B
BillNap
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- Last seen
- Joined
- Jan 20, 2022
- Thunderbird Year
- 1963
What are some causes of hard cold start on my '63 with a 390-4 bbl?
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Describe what you call a hard start. I have a 292 4BBL and a mechanical fuel pump. Birds were notoriously hot runners. When they sit for a short time after shut down, somehow, the fuel either escapes from the bowl or is forced back and must have a lot of pumping to fire. I must pump for quite some time to ignition during cold starts. You could experiment with an electric fuel pump (they're cheap) install it and then try turning on the ignition for a few moments (without engaging starter) before attempting to add fire. (I am assuming you do your own work). Also, you can check your fuel pressure produced by your mechanical FP for spec pressure during start. Just suggestions.What are some causes of hard cold start on my '63 with a 390-4 bbl?
The only problem I have with that is nothing is lubricated before firing. It's better to have several turns of the crank to build up oil pressure before it fires off. learned that from an engine builder who built race car engines. That's why they have a starter switch and a separate ignition switch. Crank it until the oil light goes out and then pump the throttle to fire it up. The worst thing you can do to an old cold engine is not building up the oil pressure before firing off. These are not new cars which are designed to fire at a turn of the key. If you have any knowledge of the old WW II rotary engines they spewed oil and clanked until they warmed up and then performed.Describe what you call a hard start. I have a 292 4BBL and a mechanical fuel pump. Birds were notoriously hot runners. When they sit for a short time after shut down, somehow, the fuel either escapes from the bowl or is forced back and must have a lot of pumping to fire. I must pump for quite some time to ignition during cold starts. You could experiment with an electric fuel pump (they're cheap) install it and then try turning on the ignition for a few moments (without engaging starter) before attempting to add fire. (I am assuming you do your own work). Also, you can check your fuel pressure produced by your mechanical FP for spec pressure during start. Just suggestions.
All very valid points. The modern gas especially with ethanol has a lower flash point and evaporates much faster than pure gas. Also Premium fuel also has a higher flash point to prevent pre-ignition ping. From what I've seen non ethanol gas has a higher octane rating to prevent pre-ignition which can be damaging. But that doesn't solve the cold start issues.Lots of folkslore abounds. A cold cranking issue is not the same as a "hot soak" issue; lots of 60's cars using modern gas are notoriously hard to start within 20-30 minutes of a "hot" shutdown. When a hot enigne is shut off the underhood temperature spikes and old carburetors will boil the fuel (e.g. percolation - (just like an old coffee pot) and put raw gas out of the nozzles that sits on the intake runners until it evaporates. Try to start the car before that evaporation occurs (about 30-45 minutes) and you are starting a "flooded" car - so cold start procedures apply - like holding the accelerator on the floor and "feathering" the gas pedal to move the car for a short time. You can determine this several ways after shutting down a "hot" car:
1. Look down the carb throat to see if fuel is dribbling down them
2. Use a cheap Harbor Freight IR temp gun and "shoot" the bowls, any temps north of about 140* with modern fuel is a problem.
3. Listen for the sound of fuel boiling in the carb.
Most classic cars are not driven enough for cold engine starts to produce unacceptable wear...
Moreover, most cold start wear is because of the rich fuel mixture when first started; the excess fuel washes the oil off rings and cylinder
walls. So, delaying firing up the engine is minimal help. Aircraft engines are different beasts entirely.