Lost on carb choices.

[vintageman]

My Eddy has vacuum secondaries, and the secondaries hesitate a bit while fuel starts to pull. My understanding is that other carbs have a squirter in the secondaries (like the primaries) to fix this. Does the Summit carb have squirters in the secondaries?

Off the top of my head, I don't remember but will try to remember and check when I get out to the car. I haven't had any issues though with hesitation.

Tom

 

[Bentworker]

Almost pulled the trigger on this​

M2008 Series Carburetors SUM-M08750VS . On Summit​

4.75 out of 5 stars ( 149 )


Part Number: SUM-M08750VS


4.75 out of 5 stars ( 149 )


Part Number: SUM-M08750VS

What is making you lean towards an Autolite clone?

 

[Spike Morelli]

Carb choice, everyone ( who has a few grey hairs on their head) has had experience with carbs. The overwhelming choice for performance is the Holley 4160 / 4150 model. Incidentally, the modern Holley squarebore 4160 that we all know today was ORIGINALLY designed for being OEM equiptment on Ford's 1957 Thunderbird, to replace the "teapot" style 4 barrel carb used by ford up to then, so historically, if nothing else, the Holley is a more acceptable choice for any Ford, Then, 12 years later, Holley designed the Dominator for Ford's Nascar and Road Race program. Revel in the fact that every Chevy today is running induction designed , and introduced, for Fords.
The Carter AFB ( aluminum four barrel ), is a good carb, and it has it's good points. The very best Carter carb for performance was the "Competion Series", I believe made in 500cfm and 750 cfm ratings. I'm talking about the real AFBs, not the Edelbrock re-pops. The Carter carb was used as OEM on many Mopars during the Musclecar era, and should be considered proper induction for those cars. The Carter carb is not made today, hasn't been in quite a while, so don't think that Edelbrock IS a Carter. The Edelbrock carb is/was manufactured by Weber. I know the Edelbrock carb, though mimicking a Carter in every way, still doesn't run as good as a for real Carter AFB. If I had my druthers, I'd stay away from AVS ( air valve secondaries) for any serious performance.
All that said, the Holley style carb design , and components, have been produced by many aftermarket carb builders. Many of the features of these new race themed carbs are an improvement FOR RACING, most street cars however, should not be lured into purchasing one of these for everyday driving. Cars driven on the street need the choke, don't need four corner idle screws, double accelerator pumps, and MOST don't even need mechanical secondaries. Proper carb selection requires giving the engine what it needs, what it wants, NOT what you want to give it .. Even if an "X" sized carb made the most HP on an engine dyno, ever see a dyno pull? The numbers are made with a constant accelerating, wide open throttle, up to maximum designed-in RPM limit. You don't drive a car on the street that way, so fuel delivery is a whole different animal at idle, cruise, part throttle tip-in, so dyno numbers don't accurately reflect the carb that will run best in the car on the street, or accelerate out of corners, etc.
It is a stone cold FACT, that the vast majority of enthusiasts cars driven on the street are overcammed, and over carbed. Are you in that category? Don't be. A standard 4160 / 4150 Holley of proper cfm ( not drag race specs ), should always be the first choice on the street ,and looks good, and, is the appropriate aftermarket design for these cars. Now, for those of you who have cammed their engines to the point of not having proper vacuum signal at the butterflies, sure, we used to drill holes in the secondary butterflies. TODAY, you can order a new Holley with an adjustable idle air leak , which is hidden down the center where the air filter stud threads are, and can be adjusted for idle quality with a thin screwdriver, making drilling butterflies, somewhat of a thing of the past. Just stay away from "Trick" carbs, .....andwhen in doubt always, buy new. A friend's used carb can be a crapshoot.

 

[giantpune]

My Eddy has vacuum secondaries, and the secondaries hesitate a bit while fuel starts to pull. My understanding is that other carbs have a squirter in the secondaries (like the primaries) to fix this. Does the Summit carb have squirters in the secondaries?

I believe one fix for this is to tighten up the AVS spring.

 

[73inNH]

I believe one fix for this is to tighten up the AVS spring.

I've played a bunch, but I'll try a bit more. The carb works well except for a quick blip of hesitation when flooring it.

 

[giantpune]

I've played a bunch, but I'll try a bit more. The carb works well except for a quick blip of hesitation when flooring it.

This video talks about it a bit.

 

[Stanglover]

As far as looks go, an Edelbrock looks right at home on a Mopar. I've had more problems with Edelbrock carbs than I ever had with Holley carbs. As to the vacuum vs mechanical secondaries, I like mechanical with a manual transmission and vacuum with an automatic. Just me.

What's wrong with Mopar's? Those are my next fave vehicles. Now Chevy, that's another story!!
Actually to be truthful, all brands have some great cars and all deserve to be loved...... by someone.

 

[Sheriff41]

What's wrong with Mopar's? Those are my next fave vehicles. Now Chevy, that's another story!!
Actually to be truthful, all brands have some great cars and all deserve to be loved...... by someone.

Nothing wrong with Mopars. My comment was the Edelbrock carbs look at home since Mopars used Carter carbs, which the Edelbrock resembles.

 

[Hemikiller]

I ran an original Holley 4010 for many years on my 71's 302. This is the carb that later became the Summit M6008 series, It was the 600 double pumper and it always ran flawlessly. I currently have a Summit 600VS on the 429 in the wagon and am very happy with how it runs. Both were swap meet finds for pennies on the dollar.

The 2V headed engine in the Cougar has an Edelbrock AVS2 #1906 650cfm. This carb has really surprised me with how well it runs. I have an AOD in that car, so there's no wonky kickdown setup to deal with. I stick my foot in it and it goes, it cruises nicely on the highway. IMO, it is miles ahead of the previous AVS series carbs I've driven.

The 71 Mach now has a fairly stout 4V headed 351C with a double pump Holley 800 on it. I have no issues with that either. I'm more of a Holley guy and tuning them is somewhat second nature to me.

No matter what carb you get, be sure to check it over 100% before bolting it on.

 

[Dinger]

I was thinking of this. https://www.amazon.com/BRAWLER-CARB...3b24bcb5&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

 

[Hemikiller]

I was thinking of this. https://www.amazon.com/BRAWLER-CARBURETOR-ELECTRIC-MECHANICAL-SECONDARIES/dp/B088P9XTBM/ref=sr_1_1_sspa?crid=3QNKUL48YFA9B&keywords=holley+brawler+650&qid=1693847487&sprefix=holley+bra,aps,121&sr=8-1-spons&ufe=app_do:amzn1.fos.ac2169a1-b668-44b9-8bd0-5ec63b24bcb5&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

No experience with them, but they seem popular. I'd say that's a good choice for a near stock 351C. IMO, buy from Summit, not Amazon.

https://www.summitracing.com/parts/qft-br-67276
You'll also need the ball stud kit if yours isn't removable.

https://www.summitracing.com/parts/qft-28-100qft
Hook your electric choke to the Red w/Yellow hash mark wire in the engine harness. That's a hot wire with the key in run.

 

[Bentworker]

That Brawler carb isn’t shown as having a ford kickdown assembly.

 

[mrgmhale]

My Eddy has vacuum secondaries, and the secondaries hesitate a bit while fuel starts to pull. My understanding is that other carbs have a squirter in the secondaries (like the primaries) to fix this. Does the Summit carb have squirters in the secondaries?

Our Holley 750s are vacuum secondary (VS), and have no secondary accelerator pump (aka "squirters"). I figure they are counting on the secondaries to open gradually enough to not need an extra shot from the accelerator pump. That was only a problem with a 780 CFM Holley VS I once had on a pretty heavily built 351W back in the mid-70s. I ended up installing a 50cc Reo brand accelerator pump, and recurved the accelerator pump actuating cam, to make certain I was getting a shot of fuel from the accelerator pump throughout the entire throttle opening range, not just the first 50% of throttle opening or so. I was able to get rid of the mid-range WOT hesitation.

Some, or maybe all, of the mid-range WOT hesitation could well have caused by me as I had installed a few different springs in the VS Diaphragm housing/chamber to get the secondaries to open a bit sooner and faster than the factory spring provided for - just because it felt like the engine could handle more (it could and it did).

On our 2 current 750 VS carbs (one is a stock 69 Shelby 428CJ, the other is another built 351W in a 73 Mach 1), I have opted to leave the factory VS Diaphragm springs in place, and have not had to upgrade the accelerator pump to the Holley 50 cc unit. When I go WOT on either, I can both hear the roar from the intake (Ram Air, so I can hear a lot of the intake noise), and definitely feel the increased pulling power of the engines as the secondaries are opening. I always need to back off the throttle before the VS blades are completely open, either because I am running out of strip length or roadway, I am catching up to traffic ahead of me too quickly, or I have decided I have no need to see what the top end is for whichever car I am driving in.

For the 428, I do not feel I am over-carbing the engine because it is the manufacture selected CFM rating and oem carb. If anything, it feels like I could move the size up a bit if I was craving more power (I am not craving more power, it is perfectly fine as it is). At about 90 MPH The roar of the carb is no longer increasing, which is indicating the throttle blades are all open completely. I guess I could rig up a small camera above the carb inside the air cleaner housing and watch for the throttle activity, or safer yer, place a small camera outside the carb and see when the secondary throttle blade shaft is done opening (no risk of a small camera accidentally dropping into the intake manifold).

For the 73 Mach 1 with the transplanted Street/Strip 351W, I am certain 750 CFM is over-carbing the engine until it begins to crack into the 6,000+ RPM range. Perhaps someday I will be out driving and find I have no traffic ahead of me for 2 miles or so (and hope there are no state troopers along that stretch head of me) and just open it up to "blow out the carbon." I swapped in an AOD with its 3.5:1 TractionLok gears, and am curious how well the Street/Strip built 351W will fare when pushing through air resistance in triple digit speeds with the AOD in overdrive gear. And I am also curious at what point the secondaries will be fully opened.

I do believe I just talked myself into installing a small camera outside the two carbs to watch the secondary shafts opening up at WOT. And, given the very intentional nature of what I planning to do I also think it is high time I visit our local speedway so I do this "all important research" somewhere other than on the public highways, despite the high level of temptation I am fighting... I have never tracked either car, and have been curious about how they would do on a sanctioned 1/4 mile strip. Prior pony cars I have tracked - something every car buy/gal should do at least once in a lifetime.

Getting the final top end out of them may be a bit dicey as I am not sure how long the track is at our local strip when it runs past the traps. With power disc brakes in great condition on both cars I could probably stand on the throttle a bit past the traps, but at other strips that grave/sand pit at the end comes up awful fast at 140+ MPH (2020Shelby GT500 I did track one day the other year - Ford Track Attak for new Shelby buyers).

 

[mrgmhale]

Most Clevelands can handle more than the 600 cfm most calculators recommend. I ran a 750 Holley with vacuum secondaries, the engine shop dropped down to #70 jets from #72 and it ran perfect on my low compression cleveland. Good luck!!

With good breathing engines (like the 351C) I have found 750 Vacuum Secondaries (VS) to work well. Those VS systems do a lot to forgive overcarbing, as the blades open only as much as the engine can use, unless the VS diaphragm spring being used is too light for the engine. I had a 69 351W 4v back in the 70s that I had built to be a nasty little beast, and currently have a 73 Mach 1 that a 351W was built and dropped in (prior owner) to replace its original 302.

The 69 had a 780 CFM VS carb that ran tremendously. I succumbed to other folks telling me I was running too large a carb. I installed a 650 or 700 CFM (can't recall which it was) double pumper with mechanical secondaries. After trying do dial in the jets and power valve I finally took it off and reinstalled the 780 that had been doing so well. The 650/700 just could not deliver the top end and performance smoothness of the 780 VS carb.

The 73 Mach 1 came to me with the built 351W and 750 VS carb. I have not felt the need to try improving the 750 carb performance, it really does a nice job the way it is set up. I suspect the prior owner, and his brother who is a really good tech, did a lot of setting up over the years he had it (35 years).

At the other end of the engine size spectrum we have a pure stock 69 Shelby GT500 with a 438CJ sporting an oem Holley 750 VS carb. That is a perfectly sized carb for that engine in stock form. I have never felt the need to try to improve its performance.

 

[Stanglover]

Nothing wrong with Mopars. My comment was the Edelbrock carbs look at home since Mopars used Carter carbs, which the Edelbrock resembles.

Ah, didn't know that. I though Mopar's use Rochester Carbs.

 

[trillizo_y_uno]

My Eddy has vacuum secondaries, and the secondaries hesitate a bit while fuel starts to pull. My understanding is that other carbs have a squirter in the secondaries (like the primaries) to fix this. Does the Summit carb have squirters in the secondaries?

You need to swap out the springs so the secondaries open sooner. That will definitely fix your issue.

 

[Hemikiller]

That Brawler carb isn’t shown as having a ford kickdown assembly.

The OP's is a 4 speed car.

 

[Dinger]

I decided to go with the Brawler. I will post how it goes.

Thanks for the help.

 

[Dinger]

Not a good start for the brawler

 

[Dinger]

I think I found the problem