The Stovebolt Site Forums The Shop Area Engine Shop Sputtering 216 problem solved

I'm proud and happy I figured out this issue with the carburetor.
The engine runs beautiful now !

My problem was a too stiff spring inside the Rochester B power valve piston.

You could punch the gas pedal without any hesitation, but if you left it too wide open, the engine eventually started sputtering until you backed off the gas.
After eliminating all other factors, I realized the power valve piston must be too open at low manifold vacuum, supplying too much gas.
So I went through my old Rochester B parts collection and found a lighter spring.
Amazing what the right little spring can do.
I can push the gas as hard as I want now and the engine responds very well.

My theory was correct and the solution worked - feels great!
Anyways - just posting this in case somebody has symptoms like I had.

Great job! I'm always amazed at how some problems are corrected by the most minor parts. I had an engine flooding problem on a Jeep I once owned. Only happened when off-roading. At the insistence of a very knowlegeable parts guy, I installed an spring-loaded needle and seat kit in my Carter 4bbl carb and it instantly and completely cured the problem. I didn't believe it would work and put the decision off for about a month before I caved in.

Good work, :hammering:

Thanks for sharing my happy moment!
Nothing like a great running original old chevy.
I hope I will be in that shape when I get to be that age.

I agree, when it comes to carbs, it's amazing how the slightest adjustment can make all the difference.
Carbs and carb parts selection and adjustments really seem like THE most critical factors in engine tuning.

love your little 48 coupe.......a lot time folks will assume that a problem is a carb and many times they are wrong.... thanks for the post..

My new pride & joy....a dream of many years come true.

All I learned from my truck the past 12 years comes in really handy with the coupe.
It was pretty neglected and hasn't had anybody working on it who knew anything about old cars in a very long time....
Frozen/corroded/leaky brake cylinders, ancient oils, spark wires in wrong order, wrong timing, bad carb, bad steering/alignment, etc.
Amazingly the valve lash was correct on all 12!

So rewarding to get it running again.
My first car I ever owned - quiet an experience!

Alright! We have another Rot "B" expert in the house. Nice work.

Are you somewhere near Hesperia? I'm trying to place the background scenery in your pictures but I'm just not sure where it's at.

Love that coupe! My first car was a '48 Aero sedan. rebuilt 216, Fenton's, Smitty's, lowered, painted suede black. Loved that car.

Not quiet an expert, but I rebuilt 5 of those so far and know enough to tweak them by now.

The original Carter W1 is what should really be on this engine - I love that carb.
Got two on my daily 235 and can't imagine a better match.

I am where the desert turns into the Sierra mountains.

42-48 Chevy cars rule...!

Hey that little tid bit of info may help many. Good job.