Edelbrock 1407 off idle bog

[78Delta88]

Well closing the choke a bit strengthens the vacuum signal. Stronger vacuum ... Pulls more gas.

Bernoulli principle.... Basic fluid dynamics though a venturi.

Bernoulli's principle - Wikipedia

en.m.wikipedia.org

 

[78Delta88]

Richen idle 1/4 turn out reduce curb idle timing to 12° see if that helps.

14° is OEM for a 8.5 305/Automatic with puke rotten converter and too tall rear gears. It's great for MPG (actually is not), but rotten for launch and acceleration.

 

[Baker7888]

If you engine works with what you have, just try richen idle a bit and see if bog goes away...

Richened the idle screws, made it worse. Made idle drop.

 

[78Delta88]

Richened the idle screws, made it worse. Made idle drop.

Made bog worse?

 

[Baker7888]

Made bog worse?

Yes.

 

[78Delta88]

Ok top heavy, reset to original setting.

Did you try lower timing yet?

 

[Baker7888]

Ok top heavy, reset to original setting.

Did you try lower timing yet?

I did not but need to wrap it up for the day but can still continue the conversation in the mean time.

So I put a lot of effort into my timing. I spent a fair amount of time with springs and weights to get my all in as low as possible without pinging. It runs really good where it’s at. It would take more timing but i actually ended up settling 34 to be modest. I do intend to cruise with it and want it to last. If i drop the initial to 14 it’s only going to run like a dog. May I ask what your theory is? I really feel like this can be corrected in carburetion.

 

[78Delta88]

If you drop to 14 or 12 curb idle timing and bog is still there then it's in the carb.

At high vac signal the metering rods stay down and little or no fuel goes through metering jet.

As you open throttle vac signal reduces and springs go up to open the jet to meter the fuel through. Curb vac goes down venturi vac increases and pulls fuel through jet to venturi booster, atomizes it and enters intake manifold.

So... If you are not moving enough fuel and everything else is fine, then you need to increase metering in the carb itself.

Plus are you sure you don't have piece of dirt partially plugging a jet? Partially plugged inlet filter?

 

[Baker7888]

At high vac signal the metering rods stay down and little or no fuel goes through metering jet.

…..

Plus are you sure you don't have piece of dirt partially plugging a jet? Partially plugged inlet filter?

Thank you.

So I am running the heaviest spring (Silver - 8”) It was my understanding you select springs by going with half your vacuum. I have 16” of vacuum at idle (highest vacuum achieved with idle screws) so that is how I wound up with my spring selection. Am I mistaken, and should try a lighter spring?

Secondly. I suppose a partially plugged anything is always a possibility. But i do doubt it. The entire fuel system is new. I have a coarse filter before the pump and then a fine before the carb.

 

[78Delta88]

Did you do a dry and wet compression test when you built the engine?