Re: Tuning a road demon 625 cfm carb

[Brian Safford <hzf9vv@xxxxxxxxx>]

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No, my mileage is terrible *all* the time.  Don't think I've ever
witnessed a backfire.

The video I have of a guy taking a Demon carb apart and checking
everything indicates jets in the secondaries.

Since I have vacuum-operated secondaries, I've always been concerned
that they're not opening due to low vacuum.

The BG guy said 14 at idle was pretty low, so I was wondering if the
other vacuum stuff ( brakes, PCV ) was getting in the way.

Can I use the vacuum connection for the heater to do that WOT test?

And I presume that removing the bowls to even look at stuff should be
done with the carb off the car so as to not have fuel spill all over
the place ...

Thanks,
Brian

On Wed, Jul 28, 2010 at 10:58 PM, 65 <65Val@xxxxxxxxx> wrote:
>
> Brian...are you getting reasonable mileage when just cruising around? If so,
> then your primary jets are probably pretty close. I would suspect the
> secondaries are a bit rich. Does the carb have a secondary metering block,
> or metering plate? If its a block, you can change the jets in the
> secondaries. they are the same as Holley jets. Vacuum could very well be
> below 6.5 at WOT. Easy way to check...plumb in a vacuum gauge with a hose
> through the firewall, and take her for a ride. Floor it and check the gauge.
> I will bet its closer to 0 than 6.5 . The power valve could be blown as
> well. This is caused by a backfire.
>
> Just my thoughts...
>
>
> Darwin/Victoria BC/Canada
> '65 Cdn. Valiant Custom 100 'vert
> --225/A833...in a million pieces...SOLD
> '67 Dart GT 'vert
> --273/904...in "enjoying" condition
>
> Check'em out...  http://s41.photobucket.com/albums/e285/65val/
>
> ----- Original Message ----- From: "Brian Safford" <hzf9vv@xxxxxxxxx>
> To: <1962to1965mopars@xxxxxxxxxx>
> Sent: Wednesday, July 28, 2010 7:41 PM
> Subject: Tuning a road demon 625 cfm carb
>
>
>>
>> Am re-posting as I did this first from my cell phone and am not sure
>> it posted properly ...
>>
>> I talked to a tech at Barry Grant about tuning my 625 cfm road demon
>> on my poly 318. I get black smoke whenever I floor it. He asked me
>> three things - timing at idle, vacuum at idle and cam duration at .050
>>
>> Timing is 12 degrees btdc,  vacuum was around 14 and my Daytona cam
>> has 218 at 50.
>>
>> He suggested I switch to a 4-hole spacer rather than the open one I'm
>> currently using, and also thought I should move the timing to 14 or
>> 15. He also wondered if I had good hot spark. Not sure how to check
>> that.
>>
>> I asked about the power valve and he said it probably isn't even
>> opening as the vacuum would have to drop below 6.5 for that to happen.
>>
>> I have power steering that uses vacuum as well as a pcv valve - do
>> those use up too much of the available vacuum?
>>
>> I don't want to risk damaging my engine - are any of his suggestions
>> potential problems?
>>
>> Thanks as always,
>> Brian Safford
>> 62 Dart / Poly 318
>>
>>
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>
>
> ----
> Please address private mail -- mail of interest to only one person --
> directly to that person.  I.e., send parts/car transactions and negotiations
> as well as other personal messages only to the intended recipient, not to
> the Clubhouse public address. This practice will protect your privacy,
> reduce the total volume of mail and fine tune the content signal to Mopar
> topic.  Thanks!
>
> 1962 to 1965 Mopar Clubhouse Discussion Guidelines:
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> http://www.1962to1965mopar.ornocar.com/general_disclaimer.html.
>
>
>

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Please address private mail -- mail of interest to only one person -- directly to that person.  I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic.  Thanks!

1962 to 1965 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html and http://www.1962to1965mopar.ornocar.com/general_disclaimer.html.

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