tuning on the 200

Although my little engine seemed to run ok, I didnt feel like it was right. I found the tune up specs for my motor and went to work. Fyi, its a 70 200 i6. I wrote down all the current readings before I changed anything. Ignition timing was 10 degrees btdc, dwell was 40, idle speed in drive was 800 rpm and my fuel mixture screw was turned out 4.5 revolutions. Plugs were gapped at 36, but number 6 was gapped at 44. My vaccuum advance was direct to the manifold.

I started by getting my idle right and boy did that change things. My dwell jumped to over 50. I also turned in the mixture screw to just 1.5 turns out. I regapped all the plugs to 34 and set the dwell at 37.5. My timing is set to 8 degrees btdc. The idle was 550 and I moved the vaccum advance to the carb. I have never had my idle set so low and in fact, bumped it up to 800 in park when I finished.

Other than a slightly rough idle, it seems to run pretty well. I have to say I think its time to convert to electronic ignition. Going to start researching Petronix and Duraspark. Someone I trust seems to like Duraspark better. Any thoughts on this are welcome.

 

With todays gasoline you can bump your timing up to about 10* then set you idle back down to around 650 in park if the engine likes that rpm. If you use a vacuum gauge you will know where the engine wants to be tuned. Really doesn't matter where your getting vacuum, once you crack the throttle plate you will have the same amount of vacuum going to the distributor. The reason they say port vacuum was to increase exhaust temp at idle to lower emissions with yesteryears gas formula . Either Dura Spark II or Petronix will work great on a street car

 

You'll be amazed at the difference electronic ignition will make. I got my Duraspark II distributor out of a junkyard 8 years ago and have had it in 3 different motors over 200k miles, and it's still working good. When I initially did the Duraspark II swap, I could idle my 250 down to like 400 rpm, it was insane. You could practically read the numbers on the fan belt with it running. Never had much luck with Pertronix, burned one out in another car I had, but someone had wired it wrong. Still, don't think I'd run another.

 

Jeff, I bumped my timing down because I thought it might be contributing to my temp issues at highway speeds.

Jamie, I just ordered an ignitor from petronix. Looks like it will work fine with the accel super stock coil I have on the car right now. I have a complete Duraspark set up on a 76 donor car that I might install. Just seems easier to install the Petronix. Am looking forward to a smooth running motor!

 

I had an Accel coil in my Comet a long time ago. For some reason, there needed to be a Mopar-style ballast resistor wired in. I think it was needed drop the voltage to keep from burning up the points.

I switched to a first gen Pertronix with their coil, and it really made a big difference. My point for mentioning this is that resistor had to go when I made the switch.

My 351 has a bigger cam and other mods and was a bear to deal with until it warmed up. The Pertronix made a lot of those issues go away.

Something else you might want to consider while you are in the distributor is speeding up the mechanical advance a bit. If the six cylinders were like the V8s, Ford was very conservative in this area. Basically they ran a medium weight spring on one advance weight and a heavy one on the other. Just getting another medium spring to swap in place of the heavy one really wakes things up. It will get the advance in place earlier in the range where you can use it. Very cheap mod with startling results each time I have done it.

Really light springs for racing purposes are sold through speed shops. These are too much advance too early. Stay away from those... you need racing fuel, etc.

 

Thanks, I appreciate that. Ive researched previous threads and read about resistor wires. I will check my voltage and make sure it is within spec. Ive seen threads about the advance springs. Ive always felt like it was too slow to advance but was afraid to mess with it. I will certaily change it now.

 

if you had wired up the...Duraspark II distributor...wrong and burned it up, would you ever buy another one of those...

 

Your rough idle issue can most likely be solved by adjusting your air-fuel mixture with a vacuum gauge. Set it for the most vacuum and it should be smooth.

The timing should be fine at 8 degrees (I think 6 was the factory setting).

Personally, I like a 750-800 RPM idle in Park/Neutral.

 

Im not edumicated on a vacuum gauge, nor do I have one. I would love to know how to use it to set the carb. Im sure I can pick one up at a local parts store, yes?

 

They cost about $15-$20 at you local parts place. Here is a good site to know how to use a vac gauge http://www.secondchancegarage.com/public/186.cfm

 

Thank you! :Handshake I didnt see the scenarios listed, might be because Im on my tablet. At least I know how to hook it up. So I reckonI just turn the mixture screw in or out until the maximum vacuum is achieved?

 

Got a vacuum guage on Monday, 14.99 , got to play with it today. It read 15 inches when I started. Adjusting the mixture screw didnt change much, but it was clear leaning it out was wrong. Got it to 16 inches then played with the timing. I had the timing set at 8 degrees and advanced it a ton! Now the vacuum guage reads 19 inches. I am sold on the vacuum guage! Made a big diffrence in idle and throttle response. Pertronix unit should be here in less than a week. I have a new set of plugs ready to put in. Thinking I neednto open up the gap on them. Anyone have any suggestions? I was thinking 42, they used to be at 36, I have them at 34 right now. Cant wait to tinker some more!

 

Keep playing with the carb and timing to get to get maximum vac then back the timing off enough to loose 1" of vac. If you feel advantageous...read up on how to play with the advance springs inside the distributor. Sometimes all that is needed is to bend the spring anchor toward center a few thousands of an inch. That can be done without removing the distributor. .042 sounds good on a plug gap with the Pertronix.

 

Ive read up on the springs a little. I kinda get the jist of it. I believe I have a heavy spring and a medium spring. Im going to remove the heavy spring and replace it with a medium spring from an old dizzy I have. I am assuming it will be obvious which spring is which. My dizzy is a reman unit I got almost 15 years ago from Auto Zone, Ive always felt like it needed to advance quicker.

 

Got the lighter spring out of the 72s dizzy. Gonna wait til the Pertronix comes before I swap it out. Im running Autolight 46s for plugs. Will those be ok or do I need something else?