The Stovebolt Site Forums The Shop Area Engine Shop 49 chevy 3100 sputtering in 3rd gear

No blown head gasket thank goodness. But truck sputters in 3rd gear only. .. any suggestions? Also where is the Trans refill cap? That's the only fluid I haven't changed. 216 motor

Timing could be off a smidge for the sputtering, or could be the points- is this original/stock distributor setup with a vacuum advance?

Full tune up usually solves a "sputter" if it's not trash in the carb.

Brad

upgraded to pertronix electronic ignition. Just got mufflers put on and wasnt doing this before. Also new gas tank, freshly rebuilt zenith. It only does it in 3rd gear?....wierd

I can't help you with the pertronix (no experience there), but since there's a new muffler in the equation, I'd look there. It may not be allowing the engine to "exhale" as well as it needs to be. (Me thinking out loud here, and only speculating:)You may have to reset everything to allow for the changes in the exhaust gas release. Again- that is me speculating, but it does make sense.

I did have a mouse house in my exhaust pipe once. It caused a little more than a sputter, though. Hopefully, somebody will come along soon & give you some pro tips on where to look.

Brad

What procedure did you use to adjust the carburetor?

What procedure did you use to adjust the timing?

Got it up to operating temp then turned mixture screw in until engine started to stumble then backed out quarter of a turn

Sorry - my second question was a duplicate - I changed it.

How did you set the timing?

Your mixture setting should be OK, but if you have a vacuum gauge, try setting the mixture to maximum vacuum.

Try setting timing to maximum vacuum.

I haven't moved timing and runs fine just don't want to accelerate

If your ball is on the pointer at idle, check your counterweights inside the distributor, or check your total advance at 2,000 RPMs with an adjustable timing light (if you have one).
Carl

pking75- from the other thread:


I know you you have the pertronix, but a tune up solved heavy40chev's issue. It's a process of elimination sometimes. First off, try setting your timing to maximum vacuum as Tim suggested.

If you didn't move the timing, and it "runs fine" I'm a little confused why it won't accelerate properly...unless your vacuum advance has lost its vacuum- making it not advance the timing.

The vacuum advance is a mechanical operation and independent of the electronic upgrade. Keep posting updates- I hope you get it figured out!

Brad

put the points back in. There is about a 50/50 chance it is the pertronix not working.

new plugs and wires last night and seemed like it ran worse...? Anyways could this be caused by not having a heat plate on my intake manifold? It wasn't doing this before...without one... Gonna check distributor, carb, coil and other ignition problems tonight. Something has got to give.

An unheated intake manifold could/should cause problems.

Update:

It aint the heat plate... vacuum advance aint working. Gonna pull distributor later today.

Whats usually the issue with this? I got it freed up and pulled... what do i need to look for as to why it wasnt working?

How can I test the diaphragm in my vacuum advance with it off?

Vacuum advance is easy to test. If you are not afraid you can apply suction to the port, the arm should move. Block the port with suction and it should stay. I use my tongue to block the port, and lungs to provide the suction, but then I am old and not afraid I will get any ill effects from the procedure. If it leaks, you can feel the vacuum drop. If it has failed, it won't move the lever. About as simple a test as you can get.

Yup she's done. .. cheapest place to get another one? Ebay was like 55 shipped?

This will work with a few parts from your unit.

Thanks cheaper than i found. Ordered

you will nee to reuse your clamp , don't dispose of it