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  #1  
Old 30-10-2015, 06:27 PM
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What carb? 750 or 850cfm?

Hey guys, need a quick bit of advice / opinions. I'm ready to buy a decent carby, and I only want to be doing the exercise once hopefully. You see so many people on selling carby's because they have made the wrong decision when purchasing.

I'm pretty keen on the quick fuel carbs, based on the features / looks i'm looking for.

I have a 454 cu BBC, it will be running AFR 265 oval port heads, a weiand team-g single plain intake, and a comp cams xr292r cam. This combo will be in a 68 camaro, and will be for street use only. Auto transmission, probably a 3000/3500 stall a bit further down the track.

So what carb will suit me best?

- 750cfm or 850cfm?
- Annular boosters?
- What brand? Quickfuel, Holley, AED, Barry Grant, Proform
- 4 corner idle necessary?

I was looking at going with the following Quickfuel 850:
http://www.ebay.com/itm/380671185864...%3AMEBIDX%3AIT

750cfm from the same seller:
http://www.ebay.com/itm/170713009873...%3AMEBIDX%3AIT

Same series of Quickfuel 850cfm from another seller (fair bit cheaper though):
http://www.ebay.com/itm/HOLLEY-QFT-8...531812?vxp=mtr

Considering this too:
AED HO 750cfm:
http://www.summitracing.com/int/part...o-rd/overview/

The seller mentioned above actually recommended me to go with the 750cfm equivalent carb for this combo. Will the 750cfm be okay for this setup, or do you think i need to be looking at an 850cfm?

I note that some of these 750cfm carbs actually state that they'll flow 830cfm. I have read that a carby with annular boosters will run smoother and be more responsive. Am i better off buying a 750cfm with annular boosters, or a 850cfm without?

I would prefer to have the vacuum ports in the base plate, so that rules out the holley ultra xp range, and the quickfuel race series and some others.

After a while at looking at carbs, it's all becomes a bit confusing comparing features.

Should i consider a secondhand carb? I'm worried about someone having mucked around with a carb too much before me, and having to spend too much money to set it up to work well with my combo.

I like the idea of buying a 'custom carb' from one of these smaller custom carb builders on ebay. Hopefully i can get them to set something with the right size jets/power valve etc that's going to bolt on and perform well out of the box. I still have the paypal purchase protection etc.

Trying to keep my purchase under $1000 if it's coming from the USA to avoid extra tax. I'm happy to consider an Australian distributor if it works out to be a better deal.

Last edited by *rayman*; 30-10-2015 at 06:59 PM..
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  #2  
Old 30-10-2015, 07:30 PM
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holley HP 4150 830cfm annular would be perfect
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Old 30-10-2015, 07:41 PM
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http://www.summitracing.com/int/part...make/chevrolet

This one
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Old 30-10-2015, 07:45 PM
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http://www.ebay.com/itm/Holley-0-805...lUrv1o&vxp=mtr
This is a good price for a factory refurb unit. New , this list number is $850USD.

Haha, Anchor. I've heard good things about the Fast injection kits. Maybe one day down the track a bit further. I just want to get it running and drive it after all these years. Don't want to be setting up a whole new fuel system etc at the moment.
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Old 30-10-2015, 07:48 PM
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Haha yeah it's good to stick to something and a budget as well... I wish I did. I never seem to have luck with carbs. The quickfuel 750 race on the LS2 is an absolute pig even after a year of different carb pros giving me tips and stuff.
Although, the quadrajet on the c20 is perfect. Probably cause it's stock.
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  #6  
Old 31-10-2015, 08:52 AM
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Suggest you fill in the carb recommendation form and speak with the techs at Quickfuel. They are very helpful in my experience and advice is free...then you are atleast better informed.
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  #7  
Old 31-10-2015, 12:55 PM
qik66 qik66 is offline
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Ray

To select the best carb you need to pick the smallest that will supply the engine at the rpm you want. A carb works at its best when the air flowing through the venturi's at its fastest. this allows for the best atomisation of the fuel. If you fit too big of a carb you will tend to end up with an engine that is sluggish and less responsive at lower rpm, and if the carb is too small it will run out at the top end. So the first thing you need to do is look at the operating range of the cam you have fitted, and the engine rpm you will be running most of the time. It is no use picking a carb that will work its best at 6500-7000rpm when the engine will spend 90% of its life at 4000rpm or lower.An engine is just a big air pump and most V8's have a volumetric efficiency of somewhere around 70-80% at so it is quite easy to work out how much air the engine will flow at the desired rpm. I did a quick calculation and a 454 at 4000rpm and 75% efficiency will flow just under 790cfm. if it was mine I would go with the 750 as I think the improved low speed drivability will far out way any loss of top end power. the other option if you want to run a 850 vac secondary, this will give you the bottom end drivability along with the extra flow in the top end if the engine demands it. As for new or second hand, bye New at least that way you know what your stating with and not inheriting someone else's problems or stuff ups.
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Old 31-10-2015, 07:18 PM
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Thanks for the feedback guys.

It seems that while an 850 wouldn't be over carbing this engine, a 750 would probably be more responsive on the street. The street is where this car will spend it's time, so best to cater for that.

I think i'll go with a 750 annular booster.
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Old 01-11-2015, 03:43 AM
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I have a similar engine and had a 750 Quickfuel dp, changed it on a recommendation from my tune guy to a 880 vac sec Quickfuel runs so much better and great on the street
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Old 01-11-2015, 04:26 PM
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Years ago on my 454, I had a 780vac with a Weiand Action Plus dual plane with a Crane 134781 solid flat tappet. (248/258@0.050" which is similar in an apples to oranges comparison to your XR292 with it's 254/260@0.050".
I swapped the dual plane for a Victor Jnr and the engine responded very well..
I then swapped the 780vac for an 850DP and began laying rubber into high gear. It fxcking loved it. Converter was ~3500.

Me, I'd go the 850DP or an 830DP annular.
Forget annular if you are thinking vac secondaries, because they don't make 'em.
Also, the beauty of annular boosters is that if you happen to over-carb the engine slightly, the more responsive annular boosters do begin flowing at a lower air speed than regular down-leg boosters.
Regardless, I doubt that an 850 is over carbing on that engine with that cam and converter speed.
Buying used is fine. Buy a used, rebuild it with new needle & seats etc, adjust it properly and put it back to box-stock as far as jetting etc goes.
Buy a How-to Holley book if you need to, there are plenty out there.

Other fancy Holley copy-brands are nice, but there is nothing wrong with a good ol' trusty used Holley that's been un-fxcked with.

I think Deano (RAW454) had an 830 annular that he was selling not that long ago..
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Last edited by BlackoutSteve; 01-11-2015 at 04:29 PM..
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Old 01-11-2015, 07:38 PM
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I run quickfuel carbs on all my cars, (except for the 6 pack cars and the tri powers) and couldn't recommend them more.
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  #12  
Old 01-11-2015, 08:58 PM
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Quote:
Originally Posted by PGM View Post
I run quickfuel carbs on all my cars, (except for the 6 pack cars and the tri powers) and couldn't recommend them more.
Your combo is similar to mine. I had a Holley 850 hp on mine and it was great. 750 is definitely to small.
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Old 04-11-2015, 03:56 PM
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Thanks guys. I ended up going with a q series quick fuel 850 annular.
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Old 04-11-2015, 04:16 PM
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Sweet, make sure you at least pull bowls off. Not uncommon to find metal swarf in them.
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Old 04-11-2015, 05:10 PM
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Really?
I thought that was an issue that just the Demon/Barry Grant carbs had years ago..
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