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Old 05-23-2010, 04:59 PM
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Making a big carb smaller?

Hello everyone,

I just installed a Mighty Demon 825cfm & Victor copy intake on my 357ci SBC. The low end throttle response is great and it wraps up the RPM's in a heartbeat, however... when I put my foot into the throttle more than 75% I get an obvious sign that the carb is too big for the motor... I intend to run this carb & intake on my 385ci stroker SBC, but is there anything I can do for my 357ci to help make the motor think it's receiving a smaller carb. Can I block the power valve? I don't intend to go smaller in the jets because the venturi is a fixed size, how about a four hole spacer with smaller holes than the carb venturi? Any ideas would be helpful.



Also, I figured I could bring up the ignition timing to help compensate for the more air & fuel. I don't really trust where my balancer mark lines up with the timing cover. How do you guys set timing by ear? Do you bring the motor up to around 5000rpm (with the vac advance unhooked) and than advance the timing until you hear the sputter or 'miss' in the exhaust note and than bring it back down untill no more miss?

Cheers ~Mykk
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Old 05-23-2010, 05:30 PM
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Disconnect the seconday linkage.

Vince
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Old 05-23-2010, 05:40 PM
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What is the obvious sign that the carb is too large ? Perhaps some tuning of the accelerator pump circuits will fix it.
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Old 05-23-2010, 06:19 PM
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Many people proclaim the that 4 hole spacer does inhance throttle respond by increasing air velocity near the venturi due to the flow restriction I suppose.

Also, since you got the Mighty Demon (why that big?); you can send that carb into Barry Grant and have them install Annular boosters which are supposed to enhance signal and restric flow somewhat (I think it's usually rated at a 30-50CFM loss).
check out the article:

http://www.carcraft.com/techarticles...wn/index1.html

I don't pretend to understand the 825 DP carb... Is it better/more powerful than with the 650???
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Old 05-23-2010, 06:58 PM
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Quote:
Originally Posted by 04SilveradoMykk
I get an obvious sign that the carb is too big for the motor.
And what, pray tell, is this obvious sign?

Quote:
Originally Posted by 04SilveradoMykk
I don't really trust where my balancer mark lines up with the timing cover. How do you guys set timing by ear?
Ummmm, you must be thinking about some other forum. I'm pretty sure all the guys on this forum use a light.

As far as finding top dead center on the damper inertia ring, here's a tutorial for you.....
http://www.crankshaftcoalition.com/w...op_dead_center
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