How to solve heat soaking for hard re-starts

[jt4406]

    

33 dwell. Initial at -5

[72 Challenger]

I was running 10 degrees initial on my 340 had the same issue with the hot starts. Backed it down to 8 and it works like a charm now.

[kawahonda]

   

33 dwell. Initial at -5

Is this bad? This is what the service manual said....

What is most peoples initial and total set to?

[Chryco Psycho]

Most engines will run best with the timing at idle at 12-16 * & total timing above 2500 around 34-36 *

[Cuda Cody]

 

[1 Wild R/T]

   

33 dwell. Initial at -5

Is this bad? This is what the service manual said....

What is most peoples initial and total set to?

Most folks interested in performance start with a minimum of 10 BTDC as base timing, many are close to 20 BTDC for base.... Total is typically 34-37 BTDC....  Apparently Cody feels to much timing cause a hard start & while I agree to much to the point of causing  the starter to have trouble turning the engine over will cause a hard start the idea that simply a little more causes a hard start I've never experienced......  But then I've only been tuning cars for a short time...... Maybe 40-45 years....

The majority of hard starts these days are fuel related & when you realize pump gas is formulated based on 99.9+% of the cars being fuel injected you can see why carbureted vehicles aren't really considered.....  And since vehicles with EFI keep the fuel under pressure whereas a carbed vehicle tries to let fuel sit in a bowl on top of a hot engine unpressurized you can see how taking anti boiling additives out of the fuel leave us with a problem...

On a hot soak situation you have the fuel boiling but the vapor is trapped so it doesn't escape, the whole intake & air cleaner area gets to be a super rich mixture... But the fuel bowl is empty cause all the fuel boiled away....

Trying to start it hot? Your best choice is wide open throttle to get enough air in the fire the super rich mixture but chances are it won't fire till all that has been purged.... And when it does fire? Well the fuel bowl was empty but now fuel is pouring in so it may or may not stay running....

Trying to start it cold? Well remember all the fuel that boiled out when you parked the car? The fumes have dissipated but the bowl is dry...... This is when an electric pump can really help you....

Yes keeping the heat out/away from the carb helps.... Fuel formulated for carbureted vehicles would help allot more.....  Or go back to my first post....

[kawahonda]

Thanks Wild! That's stuff you just don't read in the shop manual.

Until I get my timing tape and new points, condenser, cap, rotor...for the time being I'll just set it to 10 BTDC! With timing tape, I can verify total BTDC to make sure the advancer is working properly, and then continue to bump it up more. Safer that way.

Totally makes sense now, I was confused. At 5 BTDC, you're leaving some horse power on the table. Probably quite a bit.

[kawahonda]

I'm not checking advanced timing until I get the tape and install new points/condensor/cap/rotor.

But I did change my BTDC to 11-12. I get pinging on hard accelerations.

2700 elevation. 91 Octane.

So....reduce initial timing...maybe to "10" should be my next go-around?

I definitely should go with a recurve to get more initial timing! Maybe I'll look into that over the winter time. And chose to install my points and everything thing. Do a whole package thing.

[Cuda Cody]

IMO, you really need to set both the initial and fully advanced all at once.  You don't need tape, just get a timing light that will allow you to set the timing with the light and the 0 mark.  I'm guessing a digital adjustable timing light will be $50 to $70 bucks and you get an accurate reading and the exact RPM.    

I'm not checking advanced timing until I get the tape and install new points/condensor/cap/rotor.

But I did change my BTDC to 11-12. I get pinging on hard accelerations.

2700 elevation. 91 Octane.

So....reduce initial timing...maybe to "10" should be my next go-around?

I definitely should go with a recurve to get more initial timing! Maybe I'll look into that over the winter time. And chose to install my points and everything thing. Do a whole package thing.

[Cuda Cody]

In case you have not used a digital timing light, here's video on YouTube that shows how easy it is to adjust them to just the zero mark.  Start the video around 9:20 and you'll see a quick clip on it.  I'm sure there's better videos out there but you'll get the idea.

[kawahonda]

Is the vacuum advance on these stock dizzys adjustable?

[Strawdawg]

I got a bit over 60 years of tuning, but honestly?, about every ten years, I seem to relearn a lot of what I thought I understood   In other words, depending upon when the latest cycle began, I may not have that many valid years of experience.

This is not a one answer fits all subject.

Gasoline qualities have changed over the years, and depending upon where you live, it may be different winter to summer as well as being aimed at fuel injected cars which behave differently than carbureted cars.  Timing depends upon the combination being run.  Factory, or near factory cams will not take as much intial timing while cars with longer duration cams will usually take a lot more initial.  Compression is a factor as well.  Too some degree, the more initial you can run without difficulty in spinning the engine over on the starter, the better.  Of course, we tend to know the upper limit on timing to be around 34-36 degs again depending upon engine/cylinder head configuration.

If the engine pings under light load with a reasonable total timing, then we have a couple of possibilities, and maybe more.  If we are running a vacuum advance, we may be getting too much total advance, or the springs in the distributor are allowing too much mechanical advance at the particular rpm band.  Or, we may simply be a bit lean.  One size does not fit all.  We definitely do not want initial timing to be after top dead center...that was for emissions standards 40-45 years ago...not for performance.

Heat soak is usually the primary problem.  My car has no problems starting when it is 110 degs outside after turning it off.  I have a wood composite spacer which stops more heat than the phenolic. The one Chryco mentioned appears to work very well and a heat shield ala Holley was used in the '60's on some cars.

Insulating the fuel lines where they pass the headers is always a good idea.

I also use an electric pump-a quiet gerotor pump with a regulator and return line to the tank.  If nothing else, this insures I can have full bowls of fuel when I turn the key on.  I always hit the key first without touching the gas to keep from  adding more fuel into the intake than boiled into it while sitting.  In my case, I don't have to put the pedal on the floor to clear a flooded condition.  If you have a carb that boils so much fuel into the intake, you may have to hold the pedal to the floor to get as much air into the engine as possible.  Don't slam the pedal down fast and spray a bunch of fuel into the air going in.  ease down and let it dribble slowly rather than being atomized.

There is definitely an advantage to fuel injection, but you should be able to avoid a lot of the hard starting problems in the heat.  With a Holley style carb, you can generally look thru the sight glass and see if the bowl is staying full after being turned off or it is all disappearing.  Some carbs have a reputation for dribbling gas out thru the well plugs, etc.

What I have just said in a bunch of words, that you have to figure out what is going on with your car and figure out how to deal with it.   

[Bullitt-]

Guys , does the 70 intakes have the heat crossover that can be blocked like the later models? ... 

I know the OP is talking about replacing the intake gasket soon & that would be the time to do it

[kawahonda]

Engine compartment does get hot. Ill check for that.

I ended up at 8 BTDC timing. No pinging.

Question, I have mikes carb kit here. Includes a thin flange gasket, and what appears to be a thick wooden one. I know there's a vacuum leak at the carb to intake. I'd like to replace it now, assuming I can reuse them in the future when I pull intake (and repaint it).

1) do I chose one or the other gasket? Or use both, in what order? I'm assuming the thicker wooden like one may be more beneficial to use....

2) my carburetor mounts by bolts, not studs. Is this correct?

[Chryco Psycho]

|All wedges have a heat crossover port that can be blocked off except max wedge ! this really helps as most of these cars are never driven in cold weather & with new fuels it will help with evaporation also