48 dodge won't go over 40

[Tom ark]

HI all, new member, but first older Dodge. I'm from Northern California.

I have a 48 Dodge 4 door with fluid drive.       We changed points, plugs, cap ,rotor ,new gas, wires ,coil, new vacuum advance, adjusted carb...,adjusted valves..

Just seems to flutter a bit at 20mph and then has good power up to almost 35/ 40. when the motor "can't go faster"... seems to be held back by something..

.doesn't stall, just poops out .   The muffler doesn't sound plugged. There is spark, gas is flowing.

any suggestion appreciated!

Tomark

 

 

[Brooklyn Beer]

Have you checked compression in each cylinder?  Vacuum ?  Correct carb ?

 

 

[Mattml430]

Sounds like it’s starving for fuel. Try a separate small fuel tank and give it a run with that. Might be getting enough fuel idling and free reving  it but not enough at 40mph. Old lines and tanks can have blockages. 

[Fossil]

Dirty fuel filter or weak fuel pump. Are you sure the throttle is opening all the way?  If so it does sound like a restriction in the exhaust system.

[Pete K.]

You adjusted the carb I see in post, but did you tear down carb to clean it out? Problem may be in float bowl or restriction in a jet. Sure sure sounds like fuel starvation.

[Brooklyn Beer]

I am tracking down a some what similar issue and think mine is crap gas.  I get fuel starvation at idle AND driving intermittently.  Just cuts out and restarts though. (before rebuild and now) The carb rebuild is easy to do on these but still looking to get the dash pot dialed in.  New fuel pump. I am going to hook up a satellite 1 gallon tank and by pass the fuel line to see if that stops it.  Car sat for some time and the new gas I am sure is dissolving the old dried up varnish. This is the second filter in 2 months.  Gas I just pulled out had turned an orangish yellowish nasty smelling liquid after adding some Berrymans to it in May. It starts easily, idles nicely, drives really good, then just cuts out.  Sometimes it stalls, sometimes it drags way down. Has a pertronix swap.  The crud that was in the carb looked like the Gowanus Canal at low tide.  So am yanking the gas tank today to boil it out

 

edit.  yep, crud gas in the tank.

Edited July 19, 2020 by Brooklyn Beer (see edit history)

[Tom ark]

Thank you for the tips, Ill drop the exhaust to try that, but not not "noisy"

Then check fuel pressure, and filter. satellite tank....we shall see.

[Fossil]

1 hour ago, Tom ark said:

Ill drop the exhaust to try that, but not not "noisy"

Been my experience a restricted exhaust is quiet and if anything will make a sort of hissing sound. 

[Grimy]

Before you drop the exhaust to check for clog, try this:  Car at rest with warmed up engine, attach a vacuum gauge.  Have an assistant run the engine at 1500-1800 rpm as steadily as possible for two full minutes while you monitor the vacuum gauge.  Gauge will settle within 15 seconds of this rpm--note the reading.  If the gauge steadily drops during the second minute, you probably have clogged exhaust so go ahead and drop it.  If there's no drop in vacuum, it's not the exhaust--and you've stayed cleaner.