Holley V Qjet

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Holley V Qjet

Postby AusRs » Fri Aug 22, 2008 9:43 am

i have a spreadbore manifold
i also (if you have read ) have a small drama getting fuel to my carb :(
one way or another it looks like i will need a different carby ,cost wise for me either of them is going to be a similar cost ................opinions please !
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Re: Holley V Qjet

Postby Hauge » Fri Aug 22, 2008 3:40 pm

Anthrax or cholera ??

The Rochester is the "better" carb, no doubt about it. That means it has the capability of running smoother, draw less fuel etc.

But better is not always better. The rochester is more complicated which means it has a higher learning threshold. If you get into problems tuning it, your much on your own (at least here i sweden). Jets are harder to find, spareparts as well.

A holley is an "ugly" design for a carb... for example: big shallow float containers (cant find the right word now), which makes it sensitive to centrifugal/accelleration forces. Only one main jet, with a fixed sized jetting for the power valve, which makes some kind of pseudo double jetting. If you manage to get GOOD milage on a holley, you are lucky or has sacrificed a few hp on the top.
Whats positive with the holley is low build height, a lot of knowledge on the net, pretty cheap parts, modular design, easy to make it work decently.. works almost always right out of the box.

In essence if you know somebody with great knowledge of the rochester or can afford to pay someone or you have great patience/time or can buy one with the right jettings go with the rochester.

Personally I live with the milage on my holley the few summermonths we have in sweden. Well a holley is not foolproof either, right now i´m trying to persuade my reversed idle holley to accept my camshaft at idle.

that´s my cents
Let´s see if i have stirred up a bee´s nest
-76 Monza 2+2, 400", 8.8 rear ... if Ispell funny sometimes, Its because I´m Swedish and Hauge is a Norwegian name
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Re: Holley V Qjet

Postby v8astregt » Fri Aug 22, 2008 6:04 pm

Me, I love both. The Holley is such a simple performance carburator. Even I can tune it great. My Astre ALWAYS, and I mean ALWAYS fires right up, and idles great... without a choke even. Performance is great, and it never stumbles. Gas mileage isn't too hot, but that's not why I built this car.

The Q-jet is a great carb. The only problem is you have to pony-up to have a pro rebuild it. I won't even attempt a Q-jet. I would, but I know I wouldn't be able to tune it, I've seen enough problems with people I know. Just bring it to a specialist and call it done.
75 Pontiac Astre GT: 406SBC/TH350, roll bar, S10 goodies, down to 11.47 so far, more to come later.
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Re: Holley V Qjet

Postby GizmoN » Fri Aug 22, 2008 7:44 pm

I support the above comment. The Rochester is great if professionally built. A buddy of mine always sends an old Q-jet to the Carb Shop when he builds a new engine. They rebuild for a fair price, bush the throttle shafts, etc. Rumor has it that Q-jets have better low speed metering, so you may get better response and mileage. I personally run Holley's and also do not use a choke. No problems, probably because they are rich at idle.
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Re: Holley V Qjet

Postby BillPappy » Fri Aug 22, 2008 7:52 pm

All I can tell you. If you got a stock engine. (Meaning Small cam with alot of vacuum) Put you a Qjet on there.. No tuning Plug and play Carb.
Qjets are junk when it come to performance. Small float chambers. Small pumps. Don't like big cams at all. I can tune Qjets make them run
fair. I allways did like the Doowaap sound when the 4 barrels open.

Holley/Demon is a tuners carb. Who really wants the best.. With Demon/holley metering blocks you have 4 corner idling.
4 Jets. (NOT ONE JET) and 2 power valves that can be Two-Stage Power Valves Very good Gas milage. With out loseing big HP
Very smooth idling. As Smooth as the cam will let it idle. Foam filled Floats are heavier ..Resist alot of the accelleration forces
the older holleys had when stopping fast. (Over rich stumble)
Holley carbs require you to run very clean gas. Any kind of micro dirt will let them flood.
It's hard for an old street racer to stay on the safe side of stupid

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Re: Holley V Qjet

Postby Astre-mutt » Fri Aug 22, 2008 9:03 pm

I'm voting Holley. Lot easier carb to deal with, and easy to tune when you make changes to you motor. (and you will make changes) Holley makes spread bore styles carbs that will bolt directly to your manifold, if you don't have room for a carb adapter. Chooses are limited in this style, but there around.

Quick search, found this example on ebay. It's a Holley 650cfm Spread bore ($125 buy it now) for a boat. It will work find in a car, and would have a better chance making it to Australia! :D

http://cgi.ebay.com/ebaymotors/Parts-Ac ... 06.c0.m245
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Re: Holley V Qjet

Postby GMDAD » Sat Aug 23, 2008 4:10 am

Personally I've run Edelbrocks, Holleys and Q Jets. All have their pros, cons and place as mentioned by the previous posts. I've had success and failures with all from stock up to 400hp motors, 500-780cfm, vac., mech sec., just a matter of tuning, patience, tuning, and not trying to beat a dead horse (warped, wore out carbs) IMO there are really no plug and play carbs without sacrificing optimum operation weather it be fuel economy or performance. Then again most play it safe, stay middle of the road and give up a good part of the overall spectrum. I've done this myself a time or two (convenience, lack of time, money) So not too much to add...... bases where pretty much covered by all who previously and intelligently responded.
Some Summit prices; Summit Q-Jet 750cfm elec. 299.95 spreadbore(reman)
Edelbrock 1411 750cfm elec. 310.95 squarebore
Holley Avenger 770cfm elec. 399.95 squarebore
Holley 4175 650cfm elec. 369.95 spreadbore
Don't know your combo (c.i.d. cam etc.) or intended use, so this isn't comparing apples to apples just food for thought.
Now not really knowing your situation (access,availability,parts/service) or lack thereof, things must get complicated and expensive for you including shipping from the states (if need be) down there. My post is probably not much help (sorry) but still best wishes with your current dilemma. Take care, G.
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Re: Holley V Qjet

Postby NixVegaGT » Sun Aug 24, 2008 2:41 pm

I have always been kinda CON Holley design because I can't figure why you'd want to mount the float bowls sideways??!!? I initially choose to go with a Q-jet. I learned a lot about them and it's really an amazing carb. Economy, efficiency and performance if modified carefully and correctly. I built/modified a Q-jet right in my kitchen. (thanks honey!) It was a lot of fun. There are little tricks to do to modify them for reduced or inconsistant vacuum. I made those mods too. It was a lot of fun.

Then I changed my engine build plan like I always do. Now I'm running a pretty wicked solid lifter cam. I will have some pretty inconsistent vacuum at lower RPM and for a vacuum referenced carb like the Q-jet I will likely run into problems. As I did more research and learn more about carburation I gave the Holley design more time. I approached the process with a pretty open mind and for my application the Holley design will probably be a more accurate and effective solution. It really comes down to application.

I still have the Q-jet I built and I'm hoping to do a comparo on the manifold I've got. There are some ways to make a Q-jet more vacuum tolerant but it will only go so far without some playing. I'm with G in that any carb is going to need tuning to be correct for the engine.

With what I've learned there is no better carb than the Q-jet for accuracy and efficient performance when tuned properly in an engine that has a strong and consistent vacuum signal. It is a sensitive mechanical instrument and needs to be treated that way. One area that is consistently screwed up by some Neanderthal trying to fix a vacuum leak by cranking the hold-down bolts until warping the carb body. STUPID!! Fixing this problem is almost always the issue with a malfunctioning Q-jet.

With an engine that has very inconsistent vacuum signal you really can't beat the old Holley design. It's vacuum tolerance is really astounding. I still hate the bowl design but I have to admit the main circuit being throttle based is a pretty smart and simple solution for hot performance engines. The Holley can also handle a lot of fuel volume by comparison to the Q-jet. That can be rectified with some modifications to the needle valve and the like but the Holley does not suffer from this problem as the float bowls are much larger.

Good stuff!
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Re: Holley V Qjet

Postby jdandboo@hotmail.com » Thu Aug 28, 2008 11:18 pm

personally,love a Q-jet,,but next assault is gonna be MFI-possibly holley or edelbrock systen
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