Hi all.

I'm having a weird carb issue on my 72 Delta 88 with a 350 2bbl.
I rebuilt the carb, I know red flag right! But I did a good job I promise.
From a dead stop it accelerates perfectly, no issues.
Here's where it gets weird... If I'm already moving, coasting and not on the accelerator, when I hit the gas I get a pretty deep hesitation. It doesn't stall, and will regain power, but it just falls on its face for a moment.

I did add a dual exhaust last year, other than that she's stock.
Timing is good, points are correct dwell.

Any ideas??

Thanks!

 

Is the choke pull off operating correctly? If it's good, then you need to figure out if it's going rich or lean. Lean is usually accompanied by some detonation/knock.

 

I will check the choke pull off for sure! But I'm pretty sure I checked it when I was rebuilding the carb.

Running too rich or lean, that's in the air fuel mixture needles/screws correct? OR are they for idling only? Honestly not sure.
I set them with a vacuum gauge as best I could.

 

Does it do it every time or intermittently? I had a bug get into the float bowl once. It was floating around and every so often would get pulled into one of the main jets and four cylinders would go instantly lean and bog the engine down. Then it would kind of hiccup and blow the bug off the jet and back to normal it was. Did this for a week before i pulled back apart and checked.

 

Mixture screws are idle. Part throttle is the rods and jets. If they're all the same parts, it should work.

As mentioned above, trash in the bowl could clog the jet. A bug?! That's a good one! 🤣

Also, make sure that the throttle blades aren't open too far at idle, uncovering the transfer slot(s). Maybe, back the idle off and reset?

 

GREAT INFO HERE GUYS, thank you!!!!!

Looks like I have a nice Saturday of tinkering tomorrow.

 

Sounds like an accelerator pump issue to me.

 

So you have ANY fuel leaking from the mechanical fuel pump? Is is wet in that are at all? Do you smell fuel after you shut down? Prior to and upon the fuel pump interior diaphragm becoming weak and failing, you'll often notice hesitation at speed when you hit the throttle and it catches up very quickly. Mine was performing exactly like this the past 1/2 year. I knew it was time to replace the mechanical fuel pump. I replaced it last week. Hesitation completely eliminated. The thing is, it won't often hesitate all of the time, but often enough you know it's a fuel starvation issue when you hit the accelerator at speed and get that slight hesitation.

 

Super interesting!

I can check it with a vacuum gauge tomorrow for sure.
Thanks for the suggestion and your past experience.

 

When/If the mechanical fuel pump's internal diaphragm gets weak (failing) or if the seam between the top & bottom begins to fail (open slightly) you'll either leak a little fuel out the fuel pump vent or at that seam. Most often though, you'll see whispers of a hint of fuel lightly begin to cover the fuel pump or that general area.

 

"If" yours turns out to be the mechanical fuel pump, I believe your 88 takes the exact same mechanical fuel pump. I purchased the GMB model - a really, really nice fuel pump.

https://www.rockauto.com/en/moreinfo...komocFA%2BcYUu

 

Some 2GC carburetors have a check valve in the bottom of the accelerator pump well and some do not. If yours is supposed to have that and you missed it on re-assembly it may adversely affect the accelerator pump function under certain conditions. This may not be causing your problem just grasping at straws here if it is not the fuel pump diaphragm problem.

 

I would check the pump and discharge ball, be sure you have a strong steam discharge from the cluster nozzles, and double check your float settings.float closed and float drop.