# Best Carburetor for 350 small block?



## The1965Ghost

What is the best carburetor to slap onto a Chevy 350 small block? Only current mods to the engine are a racing cam, doug thorley headers, an Edelbrock intake manifold with venturi pattern to fit a Rochester but not like stock. Image will be available. If I get an Edelbrock carburetor with the 4 venturis the same size, then will I need an adapter plate? My Rochester was damaged due to a friend's stupidity with it. I need something cheap too. Are there any suggestions?

First Image shows venturi pattern in intake manifold. If a better image needs uploaded, I'll do that. Second Image is the engine put back together with faulty Rochester put on it. Does not run right at all, needs new carburetor. Need some possible pointers.


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## octaneman

Hi The1965Ghost


How about trying to locate another Rochester carb from your local scrap yard or ebay ?


http://motors.shop.ebay.ca/Carburetors-/33550/i.html?_nkw=rochester


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## The1965Ghost

The scrap yards here usually don't have anything good. I've looked on ebay. I'm just not so sure and trusting in the conditions of the used carbs.


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## Basementgeek

Check with a place like Jeg's:

http://www.jegs.com/c/Fuel-Carbs-Intakes_Carburetors/10271/10002/-1

Get out the plastic, not cheap.

BG


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## The1965Ghost

What about a 750CFM Edelbrock at Autozone along with an adapter plate?


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## SABL

750 sounds about right......primaries are the same size as secondaries?? Been a long time since I did any carb mods......:laugh:. The manifold you have should accept the Edelbrock with no adapter.....it is an Edelbrock. I once put a 715 dual inlet Holley on a 283 small block........no major mods to the engine but it would take all the gas the Holley could throw at it. Wasn't too long ago......brand new Holley from Jegs was $45.....:lol:.


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## Wrench97

IF it had a QuadraJet on it it'll be a spread bore manifold and will need the adapter, unless you get the spread-bore replacement carb, for 5000 RPM and under 650 CFM is plenty.


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## pat mcgroin

Wrench is correct on both points.
If the carb is too big, partial throttle response is effected and reduced. Air must pass through the carb at a certain spped in order for the venturi effect to happen correcly. With a carb that is too big, the vacumn drop is insufficient to draw the fuel and to atomize it correctly.


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## dai

i seem to remember they used holly double pumpers on them a few years ago


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## Wrench97

Yes`they did but at lower RPM's the torque curve flattened out from running too lean(not enough air flow to draw fuel through the venturi, the larger CFM allows higher RPM but for street use the 650 has better drive-ability and a better low end torque curve.


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## Jimispeed

What rpm/powerband is the cam for? It is hard to under carberate easy to over carb your engine.600 cfm is a good start.


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## The1965Ghost

The Edelbrock 750 does has primaries same as secondaries. If this manifold can take a Quadrajet then I'd need that adapter I thought. rpm/powerband for that cam I never checked that out. I wasn't the one to install the cam. This 750 is cheapest. If it has a good possibility of being too much CFM then I'll keep lookin.


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## Wrench97

750 will work but, the drive ability around town would be better with a spread bore(small primaries, large secondaries) and by the time you add the adapter and make sure you have hood clearance after raising I would look for the Qjet replacement.


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## The1965Ghost

Oh yea in this truck theres enough clearance. Quadrajets are expensive though. I guess I'll just look for them. Does Edelbrock still make their Quadrajet style carburetor? What other brands make them too? Just Rochester and Edelbrock?


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## Wrench97

Holley still makes one > http://www.jegs.com/i/Holley/510/0-80555C/10002/-1?CT=999
Edelbrock stopped a couple years back but they are still around the only problem is the electric choke models were all 795cfm and above, the smallest was 750 but used the divorced choke setup where the bimetal spring was mounted to the crossover runner on the manifold. 

Look around at your local speed shop for used ones sometimes you can get a really good deal.


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## Indiandog

Just a thought... Could your issue be resolved by rebuilding the carb, or was the damage done by dropping the carb?


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## pat mcgroin

That is a good point.
A rebuild of the original, with some bigger jets to work with the cam, may be a good idea.

Here is a Holly for a cheap price, but will need a rebuild.
http://cgi.ebay.com/ebaymotors/Holl...r_Truck_Parts_Accessories&hash=item45f577b841


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## Indiandog

pat mcgroin said:


> That is a good point.
> A rebuild of the original, with some bigger jets to work with the cam, may be a good idea.


lol and the cheaper route than going out and buying a new carb... most rebuild kits are less than $70. Very easy to do, just takes a little longer to get the carb set up after a rebuild. Local parts shops usually carry them in stock.


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## The1965Ghost

Cool Holley wrench97. 
My Rochester was dropped in DIRT and the choke was broken off. Secondary flaps (top flaps) do not open with throttling. I have some videos on youtube of the thing running before and one after the carburetor was screwed up. Engine sounds like a pile of junk with it now.


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## SABL

The Holley I put on my 283 did not have a choke.....:laugh:. No problems with starting in the winter....pump the pedal about 8-10 times (before hitting the key) and it fired right up. Driving was another matter....had to baby the pedal for about a mile. Try to give it too much gas and it bogged down....

Secondaries were pinned and I knew just where they kicked in. First time riders thought it was pretty quick.....I let em get used to the acceleration for a few short romps going through the gears (4 spd)....then when they least expected it I set em back in their seat.....:lol:


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## The1965Ghost

Haha excuse my stupidity on the whole subject here. Only at 18 of age and beginner at engine work. Not at UTI but thats going to be my Vo. Tech. Anyway I do want to stick with a spread bore carburetor. The square bores aren't to my interests since I do want more fuel economy from a spread bore, yet the massive kick of the secondaries when WOT to get the heck out of somewhere. Atleast I narrowed that down.
Checkin' out my manifold and yes I realized that square bore would fit on it anyway due to the double bolt pattern (if I'm correct) but I'd still would stick to a spread bore carburetor. They all seem expensive though. Pullin' my hair out.:upset: I've looked for Carter Thermoquads, that Holley, Rochester and Edelbrock Qjets. I just prefer mine new but yes thats gonna be expensive.:sigh: If I get a used one, it better be in a good looking condition otherwise it worries me to get it. Then I'll check out rebuild kits. I wouldn't be in this problem if my friend didn't get a hold of my Rochester.


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## Wrench97

If you find one on the consignment shelf at the local speed shop, it should have a guarantee that it will run correctly usually for 10 days some I've seen for up to 30 days.
A lot guys are getting into FI it's been awhile since I was last at the speed shop but there were quite a few older carbs to chose from, there is also a local wrecking yard where you may be able to see it run first.


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## pat mcgroin

You are wise beyond your years. The spread bore is a very good choice for the reasons that you have mentioned. It is also important to mention that all carburators are not the same. All will eventually need to be tuned to the specific engine that they are on. This is very important for the ability to respond in the correct ways.
Have you ever stomped on the gas, and waited 1-2 seconds before things kick in?

The link to the Holly spread bore that I posted above is pretty cheap.
I would not suggest the rebuild by yourself, but it is not an exspensive thing to have done either.
Most local shops can do it for you in a day or two, along with helping you fine tune it.

Some things to consider:
Due to the cam and other modifications, the shop can help with fuel jet choices, as an increase is likely necessary.
Holley parts are very much available, and easily found.
Holley parts are designed to be interchanged to ensure optimum performance and thus make provisions for this tuning.
Rochester carbs, can require some work, if extra operations are needed.
Double pumpers are great when needed, but as you have explained above, not necessary on a street vehicle.

If you decide to go this route, or something similar, it is important to explain to the rebuilder, exactly what has been done to the engine. This will allow him to make the best choices for jet sizes, accelerator pump settings, etc., for your particular application. I am sure that he will aslo set the idle mixtures after installation, if you ask.


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## The1965Ghost

My town has two wrecking yards and a truck wrecking shop. The problem there is all carburetors i looked at are 2 barrel or just low stock ones. Every gen. in my family was in mechanics. Atleast my choices are narrowed down some.
My Rochester lagged to the point of goin WOT and engine slows down then dies. I can't say the exact words my father had to say about the Rochester and what my friend did to it but it was very funny


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## Wrench97

Qjets were sensitive to float level settings and fuel pressure and dirty power valves, many years ago I played with a lot of them(but then again I was a glutton for punishment with the Rochester 2 barrel trip setup) , the older ones with a little fine tuning ran decent, but for off road the Holley would be my choice.


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## The1965Ghost

Alright then I'll go for the spread bore Holley. CFM I'll stick between 600-700 maybe?


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## Wrench97

Yes 750 max but I always found the 650's to work real well on stock RPM engines.


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## The1965Ghost

Found these on Jegs. Might check out what Autozone or Checker have later and the wrecking yards but the yards here usually don't have anything.



> http://www.jegs.com/i/Holley/510/0-80457S/10002/-1?parentProductId=743607#moreDetails





> http://www.jegs.com/i/JEGS/555/15800/10002/-1?parentProductId=752437





> http://www.jegs.com/i/Holley/510/0-80508S/10002/-1?parentProductId=743853


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## Wrench97

I'd go for the Holley 750 W/Electric choke.


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## The1965Ghost

Got eyes on this.



> http://www.summitracing.com/parts/SUM-210216/


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## wolfen1086

Where ya live at? If your anywhere near Va Beach get the one pat linked on Ebay and a rebuild kit come over to my house and be prepared to learn everything about that carb from disassembly and boiling in acid to cleaning rejeting reassembly.
If your too far away from here for that I'd recommend a 650 cfm min,750 max either Edelbrock or Holley, spread bore, but whatever you do steer clear of the stock one if ya can, when I was a kid they called them rotenchesters for a reason.


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## The1965Ghost

Well its what my father trusts. He can tune a Rochester. He's not a big fan of Holleys though. Not exactly sure why..


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## wolfen1086

Your dad ain't a fan of Holley probably cause they tend to leak more than other carbs if the front bowl isn't tightened properly.


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## The1965Ghost

Most likely. We got a ford with a 2 barrel Holley and the (tryin to remember exactly here) fuel inlet or pumper is leaking all over the intake manifold. It's the second time it was repaired or so. I guess it goes bad if it sits.

Anyway thanks for the help everyone! I'm gonna be referring back to TSF of course for any other job I have with my truck (and computer cause I do that too). Hopefully I'll gain more knowledge and be able to contribute to TSF with answers and advice as well. My knowledge is basic right now. If anything happens I'll be back haha


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## Raylo

Sounds like a fun project but, man, reading all this reminds me why I am so NOT nostalgic for the carbureted days. I haven't had to deal with those since my 70's era Trans Am. Chokes, jets, bowls, pumps, then later electronic contols. Whew. BTW, we had a nickname for the Rochester Q-jets that I haven't seen here: quadrajunk.

Good luck Ghost. Hope you get it running smooth.


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## The1965Ghost

Haha well as sensitive as carbs are and as hard as it can be its still easier than dealin with todays cars. Computers diagnostics anything could be causing one thing or another. I know its a nightmare for a lot of the old school mechanics.
Thanks Raylo


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## SABL

The worst thing about today's cars is you can't climb up in the engine compartment and get comfy....not enough room!! 

A good OBDII scanner is a must......no more guessing. Make a few bad guesses and you could have bought the scanner with the money you wasted on parts that were not needed.


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## The1965Ghost

How's it going everyone? :wave: It's been awhile since I posted on this thread but I have ran into a bit of a problem... Remember that Edelbrock mid-rised intake manifold that's shown in the first post with a photo? Is it possible for that thing to be too narrow for a Rochester Quadrajet? I have a Q-jet on it now, and there seems to be a vac leak on both sides, underneath the carb where the fuel jet opening is in front of the primaries. (best describes like a smile shape) It's like the intake is too narrow. I've never heard of that! :4-dontkno Any ideas?


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## wolfen1086

if the bolt holes line up then it shouldn't leak, I've never heard of the intake being too small either, unless you got a carb that wasn't designed to fit on that intake.


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## The1965Ghost

wolfen1086 said:


> ...unless you got a carb that wasn't designed to fit on that intake.


Someone told me that maybe my intake was designed for the "thermoquad" because they had the thinner design around the primaries. But I don't really know..
It is bolted in right though, and the venturi holes all match because its spread bore. Fuel leaked from the vac leak onto my intake and I could hear it hiss with my finger on it under the carb. Massive confusion and frustration ensued :4-dontkno
A possible solution was to get a carburetor adapter so the carb will set on it and it will be wide enough to cover up the whole bottom of the carb. But that would change my set up to a square bore on a spread bore intake and carb. I have no idea how that will turn out. I have not yet found a spacer for spread bore for cheap either. Every spacer I find is square bore... :sigh:


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## Wrench97

Match up the gasket to the manifold and then to the bottom of the card, that'll show you where the issue lies, I've also seen the wrong or mis-cut gasket cause the issue.


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## The1965Ghost

The gasket used was included in a carburetor rebuilt kit used to rebuild the carb. I have some pictures for you guys to check out. You can see the open ends where the manifold thins out near the front. Also, it looks as if it doesnt exactly center right in center (It's not camera angle either). What's going on here? If you prefer to look at the original images, I can upload those up too, along with more.


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## Wrench97

That's the wrong gasket, the one you need will not have the cut out in the front.


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## The1965Ghost

I'm an idiot. :sigh: Thanks wrench. Ill see what I can grab at my auto store. Then, hopefully I can finally roll out this thing.

EDIT: Just curious though, without that cut out, how does it still manage to stop the fuel and vac leak? Just pressure from the vac? I mean, with the carb bolted down, there's nothing to pinch it to the carb right at those areas. I really need to get to my vo-tech auto school...


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## whatup

the edelbrock carbs are not worth the time it takes to make them. i got a holley 650 dobble pump on mine it does just fine summer and winter.


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