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    500cfm vs 600cfm

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    Myloth
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    500cfm vs 600cfm

    Post  Myloth on Sat Jun 20, 2015 3:55 pm

    I didn't want to do a write up or anything but I rebuilt a 1405 600cfm Manual Choke( I can't help it I am a control freak)

    and put on in place of the 1403 500cfm on the stock 305. I just drove it and even without adjustment it runs good smooth

    and snappy. I just wanted to point out that I used stock rod springs  (Yellow) and metering rods .73x.47 but I used .092

    main jets and .086 Secondary jets. This is a little lean but it is a stock 305 and it seems to work better than the 1403

    I wouldn't recommend this for a 350 with a cam. This is my experience with the 1405 I tried .100 primaries and even .083!

    (too lean) and .098 thru .086 secondaries to arrive at this juncture. If you have a 1405 or 1406 they are jetted fat from

    the factory and won't work on a 305 out of the box unless it's a seriously built 305 . In fact I have heard complaints

    from people with 350s about the over jetting of Edelbrocks . Just a few thoughts on the Edelbrock Carbs maybe it will

    help someone. if you haven't rebuilt an Edelbrock they are a snap compared to a Holley or Quadrajet save some cash

    my kit cost 25 dollars and included everything except the jets and rods.
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    solo79
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    Re: 500cfm vs 600cfm

    Post  solo79 on Sun Jun 21, 2015 9:45 am

    I run that exact same carb 1405 600 manual choke on my mild performance 327 and it performs very nicely. I too like the control of the choke cable, never did care for electric choke on a performance engine. When we first built the engine, we calculated the required CFM street vs. race and I kind of went in the middle. My calculations netted me 522 CFM street and 676 race, so I went with the 600 which turned out to be a good match even with my higher stall converter and lower gears. To date, I've yet to determine what gears the car has because the axle stamp is missing, I just know at 60mph with a 3 speed, I'm cranking 2500 rpm and at 70, it's pushing 3500 rpm. I really need a four speed for that car. It can't be driven on the interstate at all really. It's way too much sustained RPM and it's hard on everything. Fine for drag racing, but not the highway.

    I currently have the stock springs and jets in that carb but I bought a performance kit and will be experimenting with the springs and jets this summer. When I got the carb, I had to adjust the floats as they were all out of whack (which happens in shipping I suppose). Initial acceleration has always been a little iffy, so I'm going to try stiffer springs too. These are so easy to work on compared to Holleys. I got sick of blowing power valves, so I switched to Edelbrock awhile back and have stuck with it ever since.


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    Myloth
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    Re: 500cfm vs 600cfm

    Post  Myloth on Sun Jun 21, 2015 2:06 pm

    I agree on the 3sp on the highway I usually cruise at 60-65 lol, the Posi I put in has lower gears then the original 2.41-2?

    So it does get annoying over 65 I have my th200-4r I am planning to get in before the end of the month I am just going

    over it now with a fresh shift kit and few mods. My experience with the Quadrajets is good but Holley's are very mixed

    I would swear by some old Double Pumpers but I have had 4150-4160s that gave me fits. I actually may have to rejet the

    secondaries as yesterday after I wrote this I experienced a few pops at WOT. So I am going to try a symmetrical .092x.092

    and cross my fingers but I think that will work well it works good now just lean on WOT. How are things going with your

    car anyway?

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    Myloth
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    Re: 500cfm vs 600cfm

    Post  Myloth on Fri Jun 26, 2015 11:37 am

    I did swap to .092 x .092 and it smoothed it right out throttle response is good and no hesitation or

    bog took about 8 jet swaps but seems worth it .(By now I can swap jets on these carbs in 5min and 1min for the rods)

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    Sweet Seventy9
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    Location : Upstate NY

    Re: 500cfm vs 600cfm

    Post  Sweet Seventy9 on Fri Jun 26, 2015 12:43 pm

    Ease of fine tuning is a real nice feature of Edelbrock carbs.


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    383Falcon
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    Re: 500cfm vs 600cfm

    Post  383Falcon on Sat Jul 11, 2015 3:05 pm

    solo79 wrote:  To date, I've yet to determine what gears the car has because the axle stamp is missing, I just know at 60mph with a 3 speed, I'm cranking 2500 rpm and at 70, it's pushing 3500 rpm.  I really need a four speed for that car.  It can't be driven on the interstate at all really.  It's way too much sustained RPM and it's hard on everything.  Fine for drag racing, but not the highway.
    .

    Hey Solo! You might know this already, but a trick I used to find my differential ratio was to jack the back end up lifting both rear tires from the ground, chock the front wheels and put the car in neutral with the E brake off and then chalk the inside of one wheel and manually turn the drive shaft by hand whilst counting the rotations of the shaft. When the wheel has made a full rotation, you take the number of times you turned the shaft and that is your ratio... For me I turned the shaft two and a half times or there abouts and my rear-gear ration is 2:56. If you turn just over three times I would guess you have 3:08's and if almost four times 3:73's... Has the rear end ever been modified?


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