Hard starting

[rattlesnake]

Hi y'all,
I have been having hard starting issues when warm ever since I built the car. Here's the rundown. 70 barracuda, 440, approx. 10.5 to one compression, gasket matched and polished 906 heads, big motha thumper cam, electric fuel pump, 850 DP Holley, unilite distributor, dougs 2" headers, team G manifold. Now the problem, starts right up with 4 accelerator pumps when cold. Runs like a demon at all times and is very dependable and sounds great, it idles fantastic. However when I shut it down and the car sits for 15 or 20 minutes it acts like it is flooded on restart. I have to press the pedal all the way to the floor and hold it while cranking for 15-20 seconds. It always starts back up after cranking. If it sits for a short while like 5-10 minutes this doesn't happen. It does not happen when it's cold or even after sitting for an hour or so. Very puzzled.

[73440]

Sounds like the fuel may be getting too hot at the carb.
Have you pulled the air cleaner when this happens, you can somrtimes hear the fuel boiling.
Check the routing of the fuel lines away from heat.
Insulate the fuel lines.
DEI has fuel line insulation products.

[Strawdawg]

and put an insulator\heat shield under the carb

[73440]

and put an insulator\heat shield under the carb

Right, forgot about that.
http://www.coolcarb.com/

https://www.designengineering.com//category/catalog/design-engineering-inc/line-hose-protection/heat-shroud
http://www.designengineering.com/category/catalog/dei-cycle/line-sleeving/heat-sheath-aluminized-sleeving

[cudabob496]

and put an insulator\heat shield under the carb

I had to drill the throttle plates in my 850. Made a real improvement in starting.

[cudabob496]

home-made heat shield. Just cut some sheetmetal so that it will
snug up against the carb. There is one in back of carb to.

[dodj]

I had to drill the throttle plates in my 850. Made a real improvement in starting.

Isn't that for idle quality? How would that affect starting?

and put an insulator\heat shield under the carb

x2
I had this problem with an edelbrock rpm manifold. Pop open the hood as soon as you stop, remove the air cleaner, and look down the primary bores. On mine I could see fuel wetting down the throttle plates.
I don't seem to have the same problem with the street dominator manifold but and insulator/shield is still on the 'to do' list.

[cudabob496]

drilling the throttle plates gave a big improvement
in starting, especially when engine was hot, and had been shutdown, like
at a gas station, and when I tried to restart 5 minutes later. It also
helped off idle acceleration from a stop.  The new carbs have added
an adjustment valve (idle bypass valve) that performs the same thing as the drilling
the throttle plates does.

Why it makes starting easier, I'm not sure,other than its
giving my engine more air when it needs it.

[Moparal]

Even that rubber line around that distributor gets fuel hot, Around the alternator or anywhere other then away from factory practicly. You can't even touch a distributor, head, alternator or anything else once it gets hot. Then you have modified exhaust or non vented exhaust.  vent it correctly, keep the fuel filter down low and where it catches road breeze also little block heat. stay as far from your alt and dizzy as possible with your fuel. Also if ya need one, an insulator for carb if ya need to. Then go play. Over 40 years and 100 or more cars for my toys, I actually never had that problem. But I have always avoided heat. It bites. Small tube headers are killers since they can not disipate heat and it stays above in the engine bay.

I have 2 carbs 800 hp dyno'ed 95 degree heat running on 93 octane on a stock vent system good fuel source and away from the heat. it idles in the track good to, but isnt your question.  Maybe this helped or not?  I don't know. I have been on much for health reasons, but I do build nothing but Mopar. 

[cudabob496]

I think that hard starting due to vapor lock, or hot fuel,
is not common, compared to the more likely scenario
that the carb is not adjusted or functioning properly for
easy starting.

[dano73]

Yeah I had the exact same problem on a cutlass I used to have it was great unless it sat for like exactly 15 to 20 minutes when hot turns out the gas is boiling as some other members mentioned I put in a spacer made by edelbrock between carb and manifold I got the thickest one they had think it was a one inch the increase in height barely fit under hood never had the problem again now my challenger will turn really slow if the timing is a bit to advanced on a hot shut down. I retarded just a bit and it's fine now 

[734406pk]

 gasket matched and polished 906 heads

Don't forget to block off your exhaust crossover passages if using a Cool-Carb insulator.

[john h]

I had the same issue on a bone stock 360 Crate motor with Small 600 CFM Eddy carb.  Small tube headers.  As soon as I replaced that with EFI, the problem magically went away. I thought I was losing crank Voltage too and that was causing issues with the Ignition control.    I now believe the fuel was boiling out.  The EFI always shoots some amount of fuel at start up.  a warm or hot start gets different amounts of "prime" fuel.  it also has "crank" fuel  My EFI also controls spark so it retards it back to 10* at crank.

John

[cudabob496]

there are ice/water buckets to keep fuel cold

[cudabob496]

https://www.summitracing.com/parts/mrg-1350/overview/