Duraspark/Pinto carb swap done! But..

yoyodyne · May 30, 2008

First, I have to say thanks to this site for the help in the swap. Finally got everything back together, new intake and head gaskets, new valve seals, all computer and smog junk gone. (except for the cat converter) Truck started up , set timing to 10 degrees, choke is working. Problem now is it is really hard to start when warmed up,(it almost seems like it wants to backfire when it finally catches) and wants to die when dropping down to idle (like coming to a stop light)or coming up off of idle when driving (when the light turns green and you try to go). Truck idles at 800 RPM, (i could never get to do that before the swap, it would idle around 1500 rpm)and is a manual transmission. Should I give it a few degrees more timing, or is it the idle mixture. The only adjustments on the new carb are the 2 idle mixture screws on the bottom front of the carb.

Jorley · May 30, 2008

Way to go.
OK, now to try and fix your problems. On the carb, turn the 2 mixture screws all the way in, then out 1 1/2 turns. Start a warmed up engine and turn them in one at a time until the engine starts running rough. then out about 1/4.

The hard cranking when warm is most likely timing. I didn't have a timing light, so I set mine by ear. Just adjust until the engine is running the smoothest.

It would most likely be best to adjust the timing before doing the carb. Also make sure you plugged all the vacuum ports. Removing the emission stuff leaves alot of them. I'm only using 4 of them for the dizzy, pcv, brakes and cruise.

ammocj · May 31, 2008

Did you get a new or used carb?
If used, check the base plate where the shaft turns the butterfly valves.
It could be worn.

I found that to be my problem with a used Holley 2 barrel.

Al

skippy · Jun 1, 2008

yoyodyne said:
First, I have to say thanks to this site for the help in the swap. Finally got everything back together, new intake and head gaskets, new valve seals, all computer and smog junk gone. (except for the cat converter) Truck started up , set timing to 10 degrees, choke is working. Problem now is it is really hard to start when warmed up,(it almost seems like it wants to backfire when it finally catches) and wants to die when dropping down to idle (like coming to a stop light)or coming up off of idle when driving (when the light turns green and you try to go). Truck idles at 800 RPM, (i could never get to do that before the swap, it would idle around 1500 rpm)and is a manual transmission. Should I give it a few degrees more timing, or is it the idle mixture. The only adjustments on the new carb are the 2 idle mixture screws on the bottom front of the carb.

im having same problem w/holley 350 cfm.plugs are sooting up.advanced timimg,adjusted mixture using vacuum guage as-per-holley instructions and it seems a little better.

i have tried plug gaps of .040,.042 and .044 and latter seems best.i rejetted the carb to #59 jets and still not happy with performance.

i have see thru gas filter before the carb and at idle just trickles gas in the filter,at times it is empty.wth?new pump with 500 miles on it.

i wonder if i need a different coil?using the napa canister type listed in tech library write up.anyone know?what am i missing here?

Jorley · Jun 1, 2008

I gapped my plugs at .045 and I used the TFI coil that was in it to begin with. I figured the canister coils needed a ballast resistor and the TFI coil doesn't use one. So far it's running great.

skippy · Jun 1, 2008

so put the tfi coil in or get the ballast resister,got it.this coil runs pretty hot and not sure the spark is hot enough.

enginepaul · Jun 2, 2008

I'm not sure where you are here, but the coil gets less than 12V when running, it gets 12v only when starting. It will overheat with too much voltage. The DuraSpark coils put out a great spark with the proper stock coil.
I'd start at .044 to .046 gap on the plugs.
The cars they were original installed in had a 'voltage dropping wire' feeding them at, I believe, 9V. Sorry, my old Motor's manuals that I used to use for trouble shooting are put away.

skippy · Jun 2, 2008

enginepaul said:
I'm not sure where you are here, but the coil gets less than 12V when running, it gets 12v only when starting. It will overheat with too much voltage. The DuraSpark coils put out a great spark with the proper stock coil.
I'd start at .044 to .046 gap on the plugs.
The cars they were original installed in had a 'voltage dropping wire' feeding them at, I believe, 9V. Sorry, my old Motor's manuals that I used to use for trouble shooting are put away.

thanks,12v key on,engine off.10v enginge on.i started at .044 and went down because of another post for hot coil,to the touch.napa carries a duraspark resistance wire,put that in or my tfi coil?

Jorley · Jun 2, 2008

Actually it would be 12v with the key in the start position and 9-10 v key on engine off or running.( with ballast resistor). The wiring diagram for TFI ignition shows that power for the TFI coil comes right from the ignition switch with no ballast resistor(resistance wire).
So I'd say it would be up to you if you want to put the TFI coil back in or use the resistor wire. The canister coil does need the resistance wire, they are made to work at the lower voltage.
Like I said I did mine a few months ago and used the TFI coil and have had no problems. Good luck and let us know.

skippy · Jun 2, 2008

Jorley said:
Actually it would be 12v with the key in the start position and 9-10 v key on engine off or running.( with ballast resistor). The wiring diagram for TFI ignition shows that power for the TFI coil comes right from the ignition switch with no ballast resistor(resistance wire).
So I'd say it would be up to you if you want to put the TFI coil back in or use the resistor wire. The canister coil does need the resistance wire, they are made to work at the lower voltage.
Like I said I did mine a few months ago and used the TFI coil and have had no problems. Good luck and let us know.

thats right,my bad.guess i will do the tfi coil and see how it goes,it will be cheaper for sure.

im at .044 right now,tfi loved it and plugs were firing well and inspection reveals correct color against the chart.think i should open them up a little?

i'll post up when i get to it.

Jorley · Jun 2, 2008

Before I did the duraspark I was running mine at .044 also. After I did it I ran them at .050, but it screwed up the mpg. I went back to .045 mpg is better, but haven't checked how the plugs look yet.
The best advise I can give you is to experiment and see what works best. Too big a gap will just cause misfire and bad mpg, too small of a gap can cause engine damage(pre-ignition).
Here's a site that explains it better.
http://wsapi.infospace.com/clickserver/_iceUrlFlag=1?rawURL=http://www.nightrider.com/biketech/tech_spark_plug_gap.htm&0=&1=0&4=207.97.220.36&5=64.136.26.227&9=9edbd12f295f4ece99d109467ec4c801&10=1&11=pch.blingo.v2&13=search&14=867530&15=main-title&17=6&18=8&19=0&20=4&21=2&22=WuuoE9sffxE=&40=IqHmd/czqX8YUlNMQ78UMA==&_IceUrl=true

skippy · Jun 2, 2008

Jorley said:
Before I did the duraspark I was running mine at .044 also. After I did it I ran them at .050, but it screwed up the mpg. I went back to .045 mpg is better, but haven't checked how the plugs look yet.
The best advise I can give you is to experiment and see what works best. Too big a gap will just cause misfire and bad mpg, too small of a gap can cause engine damage(pre-ignition).
Here's a site that explains it better.
http://wsapi.infospace.com/clickserver/_iceUrlFlag=1?rawURL=http://www.nightrider.com/biketech/tech_spark_plug_gap.htm&0=&1=0&4=207.97.220.36&5=64.136.26.227&9=9edbd12f295f4ece99d109467ec4c801&10=1&11=pch.blingo.v2&13=search&14=867530&15=main-title&17=6&18=8&19=0&20=4&21=2&22=WuuoE9sffxE=&40=IqHmd/czqX8YUlNMQ78UMA==&_IceUrl=true

thanks,for the most part thats what i'm doing.i'll get the tfi coil back in and start with.045 and see what happens.

i was stoked that the engine fired at the first turn of the key and idled fairly well.but test drive indicated bogging down with too much throttle.that was with .044 and #61 jets,and died approaching stop signs.

now it doesn't die but i can tell it's still not right and pulling the plugs reveals soot.so test and tune continues,i'm persistent and i will concur,just as i did tfi.

Big Jim M · Jun 8, 2008

Running an engine with a carb using a gap of 32 is ok. The only reason for a larger gap is for fuel injected engines that use such a lean mixture that sometimes there isn't enough fuel in a 32 gap to cause the fire to start. So more powerful coils are used to jump a 45 gap. The 45 gap insures there is enough fuel in there to fire the mixture at all times.
There is NO REASON to gap plugs in a carbed engine over 32/35!!! Using a more powerful coil is of no use either, as all it takes to start the fire is a small yellow spark.. Even having a more powerful coil, it will only use as much of it's power as it needs to jump the gap.. same as a stock coil.
Big JIm

skippy · Jun 8, 2008

ok,gapped plugs at .045,advanced timing a bit,installed tfi coil: and readjusted the holley using the vacuum guage.finally got some "me" time and went for test drive.

results=wow,just wow!to be planted back in the seat like i was driving a v-8 put a smile on my face,and i had pedal left.now just need a manual choke cable,like i need a excuse to return to summit racing.

thank you to all that assisted me in this endeavor.bring on the ricers! :woot:

yoyodyne · Jun 13, 2008

Finally had time to work on it. Found a fitting on the metal vacuum tree on the bottom I forgot to plug. Capped it, reset the timing. Truck fast idles (when on the choke)at 2500 RPM or so, I need to adjust that. Played with the idle mixture. Truck drops to 800-900 rpm when warmed up, but has a hunting idle. Still stalls once in a while when coming to a stop, but not nearly as much as before. I think i still might have a small vacuum leak somewhere.Takes off from a stop fine. Going down the road, it runs great.During all this ,the starter went out, got a new (reman)one . It went out in less than a day, got it replaced, but it seems to hang with a "clang" when the truck starts.

Duraspark/Pinto carb swap done! But..

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