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Thread: What kind of carb do I have?

  1. #1

    Default What kind of carb do I have?

    Got it off eBay. Was told it was a 4779, 750 cfm. I know for sure it's a double pumper, dual line, 4 corner idle with mechanical secondaries, but that's it. I took the base plate off and measured the venturis at the top. Measurements show it is a 750 according to a website I found, but the 4779 isn't stamped on it anywhere. All 4 butterflies have 172 stamped on them. Attaching several pictures. You can see some numbers. If anyone has an idea what it is, let me know. I'll take more pics if you want.

  2. #2
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    The list number that would have told you what carb it is, is on the choke horn that is removed on this carb.
    The base plate and venturi size look correct for a 750.
    But from what I see in your pics, I would say the carb was put together with different parts from other carbs.
    Look at the little tub sticking out in the one venturi. That is a vacuum feed tube for a vacuum secondary carb.
    Someone has modified the main body to make it a mechanical secondary main body. Make sure it's now plugged.
    The front and rear metering blocks do not match. They are from different carbs.
    If they were from the same carb, the hole for the idle mixture screws would be the same.
    All this doesn't mean the carb will not work. I have modified many carbs like this.

  3. #3

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    Wow, thanks for the info. What could I plug the vacuum hole with if it is open? I need a rebuild kit for it. Would one for just a double pumper work? I plan on taking it the rest of the way apart this weekend, and clean it.

  4. #4
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    Use some JB Weld to plug the passage if it is open. A rebuild kit for a double pump will work. When you have it apart, check to make sure the passages on the secondary side for the idle circuit line up with the gaskets. Also, when you get it apart, look at the front metering block. In the pic from the top view, you can see a L stamped in it. See what the rest of the number is. Some time they will have the carb list number on them as well.
    Last edited by 81 TransAm; 02-03-2017 at 06:44 PM.

  5. #5

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    OK, got it took apart and took some pics. The vacuum stem (where it was a vacuum secondary before) looks to have been plugged on the outside with a brass plug. The primary metering block number is L33102. I posted a question about what I found out about that with the pic below. Have a few other questions though. The primary metering block has a 70 and a 72 jet installed. Is this common? Figured they would be the same size. The secondary metering block also has different size jets, 72 & 74. Have another question about the double pumper squirter holes. I also have that listed below with the pics.

    Looks like the vacuum port has been filled on the outside with a brass plug. Looks to lead to the stem in the venturi.


    The number on the primary metering block is L33102. I found a listing for an R3310-2 carb. Says 750 4160 model, that right?


    Here is the secondary metering block numbers.


    Took the squirters off and found something odd. The primary accelerator squirter hole has a brass seat for the little needle plunger.


    The secondary squirter hole doesn't have a brass seat. Should this be a concern? Looks like the needle plunger wouldn't be able to close off fuel flow.
    Last edited by 406-SBC; 02-04-2017 at 06:13 PM.

  6. #6
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    The front metering block is from a 3310 vacuum secondary along with the main body. The passage for the secondary squirter was drilled & tapped by someone. That is why it doesn't have the needle seat at the bottom of the passage. The vacuum passage for the vacuum canister was plugged with the little set screw above the brass plug you mentioned. I can't tell from the pics what the secondary metering block came off of. But it will definitely have a different metering circuit in it compared to the front metering block.

    If this carb is not a 4779 double pump. It is a 3310 vacuum secondary carb that was modified to work like a 4779. If it was advertised as a 4779, then you were deceived. If you got it cheap enough and you don't care you could use it, but you would need to check all the passages to make sure the modifications were done correctly. But if it was me, I would send it back. Because you bought it on eBay and if it was advertised as a 4779, eBay will refund your money and the seller is responsible for return shipping. Get the shipping cost up front from the seller before you send it back. E-Bay does not help when it comes to return shipping costs.

  7. #7

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    I just wrote the guy to see what he has to say. I got it for $150, but if it isn't usable, I need to see if he will take it back.
    I have no idea how to check the rear block for correct passage modifications.
    He wrote back saying he has a 4779 metering block he would send me. Would it make it work right or does it need matching ones?

    UPDATE: Kinda got into it with the seller, when we couldn't agree on anything. Long story short, I'm sending back the carb, and he's giving me a refund when he receives it.

  8. #8
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    I agree with 81 TransAm, and I think you did the right thing by returning that troublesome carburetor.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  9. #9
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    Get the return shipping up front. EBay does not get the return shipping cost back for you. The seller is responsible for the return shipping, because the item was not as advertised. If he does not pay the return shipping up front, you can get a refund through eBay and you get to keep the item.

  10. #10

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    I already shipped it back out. I paid for the shipping, didn't know I could get him to pay. Oh well, at least I won't have to deal with it anymore. He tried everything to get me to keep it. Offered partial money back & stuff. Thanks for all your help. I'll be back on here when I get me another one. I know what to look for now when purchasing again.

    UPDATE: He got his carb back and he refunded my money. Now to shop for another one.

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