car is hard to start after left sitting for 10 min or more after a drive. figure it has to due w/ fuel percolation. i have a factory 4bl intake, w/ an aluminum adapter w/ an edelbrock 650 carb, new stock fuel pump. i had the fuel line/filter lying beside the heater bypass hose, and prob was bad. car would start fine cold or immediately after stopping, but not after sitting for a while. i changed hose routing to keep off engine and bypass hose, but still have prob (but not as bad).
i read another thread stating needed thick gasket for carb, instead of thin paper style. would it matter much to use thiker gasket. i figured aluminum carb adapter would dissipate enough heat.
other than this carb runs great.
eric

 

Your fuel pump could have a drainback issue.

 

I have the same problem. Have a new fule pump and carb. The other day when I was under the car I could hear fuel dripping in the tank. so think it is a drain back problem, but how do you fix it? is the new fuel pump the problem?

 

I have the same problem. Mine will also start right up after it has been sitting for a week or so but then immediately die. I then have to pump and pump the accelerator and it will finally restart and stay started.

 

I have a big starting issue after it sits a week. I suspect drainback. If it sits a couple hours, it fires right up, but coughs a bit on initial accelleration.
Anyone know of a simple check valve one could put on the suction line right next to the fuel pump?
I heard of some fuel filters having built in check valves. Anyone know? I bought the correct AC Delco one for my 72 but I doubt the check valve is on it...
My 86 does not have this issue.

 

Is it hard to start or hard to turn over. If it is hard to start it could be a bad fuel pump, but if it is hard to turn over. If you run headers they get real hot that heats the starter, and they will just barely turn the motor over. If that is the case you need a heat shield for your starter? If you don't have headers check your timing with a timing light make sure it is right? Also another thing to check is the battery and cables if the battery weak or to small that could be it. If you built your motor up any you might need a bigger battery.

 

it cranks fine. if it was fuel pump, wouldn't i have probs when starting it for first time? it starts fine when first started and if stop and immediately stop. it is after leaving it for a time 5-30 min, that it is a bear, which made me think fuel. is there any validity to running the thicker stock carb gasket between intake and carb adapter. i figured alum. carb adapter would dissipate heat enough. not sure if fuel line getting to hot or carb.

 

I have similar problems intermittantly. Immediate restarts are fine. Between 10-30 minutes takes extra cranking. However, after 1-2 hours, it will often start easily (ruling out perculation / drainback).
For this reason, i have been suspecting my original coil mounted on the block is failing when hot. When an engine is stopped, it gets hotter from heat soak before it actually cools. The timeframe my failures occur are in relation to the heatsoak times. I need to replace the coil and see what happens. I heard someone else concluding that their coil was the problem.

 

With mine, it turns over great, but once its warmed up If it sits for a little while, I have to give it some gas and crank it for a while, but if it sits just a few minutes, I can hit the key and it fires right up. If it sits over night,i hit the gas once and it fire right up.

 

i'm going to put on thicker carb gasket, check timing and see if helps. i may try to insulate fuel line
see what happens

 

I found that if I pressed the gas pedal just once, when my car is dead cold or sitting for even a short while, it would start immediately - otherwise wanted to crank and crank. I was delighted by this quick fix.

 

thanks for tip dan. i put on a thicker gasket (factory style) between adapter and intake and seems to have improved some.

 

^ What he said. An old friend's '70 350 would run great until warmed up. Then it would start laying down and get hard to start. Replacing the coil did the trick. I guess whatever was wrong internally only caused a problem when it became heat soaked.

 

Timing issue

 

car has an hei distrib (alreardy in when bought car) when restoring car, i put in new coil, module, cap/rotor. what should timing be set at, w/ factory 350 4bbl engine. using hei distrib. also what gap do most run on plugs for hei distrib. i set mine at .040.

 

red dog, i think you are right. i checked timing and it was at 8 w/ HEI, a friend advised to put it at 16 degrees and start prob seems gone, also car runs so much better and stronger. what is timing for a stock 350 using an HEI supposed to be?

 

I set my plug gap with HEI at .40 also. These motors seem to like initial timing in the 12-16 range. Mine runs the best at 15 so I think you are right on target.

 

Hvae you verified for sure that it is a fuel problem??? Does adding some fuel to the carb when this problem is happening fire the engine??

 

Stock HEI timing is 20° BTDC @ 1100 RPM.

 

If my car with an Edlebrock sits for say more than a half hour after running it usually takes a couple cranks, sitting 10 to say 20 minutes, no problem. If it sits a few hours I'll give it a pump and it starts right up. On a cold morning it starts up beautifully, never had a cold start issue just an annoyance when the engine is warm and has been sitting a bit, I've adjusted the choke with no effect.

 

Hmmm, maybe its a edelbrock thing then, sounds just like mine, and it also has a edelbrock.

 

I had the same problum with hard to start after 30 min, OK when cold and OK after 1 hour. I installed a carb spacer made of the black material to insulate the fuel in the carb from boiling. No more issues.

 

seems like prob was timing. way easier to start now. i had prob w/ quadrajet and edelbrock. car runs so much stronger. may try 20 degrees and see if improves
thanks

 

I know this is a old post, but after all this time, of playing with the timing and fuel mixture, I finally got the 71 to start like it should, I have noticed since I got the car that the plugs indicated that it was running a little on the lean side, I have tried everything but just couldn't get a good idle, and it did feel as responsive as it should, Yesterday while cleaning the engine compartment from the winter, I decided to take the return line from the fuel pump off and plug it, The car starts now all the time with just a quick turn of the key, idles like a dream, and is more responsive than it has been. will have to see what happens when the temps go up, and see if there is any vapor lock problems. Going to put in the set of new plugs I have here, and take a nice cruise and see what the plugs show now.

 

To add to the Knowledge base here. 71' 455 , had to add off road kit to Edel 800cfm carb due to living in new area with lots of hills. Car was stalling on downhill quicker 90° turns. Kit fixed that problem, but now having similar hard starts when sitting after 20-30 mins. Sometimes it happens after sitting for a week without starting car... Which to me indicates not a heated fuel thing. Sometimes its that coughing kind of hard start. None of this ever happened before the off road kit added. Started well everytime, whether cold or hot, no coughing starts either.
My best guess is Carb or Timing issue. Going to recheck timing today.

 

The Edelbrock or originally, the Carter AFB/AVS have had hot start issues since they were factory equipped carbs in the 60's. Why do you think they used the phonelic Bakelite body on Thermoquad, heat soak. Most use 1" phonelic spacers which help keep heat off the carb. I have only had this issue with a Qjet at 230+ degree temps.

 

My particular car never had the issue before. Ive used the 1413 800cfm for 8 years. Not that I love it or anything, just never had this problem before. I did have heat soak issue with OEM starter, but that was solved with aftermarket hi torque starter.

My timing was too far advanced. Fixed that and we will see now.

 

Timing didnt fix the issue. Looking to the carb now.
But its running real nice.

 

It could be needles and seats leaking back or the fuel pump as well. Another thing to check is the condition of the rubber hoses all the way from the fuel tank to the carb. They get cracks but that usually causes more issues sitting overnight or a few days. I would never run an Edelbrock, way too many issues people seem to have with them.

 

This happened to me and the fix.... I put a fuel filter with a vapor return back to the tank and re insulated all the fuel lines that are routed near and by the engine to prevent any fuel boiling. Also I rebuilt my quadrajet and epoxied the bottom side under the fuel bowl, where I found a small leak.

 

I have brand new everything, SS lines, all new rubber, new fuel pump, braided steel fuel lines to the carbs...so not that I think.

I tweaked the timing 2 more times, idle now down to 12°, all in 36°, from at the start of my post here of 22° idle. It drifted to 22° there somehow after I set it a while ago at 18°

I also recurved the advance some to bring adv in earlier with 1 lighter spring. Still need more experimenting there, but Took her for a spin and after a couple stops, letting it sit, no more hard starts. But need more drives to verify 100%
Like I said , never had this problem before.
Also noticed a slight drop in water Temp after aĺl this.

 

I did read about and watched vids on setting up return lines to help this problem. As well as thicker gaskets to isolate carb from manifold, and of course carb spacers having side benefit of isolating the carb, as well as the main benefit of that mod.

 

What we need to remember 50's, 60's & 70's performance cars were all designed to run on premium leaded fuel and ethanol was not even thought of yet... Now fast forward to 2020......All long Gone now, what we have left to deal with is....The chemistry of unleaded fuels w/ ethanol, they have a lower boiling point, that causes vapor lock, pre ignition back fires, poor idling and the insideous hard hot starts in HP engines . Unless you run racing fuel or additives (which can break the bank for cruising) the only options are premium grades of unleaded fuels that contain about 10% ethanol. Hopefully you can find a sweet spot in the timing, fuel grade, carb settings, fuel vapor return, fuel lines and carb insulators where it may help these fuels run effectively.

 

👍👍
I run Non Ethanol 90 with Octane booster. Only one station has it at 90 near me. Others at 87

 

That's awesome 90 octane and no ethanol, wish they offered that in my area..... How much per gallon with the additive ???

 

Normally Stupid expensive. $3.50 a gallon. It dropped during gas crunch though. $2.70s then. Now its $3.30.
Octane booster is $7-10 a tank full.

 

It is $4.80 Canadian, which is $3.65 US for 91 Premium in Saskatchewan. All Premium here is non ethanol.

 

I run mine at 12 advance and it runs great just make sure to undo vacuum advance when timing it

 

Hopefully the OP has resolved the issue since this thread is 13+ years old...