What Now!? Another newbie engine mystery

I’m interested in the group’s opinion/troubleshooting approach on what’s going on w/ my car. Problem description as follows:

1971 Mustang Coupe – Ford 302 w/ Autolite 2100 carb. Finally got the car running and was taking it for a test drive around the block yesterday. When I gently roll on the throttle, the engine responds as one would expect and the car gradually speeds up. On the second lap around the block, I got onto it harder than before and the engine acted as if it hit a rev limiter (like you hear on some drag cars…pop, pop, pop pop). I let off the throttle and then gently rolled back on with no issue. In park I can rev the engine w/ no issue and the rev limiter type behavior seems to happen when under load w/ aggressive throttle input. Any ideas as to where I should start troubleshooting? Vacuum advance, accelerator pump, etc…:huh:

Thanks in advance,

Dwight

if it only happens under load, I would check your ignition components...plugs, wires cap coil

With the engine not running remove the air cleaner, get a flashlight and look down in the carb venturis while moving the throttle to make sure you are getting a good stream of gas out of both nozzles. They should start squirting fuel as soon as you start moving the carb linkage. If not your accelerator pump needs work.

If it has been some time since it was last running, I would start with fuel feed, probably gunk in the fuel line, filter and carburetor from dried gasoline. Check point gap, vacuum advance operation and timing, and distributor cap. Then go to spark plugs and spark plug cables.

if the pop was from the hood area you are lean,, if the pop from from the back tailpipe you are rich.

inspect the accelerator pump. when you push the pedal the shooters should come on instantly and spray fuel down the ventris. if there is a delay you need to adjust the linkage, and or inspect the diaphragm for the accelerator pump, the shooters would need to be cleaned as well. you could have a piece of junk clogging things up.

other things are how warmed up was the motor?

a lot of our cars run Horrible until the engine reaches stable temperature.

you said you went for a ride but it can take 10-15 minutes for an engine to reach stable temperature.

usually when cold the engine feels lean and it will pop, stall, hesitate then go.

somebody could of also re-curved the distributor too much timing too soon to make more power, would be worse with a cold motor.

advanced timing, again somebody wanted to make the engine more oofy so they may of advanced timing 5 degrees.

you could retard timing to reduce the lean misfire or put stock springs back into the distributor...

first i would make sure the car is really warmed up. go for a drive and take it slow for about 10 minutes driving around. then get heavy on the throttle and see if it stopped hesitating and popping. If it did then you have the usual issue we all have cranky engines.

you can usually solve the issue with more fuel but then when the engine is warmed up it will always be on the rich side maybe too rich.

now the other end of the spectrum is when you are rich,,, the engine will also hesitate and pop but out the tail pipe and you will see black smoke.

from unburnt fuel.

in that case you want to advance timing or add more timing from the distributor to lean out the engine and make more power.

or again you can cut back on the fuel use and get some MPG back.

first confirm what happens with the engine fully warmed up.

then confirm where the pop is coming from if it continues with the engine warmed up.

as an example my car is Very cranky when it wakes up, she runs leans until warmed up so if i get heavy on the throttle between startup and 10 minutes of driving in she will stall if i get more then heavy on the throttle. once warm its fine runs normal.

but it if start up and get on the highway and gun it, it will stall out.