Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/3.73 - Chevelle Tech
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post #1 of 36 (permalink) Old Apr 7th, 20, 11:55 AM Thread Starter
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Jeff
 
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Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/3.73

Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/3.73

Whats up Chevelle family, working on the 70 quite a bit this year and now with this down time in the world, have been able to invest a bit more time.

Some of the major upgrade this year - TKO600, New Fuel Tank, Steel fuel lines, holley billet black pump (pre and post filters), new engine side wiring harness, new Distributor, fully resealed engine. New UMI spuspension all the way around


What is the ideal Carb & CFM (Mechanical or Vacuum Secondaries) combo for best street drivability and performance with my current setup. I have had some feedback in regards to mechanical vs vacuum secondaries and the info I receive has been all over the place, I am still on the fence. I hear Mechanical secondaries are the way to go with a manual trans, although I also hear there is a "flat spot" with street use/driving. I also hear that modern vacuum secondaries out perform mechanical double pumpers even with manual trans for street use. I am on the fence.

Current & Intended Driving:
Daily driver, street rod, plan to take it to the track rarely, after I get the safety items checked off.


My mildly modified setup:
383 stroker/TKO600 5speed/votec heads/mild lunato vodoo cam/MSD Ignition/heman headsers/3.73 10 bolt/electric fuel pump


What are your thoughts on the following?
What is the best Holly type carb (I have had several and like/understand them)?
What is the proper CFM given my current setup? For mostly street, and daily driving use
Should I go with Mechanical or Vacuum Secondaries? (Pros/Cons)? totally on the fence with this one

I was considering the following carbs:
1: Holley Brawler 670 CFM (mechanical secondaries double pumper)
2: Holley Street Avenger 670 vacuum secondaries
3: Pro Systems bench built carb (https://www.prosystemsracing.com)

I know there are several legends on this board, so thought I would ask here before making a decision. Thanks in advance.

Just for reference this is an old post I did a while back when selecting the carb for when I had the 700R4 and before many upgrades since then for reference or anyone who is running a similar setup below.


https://www.chevelles.com/forums/13-...-3-73rear.html
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post #2 of 36 (permalink) Old Apr 7th, 20, 12:46 PM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

Well that kind of a trick question of which carb will work the best. I have several carbs and for me on the street it's the one that has the best drivability. I have on my street car now a Holley 750 street HP vacuum carb that runs very well but the sec side is very slow to come in and it need the little tube put in to make it work right. As for the 670 deal, the Brawler is just a Holley re-badged QF carb and is not the same as 670 Avenger. I recently bought a new FST 750 carb from Summit and it has a ton of nice features and comes in several sizes. The price was really good and when I got it I was very impressed to say the least. Now I just need a little better weather to try it out. Because you have a stick car a DP will benefit you more than a VS as you can control the throttle better with the stick.
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post #3 of 36 (permalink) Old Apr 7th, 20, 1:26 PM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

Hi
Holley recommend D/P manual light weight vehicle . There are street D/P Versions
If u want some economy and ""normal "mixtures a quality vac sec might be better.

Remember a well tuned vac sec comes close in HP to a DP.
Supposedly part throttle acceleration is better in a Vac sec carb
Holley suggests size/CFM street 100VE sizing . For Racing 110% VE for cfm calculation
6000rpm street 664cfm ,,race 110% 732 cfm

Brands 670--680 cfm
Quick fuel either Hotrod or SS, super street series .
Holley Ultra street
The QF are typically more adjustable and cheaper than Holley
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post #4 of 36 (permalink) Old Apr 7th, 20, 1:46 PM
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OLIVER
 
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

With a manual I would go DP ... About 700 $ custom made carb to your engine-trans specs by Prosystems which is a 4150 dp by Holley , you will not be disappointed , it will be spot on out of the box !
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post #5 of 36 (permalink) Old Apr 7th, 20, 2:27 PM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

670 Street Avenger.
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post #6 of 36 (permalink) Old Apr 7th, 20, 5:16 PM
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Bob
 
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

lots of misinformation in this thread, vacuum secondary carbs work well in manual trans cars-probably hundreds of thousands left the showrooms back in day, if you like to tinker and tweak use a double pumper it will accelerate better, if you want to bolt the carb on and ignore it afterwards use a vaccum sec
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post #7 of 36 (permalink) Old Apr 7th, 20, 5:32 PM
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Kerry
 
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

When you say street/daily driving, and mild 383, my choice would be a vacuum secondary, electric choke Quick Fuel SS735VS. The reason for this is that it has 1.312" primary venturi, the same as a 650/680, but larger 1.437 secondary venturi like a 780. Both primary and secondary throttle bores are 1.687 the same as a 750/780. This way you have the better throttle response and atomization for cruising of the smaller primaries, but the higher cfm for full throttle, getting as close as you can to the 780 size carb which would make the most power on your engine in all likelihood.

Be aware, that almost every Holley carb needs the IFR relocated in the blocks, the excessive emulsion fixed, and transfer slot restrictors in the primary side of the main body to control the 1500-2500 rpm fueling properly/best for the street.
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post #8 of 36 (permalink) Old Apr 7th, 20, 8:06 PM
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Mark Whitener
 
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

I wish I had an answer for a good out of the box. The Quick Fuels are fine with some work, t-slot restrictions, lowered idle feeds, and emulsion/main air bleed changes. I'm trying to get an FST to see what they are like, they are still having trouble getting parts. I'm told another week they should have the stuff, if it looks good I may buy them to sell for budget street cars, making changes I see necessary.

Mark Whitener

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post #9 of 36 (permalink) Old Apr 7th, 20, 8:12 PM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

Jeff my personal preference would be to go with Mark. This is a custom DP he did for my 406...

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post #10 of 36 (permalink) Old Apr 7th, 20, 10:00 PM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

Calculate the CFM needed for the engine size and max RPM.

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post #11 of 36 (permalink) Old Apr 7th, 20, 10:14 PM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

Vacuum secondaries can be dialed in to open very quickly.

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post #12 of 36 (permalink) Old Apr 7th, 20, 10:56 PM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

Quote:
Originally Posted by chasmalo View Post
Vacuum secondaries can be dialed in to open very quickly.

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While that is very true, when they open nice and fast for a speed contest it has some bad side effects on fuel mileage opening too soon going up a hill for instance. The DP with a stick is the best way IMO.


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post #13 of 36 (permalink) Old Apr 7th, 20, 11:33 PM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

HI
Nothing beats a Quick fuel for adjustability
4 cnr idle
screw in high low bleeds
screw in IFR idle feed restrictor
screw in PVR power valve restrictor
thread taped for screw in emulsion jets,, outta the box drilled but ready for jetting

elec choke
fine tune screw for secondary [screw adj is equal to 1/2 spring change ]

Might have better butter fly shaft seals/bearing

Go the QF SS Super Street
Only the Ultra street gets close but still not the same
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post #14 of 36 (permalink) Old Apr 8th, 20, 12:04 AM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

Get a 800 cfm quadrajet from smicarburetor.com

https://www.smicarburetor.com/produc.../productID/854

And lose that electric fuel pump. Talk about headaches....

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post #15 of 36 (permalink) Old Apr 8th, 20, 12:07 AM
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Re: Title: Best Carb CFM (VS/MS) Combo? 383 stroker/VORTEC/TKO600/MSD/

I replaced my Chevelle's Quickfuel with a Holley Street Demon, and am doing the same for my truck, which currently has a pretty well tuned 650 DP. My stuff is only street driven, but I'm impressed with the snappy response from the Demon. I should pick up a few MPG too.
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