED427


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That's why I did a 600 vacuum on my 327. The place I bought it dynos each carb. I told him what I had and he said this would be plenty. He even runs this carb on street 350's.

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ak 67sd


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for a driver, try a holley 770sa -street avenger. holley lists them reman direct on ebay, great price and a warranty...i use one on my 396...

ak

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Wpg, MB to London, ON

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73SC


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Click Here  for a calculator of correct CFM. As Brad says too many guys use too much carb. You will be surprised. In fact it calculates the 327 to be 579 cfm and Carl's 600 comes out right for the 427.

It shows a 750 just about right for the 454.

-- Edited by 73SC on Tuesday 28th of September 2010 11:27:34 PM

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Beaumont4008


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ak 67sd wrote:

for a driver, try a holley 770sa -street avenger. holley lists them reman direct on ebay, great price and a warranty...i use one on my 396...

ak


My budy runs that carb on his 355 S10 and loves it. It has the quick change  vacuum secondaries . Easy to dial in ,Good carb for sure.

 



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dualquadpete


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Everybodys going on about the Holley's How "aboot" the Carter AFB or the Edelebrock Performer Carbs. I've always had problems setting a Holley float level & other adj. these Performers & AFB's work well!!! Have 2 older Carters on the Catalina jetted down to 64's all around, 17mpg on hwy. with a light foot, nail both 4bbls, mileage goes in the TOILET but the acceleration is "WILD"

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67SD396


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Until recently, I'd always run Q-jets and Holleys but last year I bought one of the Edelbrock Performer carbs to try on my 65 Acadian. It seems pretty good. Works better than the rebuilt Q-jet that was on it. Seems a bit thirsty like a Holley but throttle response is amazing.

If you want all out performance and infinite tuning possiblities, then a Holley is the answer. They are the easiest carb to work on by far. Jetting can be done in minutes right on the car. My biggest complaint I had about a Holley carb was that every spring, after storing my car for the winter, the thing would leak like a sprinkler. So off I would go and buy another carb kit. I would assume that if you were to use them more often, they wouldn't leak.

Mechanical or vacuum secondaries.....hmmmm. Had great success with both but prefer the mechanical for a stick car and the vacuum for an automatic car.

If fuel milage is your thing, then nothing beats the proper Q-jet for the engine size. They also have great performance and the secondary opening rate is adjustable so they can be set up not to have the notorious "qudra-bog". 25 years ago, I wouldn't run anything else.



-- Edited by 67SD396 on Wednesday 29th of September 2010 08:18:17 AM

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ak 67sd


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A quadrajet can be built to hang with any holley on a dyno up to around 600hp... I've never had any desire to learn how to build them and set them up... if you get one built, this guy has one of best reputations...i also like the teary eyed red lights you get with a holley double pumper... i had a 750 flowed to 900cfm on my 350...all depends on your build and your intent!

http://www.smicarburetor.com/

ak

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48 poncho


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thanks for all the posts guys im leaning towards a holley 750 with vacume sec

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48 pontiac silverstreak 454 big block
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427carl


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48 poncho wrote:

thanks for all the posts guys im leaning towards a holley 750 with vacume sec


I ran a 750 vacuum sec Edelbrock on my 355 Sunbird   it hauled the mail  (right out of the box  no adjustments)

 



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