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Tuning help

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drooartz

drooartz

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Okay, so I'm trying to get the Tunebug dialed in, with minimal success so far. My biggest problem is that I don't have much of a frame of reference for how the car is *supposed* to run -- I've never driven a properly functioning LBC before. It's really hard for me to know from the symptoms what I should do.

How do I really tell if I'm running rich or lean? I'm still having some trouble off the line (below about 2500 RPM) -- engine will bog down -- and the idle is not particularly consistent.

I really wish y'all lived closer. I'm sure an hour or so with a bit of experienced help to show me the finer points would be get me on the right track. I really want to learn how to do this myself, just feeling a bit overwhelmed by all the variables involved.

I will say that in the upper ranges (above 3500 RPM) the motor really sings. Had it up to about 5500 RPM so far; it's quite addictive.
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At this point the easiest way is to run it under load, switch off as you enter the driveway and coast the last bit, pull the plugs and read them, adjust accordingly - they will tell you most of what you need to know.
 
Take out the plugs and take a look. If they're covered in black soot you're too rich. Reading plugs isn't like it used to be, but you can get close.

If they are sooty, clean them off and reinstall. Lean it a flat or two and drive some more. Keep checking the plugs until they look normal (no sooty mess, etc.). It's a trial and error process.
 
Drew,

Make sure the timing is completely dialed in before you fiddle with carbs. Advance (dynamic), points, rocker gap. Once you know everything is good there, then I adjust the mixture. Oh, you also need to make sure you're SU's are properly balanced first, do you have a unisyn? As to the mixture, I do mine by looking at the plugs. It's hard to read plugs these days with the clean burning fuel, but you'll definitely know if you're too rich. Too lean and you'll ping. Here's a link to John Twist tuning HiF's. Same idea. Check out all his SU videos on youtube. great stuff

https://www.youtube.com/watch?v=ASeMfXfjNpw
 
I do have a unisyn-type device. Timing should be good (it's set as Hap recommended). Need to double check the point gap tonight, but it should be okay.

So what do I look for on the plugs?
 
drooartz said:
-- I've never driven a properly functioning LBC before..
grin.gif
Click to expand...


Don't feel bad, none of us have ....
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Too lean at idle will "putt putt" out the exhast intermitenly. Who had the link for the exhast pulse pic? I beleieve it is Doc.

O.K, want to learn the difference b/w lean and rich running?

That's easy. Mark ( on paper) your baseline of how many turns out you are, then screw it in lean. Keep going till the car runs like crap, but don't drive it. Rev once ot twice as you go a flat or two at a time and notice how the car runs. Once you've gotten it to not run anymore, turn back to your baseline, then turn out to rich, counting from baseline as you go. Once again, a flat or two at a time till it runs like crap. Notice the black sooty exhast. Once you kill it. Clean the plugs and go back to baseline. At some point, you noticed the car ran really well. Turn back to that point. You should know exactly where it as as you were supposed to keep track ( in your head if possible) the whole time and you should now know exactly where that point is.

There, now you have experence knowing what your car runs like when it's: lean, rich, just right.

It's allot like setting balance/fade, an EQ or console. Turn the knob till it sounds/feels right. You should be better at this than most !!!!

(in my best stoner voice) ...you've got to ~FEEL~ the car ~MAN~ !!!!

You may not be able to get it spot-on the first time, that's o.k. This exersize is mainly to give you knowledge of what a poorly tuned car runs like in either direction.

Soon you'll be able to tell if it's sharp or flat on the first note...just make SURE you know where you started off at and are able to set it back to that point.


Dude, I'm teelin' ya, if you just woulda named the thing, " runs great bug" you wouldn't have this problem. :jester:
 
good advice- but you know you are rich. tune them with the unisyn- now start bringing it lean, ccw as viewed from above or -wrench to the rear of the car- Your idle will start to increase as you do this. you will reach a spot that just sounds good. Remember a bit rich is ok. I take you don't have the lift pin? you will have to turn your idle down as you go leaner. This is a good sign you are getting closer- Leave the timing alone. Good Luck.

m
 
John Moore said:
Drew,

Here's a link to John Twist tuning HiF's. Same idea. Check out all his SU videos on youtube. great stuff

https://www.youtube.com/watch?v=ASeMfXfjNpw
Click to expand...

So why did he leave the front carb all the way rich?
I've watched that vid a few times now, those are the carbs I'm having such a headache with. I got the whole part about what John was doing with the rear carb but leaving the front carb set fully rich just confuses me.
 
Drew, if the ignition timing is dialed in at about 30 BTDC at 3000 rpms, you can even go for more if you like, like 32 BTDC, then move on to the carbs, make sure you not ggeeting air/vacuum leak anywhere. OK, for memory, you have #3 needle, which is lot like the stock AN needle, just rich at more open throttle postions. The jets should be about .070 down for the bridge when measured with the end of dial caliper. You need the plugs to be clean to test them as meantioned above, do what they recommend, pulls under load, then kill the igniton while still on the trhottle and coat back to the driveway, chack the plugs for color as mentioned above, at that point make fuel mixture change, I would recommend you move in increments of .010", and test again with clean plug.

I have a little plug balster/cleaner here at the shop that makes this easy, but you can achieve the same thing as far cleaning plugs in between runs if you have bead blast cabinet, just wrap your gloved hand around the plug exposing the tip side and blast it clean then blow off extensively with compressed air.
 
No blasting cabinet for the plugs, but I do have a little wire brush I use for cleaning electrical contacts and the such. Will that work for plug cleaning?
 
Hmmm... maybe a soft wire brush for a drill and mounted in a vice?
 
drooartz said:
No blasting cabinet for the plugs, but I do have a little wire brush I use for cleaning electrical contacts and the such. Will that work for plug cleaning?
Click to expand...

worked just fine for me - and then when I was done I bought new plugs
 
Like Hap mentions, you gotta get one of these :

https://www.bosstoolsupply.com/index.asp?PageAction=VIEWPROD&ProdID=3651

I used to work at a shop years ago that had one on the back wall, always found it so handy. Fortunately a few years ago I found one at one of those tool sales that comes to town for a couple days. I don't use it all the time but when I do it sure comes in handy.
 
Thanks for the link, Jer. May have to look for one of those.
 
Handy tool. The abrasive can be had from HF, NAPA, etc. too.

But be SURE to clean the plug throat of ALL abrasive after you blast 'em. And after you're satisfied you have an acceptable setting, renew the plugs. :wink:
 
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