If it's lean and stumbling, ease the choke on, it will improve. If it's rich it will run the same or worse.

2 hours ago, MM569457 said:

Thanks for the pointers. An update. I adjusted the floats appropriately per specs, had a mechanic friend assist (he be doing a lot for free/beer/steak/etc.)

Zcar parts came in, gaskets and last chance filters. Installed them onto the carbs.

The front carb almost immediately had fuel gushing through the vent line. Removed the front float and raised the metal tab, using the blow method.

Rear carb had fuel leak, but found the source was the banjo nut where I installed the filter. Tightened it down. Car ran for 15 minutes about the same. Not sure if it’s lean, but it’s not rich. It’s probably within the ball park to take to a specialist for tubing.

I installed the new Coolant Sending unit. Temp Guage now works.

 

Sounds like it has a healthy lope to it. What are the engine details? Compression, cam, stroke?

 

 

It’s a second hand Rebello 3.0. I haven’t tested the compression yet.

I believe it’s stroked around with 3.18.

I'll bet that SU's have problems with high performance cams due to the nature of how they work.  One problem with cammy engines is that they tend to run poorly at the low RPM where they sound the coolest.  Really, to smooth things out, idle PRM should be raised to give a more consistent intake vacuum.  But then you lose the lope.

That piston is probably jumping up and down with each intake pulse.  

Found a book.

https://www.amazon.com/Carburettor-High-Performance-Manual-SpeedPro/dp/1787111687

I'm about to install a fuel pressure regulator... would the best location be before or after the mechanical fuel pump?

Have you measured the pressure coming out of the mechanical pump, between the pump and the carbs?  Don't know if you mentioned it, this is page 11.

1 hour ago, MM569457 said:

I'm about to install a fuel pressure regulator... would the best location be before or after the mechanical fuel pump?

 After the mech. pump.

Think about plumbing. 

I’m troubled here. Why wasn’t the pressure measured after the mechanical pump before you made any decisions. The pressure is probably ok as @Racer Xmentioned earlier. Probably over thinking this. You don’t have a threshold of the current pressure.

On 4/9/2023 at 1:01 PM, siteunseen said:

Are you using a carb fuel rail, supply and return? That's where the reducer is. Small hole on return keeps it bottled down to 3-ish pounds.

I found this early this morning looking for a paint brush.

The return is the small hole and as I understand it's the restriction that makes up the fuel pressure for our carbs.

 

R2D2's beep-beep-boop.