Q-jet flooding under load

[rwberinger4x4]

Hi all,

I have something of a frankenstein set-up, so bear with me!

1965-66ish Small Block Chevy 283
350 Edelbrock SP2P intake
1967 Buick A/T Quadrajet S/N: 7027244
I believe it has an RV cam but I have never confirmed
All of this is loaded into a 1975 Toyota Land Cruiser with the rest of the drivetrain remaining stock Toyota

I rebuilt this carb with Cliff's SR Kit 3 years ago.  At that time I also tapped, capped, and epoxied all the well plugs.  Throttle plates didn't show significant play. 

After the rebuild, and for the past 3 years, the carb has run pretty well.  Always a BIT rich, but I equated this to overjetted/oversized for the engine. 

I just installed a new Carter 5.5-6.5psi fuel pump (30gph), and hard fuel lines to the carb this week, and all hell broke loose!

At idle: Truck idles fine, it's very responsive to idle screw and mixture screw adjustments
When "revved" standing still - Throttle response is good.  Small amount of black smoke from tailpipe (rich)
When held at about 2000RPM for about 10-15 seconds, the truck tries to stall when I come OFF the throttle.

When DRIVING: The truck gets about 100 yards in 2nd gear, then the carburetor completely floods out, truck stalls - gas out the accelerator pump shaft, the baseplate gaskets, backed up into the venturis, and all over the manifold. 

What is going on here?  Normally this points to a float or needle and seat problem, right?  I suppose it's possible that some "crud" in the fuel lines made it through an inline filter AND the carb inlet filter and plugged them, but it seems unlikely. 

Wouldn't a clogged needle/seat to a sinking float cause problems all the time (idle, revving, moving, etc.)

Any input would be greatly appreciated!

[rwberinger4x4]

In addition, for what it's worth - I strongly suspect the stumble/stall coming off a rev is possibly the carb trying to flood. 

I haven't checked the pressure coming off the new fuel pump yet to confirm it's really 5.5-6.5psi. 

[Cliff Ruggles]

If all the problems started with the pump install, that's the first thing to check....Cliff

[rwberinger4x4]

Well, I went to check the fuel pressure tonight, and the barbed T-fitting for my gauge cracked - I have another one on order, I'll get back to you soon.  Thanks for responding!

[rwberinger4x4]

Hi Cliff -

Checked my fuel pressure tonight.  Connected the gauge with a brass T-fitting.  The results were...odd..to say the least. 

The first time I started the truck (cold start) the fuel pressure was jumping around 6-9 PSI (too high, it should be a 5.5-6.5PSI pump). 

here is a video:

https://youtu.be/oG6-fj_bp-4

I shut the truck down before it even got fully up to operating temperature -  (the engine then flooded on shutdown)

When I started it back up about an hour later, the gauge went completely haywire.  Became unreadable when you revved the engine:

https://youtu.be/uJ2rDaBIudE

And lastly, here is a (not great) video of the carb primaries - does this seem like excessive fuel to you?

https://youtu.be/5ca80rJhhKk

After the engine is shut down, the gauge sits at about 7 PSI. 

[Cliff Ruggles]

I don't like to see past 6psi on those early carburetors for any reason.  The later designs will easily take more pressure without any issues, but I've tested enough of the early carbs to know that they can be problematic with high fuel pressure.....Cliff

[rwberinger4x4]

I'm wondering how accurate the gauge is - It bounces between 7 and 10 at idle, but then smooths out and drops to around 6PSI when I put about 1800 RPM to the engine.  I'm not sure which reading I should trust more. 

What's weird is that it loads up/floods when the gauge is reading 6 PSI (running at 1500-200 RPM) but will continue to idle and NOT flood when the gauge is bouncing between 7 and 10...

[rwberinger4x4]

Even weirder is it will try to flood, but won't actually stall, when sitting still, but floods in about 100 yards of actual slow driving.