Technical New stromberg big97 issue

I switched to a 4 deuce setup.

Everything runs good on the street. But when I attempt to launch I get a small geyser from the front carb position at the accelerator pump hole. It will put a heavy mist across my windshield.

These are new Stromberg Big97s on a weiand intake. (on a 392 Hemi) The intake is flat, so the carbs have a 3* tilt to the rear. The linkage is straight as the intake is not at all open plenum. Accelerator pump is set to summer. I have the pressure down to 1.5 lbs. Verified by multiple gauges and a snapon pressure gauge. Running a Carter p4070 pump and a holley low pressure regulator.

I have also switched different carbs to the forward position and the problem continues. I have also put a brand new carb in its place and it continued to spray.

If i shut down the fuel pump for 5 seconds before launch it does NOT spray. This sure seems to indicate the float needs to be lower. So, I have incrementally lowered the front float to the point it may stall when braking. This doesn't seem to help.

Again, this only happens when I launch hard from a stop. I'm looking for suggestions.

 

Contact Clive at stromberg

 

@uncle max

Uncle Max can solve all Stromberg problems

 

I talked to clive a month or so ago. It was mainly about a worse issue. But I mentioned this to him. He didn’t really have much to say. I’ll try again.

 

Seems like it has to be related to that fuel rail
Seems the angle of the manifold would put all the carbs parallel so I do not think it should only do it on the front placement if that were the problem

I would try turning the fuel rail around so the end of it is on the back carb not the front and see if your problem moved to the back?

 

That’s one thing I haven’t tried.

i also can’t guarantee it’s only the front. It clearly comes from that carb. It may be doing it at a smaller level from the others. It is difficult to watch when launching.

 

Sounds crazy, but could the front carb be in the airstream that the other carbs are shielded from and the air flow around the pump rod is ****ing the fuel out? Try putting a little vertical sheetmetal air dam under that front float bowl screw and see if that helps. Good luck!

 

You could try turning all the carbs around so that under launch the fuel would slosh away from the pump holes rather than toward them.

 

Borrow or buy a gopro recorder and attach it where it can clearly monitor what is happening on launch. Might give you a better idea of what is happening and from where.
Does it do it with the scoops off?

 

My guess is that you're seeing a fuel pressure spike - probably when the pressure regulator suddenly opens. You might consider running a return line from the regulator - so it is not "dead headed". Trying to get a fuel pressure regulator to correctly work at low pressure is a bit tricky without a tank return line.

 

Are you talking about the hole in the carb top where the accelerator pump rod goes through? Is the felt grommet going down with the pushrod and not staying in place up against the carb top when you stab the throttle?

 

There is a return line after the regulator and before the fuel rail.

 

Thought the same, but it happens even when he swapped the carbs around and only in the front.

 

I'm not aware of Holley making a low-pressure return/byp***-style regulator? I think the lowest they go to is 4 to 4.5 PSI (in a return style). What is the part number?

Here is one from Summit that goes down to 1.5 PSI:

Summit Racing SUM-220058 Summit Racing™ 4-Port Fuel Pressure Regulators | Summit Racing

 

The regulator does not have a return. There is a wix filter with a return line after the regulator. I plumbed it at the highest point to return vapor and keep the fuel flowing.

 

If you continue to have an issue, you should consider a return style regulator. You might be getting a big pressure surge when the current regulator opens up (which is quite common on dead-head regulators). What type of manifold/carb combination were you running previously?

 

Two carters on a weiand.

 

So the carb is not problem, you would think enough fuel would be used in the last 3 carbs so that a volume/ pressure spike would be minimal at #1, but it is dead headed at that point. That's a great looking plumb job by the way, maybe a "T" fitting at front gauge position looped back to rear inlet at rail with hose, just to see if it helps, just an experiment, or plug rear inlet and reroute inlet between 2 and 3. Would 1 and 4 puke gas out pump rod? Something to think about if regulator/ plumbing change before rail doesn't help.

 

I'd ponder a return style regulator AFTER the front carb - attached to the fuel rail, with a return line going back to the tank - similar to how some EFI systems do it (after the throttle body).

 

Got a video of it.

 

Yeah, that would bug the Hell out of me . . . and I wonder if it is a pressure spike to the front of the fuel-rail?

 

What would cause a pressure spike? It only happens in the exact situation. It’s an electric fuel pump.

just seems to me that it’s an inertia thing - sloshing in the bowl.

 

Could be inertia, but why don't all four have the same inertia effect?

 

Good point. I might try and run a return line from the forward end of the rail. Where the gauge is.

 

Agreed. Even more odd is the OP said he switched the carbs around and it still happens. The one neat thing about Strombergs is you can run them (while stantionary) with the tops off.

Maybe rev it up in the driveway with the top off of the front carb to see if there is some sort of odd blow back happening at initial off throttle. Have lots of rags around to catch any gas that may spill out and a fire extinguisher at the ready.

I wonder if some other issue is causing a surge of air into the bowl of the carb at initial WOT and forcing the fuel past the felt gasket.

 

you cannot run the new strombergs with the top off. I’ve tried. The needle/seat was replaced by a ball valve.

but I have also suspected vapor as the cause. I had fuel boiling issue that was fixed by changing from steel to rubber fuel lines near the motor.

 

Hmmm. By ball valve, you mean the grose jet set up? It is still float activated. Not doubting you since I haven't tried with my Strombergs that have the same set up, I just didn't think it would make an difference.

 

Fuel shoots out in all directions from those holes. Including straight up.

 

Ahhh. I never thought about that, but yeah. Makes sense. LOL! Needed to look at a picture of one to jog my memory.

https://www.amazon.com/Grose-Needle-Float-Stromberg-Carburetor/dp/B07B917PDK

If you'd like, I have a "traditional" NOS Stromberg needle & seat set you can have to help you diagnose the issue if you'd like to try that.

 

Never thought of that. Do they have needle seats for 5/16 line?