It almost sounds like a faulty accelerator pump in the carb. Remove the air cleaner and look down the carb air horn as you snap the throttle open and look to see if you see gas squirting into each front barrel.
Yes the accelerator does in fact squirt in raw fuel.
The starving like sound comes as I accelerate at 40-45 mph
either at light or heavy throttle . . . ?
Ok, check the fuel pressure. Have you changed the fuel filter?
At 45 mph, I would assume there is little vacuum advance any more if even equipped but mechanical advance should still be coming into play. Do you have a timing light to check mechanical advance? If not, just remove the cap and rotor and make sure the weights open and spring back and the springs are still on, the bushings are still ok.
I have not checked the fuel pressure but have to assume it is ok
as from a start I can floorboard the accelerator pedal and everything
is fine up to about 45 mph . . . by then it has max rpm in both 1st
and 2nd gear . . . it is really baffling me as I have been keeping
keeping my vehicles tuned and running since my 1st 1937 DeSoto
all they way through the acquisition of my 1st computer controlled
car when I had to give up . . . . this Chinook is our weekend cabin
on wheels and the 1st conventional carb/no computer vehicle
I have had in years . . . .I am not conversant with PVC and EGR
valves is there a possibility that either or both of them are gunny.
As I mentioned up until the time I let it sit for six months it at all
speeds and throttle settings ran like a champ. Used to rebuild
my own carb's with ZIP kits and the thought has occurred to me
that possibility some of the additives in todays petrol might have
during the period it sat idle gummed up the jets . . . but, she starts
right up and after warm up goes like new until about 40-45 mph.
In the for what it's worth department I'm 80 years old which has
nothing todo with anything other than the fact that I'm no longer
the shade tree mechanic I thought i once wuz . . . .? ? ? ?
Ok, so then in 3rd gear or drive, you are already traveling at 45mph, then try to go faster when this happens? Are you gradually moving the gas pedal down further, the same amount or suddenly going wide open throttle?
If wide open throttle, is the transmission downshifting back down into 2nd for awhile and then back to 3rd?
If not, manually shift it back down into 2nd when you get to 45 mph and give it wide open throttle then see how it responds.
If you are gradually giving it more gas, again does it downshift? It may want to or not. Remove the air filter and leave it off just for now, giving it a little more breathing just for now. Check that the air filter is not dirty if it runs better now and if the air filter is covered with oil ,change the pcv valve. Check the pcv valve at idling, first by pulling it out of the valve cover and making sure it has vacuum, then put your thumb over the hole and listen/feel for the valve to snap closed.
If you are just giving it the same amount of throttle, I would change the fuel filter, check the ignition timing, check the fuel pump pressure.
How is the engine in neutral or park? Can you rev it high and no problem?
accelerating past the 40-45mph magic speed either by feathering the
throttle or really punching it has the same effect, the starving gasping
sound. . . . .I have run it up in both 1st and 2nd and everything is fine
at higher rpm with no real load . . . .I have tried manually shifting down
to 2nd at 40-45 and get virtually the same response "starving/gasping" . . .
I have a K&N air filter and it is clean and not over oiled . . .I have yet
to check the vacuum on the PCV valve but will tomorrow after church..
Unfortunately I have long ago got rid of my timing light, dwell meter,
vacuum and pressure gauges as they were of no value with our puter
controlled cars . . . .In neutral or park I can rev it up to what I estimate
is around 4 grand . . . .am reluctant to go much higher . . .and it
runs fine . . . .as I have said it's a sweetheart up to 40-45 and
to that point purrs like a kitten for the big ole 460 that it is . . . .
At what rpm is 45 mph in 3rd?
Have you changed the fuel filter?
I am guessing (no factory tach) 4 grand or so and no check engine light.
I will check the vacuum at the PCV and put in a new fuel filter tomorrow after church. Thanks for your help. Is there any way I can let you know
if it worked or not.?
Just installed a new filter element and housing gasket
and checked the PCV valve. The valve has a ton of
vacuum. Test drive was just that a test drive with the
same results. Did run it up in 1st until it would not go
any faster then ran it up in 2nd and right at 40-45 mph
she acts like she is not getting enough gas , , , shifted
into third and motored along nicely at just over 40mpg
but with the slightest depressing of the accelerator in
a gentle attempt to speed up a little or by floorboarding
it samo samo . . . . . the gas in the old filter element
did not appear to be contaminated and there was a
minimum amount of particulate in the bottom of the
bowl. . . .lightly greased the new filter gasket and the
"o" ring on top of the new element . . . primed the filter
and reinstalled hand tight. . . . couple pumps on the
accelerator and she started up like new . . . . warm
up to operating temp (warm air coming out of vents)
and did the test drive . . . .? ? ? ?
For your info . . . . after all the fixes and attempts I followed the
advice of a friend who suggested I change the small bronze
filter at the gas input fitting on the carb . . . . . .
Wow, $4.95 filter and the old girl runs like new . . .
I first took the old filter off and blew through it,
there was a small amount of resistance to my blowing
and it did not seen like enough to prevent fuel flow,
however it was as when I blew through a new one there
was virtually no resistance ...... Thanks for your help...