spokewrench

I have been following the threads about oversized carbs here, and thought about taking my 700 double pumper apart and installing a 750cfm ProForm main body and ProForm secondary metering block ( to have 4 corner idle mixture adjustment), so I did it! I now have 4 corner idle mixture adjustments and the plugs finally all read the same! I followed Lars tech paper to set this thing
up and the Power is unbelievable off idle and in the upper rpms is just scary fast! I took the car out and at about 25 mph in first gear and floored it, the power was so instant that both back tires broke loose and the car started getting sideways! That never happened with the 700! Oh well all I can say is Wow, this is definately what this ZZ-430 Clone needed! If you guys buy this main body be careful to drill out the secondary idle circuits in the throttle base plate- They do not mention this in the instructions- :eek: :eek: :eek:

The Dude

DUDE! :eek:

Don't you know what "they" say? How dare you fly in the face of conventional, "I-heard-it-from-the-guy-at NAPA" wisdom? You want this little episode to go on YOUR PERMANANT RECORD?! Now, say 25 Hail Marys and trot right back out there and install a 600 CFM carb this INSTANT.

:jester

Jvette73

You say ZZ-430 clone. How many cubic inches is that?

spokewrench

350 c.i.

Guru_4_hire

Sounds nice

PRNDL

Back to the track!! :) When were you able to drive? Today was sunny but windy and blueballfrickiingfreezing!! :cuss MJ

spokewrench

MN Jack-

I was out terrorizing my neighbors in downtown Watchung yesterday, they seem to like the sound of the hookers with the JCL inserts, and the howl of that new carb! :party: :party:

MotorHead

Sounds great those Proform main bodies are the cats azz :cool:

I wonder who will think I'm overcarbed this time when I put a 1050 Pro Domintor on my new 406ci :lol:

Older Than Dirt

:thumbs: I too have a ZZ430 clone in my 81. I'm in the process right now of installing a ROD 6, hookers w/ sidepipes and JCL's. I also have a 750 SD to install. I hope with these mods I can get the full power potential out of my engine. :cheers:

73 Vet

That is so :cool: Where do I go for info on this set-up?

spokewrench

E-mail Lars for setup papers on holley and barry grant carbs- to buy the hardware goto summit racing.

lars

Spoke -
That 750 is WAY TOO BIG for a 350...!!! It will stumble, hesitate, and it will run so rich that you can't jet it down far enough...! BIG CARBS are BAD! 350s need NO MORE than 600cfm: I'd highly recommend an old Carter AFB 600 off of a 389 Catalina - that's about all a 'Vette can handle.... :lol: :rolleyes:

Great to see that you're getting set up with the "right" sized carb - they do run nice when they breathe well, don't they? But as you've noticed, the setup process is really key to extracting that performance out of the carbs - great to see you got that 4-corner throttle angle and mixture setup down pat - that's what really makes 'em come alive. And it's fun to do, too! Good job!!

comp

i'm going to play the game later (big carb) :thumbs:

427Hotrod

Jeez..now the secret's out! Everyone is going to want big carbs!

I've always loved racing the guys who believes every conservative thing he reads.

"Safe" isn't always best. You just need to tune it some!

JIM

noskillz

What about the story on metering signals? The one where you want the a smaller venturi in order to boost metering signals in increase air speed?

gerry72

Depends on a lot of things. A straight vs downleg booster, kind of manifold used, and how well the carb is tuned. It's not as big of an issue as some make it out to be. If the booster is lazy, tune the pump shot to overcome the response. For some folks, a smaller carb with a vacuum or air valve secondary is not a bad choice. If you're interested in and get the information on how to tune the carb, you have a lot to gain by doing so. It's the same with a distributor and the rest of the ignition system.

verskel

I'm there, too.......750cfm upgrade to an 830cfm !!! ;) Proform is also the best deal for the money if you already got a Holley. :cool:

spokewrench

Hey Lars-
I think you've started a carburetor sizing revolution and a way of thinking not limited to corporate $$$$$ decisions . Like you mentioned in one of the other numerous posts on this issue-" smaller cfm carbs are much more forgiving to setup" and probably the push to sell them- fewer returns and less tech support calls- and also a significant loss in power to the consumer!
I truly believe that the addition of a secondary idle mixtures improves these double pumpers in three ways- 1. All the plugs burn the same color. 2. It takes the harshness out of lopy cams. 3. If tuned correctly, greatly enables better idle to cruise transitions ( eliminating stumbles). These are my positive
observations after doing this upgrade, there are probably other benifits I have not yet noticed, but anyone can tell when a engine is working just right, you can just feel the difference! I bet sales of B.G.-Holley in the 750cfm and over are on the Rise!

lars

Spoke -
You're absolutely correct in your comments and observations. But as you also know, the 4-corner system needs to be set up correctly, and it's certainly possible to really screw it up if you don't understand the tuning process. Once done correctly, you obtain all the benefits you noted and more.

Personally, I think BG should hire me as their spokesman and tech advisor, and they should send me around the country with a trunk full of carbs and beer, tuning Vettes and showing people how to set up big carbs for great performance. Think we can get them to sponsor that idea...?

Brettmc

Hmmmm, I wonder if I should move up to a Holley 950 HP....

Brett :thumbs: