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  #16 (permalink)  
Old 11-28-2010, 09:06 PM
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Thanks for the advice all sounds good and will take in consideration, is it wise to jump up three sizes on the pump nozzle (squirter)? I watched some of holley's video online and they said move up three nozzle sizes from your stock nozzle your working with. And maybe the orange pump cam would be suitable, using the number one hole for a good crisp pump shot from idle.

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Old 11-28-2010, 09:24 PM
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Holley squirter nozzles increase in size about .002-.003" at a time as it takes that much of a change to make much of a difference. Thats is where the "3 sizes at a time" comes from. Sizes are 25, 28, 31, 32, 35, 37, 40, 45.

Sizes in between these offered by Holley can be made frpm a smaller size with a pin vise and #61-80 size wire drills. I have made lots of 33's out of the almost useless 25's you end up with after modifying a few dozen carbs.
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Old 11-28-2010, 09:52 PM
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670 carb

the above is dead on advice.a correctly sized carb should do great right out of the box.it can be wrenched on to run decent but wont ever deliver the throttle response and fuel curve through all rpms if oversized.if it were me id go with the 600cfm holley also.if that engine spends most of the time between 4500 and 8500 rpm different story.
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Old 11-29-2010, 04:23 PM
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I have both a holley 1850 600 cfm carb and a holley 670 street avenger and I ordered a metering block for the rear of my 1850 carb and both carburetors are basically the same thing except the fuel bowls.

Both carburetors have the same tower,boosters,squirter's, metering blocks and same base plate. Everything is identical on the carburetors.

Makes me wonder if holley takes the 1850 model and adds center hung fuel bowls and a vacuum quick change secondary and rate it a slightly higher cfm rating and puts a different part number on it. Its funny how quick fuel cam out with a 680cfm rated carb to compete with the street avenger models.

I setup my 670 street avenger the same settings as my 1850 and it was dead on idle and idle mixture and everything else. They are very nice carbs for mild engines.

My throttle response on my 350 in my s10 is instant and I can get the rpms up in an instant and the response is awesome all the way though my power band and way out did my old edelbrock.
Eric
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Old 11-29-2010, 05:07 PM
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670 carb

no doubt,i use holley's 750 dominator on my 358.im doing something a little different than our 327 friend though.your exactly right about those floats and blocks.the way they get 70 extra cfm is a verry minor difference in the smallest section of the venturi.makes me wonder,how is quickfuel,bg and all those guys are selling a holley copy?guess they payed for it.carter is now an eldelbrock.
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Old 11-30-2010, 03:20 AM
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the problem with holley's 600cfm is that god awful single feed setup.. I had a lot of fuel starvation problems because of that.

that 670 is ok for his 327. I agree that 600 would be better. (holley 600 with a dual feed conversion)
As long as it's vacuum secondary. (which a street avenger is) you can get away with a fair of amount of 'too much carb' with a vac. secondary because it will only offer what the engine wants.. unlike a double pumper.
I run a 650 (not an aveneger, but yer run of the mill 4150 series) and my 350 loves it. and my 350 is VERY mild.. (214/224 @ .050) i borrowed a buddies 750 and my engine SCREAMED on the top end, but drove like CRAP around town with such a big carb..


I had the same problem.. took me a few tries to get the squirters just right. I still had a slight stumble so I just bumped the idle mixture up a tad to cover it up (it was only from a dead idle)

when I race, I launch from 1500 rpm so it's no problem
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Old 11-30-2010, 06:54 PM
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670 holley

Are these higher cfm holley's better for higher rpm power versus lower end throttle response. I haven't put my foot really into it at a dead stop so hard for me to tell. Just making sure all my mechanic are square before I start tearing it up on the road. Trust it is hard to be so conservative with my chevelle. Want to make sure the drive line pitch angle is correct and everything else. This holley is stock out of the box, I just adjusted float level and idle mixtures and it runs pretty good. But I wonder if my air cleaner is to small, it is 10inch in diameter. Should it be bigger? So the carb is not struggling for air? I had a 14inch air cleaner but it seem to big and I changed it. Maybe a mistake.
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Old 11-30-2010, 07:06 PM
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cfm

cfm = rpm x displacement
-------------------
3456

so max rpm range of motor x displacement

example SBC 350 STOCK motor max safe rpm 5500

so 5500x350= 1925000 divde by 3456 = 557.00 cfm so street motor volumetric efficiency is about 85-90% so a 600cfm would be ok

but a SBC at 6500 x 350 = 2275000 divde by 3456 = 658.27 cfm

all this info is in AUTO MATH HANDBOOK by john lawlor isbn #978-1-55788-020-8 I have used this book for years and has help out great
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Old 11-30-2010, 07:52 PM
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670 carb

hi chevyrally,600cfm is best for that 327.if your going to keep that 670 i would double check some things.verify timing pointer is right when at tdc.theres a piston stop for that,be careful.aftermarket pointers are off sometimes.see what your idle timing is.?low idle timing will give you that stumble.----billy
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Old 12-01-2010, 02:07 AM
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that equation for cfm isn't strictly true. an engine that operates at the top end of the rpm range all the time, or doesn't operate in the part throttle range at all (circle track and drag cars for example) will benefit from more cfm then that equation allows for.

Remember with a vaccum secondary carb, you can get away with over-carbing it a bit because the vac. secondary system will only provide what the engine wants, but if you go too big, driveability will suffer from lack of air velocity through the carb.
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Old 12-01-2010, 07:43 AM
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Cfm

Yeah that's right a little he was talking about street car is about 80-90% efficiency and a full. race car is about 100-plus % because it a racecar bigger valves,cams,intake(2500rpm-7000rpm) ect so the rpm changes so you don't drive your street car at 5500-9000 rpm all the time on the street that is race car stuff so yeah CFM is diFfernet like you said, the math is a starting point instead shooting in the dark CARBs to $$$$ to be wasting $$$$
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Old 12-02-2010, 03:01 AM
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i hear ya.. for every person that told me my 650 was too small, I had another tell me it was too big as far as I'm concerned, it's just right lol
it drives great on the street (still not as nice as a good qjet, but oh well)
makes plenty of power at the track :>
i don't have fuel starvation problems at high rpm any more with the dual feed :>
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Old 12-02-2010, 06:16 PM
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i had the same prb with the 670 i had, i took it to a carb guy and he said it didnt apear to have anything wroung with it, i took it home still did it, the guy kept tellin me it was to bigg for the motor "350 bored 60 over" i kept tellin him nah, so another guy came along and he wasnt a carb specialist but he bulit them b4, so he took it and all he did was took ALL aparrt and just used carb spray if needed and from head to toe, ran like a charm after that, the first gut just checked the front and rear bowls and metering blocks....
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Old 12-02-2010, 09:31 PM
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my buddy had a street avenger.. it was a nice carb, but I found it really irritating that the throttle body didn't have the notch in it by the driver's rear hole.. so none of the 'standard' 4150/4160 holley throttle brackets fit it.
he ended up spending nearly $100 on holley's billet aluminum adjustable uninversal fit bracket to make it work. That's why when I bought my new holley carb, I made sure it was a standard 4150 series and not the street avenger.. funny thing is.. it came with all the same stuff except for the quick change secondaries, which I added for about $20 :>

vac. secondaries, electric choke what else does a hotrod need? LOL
and before you say I don't need a choke.. two words for ya. "Michigan winter" LOL
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