Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rear - Chevelle Tech
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post #1 of 16 (permalink) Old Apr 15th, 19, 4:47 PM Thread Starter
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Jeff
 
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Question Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rear

The 70 chevelle has been running strong until recently, the carb has once again gone haywire. I was thinking of also going to a bigger carb for my setup. I have cleaned it and now we are back to good operational condition.

What is the ideal Holley Carb & CFM combo for best performance with my current setup.

Background:
I know the issue with the carb is the ethenol is likely deteriorating my current fuel lines, which is about every year or so, the carb will need to be fully cleaned. I drive almost daily so this has been done before. Last time I just replaced with a fresh Holly 600CFM/vac secondaries a little over a year ago.

So my next step is stainless fuel lines, new tank, and new cab (better/bigger), new fuel filter, so I should be able to go more than a year without some issues with the carb contamination.

I drive the almost daily, but like to mash the throttle and would like to get as much driving performance form the engine as possible. Not worried much about gas mileage.




My mildly modified setup:
383 stroker/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 carb (I have had several and like/understand them)?
What is the proper CFM given my current setup?

I was considering the Holley Street HP 750CFM, although I saw on holleys website this is for a high stall application. Also my current full throttle 700r4 is shifting around 4200 at WOT.

I know there are several legends on this board, so thought I would ask here before making a decision. Thanks in advance.
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post #2 of 16 (permalink) Old Apr 15th, 19, 6:09 PM
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Rick
 
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

Holley Sniper Efi....


But if i was to pick a carb for that combo, 650cfm would be the biggest I would go, I like mechanical secondaries.
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post #3 of 16 (permalink) Old Apr 15th, 19, 6:40 PM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

Quote:
Originally Posted by Calculated Risk View Post
Holley Sniper Efi....


But if i was to pick a carb for that combo, 650cfm would be the biggest I would go, I like mechanical secondaries.
I would agree with this 100%. Since you're doing all that work to change tank and fuel lines, go electric intank pump and go from there.
Then the efi will be icing on the cake. I understand the cost involved, but then you will literally never have to buy a carb again!

I did the same thing you're doing...
Had a 350... went 650 edelbrock.
700 Holley DP(I would spin it to 7k, but it ran well)
Then I went to a big block and needed an 850 demon.
At the end of it, if I went with EFI(At least a throttle body set up) I would have spent way less.
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post #4 of 16 (permalink) Old Apr 15th, 19, 7:16 PM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

yes holley sniper would be the way to go.
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post #5 of 16 (permalink) Old Apr 15th, 19, 7:36 PM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

Use Viton lined lines R9 spec and a Viton needle/seat, and you should be problem free. 750 cfm is tops, and really 700 at 5000 rpm = 670 . How about a street Avenger.?

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post #6 of 16 (permalink) Old Apr 15th, 19, 10:05 PM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

I used to run an 850 Mighty Demon on my pump gas 358. Car ran great and picked up .2 tenths over my 850 Holley.
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post #7 of 16 (permalink) Old Apr 15th, 19, 10:41 PM
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Kerry
 
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Get a kit to tune your governor weights to raise your full throttle shift points.
The 750 street demon is a great carb for what you want.
The earls vapour guard fuel line is easy to work with, you won’t have to replace for many years.
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post #8 of 16 (permalink) Old Apr 17th, 19, 9:51 AM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

SuperSlickRod Quote:
I was considering the Holley Street HP 750CFM, although I saw on holleys website this is for a high stall application. Also my current full throttle 700r4 is shifting around 4200 at WOT.

750CFM DP is what they are saying. Holley 750 (780) Vacuum sec. will work fine for your application.

Louis
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post #9 of 16 (permalink) Old Apr 17th, 19, 11:21 AM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

I'm going to 2nd the Holley Sniper suggestion, especially since you're already planning on buying a new tank and electric pump anyway. I know every piece is incrementally more expensive (the EFI tank vs. stock tank, Sniper vs. carb, new EFI pump) but the end result is very satisfying. Especially for someone daily driving, like you are.

Also mentioned was adjusting the governor weights/springs in your 700R4 so it shifts higher than 4200. This is killing your performance. It's a little bit of trial and error getting the right setup of weights/springs, but I'm guessing your Vortec 383 could easily run to 5200+ (you didn't mention which cam you have) You're losing the best rpm range of your engine! Carb or EFI, this is a cheap, worthwhile upgrade.

-Dave
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post #10 of 16 (permalink) Old Apr 17th, 19, 12:13 PM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

Quote:
Originally Posted by Calculated Risk View Post
Holley Sniper Efi....


But if i was to pick a carb for that combo, 650cfm would be the biggest I would go, I like mechanical secondaries.
Best carb I ever had on a built 350 (10:1 Isky 280 DP headers etc) was a 650 dp even with an automatic
Killer throttle response everywhere and never ran out of air. Every 750 I tried felt like I was going backwards.
You can feel the secondaries in the pedal so its easy to watch mpg if thats your thing. Vacuum sec that dont always work right is irritating as hell. So dont let anyone say DP are for stick only...bs.

the 750s would accelerate real well, throttle response was avg. The 650 2x responsive and would light the tires up instantly. GM used 750 cfm carbs on a lot of stuff just calibrated them differentl I think it was a bean counter thing. None of their engines (save for a few) really could make use of 750.
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post #11 of 16 (permalink) Old Apr 21st, 19, 11:39 PM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

I think the OP has two options to pick from: a Holley Street Avenger 770 or a good ole Holley 3310 750, both of which have vacuum secondaries.

I also think the that every time an OP asks for a carb suggestion, everyone who replies back with EFI as an answer should be forced to give the OP $50 towards his new carb.
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post #12 of 16 (permalink) Old Apr 22nd, 19, 2:09 AM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

Hi Jeff,

I have a 79 Malibu driver with a 350, vortec heads, 10:1 compression, Lunati 268 hydraulic flat tappet cam, performer manifold.
I put an old 3310-1 780 vacuum secondary on it. 72 front jets 6.5 power valve, 80 rear jets (I put a rear metering block on it years ago), Purple secondary spring.
The engine idles great, throttle response is crisp and going to full throttle is seamless and pulls hard.
I have a 670 Street Avenger that I could not make the secondaries come on as smooth as the old 780. Soon I will put a slash cut tube in the 670 pullover passage to see if it will work better.
A 650DP should work good also as many have said.

Good luck.
Jason

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post #13 of 16 (permalink) Old Apr 22nd, 19, 8:01 AM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

Quote:
Originally Posted by pockets View Post
Get a kit to tune your governor weights to raise your full throttle shift points.
The 750 street demon is a great carb for what you want.
The earls vapour guard fuel line is easy to work with, you wont have to replace for many years.
I second the 750 street demon. It's a much-improved quadrajet design with small primaries for good low-end response and big secondaries for excellent top-end.

And it's only $355
https://www.summitracing.com/parts/dem-1904
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post #14 of 16 (permalink) Old Apr 22nd, 19, 8:57 AM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

If you are getting trash in the carb like you say I would invest in a better fuel filter.
I have ran my carbs for many years without issues from dirt or debris.
And I like running the E10 myself.
Run a Wix 33003 filter right before the carburetor and change it about 2 times a year.

I can't suggest a carburetor as I do not leave my Holleys stock. they all get the port treatment.
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post #15 of 16 (permalink) Old Apr 22nd, 19, 2:25 PM
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Re: Best Holley & CFM Combo? 383 stroker/vortecHeads/700r4/MSD/3.73rea

A couple of questions :

Does your msd distributor have vacuum advance ?

Why are you running an electric fuel pump ?

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