69 302 - tuning advice

[tharrold 10]

I'm at wit's end troubleshooting an issue.  It started as stalling at idle speeds, only after the engine was hot.

 

In the troubleshooting process, I'm noticing that the timing changes based on engine speed.  (Yes, I've pulled the vaccum advance, and plugged the vacuum line)

 

First, refresh my memory please:  This isn't normal, is it?   I have a pertronix ignition module under the cap.

 

Also, does anyone have any initial choke settings?  I have no idea at this point, where to set the choke.  I'd like to leave it out of the equation, if possible, but it has a huge effect on engine idle speed.

 

the last time I checked (last year) I had good vaccuum, very consistent.  (can't recall the exact value)

 

ANY help appreciated.

 

-Tom

[69RavenConv 286]

Yes, the mechanical advance in the dizzy will advance the timing as RPM increases. So that's normal.

 

What carb are you running? Stock or aftermarket? Electric or bimetallic choke?

 

Are you sure the choke is opening? Take a look when it's hot and verify it's open. If it is, you may want to look at the jets you're running or simply increasing the idle setting.

[Rsmach1 71]

+1 with 69Raven on the mechanical advance, and the choke. The choke sticking or malfunctioning is a typical cause of warm only engine issues.

[1969_Mach1 333]

Is the choke fully opening and another issue causes the engine to die at idle when hot?  Is the choke not opening completely and it is flooding causing the engine to die at idle when hot?  More carb and choke information is needed?  Is it a stock hot air type choke or is it an aftermarket electric choke?  Both types use a bimetal spring.  Only different methods of heating it.

[jholmes217 65]

Are you running a phenolic or wood carb spacer under the carb?  If not, could be vapor lock.  Not uncommon in today's lower octane, ethanol added gas, especially with the winter blends.  If you need one, I may have an extra.  Just let me know if you need a 4 barrel open, 4 barrel 4 hole, or a 2 barrel.

[tharrold 10]

Sorry for the delay.

 

I have a bi-metal choke(stock heat activated).   Carb is an autolite 2100 2-barrel.  All stock.   Choke stove tube has never been connected since I have had the car, but it hasn't been an issue.  (just thought I'd mention it).

There is about a 1/2" spacer between the manifold and the carb.  That hasn't changed, I assume it is stock, to allow for clearance of a few of the carb components.

 

I do see the choke open when the engine heats up.  In fact, if I force it futher to the closed position, RPMs increase, and the engine runs stronger.   

 

I have tried adjusting the choke so that it's about 1/16" to 1/8" open when cold. 

 

I'm wide open to any ideas.  I'll try just about anything that seems logical.  :)

[barnett468 418]

i have no idea exactly what the problem . . please explain exacty what the actual problem is.

 

 

if your engine runs faster when you close the choke slightly when it is warm, it may be lean.

 

if it is still dying, check the float level . . if it is higher than 1/2", lower it to 1/2".

 

make sure both of your fuel mix scres in the front of the carb, change the idle speed when you turn them . . if one has no affect, the idle circuot is plugged on that side . . this is common.

 

 

with your engine warm, advance the timing 4 degrees . . if the rpm goes up and it still runs smooth this is where it want to be so leave it there and drive it a listen for a slight rattling noise in your engine when you accelerate . . if there is non and it starts normally leave the timing there.

[1969_Mach1 333]

With the engine warmed up, if it idles better and the RPM increases when you manually close the choke plate the idle air fuel mixture is too lean or there is a vacuum leak somewhere.  Although the idle speed could be increasing when you close the choke plate because of the fast idle cam that is part of the choke linkage.  Instead, when the engine is warm and idling, cover the top of the carb with your hands.  If the engine runs smoother and idle increases it's very likely a vacuum leak or the idle air mixture is too lean.

[tharrold 10]

I will check vaccuum again, but the last time (last year) I checked, it was holding solid at a good value. (forget what that value was, but it was in the range it was suposed to be).

 

If the air-fuel mixture is too lean, how do you adjust that? 

[tharrold 10]

Also, I have never had the exhaust manifold choke stove connected.  It was gone when I first bought the care 20+ years ago.

I know that it sucks air.  I assume it's supposed to be left uncapped when the choke stove is disconnected.  

[69RavenConv 286]

You can adjust the idle mixture using the idle adjust screws on the carb. On the stock Autolite 2100 they're on the back side, on a Holley they are on the sides (http://www.mustang-s.com/years/1965/1965_mechanical_pgs/1965_carb_2100.htm)

 

The choke stove rotted off nearly every Ford that ever had them (including mine) but the carb shouldn't suck air as a result. They were simply a conduit to bring not air to the choke to open it up a little faster. Not having one shouldn't affect much They are reproduced if you want to replace it.

 

BTW, is your vert royal maroon? My Dad had a royal maroon '69 vert back in the 70's. It was pretty unique - it was a base F-code 302 3-speed manual with manual top - but optioned out with PS, PB, AM/FM stereo and A/C. I took my first driver's license exam in that car when I was 16. I wish I had that car today :)

[tharrold 10]

69RavenConv, thanks for the info.   Actually, my convertible is painted "Arena Red", it is a '96 Porsche color, as I recall.   When I purchased it, it was pretty well butchered up, bondo buggy, painted some horrible  bright red color.

I wanted something that was close (loosely) to a factory color when I re-painted it, but was still unique.

 

Regarding the choke stove tube..I do feel a fair amount of vaccuum coming through that connector on the back of the choke assembly.  Perhaps because my idle is still too high?

[tharrold 10]

Update, Not so much vacuum coming through the choke stove connector as I thought.

 

Tried setting the idle mixture screws to "first start" setting (all the way in, back out 1.5 turns).

 

Again, car starts with no issues.  I can get it to idle (in park) at about 900-1000RPM.   I checked the timing, and set it to 10BTC.

 

As soon as it gets warm, I'm having a hard time keeping it running.

 

This is so frustrating, as I just dont' know what to check next.   And I only get a short amount of time before things heat up, and I can't keep it running on my own.  :(