Hot Rods Multi Carb Issues

I have an Offenhauser 4x2 intake with 4 new Holley 94 carbs on a completely rebuilt Chevy 327. I have checked and re checked the wiring, timing, points dwell etc. The engine is hard to start , but sounds good when I get it running, but after a minute or two it starts popping and spitting through the carbs and then stalls. I am thinking carb issue. I plugged off the power valves, so it is not that, but not sure where to look next. Thanks for any help or advice .

 

Pictures?

 

I have tried that manifold 2 different ways. One with Stromberg carbs on my old coupe and another time with 4 matched Rochester carbs on my V8 Corvair. . I got it to start , and idle great but nothing over 2500. Then got it hard to start, nasty idle, barely runs until about 3000 rpm and then it ran great.
I wish you luck with that setup.
Here is the one I took off my V8 Corvair

 

welcome to the fun world of multi-carbs. so, all four used at start up?

 

Thanks for the advice, I noticed that there wasn't a lot of choices of intakes out there for the 4x2 setup. I'm thinking I have carb issues, I thought since I got new ones everything would be ok ! LOL

 

Yes, on the 4x2 set up they run in unison. I had a 3x2 setup that was progressive and ran great.

 

It's not the manifold... I put one together years ago for a 348 and it ran fine. Only one leaking fitting !

Ignition -
"Popping and spitting", to me would be to look into the ignition (more).
Is the distributer shaft tight in the bushings (doesn't wobble, side to side)? Is the gear in good condition ? You say "timing"...what are you setting it to ? Should be at least 32 to 34 total degrees advance. The advance weights tight on the pins, and has good springs holding them together ? NOT tight, just equal.
Are you sure that you don't have number 5 and 7 spark plug wires crossed ?

On the carburetor side -
How did you set the throttle opening the same on the carburetors BEFORE bolting them to the manifold ? A drill bit is the, "BEST" equalizer, NOT a feeler gauge leaf.
Have you had it running long enough to do a synchronization step to the carburetors ?

There's a few things to do, redo. Check your plug wires...again.

Mike

 

Lots of questions, but first, do they all have automatic chokes? Manual? Did you synchronize the carbs using a Uni-syn or equivalent?

 

Did you check all the float levels on the carbs?

A bad ignition condenser can cause those symptoms....among many other possibilities.

I'd want to break in a fresh engine with a known good carb/ignition setup. Then switch the the difficult one.

 

Another vote for either ignition or timing issues.

If compression is good, and ignition tests OK, then:

For the carburetors:

Initially, set all four throttle opens identical (as Mike suggests, with a drill bit) to run at a high idle.

Install carbs WITHOUT linkage.

Start engine and warm to normal operating temperature. Then synchronize using your choice of manometers.

Install linkage.

Jon

 

Did you rebuild the engine yourself? What was done to the heads?

Does it have solid lifters? Where did you set the lash? If it's a little too tight, when things warm up the lash gets even tighter and it will try to keep the valves from closing completely. If the intakes don't seal it will pop back into the intake and can be hard to restart until things cool down.

Maybe check the cranking vacuum as well, with the throttles completely closed. Should pull at least a couple inches cranking.