Hey wuz up guys,

I have question should i upgrade to bigger carb or stay w/ the the one i have. its a holley 600 vac sec.thanks for the help,

J.P.



[This message has been edited by Buzcarlos (edited October 25, 2001).]

 

sorry guys heres what i have in the engine
on my sig.


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J.P.
84 Z-28 L69 T-5
rebuilt 305,350 heads 2.02/1.60valves ported,isky cam .485" @234 Dur.,edl torker intake,600 holley vac sec.gear drive,hooker shorty's with spintech muffler.3.73's more to come!

 

Oh sure. A 750 cfm with vacuum secondaries would be the cat's meow for your car

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1986 Camaro Sports Coupe
Flame Red Metallic with Black accents and Red interior
T-tops, variable wiper, power hatch, rear defrost, third brake light
LG4 305 V8, Hooker Shorty headers, 3" pipe into Walker Quiet Flow dual exhaust
Edelbrock Performer intake, "Damonized" Q-Jet 4bbl, K&N filter, Crane ignition kit
TH700R4 transmission and Derale cooler
Air conditioning, power windows, power door locks, power brakes, power steering, tilt wheel
Kenwood cassette, Pioneer 6x4 component front speakers
Rockford Fosgate 6x9 Punch rear speakers
Z-28 front and rear sway bars
Aluminum slots and Goodyear 225x60R15 Eagle HP tires
243 horsepower and 326 foot pounds of torque at the flywheel
_ _ _ _ _ __ _ _ _ _ _
Yea verily, and he smote the smog heathens from his small block Chevy, even from the air pump to the converter ...
Todd 1:1

 

I hardly think so. Holley's own data shows a 350 barely getting the secondaries fully opened with the weakest spring by 5500 rpm. A 305 would have to wrap even tighter than that.

Your 600 is fine for what you've got.

Speaking of what you've got, did you shave those heads? I can't imagine you've got much compression if you didn't. How are you keeping the valves off of the cylinder walls?

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

[This message has been edited by five7kid (edited October 25, 2001).]

 

thanks for the help.oh and Five7Kid i had them mill down to 58cc and using a .035" head gasket i believe.So far no problems with valves hitting the block or any thing.



------------------
J.P.
84 Z-28 L69 T-5
rebuilt 305,350 heads 2.02/1.60valves ported,isky cam .485" @234 Dur.,edl torker intake,600 holley vac sec.gear drive,hooker shorty's with spintech muffler.3.73's more to come!

 

57,

Even GM equipped 305s with a QJet from the factory. From what I understand, they are all basically 750 cfm carbs. So what's the problem? Mine works fine.

 

Our q-jets may have the capacity to flow 750 or 795 CFM, but that doesn't mean they do. Most LG4 q-jets, for instance, did not allow full opening of the AV, so they could not flow that much. Even if the AV can mechanically fully open, it is air flow that determines how far they actually open. So, if adjusted correctly it will still flow less than it is capable, and if improperly adjusted (so the AV flaps open all the way, such as a bog situation), the manifold vacuum will be lower than the 1.5 inches at which carbs are rated, so the flow will still be less.

Make sense?

 

That sounds good to me, and therefore a vacuum secondary 750 cfm carb should work very well with his 305. Like I said previously ... though the 600 will work just as well.

 

Off-idle response will suffer, as likely will part-throttle response. Why have 750 cfm-size primaries all the way open with the secondaries partially open, when you could have both sides of the 600 all the way open?

Without spending any more money, by the way...

Tune the 600 until you get a bigger engine.

 

You can't compare a Spread bore Q-jet with a holley. The primary's are smaller on a '750' Q-jet than a smaller 600 holley. 600 is more than enough for your 305--a 750 will give you the same or less power and probably hurt throttle response.

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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

 

I find that the tiny primaries on the QJet give me really great throttle response, and far better gas mileage than any square bore carb.

 

82Camaro,

I LOVE your Camaro! It is really sharp--and the same colour as mine. You are obviously a scholar and a gentleman, and a fine judge of automobiles

 

thanks for the info guys

------------------
J.P.
84 Z-28 L69 T-5
rebuilt 305,350 heads 2.02/1.60valves ported,isky cam .485" @234 Dur.,edl torker intake,600 holley vac sec.gear drive,hooker shorty's with spintech muffler.3.73's more to come!

 

"a 750 will give you the same or less power and probably hurt throttle response." seriously should have been "a 750 holley" My point being a 'rated 750' q-jet is a whole different animal than a 750 holley.


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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

 

Not to beat a dead horse...
A 350 will flow at 100% VE (volumetric efficiency)
5000 RPM 506cfm
6000 RPM 607cfm
A 305 @ 100%
5000 RPM 441cfm
6000 Rpm 529cfm

I imagine your 305 at best only gets 80% VE. So the 600 is doing well. If your max RPM is at 6000, then you will see an increase in peak Hp, as well as a slight increase in peak Hp RPM. This will sacrifice your bottem end. All depends on the gears etc. Try changing the springs on the vac sec. Make sure the power valve is not on when cruising etc. Tuning a carb is more difficult to tune than fuel injection. Get a book on Holley carbs and actually read it. Not many people actually tune theur carbs.