A guide to building the lil guy. The Mighty 300

Discussion in 'Small Block Tech' started by Joe65SkylarkGS, Oct 27, 2009.

  1. 64SkyConvert

    64SkyConvert 1964 300 ci

    Thanks a million Bill! :beer
  2. 64SkyConvert

    64SkyConvert 1964 300 ci

    Well, it looks like I have an odd-ball carb:

    Carter Competition Series 9655 (Made by Federal Mogul way back when). No carb supply houses can tell me the CFM rating, but I am guessing that it's either 625 or 650, using Carter's normal numbering system.

    In your guys' opinion, is this too much carb for a stock 300 4 barrel automatic?

    Before I start rebuilding and tuning this carb, I was wondering if maybe someone would have a good place to start with jet and metering rod selection? :Do No:

    Any replies are greatly appreciated
  3. Big Matt

    Big Matt Well-Known Member

    Check out this thread:

    I would use manifold vacuum source on the carb to connect the vacuum advance on the distributor. On my 300 I set the initial timing at 14* advanced, and used an adjustable vacuum advance canister. I also tuned the mechanical advance with different springs/limiting bushing.
  4. 64SkyConvert

    64SkyConvert 1964 300 ci

    More questions...:confused:

    I got under the hood today again and discovered something that I have never seen before- somebody had placed a very fine metal screen (just like the kind of screen that I have seen used for old aircraft engine oil filtration) between the intake manifold and the carb spacer- it covered the entire area that the carb spacer covers.... I removed it- and it idles great now, but I am still convinced that my secondaries on my Carter 9635 (I had the carb number wrong earlier) aren't operating normally- I think that someone has fiddled with the linkages to make it essentially a two barrel.

    Trouble is, I have no knowledge of which of parts should be moving at which time with this carb, as throttle is opened- there are 2 sets of butterflies and another door over the secondaries, in addition to the choke flapper- I have to admit that I am a little lost with this carb- I have worked on Webers, SU's and Stromberg's and they all made pefert sense to me! What is that extra door above the secondaries (not the choke), and why is it stuck on a nearly closed position?

    My vacuum advance is not working, and I have some kind of later model GM distributor that has no points... with idle timing set at about 5 degrees, I get something like 32 degrees total advance at somewhere around 3500 rpm. The ground wire inside the dist was disconnected, so I re-fastened it to the plate.

    The engine is lacking a LOT of power, but the spark plugs looked really nice, though- a nice tan color. No overheating, no strange noises- It just drives like it's got a one barrel carb on it...

    I cannot find a good online resource to educate myself regarding this Carter Competition carb- will I have to bite the bullet and buy a Carter book, or does anyone know of a website that actually shows how the linkages should be moving as throttle is advanced??? I think mine have been sabotaged. :Do No:

    Now the car is surging at cruise speeds, which it never did before...

    If this carb is damaged, and I decide to replace it, Edelbrock has some good deals on some reconditioned 500 CFM and 600 CFM carbs- which do you think would be more suitable for my car? I have heard that Buicks like larger carbs- so would a 600 CFM carb be the ticket?

    I really appreciate your replies- thank you.
  5. BillA

    BillA Well-Known Member

    The only two mods I've made to my '64 are 1). relegated the original Rochester 4GC to the attic and replaced with an Edelbrock 1406 (600 CFM w/ elec choke.) and 2). replaced the points in the distributor with a Mallory uni-lite conversion and internal ballast coil. Runs great now. You can probably get away with a 500 CFM since that is the rating of the original Rochester. I got the 600 since I plan on doing some engine mods in the future.
  6. Big Matt

    Big Matt Well-Known Member

    I've added numbers to each section and will make my responses in order. I hope I can explain things so it makes sense, if not ask for clarification and I will try again; or someone else will chime in to help if I've made a mistake.

    1. The extra door above the secondaries is called an air valve. It's designed to keep the secondaries from opening up until a certain amount of air is flowing through the engine/carb. Similar in function to the vacuum secondaries on a Holley carb, where there must be a certain load on the engine before they open up; providing fuel economy and smooth engine operation. The Carter/Edelbrock style carbs have mechanical secondaries though. I don't remember the exact number, but the primaries must be open so far before the secondaries open (but remember that there won't be any flow unless the air valve opens based on engine load). I also believe that the choke affects the air valve to prevent its opening if the engine is cold; you may want to try adjusting the choke and see what happens.

    2. It sounds like you have a HEI distributor. Is the top cap square with the coil in the middle of it? A lot of people switch out the points distributor for an HEI. I know you can get an adjustable vacuum advance canister for the HEI as well as different springs/weights to tune the mechanical advance, like I discussed in an above post in this thread. As to the actual problem you're describing - I have no idea. Hopefully somebody with better HEI experience than I can help out there.

    3. If your secondaries aren't opening this would/could/should explain this.

    4. The aftermarket Carter carbs are identical to the Edelbrock carbs, of this style. You should be able to hit the Edelbrock website and download an owner's manual that would apply. It's been awhile, but I'm certain that I downloaded a manual there before. If not, call them up and ask for a manual (you may even be able to talk to a tech person). I wouldn't tell them it was a Carter though...

    5. I use a 600 cfm (Edelbrock #1406) on my 300 and think it works great. I am planning on trying a 500 cfm one though to see if it makes a difference. With a relatively stock engine though it's probably a wash.

    I hope that helps you out. If not, shout back and I will try again.
  7. 64SkyConvert

    64SkyConvert 1964 300 ci

    Thanks for all the detailed information, guys. :TU:

    I went ahead and ordered an Edelbrock 1406 carb for my car, and I'll let you know how it goes after I get it installed. I also ordered the Edelbrock carb spacer # 2696 Square-bore to Spread-bore Adapter, for it, since my car had some kind of ill-fitting universal adapter installed.

    I do not have an HEI distributor- it doesn't have the internal coil- it has the stock external coil. This dist cap is not that massive- more like a 70's GM dist cap with a metal sliding window on the front- but nothing in there to adjust, since it has a round rotor with some kind of electronic unit up under the round rotor it- I will post a picture later this week to see if somebody can tell me what it is so that I can order up a new vacuum advance.

    Thanks for all your help. As soon as I get a day off, I'll get some photos up.
  8. BillA

    BillA Well-Known Member

    The 2696 adapter is a square to spread bore adapter. The 300 intake is a square bore manifold so you don't need an adapter. I replaced the open plenum gasket that came with the carb with a 4 hole gasket but I did not need an adapter.
  9. Big Matt

    Big Matt Well-Known Member

    Technically correct, however with a Edelbrock 1406 carb I DID need a 1" spacer on my 300 intake so that the linkage would clear the intake and that the secondaries would open. It's a square bore carb, but the secondaries are slightly larger than the primaries; and on mine the blades would hit the intake and not open.
  10. 64SkyConvert

    64SkyConvert 1964 300 ci

    Interesting- When I lifted up the carb (and the 1" spacer under it), the aluminum intake manifold that I have has 4 holes in it- isn't that a spread-bore intake?

    When I watched the Edelbrock install video on youtube, the guy placed the same spacer I ordered under a performer carb before installing it onto an old Camaro small block that had a stock iron manifold with 4 holes in it.... :Do No:


    I took a closer look at my distributor, and it is a Delco 1110376 with some kind of aftermarket electronic kit in it (photo attached). I think it is a later model GM (after 1966?) distributor.

    Big Question: The engine appears bone stock (but who really knows)- any advice on what I should do to re-curve the distributor- which weights and springs and where I might find them? Like everything else on this car, I assume that it was not set up properly... and thank you again for all your help- I am on an island that has no performance shop!:Dou:

    Attached Files:

  11. Big Matt

    Big Matt Well-Known Member

    A spread bore intake has the rear 2 holes MUCH larger than the front two (like twice as big or more). A square bore is where all four holes are (approximately) the same size. Spread bore intakes were used from the factory with Quadrajet carbs (and Carter Thermoquads on chryslers). Square bores were used with the rochester 4GC/4jet and Carters (and some Holleys on high performance chevys).

    The camaro mentioned above - was the iron intake for a quadrajet? I assume it was and then the adapter is correct. There was no spread bore intake made for a 300, and so you either need:
    a) no spacer if the linkage works fine and the secondaries clear the intake
    b) an open spacer
    c) a four hole spacer

    Your distributor appears to be a stock one with a Pertronix electronic upgrade added. There are several manufacturers that offer this upgrade, so it might not be a pertronix but the idea is the same. Either way, your rotor/cap/vacuum advance can/mechanical advance springs are the same as stock. Here's one set of springs that will work:
    and another with adjustable vacuum canister:
  12. 64SkyConvert

    64SkyConvert 1964 300 ci

    Hey- thank you very much. I thought a square bore meant that the intake had a big open square...I see I have much to learn.

    Thanks for the link to the springs and advance- I've got them on order now, and we'll see if the motor peps up again after I get the ignition and carburetion sorted out.

    Attached Files:

  13. BillA

    BillA Well-Known Member

    Wow. Very nice. The video you saw on YouTube comes with the carb. The Camaro in the video does have a QuadraJet and that's why he used the adapter. You may want to return the Qjet adapter in exchange for a 4-hole spacer. I like the 4 hole gasket and spacer since it seems like it would be a smoother transition from the carb into the manifold.
  14. 64SkyConvert

    64SkyConvert 1964 300 ci


    Yes, I agree about that spacer- it's going back.:TU:
  15. Alssb

    Alssb Well-Known Member

  16. 64SkyConvert

    64SkyConvert 1964 300 ci

    alssb- Nice link. It would be really great if they sold those modified pistons & rod bolts...
    Last edited: Mar 17, 2010
  17. 1965GSDOUG

    1965GSDOUG Doug Dougherty

    I have been reading thru this thread but have not seen anything regarding a Neoprene Front Seal to fit the 300ci V8 with a Stock Rear Mounted Timing Cover.
    Does anyone have any aftermarket Seal #'s for this?
    Thanks in Advance!!
  18. 87GN@Tahoe

    87GN@Tahoe Well-Known Member

    should be the same as a 350 or a 3.8L :Do No:
  19. 1965GSDOUG

    1965GSDOUG Doug Dougherty

    Any Part Numbers?
  20. 87GN@Tahoe

    87GN@Tahoe Well-Known Member

    TA Performance- TA1513

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