carburator choice

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Sep 17, 2001 | 03:39 AM

keithab

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5th Gear

Joined: Mar 2001

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From: Sumner, Wa USA

carburator choice

Have a stock 1972 LS5 454, automatic and am looking to change carb.Currently it has a Rochester Q-Jet # 07029207 ( origanlly off, I believe a '69 vette w/350/350hp). Holley tells me to use their 650cfm # 0-6210 w/mechanial seconds while Edlebrock says their 750cfm Q-Jet # 1901 is the right choice. I'm leaning towards the Edlebrock...Been told the Holley will give me more low end torque, along with lower gas milage, while the Edlebrock is pretty much the same carb as what car originally came with. I'd sure like some opinions..thanks

Sep 17, 2001 | 05:26 AM

Les

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From: Sierra Foothills CA

Re: carburator choice (keithab)

Of those 2 choices I'd go w/ the Edelbrock- 650 cfm is too small for a bigblock. Why are you changing from the Q-jet? If it hasn't been properly set up for your engine it's set up too lean, since the jetting is quite a bit different for the smallblock. I know because when I bought my Vette it had what I was told was the correct Q-jet on it. Turned out it was a smalblock carb for the same year & was way too lean, as was evidenced when I kept overheating after my rebuild.
I only bring this up in case you've had problems w/ yours due to the same thing. It could be that all you need to do is spend a few $ on jets & metering rods. Good luck.

Sep 17, 2001 | 08:13 AM

SteveG75

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From: FL

Re: carburator choice (Les)

Get your Q-jet redone by Lars. $100 or so is a lot cheaper.

Sep 17, 2001 | 08:41 AM

norvalwilhelm

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From: Waterloo ontario Canada

Re: carburator choice (keithab)

Is there a big difference in jetting between a small block and big block? Don't both engines require the same fuel air ratio? The big block just requires more air when pushed but at low cruising and idle speeds wouldn't it take the same ? Doesn't the big block just require more cfm on top end?
Norval

Sep 17, 2001 | 10:47 AM

gkull

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From: Reno Nevada

2024 C3 of the Year Finalist- Modified

Re: carburator choice (norvalwilhelm)

I agree with Norval jetting the correct air fuel mixture is the same no matter if you have a small block or 510 ci big block. Factory carbs have a variance in design and jetting if it's leaning towards an economy car or a performance motor.

Unless a q-jet is spewing gas above the throttle blades it can be fixed.

Sep 17, 2001 | 12:07 PM

PRNDL

Team Owner

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From: Huntersville NC

Re: carburator choice (gkull)

I have an Edelbrock 1901 and it is a nice carb - runs well, looks nearly identical to the old Qjet it replaced, except it looks like the primaries and secondaries might be just slightly smaller than the Rochester. I still havent measured with calipers to check.

HOWEVER, as long as Lars continues to offer his rebuilding services at the price of $100, you should go for that (unless you feel guilty about it

) . You will save $200 - $300 and very likely end up with a better running carb. I will ship my circa 1968 Rochester Qjet to Lars eventually and then run some comparison tests - Gtech or dragstrip or both, and we shall see!

Sep 17, 2001 | 01:07 PM

BSeery

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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."

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Re: carburator choice (MNJack)

Have you looked at the Holley Avenger 670 or 770 CFM carbs ?

I have a 670 sitting on my desk waiting to go on a ZZ4 small block. It is a really nice piece of quality work.

Sep 17, 2001 | 01:46 PM

yellow69

Cruising

Joined: Sep 2001

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From: Birmingham AL

Re: carburator choice (keithab)

I put the Edelbrock Performer 650 on my 350/300 as a Q-jet replacement and have had numerous problems with it. The most serious is that it doesn't fit my stock intake exactly right and has to be constantly tightened to avoid leaking on the driver's side. Once I tightened it too much and broke a bolt off in the intake. That was an expensive fix! The Performer has a multitude of fittings for different applications and they don't give you plugs for all the unnecessary holes and nipples. It cost me more to get it set up properly then the carb cost! My advice is to have the Q-jet rebuilt if it needs it or to consider a Holley replacement.