Which Carburetor ?

[Cobraman]

Which Carburetor? Holley or Summit
The prices are very different but all the research I've done the Summit product preforms very well and the price is much better any comments to what others think. This is going on my 408 450hp stroker. Here are the two I'm comparing.

Summit Racing™ M2008 Series 750 CFM 4-Barrel Carburetor SUM-M08750MS
Or
Holley 4150 Double Pumper 750 CFM 4-Barrel Carburetor 0-4779S:confused:

[BUDFIVE]

Cobraman,
I am a big fan of Holley carburetors and of Summit Racings branded products. In fact my fuel pump is a Summit branded in tank pump.
I wasn’t familiar with the Summit M2008 Series so I watched their online video. A couple observations:
-The Summit carb is an interesting design that comes apart easily by pulling the top off (like an Edelbrock version of the old AFB) which reduces the need to replace vertical gaskets on a Holley.
-The Summit carb seems to share some parts (like jets) with Holleys which makes them readily available.
-The Summit carb will run and therefore need to be tuned differently. For example, Summit’s website shows the primary power valve from the factory is a 9.5 in-hg valve. Most street Holleys come with a 6.5. That’s a big difference-why would the power valve need to open that much earlier? The power valve opens when you apply enough throttle to lower engine manifold vacuum through the rated value to enrichen the mixture until rpm increases and the boosters have enough airflow to provide the fuel. Some performance engines idle with 10-12 in-hg of vacuum so you touch the throttle and the power valve would kick in.
-The Summit carb is new and gets decent reviews with a small community of people with reviews and observations on YouTube.

Observations on Holleys:
-Holleys have been around since at least the 60s. They are old but there are new ones with features and bunches of folks who know them and many know them well-a huge offering of YouTube videos and great books (David Vizaard). It is easy to get help. Look at last weeks thread started by ProfessorB-

https://thefactoryfiveforum.com/showthread.php?52103-427W-Holley-carb-jet-recommendations
-Holleys are nostalgic and belong on a mid 60’s muscle car.
-Properly sized (750cfm is good for a 450hp 408) Holley carburetors generally run fine out of the box. Set the idle speed and mixture and they run. Fine tuning takes more work but you’ll get help.
-Holley branded and 3rd party parts are readily available

So I would suggest buying a Holley or one of the Quality knockoffs (Quickfuel now owned by Holley). I would pick one with 4-corner idle screws in case you need to use the secondary throttle plate to get it to idle well. Our cars are light so either mechanical or vacuum secondaries will work and electric vs mechanical choke is personal preference.

[Railroad]

See if you can find the episode of ENGINE MASTERS, doing carb comparisons.
Edelbrock was not even in the game, Holley had an OK review, Summit was deemed, best buy and performance, with good features, AS I REMEMBER.

[Cobraman]

I did see the Engine Masters review and that did get my attention. I also found all the comparisons between the two. I guess the price and the ability to use holley jets and such seems right also. I remember reading somewhere that this was a holley design in the early years but now is much improved. I also looked at the ProfessorB post lots of great input. So maybe more information on what I'm running would help such ad cam specs manifold. So here it is
HOWARD BIG DADDY RATTLER HYDRAULIC ROLLER CAMSHAFT WITH
MOREL LINK BAR ROLLER LIFTERS 228085-09
243in/251ec DUR @ .050. .565in.549ex VALVE LIFT, 109LSA + 103ICL
EDELBROCK RPM AIR-GAP INTAKE MANIFOLD

[cv2065]

Quickfuel Brawler and HR Series are great. Still Holley, but look better.

[BUDFIVE]

I did see the Engine Masters review and that did get my attention. I also found all the comparisons between the two. I guess the price and the ability to use holley jets and such seems right also. I remember reading somewhere that this was a holley design in the early years but now is much improved. I also looked at the ProfessorB post lots of great input. So maybe more information on what I'm running would help such ad cam specs manifold. So here it is
HOWARD BIG DADDY RATTLER HYDRAULIC ROLLER CAMSHAFT WITH
MOREL LINK BAR ROLLER LIFTERS 228085-09
243in/251ec DUR @ .050. .565in.549ex VALVE LIFT, 109LSA + 103ICL
EDELBROCK RPM AIR-GAP INTAKE MANIFOLD

Cobraman that’s quite a cam-it will have 29 degrees of overlap (intake and exhaust valve both open) at .050. Big cams need a lot of air to idle. As in my original note, you will need to open the secondary throttle plate at idle to keep from having the primary too far into the transfer slot. You’ll know this is a problem when you turn the idle speed screw to open the throttle for a decent idle speed, the idle mixture screws seem non responsive. You will also have a stumble when slowly giving it throttle (even in neutral) since the transfer slot (transition circuit) is already being used. On a Holley, you turn the secondary throttle plate screw (usually on bottom of the throttle plate requiring carb removal) to open that plate to give it more air so you don’t need the primary open so far. Then you tune both the primary and secondary idle circuits with the 4-corner idle screws which the 4779 has. This is my point-I don’t know how this works on the Summit carb. Just to see, If anyone on the forum knows how this works on the Summit carb, please jump in?

BTW, I went through this exact learning last summer with my Quickfuel Brawler 650 and 14 degrees of cam overlap @ .050.

[Cobraman]

Budfive
Thanks you diffently have educated me on the subject and I now have a better understanding of how it works, its been since the the late 70's since I've worked on tuning Holley carburetors.

[BUDFIVE]

Cobraman, me too on late 70s Holley tuning so re-learning what I knew and learning more in depth this time for higher performance motors.

[ProfessorB]

Cobraman, me too on late 70s Holley tuning so re-learning what I knew and learning more in depth this time for higher performance motors.

Budfive and Cobraman...me three. Its been since the Seventies.
.
I got as far as pulling the trigger on the carb. I bought a 750 Holley double pumper, mechanical secondaries no choke. It's not the "race" version as it has all the usual vacuum hookups. FYI, Holley is having a Labor Day sale thru Sept 14th. I ordered it direct from Holley, free shipping and for some reason they didn't bang me for SC state sales tax. Now, I've got to wait to get other stuff as my budget is shot for the month. Probably gonna get a wideband air/fuel gauge, adjustable regulator, some stainless braided fuel line and fittings. But at least I have the carb....

[Mike.Bray]

Check out this regulator https://www.summitracing.com/parts/hly-12-880

It will work on your carb and when you decide to upgrade to EFI all you have to do is change the spring out.

[MB750]

I like my Edelbrock AVS2. I used a sizing calculator and it recommended I only need a 500 CFM carb so that's what I went with.

I went with that carb because I liked how you could change Jets by just taking the top off. I also liked the new annular boosters and how they did a better job atomizing the fuel.

I bought the tuning kit with it, and using my wideband oxygen sensor I have that thing tuned in as good as any EFI system.

[Mike.Bray]

As in my original note, you will need to open the secondary throttle plate at idle to keep from having the primary too far into the transfer slot. You’ll know this is a problem when you turn the idle speed screw to open the throttle for a decent idle speed, the idle mixture screws seem non responsive. You will also have a stumble when slowly giving it throttle (even in neutral) since the transfer slot (transition circuit) is already being used. On a Holley, you turn the secondary throttle plate screw (usually on bottom of the throttle plate requiring carb removal) to open that plate to give it more air so you don’t need the primary open so far. Then you tune both the primary and secondary idle circuits with the 4-corner idle screws which the 4779 has.

Jeez this brings back (bad) memories. Had a pair of Holleys on top of a 6-71 blower one time, got to where I was seeing Holley carbs in my sleep. Ended up with Carter AFBs, they just worked better with the blower.

My next blower had EFI from BDS on a 468 BBC. 16 injectors with a special ECU that ran the engine on 8 injectors up to 80% capacity and then kicked in the other 8. Allowed for a lean idle and low end but still had the fuel flow on the top end.

218395218396

[BUDFIVE]

Cobraman , Mike has a good suggestion. But, look at all the HLY-88X regulators-they are footprint compatible and offered in different finishes and pressure ranges. If you’re preserving cash you can buy the 887 for $82 (Summit) and achieve 4.5-9psi, perfect for a carb. You can plumb the system with 3/8 (6AN) lines and fittings on both the feed and return lines with an in-tank 255 or 340 lph pump. Then, if you choose to switch to EFI later, swap only the regulator for 12-886 ($99) for 15-60psi.

Edit-side comment for background: The full size (6AN) return line is important for carb applications with in-tank pumps. If the return line is too small the high flow EFI capable pump will defeat the regulator-the flow must go somewhere and if not the return it will go to the output and pressure will rise above the desired range. There’s a great video on this on PRO-M racing.

[Cobraman]

OK I already have the regulator that Mike suggested and have set up everything to change to EFI later if need be so I'm going with https://www.summitracing.com/parts/qft-br-67257 thanks for all your help

[cv2065]

Another regulator suggestion. The X1 has conversion kits available if/when ready for EFI. Aeromotive....there is no substitute! :p

https://aeromotiveinc.com/products/x1-series-carb-standard-return-style-regulator

[CraigS]

I have never had a cam like yours but...on my kind of mild 351 I killed myself trying to get a vac secondary carb to work. Put a mech secondary on and felt like I gained 30hp in the 2000 to 4000 range.

[rich grsc]

Carburetors just give an approximation of the correct fuel your engine needs, only correct part of the time. Fuel meters, jets, power valves & air bleeds are all fixed in place, not adjustable while in use. A quality EFI adjusts fuel needs thousands of times per minute, using engine speed, vacuum, load, temperature and oxygen meters, and spark timing. Carbs can't be 'as good' as an EFI. Take a car with a carb tuned at sea level and drive to Pikes Peak, it won't run the same.

[Cobraman]

I have never had a cam like yours but...on my kind of mild 351 I killed myself trying to get a vac secondary carb to work. Put a mech secondary on and felt like I gained 30hp in the 2000 to 4000 range.

So I pulled the trigger on a quikfuel Brawler 750 mechanical secondary after some serious hours on the phone with engine builder,Holley, and Howard cams now I feel like I just earned a degree in the subject. But I have their #'s on speed dial. On to the next episode of build you're own Cobra:cool:

[Mike.Bray]

Carburetors just give an approximation of the correct fuel your engine needs, only correct part of the time. Fuel meters, jets, power valves & air bleeds are all fixed in place, not adjustable while in use. A quality EFI adjusts fuel needs thousands of times per minute, using engine speed, vacuum, load, temperature and oxygen meters, and spark timing. Carbs can't be 'as good' as an EFI. Take a car with a carb tuned at sea level and drive to Pikes Peak, it won't run the same.

And that is why there hasn't been an OEM car sold with a carburetor since the early 90's, 30 years ago. Emissions and fuel economy drove the OEMs to EFI, they had to increase the efficiency of the engines over all ranges, temperatures, and parts of the country.

[cv2065]

So I pulled the trigger on a quikfuel Brawler 750 mechanical secondary after some serious hours on the phone with engine builder,Holley, and Howard cams now I feel like I just earned a degree in the subject. But I have their #'s on speed dial. On to the next episode of build you're own Cobra:cool:

Good choice! Aside from minor adjustments, should work right out of the box.

[rich grsc]

Mike, that is a truth anyone can understand, unless you're a carb guy, with carb monkey. ;):p

[cv2065]

And that is why there hasn't been an OEM car sold with a carburetor since the early 90's, 30 years ago. Emissions and fuel economy drove the OEMs to EFI, they had to increase the efficiency of the engines over all ranges, temperatures, and parts of the country.

Manufacturers primarily switched to EFI in order to satisfy more strict government emissions standards, i.e. GREEN. Lots of money to be made through production standardization. Not really something I care about when driving a Cobra. And you won't get me to put a catalytic converter on my car either no matter how emissions friendly it is. :p

[Mike.Bray]

Manufacturers primarily switched to EFI in order to satisfy more strict government emissions standards, i.e. GREEN. Lots of money to be made through production standardization. Not really something I care about when driving a Cobra. And you won't get me to put a catalytic converter on my car either no matter how emissions friendly it is. :p

That's what I said, they had to increase the efficiency of the engines to meet stricter standards. Precise control of the air/fuel ratio in all conditions and engine speed/load is required, something a carburetor can never achieve.

[cv2065]

That's what I said, they had to increase the efficiency of the engines to meet stricter standards. Precise control of the air/fuel ratio in all conditions and engine speed/load is required, something a carburetor can never achieve.

Strict environmental standards. Which means big political money as well as production standardization, which saved manufacturers money. Had little to do with performance for the average driver getting to work and grocery store. What do they care? It's all about the money. When a car is easy to fix at home, that's less a dealer can make in repair. Computers ensure that EVERYONE has to take their car to the dealer for diagnosis.

Look at the catalytic converter they force on vehicles today? $1200? For what? All I know is that they are constantly getting stolen off of our store delivery trucks sitting out in the parking lots.

EVs are the next big environmental push and the "EFI" of the current decade that will eliminate fuel based cars altogether. Again, all about the money.

[rich grsc]

NOT about the money, it's improved efficiency, better performance, smooth even power and still decent mpg. No carb can match EFI in performance.
EFI has nothing to do with stollen catalytic converters, and EV's aren't about "the money" either. Take that false story up with environmentalists who are convinced they are destroying the planet

[cv2065]

NOT about the money, it's improved efficiency, better performance, smooth even power and still decent mpg. No carb can match EFI in performance.
EFI has nothing to do with stollen catalytic converters, and EV's aren't about "the money" either. Take that false story up with environmentalists who are convinced they are destroying the planet

It’s ALWAYS about the money Rich. The environmental scam is just a way to launder it

[Cobraman]

Well with all that being said I agree that EFI is diffently more efficient but i like my Holley 750 I can work on it on the side of the road and every auto parts store has parts for them if needed EFI not so much. That's my story and I'm sticking to it.

[cv2065]

Well with all that being said I agree that EFI is diffently more efficient but i like my Holley 750 I can work on it on the side of the road and every auto parts store has parts for them if needed EFI not so much. That's my story and I'm sticking to it.

Agreed. Here’s a great article from Hotrod.com

https://www.hotrod.com/how-to/carburetor-vs-fuel-injection-we-put-both-to-the-test-on-ls-engine

[Mike.Bray]

218523

[Cobraman]

218523

Sorry Mike budget vs realality it's setup to receive EFI at a later time. And yes I have a red neck.