The Stovebolt Site Forums The Shop Area Engine Shop I think the stumble is gone!

After playing with the accel pump linkage a bit I was able to reduce the initial throttle stumble on my '56 235 with stock 1bbl Rochester on my '53 3100, but haven't gotten rid of the acceleration dead spot until now. I have been taking it for a few short trips around the neighborhood since I got it minimally drivable, no air filter and only a few feet of exhaust pipe. Well, yesterday I finished up the new exhaust and mounted an element style air filter and took it for another ride to see how the exhaust performed. Lo-and-behold the stumble was hardly there, if at all. Air filter? Exhaust back pressure? Whatever made the difference I'm not sure, but it feels good knowing I own a pretty good running stovebolt! I suppose it's too much to ask to get rid of that hydraulic lifter tick?

Is that a '56 235 car engine? With out going back thru all the past threads
we, or at least I don't recall which engine you've got in your truck Lem.
And without knowing exactly what you've used for an air cleaner it's hard to
come to any conclusion.
Every carburetor that I've tried on my '50 216, which are several
meticulously rebuilt Rochester 'B's and a couple of W-1 carters, have left
me with the stumble on acceleration. This was true without an air cleaner,
with the spark arrestor using a paper filter, with an oil bath filter, with
the original engine and after a complete engine rebuild. You will hear some
experts tell you to jack your timing way up till it's pinging but I'm not
an advocate of that. Set to the ball was the best performance that the
engineers determined over tens of thousands of hours of dyno testing and
the way millions of Stovebolts were designed to run, so that's where
I've always set mine.
The smoothest engine performance I've been able to accomplish is by adding a
small amount of choke, which does eliminate the stumble when I apply
throttle when I start off or hit the throttle to accelerate. This is true in
all of the previously mentioned configurations. And this suggests to me
that the engine is simply running lean. Why would it be running lean if the
timing is correct, and the carburetor is correct and is metering the proper
mixture? The conclusion that I've arrived at after 10 years and 15,000
miles is, it's the fuel that we're using now a days. It's doped with
alcohol for one thing and who knows what else has been done to the refinement.
Todays engines with their computer dictating mixture and timing many times
a second can compensate for the fuel it's drinking, the simple Stovebolt can't.
In the ten years that I've been on the Stovebolt.com forum and many other
forums, I've yet to hear any other valid solutions.

I doubt very seriously if your new exhaust has anything to do with the
hesitation. If your air cleaner is choking down the engine a little that
may account for the reason the stumble is gone now. The original air
filters/spark arrestors offered very little restriction to air flow compared
to the paper filters, that's why generally the air cleaners that use a
paper element are quite a bit larger than the old oil bath or oil soaked
mesh filters.

Denny Graham
Sandwich, IL

Denny, it is a '56 235 hydraulic lifter engine out of a car with a manual transmission according to my figuring. I put a mr. Gasket paper element air filter on it (which is a very poorly designed piece of equipment) I had to run a bead of silicone around the base to plug up the gaping holes left by the poor fit on the carb. I have jacked a couple degrees of advance into the timing, but that did nothing for the stumble, I'm debating on whether or not to put it back to zero.

Thought you might have a truck engine with solids that needed
adjustment.
The hydraulics do get gummed up, they are very close tolerance,
just a few tenths clearance on the plungers. If your sure they
are getting oil and the galley isn't plugged up, you can pull
the lifter and dissasemble it to clean the varnish. What ever
you do don't use sandpaper or wire brush the them. A solvent
an fine (white) scotch bright will clean them. Also soaking
them in carburetor cleaner can help soften any varnish.
If you do end up disassembling the lifters to clean them, keep
them in order and on the same lobe and be VERY meticulous
about the reassembly. No pliers, no scratches and clean hands,
clean bench, clean lifter when you're dealing with parts have
that close of a fit. Compare this to the average human hair
which is .002"-.004" and you have some idea of how close a few
tenths is.
Denny Graham
Sandwich, IL

I took all the lifters apart and cleaned them last winter, keeping them all in order. Then very carefully adjusted them.