Passage sizing

[Rat Bastid]

Is there a (simple) way (if possible) to determine when the internal passages in the metering blocks are too small and need to be opened up? And how do you determine how much they should be opened? And how does that affect the tuneup?

TIA
RB

[BradH]

I think the simple answer is"no." However, a more specific example of what you're working on could be helpful.

[Rat Bastid]

I’m having a huge issue with what appears to a tip in issue. I get it on single 4 stuff but with the tunnel ram stuff I’m doing I have to be (IMO) overly rich to get the stumble out of it.

What happens is at a cruise, say about 2600 RPM so it still should be on the T slots, I get a little bobble and then a flat spot rolling into the throttle. I’d pull my hair out but most of it is gone anyway.

This is a stumper, because half the time I think it’s fat, and half the time I think it’s lean, and I can never tell where to look to clean it up.

[rgalajda]

"Rolling into the throttle" heavy or light?
Heavy. Lack of accelerator pump.
Light. Idle circuit and main circuit not overlapping. Due to air bleed sizing or jetting.
Are you using air/fuel gauge?

[Rat Bastid]

[1109RWHP]

I can't imagine tuning without one.

[RFSPHPbb]

Tell them to come get their car, bring it back when it has a working O2 sensor.

[ojh]

What carbs? It sounds like 4160's? single pumpers with vacuum secondaries.

[Rat Bastid]

[jmarkaudio]

What fuel? O2 sensor would help figure lean or rich.