Hi all Great site!
Let me first start by saying I am a mechanic and hobbist for 20 years. More specificly I am a Engine Performance Specialist by trade.
Well........ I recently aquired a 67 Barracuda. Nice car and runs great but very difficult to start when warm. Here is the deal.....
Thing runs fantastic!
Cold starts are great and hot starts are great.
Problem is, it's a ***** getting started after sitting 10 to 30 minutes. Still plently warm, choke wide open, great spark, plently of
fuel............ just takes 10 to 15 cranks to get it to fire......... that's not right, something is wrong.
All my other carb V8 cars (GM) were tuned to perfection and fired right up at the tap of the flywheel. It's not like I haven't figured out how to start this specific beast yet (car personality thingy) because I'm past that stage, it's been 4 weeks and have tried everything.
What I have is.........
-late 60's early 70's 318
-12 to 15k on re-build
-10.5:1
-30 over
-mild street cam
-headers
-Edelbrock intake & carb
-new: (correct) plugs, wires, cap, rotor, quality points/condenser, balast resistor, oil, belts, bla bla bla.
-Dwell 30.5
-Timing correct
-carb in very good working order
-200 HC & 2% CO @ idle and half that at 2500 RPM
Has great spark while cranking warm but not starting..... WTF?
Here is where I'm at........
Possible heat soak problem:
Voltality of the fuel manufactured this time of year (winter) will vaporize under heat much quicker than summer fuel. Coolant stops flowing & fuel stops flowing after shut down. Fuel in the carb get very hot as engine temp starts
to rise. (no spacer plate to reduce heat) When you go to re-start fuel is vaporizing stightly out of accel pump, even more in intake, and next to nothing is left before it even gets to the combustion chamber.
Problem with this theory is if you have somebody give you a "test squirt" during cranking it seems to have no affect. And when it does eventually fire there is a slight indication of load-up, which indicated plently of fuel.
Possible valve lash problem:
Does the early 70's 318 have adjustable rockers? Hydrolic lifters? If so, and if not adjusted properly, when the engine gets hot the clearence is less, and will cause hard hot-starts. This was an issue with a Typhoon we built for over 500HP. But I seriously doubt that is the problem.
Possible fuel PSI or float adjustment:
Edlebrock specificly states you can have no more than 6 PSI. (5.5 optimum) I have not checked mine yet, but reguardless that would cause a "running" problem more than a starting problem. If I had too much PSI pushing fuel past needle & seat I would have idle problems. This car idles great with excellent burn. (200 HC & 2% CO)
I best educated guess at this point indicates there is too much fuel.
If you start it withing a couple minutes of shut down there is no problem. Has to sit at least 5 to 10 minutes. And will act the same after sitting 30 minutes.
This means there has to be time allowed for "something" to happen or a "rich condition" to take place.
Thinking maybe the fuel is overflowing and or dripping after shut down. But there isn't an overwhelming smell of fumes. And if you pull a plug after tring to start it they are dry.
Basicly......... it "acts" like a dripping carb when you look at the starting symptoms, but evidence shows the plugs are dry and when it eventually fires it's not struggling, blowing black smoke, or acting loaded up.
It would have to take an aweful lot of fuel in the intake & combustion chamber to prevent a perfectly tuned engine to struggle like that. But there is not an idication of that.
It's a very annoying problem.
Suggestions or ideas?
I'm running out of ideas.............
Let me first start by saying I am a mechanic and hobbist for 20 years. More specificly I am a Engine Performance Specialist by trade.
Well........ I recently aquired a 67 Barracuda. Nice car and runs great but very difficult to start when warm. Here is the deal.....
Thing runs fantastic!
Cold starts are great and hot starts are great.
Problem is, it's a ***** getting started after sitting 10 to 30 minutes. Still plently warm, choke wide open, great spark, plently of
fuel............ just takes 10 to 15 cranks to get it to fire......... that's not right, something is wrong.
All my other carb V8 cars (GM) were tuned to perfection and fired right up at the tap of the flywheel. It's not like I haven't figured out how to start this specific beast yet (car personality thingy) because I'm past that stage, it's been 4 weeks and have tried everything.
What I have is.........
-late 60's early 70's 318
-12 to 15k on re-build
-10.5:1
-30 over
-mild street cam
-headers
-Edelbrock intake & carb
-new: (correct) plugs, wires, cap, rotor, quality points/condenser, balast resistor, oil, belts, bla bla bla.
-Dwell 30.5
-Timing correct
-carb in very good working order
-200 HC & 2% CO @ idle and half that at 2500 RPM
Has great spark while cranking warm but not starting..... WTF?
Here is where I'm at........
Possible heat soak problem:
Voltality of the fuel manufactured this time of year (winter) will vaporize under heat much quicker than summer fuel. Coolant stops flowing & fuel stops flowing after shut down. Fuel in the carb get very hot as engine temp starts
to rise. (no spacer plate to reduce heat) When you go to re-start fuel is vaporizing stightly out of accel pump, even more in intake, and next to nothing is left before it even gets to the combustion chamber.
Problem with this theory is if you have somebody give you a "test squirt" during cranking it seems to have no affect. And when it does eventually fire there is a slight indication of load-up, which indicated plently of fuel.
Possible valve lash problem:
Does the early 70's 318 have adjustable rockers? Hydrolic lifters? If so, and if not adjusted properly, when the engine gets hot the clearence is less, and will cause hard hot-starts. This was an issue with a Typhoon we built for over 500HP. But I seriously doubt that is the problem.
Possible fuel PSI or float adjustment:
Edlebrock specificly states you can have no more than 6 PSI. (5.5 optimum) I have not checked mine yet, but reguardless that would cause a "running" problem more than a starting problem. If I had too much PSI pushing fuel past needle & seat I would have idle problems. This car idles great with excellent burn. (200 HC & 2% CO)
I best educated guess at this point indicates there is too much fuel.
If you start it withing a couple minutes of shut down there is no problem. Has to sit at least 5 to 10 minutes. And will act the same after sitting 30 minutes.
This means there has to be time allowed for "something" to happen or a "rich condition" to take place.
Thinking maybe the fuel is overflowing and or dripping after shut down. But there isn't an overwhelming smell of fumes. And if you pull a plug after tring to start it they are dry.
Basicly......... it "acts" like a dripping carb when you look at the starting symptoms, but evidence shows the plugs are dry and when it eventually fires it's not struggling, blowing black smoke, or acting loaded up.
It would have to take an aweful lot of fuel in the intake & combustion chamber to prevent a perfectly tuned engine to struggle like that. But there is not an idication of that.
It's a very annoying problem.
Suggestions or ideas?
I'm running out of ideas.............