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Carb selection

Posted By napaunderground Last Year
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napaunderground
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Ok team... I have to select a 4bbl carb for my 292.

I have a number of vintage takeoff holley/motorcraft/autolite units that have been in storage for 30+ years to choose from. My initial plan is to rebuild one and keep as many vintage parts as possible on my build.

I think a 600cfm would be sufficient based on my limited knowledge in volumetric efficiency etc...

Any opinions as to jet size for the initial startup and break in? Or strong opinions of a better carb option?

miker
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Just to get started, here the link to Ted’s dyno test on single 4 barrels. Great reading and it will give you a start to look at your existing inventory.

https://www.eatonbalancing.com/2012/09/25/four-barrel-carburetor-testing-on-the-y/

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ
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That's a great link...and now I realize I made a bad choice!
Ted
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My two cents worth.

Always start off with the original jetting when installing a carburetor.  Once the engine is running and has some actual driving on it, then the jetting can be evaluated as to whether it needs to be made slightly leaner or richer to get the fuel mixture spot on.  If making more than a six number change in jetting, look for something else other than the jetting being the problem.

There are instances where the air bleeds are changed rather than the jetting as you may only be working on one end of the rpm range and not all of it.  Likewise, changing the rate at which the power valve opens is an option to changing the jetting.  An incorrect ignition timing curve can make for instances where it would appear to be a fuel mixture issue so watch out for that.

As an additional foot note, if a carburetor is grossly undersized for an engine, you may find it being on the lean side in the higher rpm band.  Likewise, if it’s too big, it may be on the rich side of where it needs to be.  750 cfm vacuum secondary carbs are a good fit for Ford Y’s that have had camshafts, larger valve heads, and/or head/intake manifold porting added.  For daily drivers and with the normal upgrades in camshafts for an upgrade in power, then the 600-625 cfm range works for many applications.

Here are some links to previous threads giving more information on carb sizing.

http://forums.y-blocksforever.com/FindPost14659.aspx

http://forums.y-blocksforever.com/FindPost135357.aspx

http://forums.y-blocksforever.com/FindPost135561.aspx

http://forums.y-blocksforever.com/FindPost130447.aspx


Lorena, Texas (South of Waco)


napaunderground
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My initial excitement at finding a stock 1273-1 (ECZ-AD) carb off a '57 T-bird has faded since reading the linked threads, and doing more of my own research.

Seems like the best bet would be a Summit 750 based on Ted's comments. I don't want to be undersized, and the comments suggest the OE carb probably is.

We have basically '57 T-bird parts cam, ECZ-B intake, with ported ECZ-C heads on this 292 with Mummert rams horn manifold.
slumlord444
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Not to disagree with Teds results but I’ve had good success with the T Bird carb on a stock 292.  That’s not saying that a larger carb can’t produce more power.  
55blacktie
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napaunderground, your engine, even with the mods, isn't going to make 300 hp. If you had ported G heads/Mummert aluminum heads, more compression, more cam, headers, and more displacement, the Summit 750 cfm carburetor would be a good idea. On your engine, I wouldn't consider anything bigger than 600 cfm. In fact, I think you would be happy with the Summit 500 cfm carburetor. A carburetor with smaller primaries will be more responsive off idle and at lower rpm and should return better mpg under normal driving conditions. 

It would be helpful if you posted the specs for that "57 T-bird parts cam." 

FYI: I bought Holley's 8007 390 cfm carburetor for my 55 Tbird to replace the original Holley 4000 "Teapot" carburetor because it wasn't compatible (as is) with the 57 distributor that had been installed before I inherited the car. However, I sold the unused carburetor and purchased a Holley Street Avenger 570 carburetor because Tim McMaster said that the 390 cfm carburetor would not be big enough. Keep in mind that street-ported "G" heads/w 1.94 & 1.54 valves will be going on my engine, block zero-decked and bored .050, heads milled .035, a Howard's cam/w 220 duration @ .050 and net lift of .485/w 1.6 rockers. , ported 57 intake manifold, and Sanderson headers. Ted guestimated that my engine will dyno at 270 hp. You can expect less with your combination. 

FYI: the 465 cfm carburetor was among the best in Ted's carburetor comparison test. 
DryLakesRacer
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Napa….. buy or get a carb that will be compatible to your engine, to your driving style, and how you’re planning on using your car. There are great usable carbs from 400-650 cfm that are normally ignored because “bigger is always better”. A good running 300” engine will perform very satisfactory on a 500 cfm especially at the crack of the throttle. Small primary throttle bores along with smooth Venturi’s will give the needed air flow and annular discharge for fuel atomization is a big plus.
If you feel that 5500-6000 rpm will be needed and used every-time you drive your car a larger carb may be for you. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.
Tealy64
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What great timing for this post.  We just managed to track down an ECZ-B intake and are now on the market for a carb to fit it.  I like the idea of buying a new one from Summit (sounds like a 500cfm will be fine for us, as we've not done any major mods to the motor).  Any particular setups that are preferred over others?  We're still on stock distributor and manual choke for our 64 F100 with a 292.

1964 Ford F100 w/ 292 Y-block
-Central Florida-
DryLakesRacer
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Tealy, Summit carbs have high rating with many Y block guys. Bolt on and run. Ted has shown the larger one makes a very good performer and very acceptable horsepower on modified engines. I personally like they have no lower base to body gasket to leak; an Edelbrock has this feature also. I also like they come with a fuel line. They also use Holley jets and other parts which are common. 
Eventually I will put the the 500 cfm I bought along with the Blue Thunder intake on my stock 292 when I remove the dual quads I currently use. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.


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