At a cold start, the engine goes into fast idle, idles smooth up to temp, and then runs well. If I park and let the truck sit for an hour or so and attempt a restart, it struggles and idles low. If I don't rev the engine up to temp it feels like it will stall. The choke at this point is wide open. Any suggestions or tricks on a warm engine restart?

 

You may want to try and hold the pedal about a 1/4 down when starting to see if that will bring the idle back up.
The choke may be cold enough to get the fast idle to kick in but not close the flap all the way.

also what happens is with todays gas and the motor sitting the carb get what they call "heat soak".
Heat from the motor not running heats the carb and boils the gas in the float bowl.
The fumes from the boiling gas is heavier than air and goes to the bottom of the intake manifold flooding the motor.
When you go to start the motor it may need a lot more cranking before it will fire off and run.
You may want to hold the throttle wide open to start it like it is flooded and it may run ruff till it "clears out" and then should run & idle normal.

You did not say what motor / carb you have and if any mods have been made to the motor.
Still running points? When you post up question you should put the trucks info in so we know what you have.
Dave ----

 

It's a 360, Holley 2300 carb, auto, and electric choke. Still running points, all that was recently checked out. Would I hold the pedal 1/4 down only when cranking/starting or until idle/temps are back up and good? This engine seems to be happier when at running temps, and if it's between temps (not cold, but not just ran and parked), it seems to struggle some. I read there is also some spacer you can add below the carb to help reduce the heat concern right?

 

Each motor running a carb has it's own way needed to start when cold, warm & hot and may take a bit to find just what your motor likes.
I would try the 1/4 before I turn the key and when it starts keep the RPM up for a second or 3 then see if it idles as it should.

If that dose not help after a few tries then I may look at the choke setting.
Before you touch the throttle pull the filter so you can see the choke and the fast idle setting.
Then move the throttle and see if the choke tries to close and if so did the step for the fast idle hit the screw for the fast idle?
If the choke moved but the fast idle step did not hit the screw maybe try making the choke rich just a little so the fast idle comes on.

If you find the choke valve is not on too far and making is run rich turn the cap back to where it was, you did mark it before you made it right right?
Then bend the rod to the fast idle steps to the fest idle is working and as the choke heats up and opens all the way, remember it was closed just a little, that should get the fast idle on but turn off when back up to temp.

I can tell you Holley choke's are a lot of fun to get right for the seasons.
Adjust for cold and it is not right for warm and the other way around too.
Dave ----

 

So I tried the 1/4 pedal trick. It works per se, but I have to hold it until the engine is at operating temps otherwise it struggles and stalled on me a couple times. Pushing the pedal to the floor briefly does the same just louder (cherry bomb exhausts), still have to rev to operating temps.

Ok, so one thing I'm noticing at cold start it fast idles, up to temp, rpms at 750-800, I drive off. After I park for an hour or so, the engine is warm at restart, I run into the starting issue mentioned above getting temps up and not struggling at idle, but here is the catch... when the engine is at operating temps on this restart, my rpms have dropped to 650.

 

Is this a auto or manual transmission truck?
I know it is a 360 with a Holley 2300 v2 carb do you know the CFM of the carb as they make 2 - 350 cfm & 500 cfm.
Have you done any jet or power valve changes from factory?

Now the motor other than the carb any other changes to the motor?
Rebuild back xxx and has xxx miles on it.
Cam and headers on it at rebuild?

Have you checked the dwell and timing and what are they set to?
Dwell needs to be set before timing. Then set idle speed.
Then adjust the idle mix screws and idle speed again.
What is the vacuum at when idling at temp?
You can use a vacuum gauge to adjust the carb mix screws.

I want to rule out the tune (dwell, timing, carb mix) before digging to far.
Right now I cant think why the idle would drop on a hot restart?
Dave ----

 

I see you have a post "cranks but no start" that was 4 pages what was that all about?
To lazy to read all the pages

Well went to last page ....... rotor was the cause.
So what did you set the dwell and timing to?
Dave ----

 

360, auto, Holley 500 cfm

No jet or power valve changes, carb was installed a month or so ago.

Engine was rebuilt about 20-30k miles ago.

Cam and headers on it at rebuild? I believe so (paperwork just say rebuilt motor, no other details.

Have you checked the dwell and timing and what are they set to? Gap, Dwell, timing was checked a few days ago.

What is the vacuum at when idling at temp? I believe it was 15 or 16

The "cranks but no start" story is about a couple issues I ran into, one was low reading at the solenoid which was revived. Another with the float bowl overfilling, also revived. The other was as the title says, cranks but no start. We swapped out the condenser for safe measure and also the rotor. There was some scrape marks on the edge/tip. In doing so, the engine fired right up. So we assumed fixed! But also yes, timing etc was done right afterwards.

My buddy thinks "it could be ignition related still, the breaker plate moves around a lot in the distributor."

 

Well you can check the plate & timing chain but I think the chain would be still pretty tight with say 30K on it.
When checking dwell, analog meter, the needle would be jumping all over the place if the plate was moving.
With timing light the timing would also be jumping all over the place.
If the chain had a lot of play the timing would jump all over also but again I thing the chain is still tight.

You dont remember the dwell & timing was set to do you?
That 15 - 16 HG of vacuum it pretty low unless you have a large thumpy cam and I dont think you do, do you?
It should be 19 - 21 if close to a stock cam.
Retard timing can also cause low vacuum and why I would like to know what you got it set to.
But the dwell need to be set before timing.

I am also thinking if timing is retard could cause the issue you are having with the hot restart.
I say 10* to 12* BTDC is a good starting spot as long as it dose not ping.
That is with vacuum advance disconnected and plugged when checking timing.
Is the vacuum advance ported (carb) or manifold?
Just a few things I am thinking of that could be the cause.
Dave ----

 

Thanks for that info!

I honestly don't believe we set the dwell. I do have an old school dwell tester that I never used, had it passed down to me. The timing is set at 9* anything more or less the engine didn't seem to perform as well. I could be wrong on the 15/16 with the vacuum, but I can check again (I should've written this down, as I've been checking values all last week). The advance port is on the carb.

The timing light wasn't jumping all over the place so I'm not too concerned its related to the chain. Like you said, with less than 30k rebuild it should be good still.

 

Look up what the dwell should be and make sure it is set right.
If dwell is off can hurt power as the coil cant build up enough power for spark.
Then check the timing. I cant believe that it would not run better with more than 9* of timing.
I was going to say bump it up to 10* to 12* BTDC as long as you dont get pinging and it will start hot with no kick back.
Dave ----

 

I have a dwell tester but aren’t dwell and setting points with a feeler gauge the same thing? We set the points prior to timing but with a gauge. My fuel tank has emission on it so the book calls for .021 on the gap. I believe it was set to just under that. But I’ll test out my dwell tester and see what it says. I would need to readjust timing if anything changes here correct? Any tips on how to do this without a timing light available right away?

 

Tried to hook up my dwell reader. The only thing is its old school, I dont have instructions and got info off the net. Says to connect black to ground, red to positive, and yellow to neg of coil. I wasn't able to get readings when it was set to "dwell" but switch it to "points" and the needle started to move, this is what it looked like. I double checked gap prior to starting and it was at .021. This time around however, the truck didn't want to start on restart immediately after running to operating temps and shutting it down. Had to feed some fuel to it and rev to idle. Felt similar to the engine flooding thought I didn't give it much fuel.

 

I am to lazy to get my Motors book to see tune up spec (guessing) 70 with a 360 motor but found this on line.

The plug gap should be .035
The timing 6 degrees btdc
dwell 24--29
point gap .017

I also found for a AMC v8 a point gap of .016 and dwell of 28*
So your .021 gap and looks like 32* dwell is a little much.

When I had to deal with points I set by gap as a starting point but dwell was the final setting.
Also note as the plastic rub block on the points wear the gap / dwell changes as will the timing.
This will throw off smog, that is one reason why everyone went to electronic IGN.

Yes dwell needs to be set before timing because point gap change changes dwell that changes timing.
As for setting timing with no light you can do this 2 ways but it still is try it and see deal.
Vacuum gauge adjust for a high reading but you will need to test drive to check for pinging and for hot start, no kick back.
The other is be ear and again you will need to test drive to check for pinging and for hot start, no kick back.

I would set the dwell then hook the vacuum gauge to see where I was at.
You were at 15 to 16 and if lower I would bump it back up to the 15/16 and see how it runs.
Then I would bump it up to say 18/20 if it will get that high based on the cam, and see how it dose.
As long as you dont get pinging and will restart ok hot you can leave it.

The restart issue could be todays fuel.
You said it was like it was flooded and that is a sign of gas boiling in the carb and the vapors going into the intake manifold and "flooding" the motor.
After we get the dwell, timing and carb adjusted and you still have this "flooded" issue we can deal with this then.
Dave ----​​​​​​​

 

Ok got around to some tweaking. Readjusted some settings based on the suggestions. The truck seems to start up each time. Idle well. But after the engine gets warm/hot it begins to stumble now. And when placed into gear, it stumbles more and stalls eventually unless I feed it fuel. Hot engine stumble.

The timing 6-7 degrees
point gap .017 (ignored the fuel tank emissions)
vacuum reading still around 17ish.

I looked into the vacuum advance, did a suck and blow test and it seems to function as it should.
Getting a better, solid spark now as well.

I did find a vacuum leak around the carb spacer, also swapped that out. I also found a leak around the valve cover, I'll need to replace those gaskets.