Hot Rods Surge while driving... What can cause that??

Happy Father's Day to all the Dad's out there!!

My '48 Chevy has a surge as you're driving, not under acceleration.
It's a 305 stock with a th350.
Have had some tranny issues and wondering if this is a new symptom in that issue....
Anything else that could be causing?

Thanks,
Mack

 

A lean condition can cause this but we need more info on your setup.

 

If the motor is basically stock its more than likely a lean surge. Check your idle mixture screws for dirt or dust, and make sure your float levels are in spec. Lastly, for good measure check your timing, if your to advanced it could cause the surge too.

Good luck!!

 

That could be someone pushing you from behind... go faster

 

I'd bet on a lean condition .

 

What carb? Maybe a miss......however, I like 2racer's answer

 

To much advance on timing

 

This problem usually stymies. Thanks guys for some insight on it!

 

Lol!! At this point a push would be welcome!!
Thanks All! Check timing & carb. I'll let you know what happens.

Thank You!!

 

Ok, timing is good, floats are good, jets are clean.
Air/fuel adjuster is non-operational on left side facing the carb. The right side adjusts as it should. I took it all the way out and cleaned it. Then blew out the carb... No change.
What to do next?

 

Inquiring (clueless) minds are listening! What might reveal in the way of change, if you backed off the timing a couple of degrees? (Any change)? If the car idles well, it doesn't sound as though you've got a vacuum leak-contributing to leaning out.

 

Sounds like a fuel pump about to go away, to me....

 

Ok, took another shot at blowing out the air/fuel idle screw. That's working & found a vacc leak!! She is running like new!!!
Thank You all for helping me through!! Time to cruise!!

 

What kind of manifold vacuum are you pulling at idle and at a steady cruising speeds? Is it steady or does the vacuum reading drift up and down a bit?

The idle mixture screws should have no real effect on anything much above idle speed.

If the engine is otherwise in a decent state of tune it could be a weak fuel pump, plugged filter, or a tank venting issue. But I've also seen instances where a float set 1/16" below specs was enough to create a noticeable surge at cruising speeds. At first I had a problem convincing myself that such a minor change could make the improvement that it did.

 

i had a car surging at cruise- new plug wires and all 8 stayed lit-problem solved- taught me to make sure ALL is right under the hood and reminds me of the saying 98% of all carb problems are ignition.-rick

 

I did change the filter this morning also, as the bowls had a sediment in them. So changed the filter & cleaned them out. That may have had as much to do with it as anything else huh?