[bigge31566]

Im looking at purchasing a new carb for a mild build 350 and was looking at a Quick Fuel
793-HR-650 and a HOlley 510-0-4777SAE on Jegs
Is there a big difference in these 2 carbs, and is it better to go with mechanical secondaries or vacuum

 

[BogiesAnnex1]

If absolute maximum performance with not a lot if any regard for street manners is the goal then mechanical is answer. If really good performance with ease of drivability is the goal then vacuum secondaries is the answer.



Bogie

 

[staleg]

Mechanical secondaries may work well on a light car with manual trans.
I have been driving with a QFT 670 SS mec. sec. w/annular boosters on my hot rod since 2013.
-Fuel consumption 25 miles pr gallon on highway cruising.
-T56 6 speed manual trans with 0,5 overdrive in 6th gear
-4,09:1 rear axle ratio.
-285/40-18 rear tires.
-Car weights app 2750 lbs.
-Edelbrock RPM Airgap intake.
-Engine is a lightly modified Chevy 350 with app 380 hp.
-Proper vacuum signal.

Works as a breeze.
I would recommend tuning with a wideband A/F gauge.
The air/fuel mixture may vary a lot with minor adjustment on the 4 corner idle screws.

 

[eric32]

Between the two carburetors, I recommend the Quick fuel carb over the Holley brand one. The Quick fuel carb will have a lot more adjusting features that will most likely be needed for your said build as no carb is right out of the box ready and will need tuned and things adjusted for your build. The quick fuel carburetors are way more adjustable. Also a word of caution on the double pumpers, you need to have a vehicle that is fast going and picks up speed very quickly in order to run it with an automatic transmission.

On what vehicle weight and how fast will vary. The thing with double pumpers the secondary side if opened up too fast on a vehicle that is a slug taking off and slow to pick up speed and with an automatic transmission it can create a bog and will cause the engine to just bog way down and take forever to pick up. A vacuum secondary carburetor will be more favorable if the vehicle is super heavy and takes time to get going a the secondary side will only open up according to engine demand.

Check out the Quick fuel brawler carburetors as they are a lot cheaper then the Hot Rod series and are the same exact thing but just with a different sticker on the side and a different name series. All the same parts are used on the Hot rod series carburetors and the brawler cast series.

 

[55_327]

I'm not a carb guru, but my all-time favorite is the Holley #80783C, which is a 650cfm 4150-series. It has an electric choke, vacuum secondaries, and the traditional dichromate finish. However, I just looked at the price and have to say I'm shocked, since mine cost less than $300 10-12 years ago. Wish I would have kept it when I sold the car it was on. 😕 And I wish my income had more than doubled since I bought the carb!

On another note, an Edelbrock AVS2 #1906 may be just the thing, and it costs only $430. It gets great reviews from the guys here, but it won't be as tunable as the Brawler if your engine has a radical cam.

 

[BogiesAnnex1]

Unless you built a really radical engine and expect to race it all that tuning of dinking with air correction jets and magical accelerating pumps is far more than the average street build needs. The average guy playing with these trying to solve simple problems using complex techniques quickly gets lost, it just isn’t necessary.

The AFB, AVS and Q-Jet which pretty much run right out of the box pretty much indicate that all the fiddling around with magic tuning is an unnecessary complication. Where over at the Holley and Holley clone houses this fantasy in the hands of the average guy souping up his daily driver sells a lot of high cost carbs and tinkering parts.

Bogie

 

[staleg]

I agree that if the numerous adjusting possibilities on the Holley carb is a argument for bying it, one must have the interest of actually using those possibilities.

 

[eric32]

Is there something wrong with wanting to buy a Holley style carb that has more adjustable features vs one that does not? If a person had a choice to choose to buy an Edelbrock AVS carb that did not have the ability to change the metering rods vs one that had that feature for the same cost and allow for tuning the carb to be proper for said build what one do you think a tuner who understand them would buy?

If your going to buy and use a carburetor of said style then nothing wrong with buying one that has better features to get a better tune vs just buying one that you can only tune a few things and just throw it on and have a generic tune on it. All the different carb styles have there pros and cons and opinions will vary. Just saying.

 

[1979Malibu]

The AVS and Summit Racing carburetors are a pretty good deal, IMO. They have remanufactured ones for sale.

I'm a hobbyist and pretty far from the knowledge others on the discussion have. Hopefully they will chime in, if any of this is incorrect. The way my thinking works, I look at annular boosters in mild builds. The annular booster, being physically larger than the down leg booster, would seemingly produce a higher vacuum signal. A little more air velocity and better fuel atomization set the stage for the carburetor to be potentially more responsive. I could be off in my line of thinking here, but I thought it worth mentioning.

The other benefit of those style carburetors would be eliminating fuel leaks. The gasket level above the fuel makes good sense to be in something expected to be in service for a long time.

 

[eric32]

The summit carbs are not bad for a mild build and have some decent features and also use standard Holley parts. They are made from the short lived Holley 4010/4011 series carburetors and Summit made some updates on them. You posted a good bit about them already and covered a lot of good things about them particular carbs and nothing wrong on the info.

 

[BogiesAnnex1]

The summit carbs are not bad for a mild build and have some decent features and also use standard Holley parts. They are made from the short lived Holley 4010/4011 series carburetors that get a lot of improvements updates on them. You posted a good bit about them already and covered a lot of good things about them particular carbs and nothing wrong on the info.

These are actually found in the old Ford 4100. Holley picked it up from Ford and there should be little doubt that Holley influenced the Ford design.

Holley made what I think are improvements to the Ford design by removing the rear mounted and integrally cast secondary diaphragm assembly for a conventional Holley fastener attached side mounted diaphragm assembly, changed the fuel inlet system to that of an adjustable Holley, moved tge accelerating pump under the float bowl but left the power valve in the bottom of the primary bowl and kept the annular boost venturies.

Here’s a picture of one on EBay which if you compare with the Holley to Summit redo you can see the fundamental similarities.

Newly Rebuilt Ford 4100 Autolite 4BBL Carburetor. $75 off for a core. | eBay

to the Summit catalog

https://www.summitracing.com/parts/sum-m08600vs?seid=srese2&utm_source=bing&utm_medium=cpc&utm_campaign=Brands+%7C+S&utm_term=4581458797600322&utm_content=GSAPI+5ca6324dae5a6

All in all not a bad carb.

Bogie

 

[55_327]

I put a Summit carb on a friend's base Goodwrench 350 around 12-15 years ago. It was almost identical to a Holley 4010-series I had in the 90s. As I recall, there were square and spread bore versions, and they used a lot of the same parts as 4160/4150 models.

BTW, I don't think that Summit carb has been touched since we installed it. Worked perfectly on that mild 350 -- set the idle mixture and speed, and then drive! But for $35 more, I'd go with the Edelbrock AVS2.

 

[eric32]

The Edelbrock AVS2 with annular boosters would be a more efficient carb vs a Holley style I can say that for a mild build that is not much more then stock and maybe something with a RV type cam size and basic heads. With a metering rod kit you could dial it in pretty well. For a build with good flowing heads and a good intake and a decent entry level performance cam with 215/[email protected] or more and more performance type of a deal I always would go with a Holley style but that is my preference as I have used both Edelbrock carbs over the years and Holley styles and for more performance I always got better overall response from Holley vs Edelbrock but just my preference.

Opinions will vary and that is why there are choices you can make. All have there pros and cons on certain ways they perform on certain builds.

 

[1971BB427]

Quick Fuel carbs are owned by Holley, so they are one company. But QF carbs have always had features stock that Holley charged extra for, so I buy QF carbs myself. I have a QF 650 Brawler on my full roller SBC 350 with Dart heads, and a Howards roller cam, and roller rockers. It's around 420 hp, and 415 ft. lbs. torque in a fairly heavy '39 Chev coupe. It runs great and although I'd recommend vacuum secondaries for lower performance engines, for my build I like the mechanical secondaries.
Only thing I changed were the air bleeds as my engine idle was too rich, even with my idle/air turned almost closed. I put in #74 air bleed jets and I was able to adjust the mixture to where it burned clean at idle, and no more eyes burning!

PS-If you haven't checked Holley's website yet, I'd suggest going there before buying anywhere else! They sell 100% warrantied "factory refurbished" carbs for huge discounts. I spoke to a tech at Holley who told me the vast majority of warranty returned carbs have no issue when they're returned, but get thoroughly examined and tested, so they're great carbs. I bought my 650 Brawler for $210 new, vs. Summit and Jegs price of $679 new.

 

[staleg]

I have a QF 650 Brawler on my full roller SBC 350 with Dart heads, and a Howards roller cam, and roller rockers. It's around 420 hp, and 415 ft. lbs. torque

Sorry to interrupt the thread, but may I ask what Howards cam you have?
Just curious, since I have a similar set up, with Vortec heads, beehive springs. Howard's cam 183215-14.

 

[1971BB427]

Sorry to interrupt the thread, but may I ask what Howards cam you have?
Just curious, since I have a similar set up, with Vortec heads, beehive springs. Howard's cam 183215-14.

118005-09

My engine is a 1990 SBC 350 with the Dart SHP heads. I didn't want the later style Vortecs simply because of the different intakes the Vortecs use. More variety with early style heads.