carb tuning help

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i have to be honest and say that i am a decent fabricator but something like this i am willing to spend the $35 and know that its goin to be accurate. i dont own a lathe or a caliper. it is a very interesting idea though.

I hear ya. Me too easier to buy it sometimes. A lot of guys do make their own. I would guess your gunna end up somewhere like Cracked is telling you ....26 initial and a 10* bushing=36* , if your ignition box has a start retard feature you can get away with even more initial timing and guys use that feature also with locked out dizzy's.
 
I hear ya. Me too easier to buy it sometimes. A lot of guys do make their own. I would guess your gunna end up somewhere like Cracked is telling you ....26 initial and a 10* bushing=36* , if your ignition box has a start retard feature you can get away with even more initial timing and guys use that feature also with locked out dizzy's.

i have a msd 6al. and its not the new digital one.
 
i have a msd 6al. and its not the new digital one. with a locked out dizzy wouldn't it cause detonation at low engine speed/high load situations as well as run hotter in street driving? I will be driving my car on the street alot?
 
I've got the same ingnition setup and have spoken with Don at FBO, in fact he talked me out of the 10* bushings because I have a vacuum advance on my pro billit dizzy. He advised me to run that off of manifold vacuum so that it would pull the initial timing way up but drop off by the time the mechanical was kicked in. I have to admit though, I don't have it completly dialed in yet. It wont even run with the vacuum advanced not hooked up because it drops the initial down so much so I had to start it up and plug the vacuum adnvance off while feathing the throttle to keep it going, then you can confirm the total timing.
However, I too am very new this. Cracked - how do you discover what the engine wants for initial? Is it the advance till the starting gets rough, then back off method you described?
 
Two of them were posted in this thread already. Here's a quick synopsis.

Here are a few ways of setting initial depending on what tools you have available. It's about making the engine efficient at idle. Efficiency = RPM in this case

1) Set at the point short of where the starter kickbacks when at operating temp. If it starts here and doesn't exceed your total number, run it. Tailor mechanical for the rest.

2) Using a vacuum gauge, note reading, advance timing, reset idle rpm. Is the reading higher, lower or same? Higher, do it again until you reach a point where vacuum will not rise. Once you get there, back off timing so the reading drops ~1", reset idle speed/mix screws and lock down distributor and get you initial timing reading using timing light.

3) At idle, feed timing into engine. If RPM increases, reset idle speed and do it again. Continue until rpm stops increasing. See where timing falls. DO NOT just turn the distributor and keep feeding it timing without resetting your base idle speed.

This is the same thing that always seems to come up about how terrible a carb runs. Burning eyes, smells like raw fuel behind car and IT'S NOT the carb causing the issue most of the time.

With automatic cars, large RPM drops from p/n to in gear, is another hint that something is wrong with your base timing settings.

I've said this a bunch of times, getting the correct timing profile (initial, mechanical, curve) on a car takes some work. There's a right way and a lazy way (total method). Sometimes with the total method you hit the lottery, most of the time, like most that play the lottery, you don't! :)


And Mad Dart... what's with the hate? My sensitive self esteem took a huge hit, now it's off to the prozac bottle so I can feel better about myself cause there are too many meanies in the world! LMAO
 
Two of them were posted in this thread already. Here's a quick synopsis.

Here are a few ways of setting initial depending on what tools you have available. It's about making the engine efficient at idle. Efficiency = RPM in this case

1) Set at the point short of where the starter kickbacks when at operating temp. If it starts here and doesn't exceed your total number, run it. Tailor mechanical for the rest.

2) Using a vacuum gauge, note reading, advance timing, reset idle rpm. Is the reading higher, lower or same? Higher, do it again until you reach a point where vacuum will not rise. Once you get there, back off timing so the reading drops ~1", reset idle speed/mix screws and lock down distributor and get you initial timing reading using timing light.

3) At idle, feed timing into engine. If RPM increases, reset idle speed and do it again. Continue until rpm stops increasing. See where timing falls. DO NOT just turn the distributor and keep feeding it timing without resetting your base idle speed.

This is the same thing that always seems to come up about how terrible a carb runs. Burning eyes, smells like raw fuel behind car and IT'S NOT the carb causing the issue most of the time.

With automatic cars, large RPM drops from p/n to in gear, is another hint that something is wrong with your base timing settings.

I've said this a bunch of times, getting the correct timing profile (initial, mechanical, curve) on a car takes some work. There's a right way and a lazy way (total method). Sometimes with the total method you hit the lottery, most of the time, like most that play the lottery, you don't! :)


And Mad Dart... what's with the hate? My sensitive self esteem took a huge hit, now it's off to the prozac bottle so I can feel better about myself cause there are too many meanies in the world! LMAO

THANK YOU! that is exactly what i needed. intitial for dummies. where should i plug in my vacume gauge? on the port of the carb base plate?
 
Yes, manifold vacuum. Off the baseplate of your holley is a good place to grab it.

If you hook it up and you don't get a reading (ported vacuum fitting), find another port.
 
Two of them were posted in this thread already. Here's a quick synopsis.

Here are a few ways of setting initial depending on what tools you have available. It's about making the engine efficient at idle. Efficiency = RPM in this case

1) Set at the point short of where the starter kickbacks when at operating temp. If it starts here and doesn't exceed your total number, run it. Tailor mechanical for the rest.

2) Using a vacuum gauge, note reading, advance timing, reset idle rpm. Is the reading higher, lower or same? Higher, do it again until you reach a point where vacuum will not rise. Once you get there, back off timing so the reading drops ~1", reset idle speed/mix screws and lock down distributor and get you initial timing reading using timing light.

3) At idle, feed timing into engine. If RPM increases, reset idle speed and do it again. Continue until rpm stops increasing. See where timing falls. DO NOT just turn the distributor and keep feeding it timing without resetting your base idle speed.

This is the same thing that always seems to come up about how terrible a carb runs. Burning eyes, smells like raw fuel behind car and IT'S NOT the carb causing the issue most of the time.

With automatic cars, large RPM drops from p/n to in gear, is another hint that something is wrong with your base timing settings.

I've said this a bunch of times, getting the correct timing profile (initial, mechanical, curve) on a car takes some work. There's a right way and a lazy way (total method). Sometimes with the total method you hit the lottery, most of the time, like most that play the lottery, you don't! :)


And Mad Dart... what's with the hate? My sensitive self esteem took a huge hit, now it's off to the prozac bottle so I can feel better about myself cause there are too many meanies in the world! LMAO

Great information. Guys always want the $$.......when the information is worth a heck of alot more!! :D

Yeah last night I was in a being a lil mean...... now don't be going and getting your panties in a wad...... LOL
 
so i don't have a vacuum gauge yet but i did reset the initial timing to 18* and the total to 35* all in by 3500. i changed the heavy springs out for the medium (blue) springs in the dizzy and the advance comes on alot sooner. before it didnt even move till about 2200 rpm. now its starting to advance at about 1400 rpm. it made a noticable change in the over rich condition. i could actually stay in the garage with out crying. the plugs before were completely black and full of soot. they are now turning to a dark tan'ish brown. I will buy a vacume gauge this weekend and play with the timing some more.


Shaynas057_zpsa6b77296.jpg
 
Find the point in step one I posted and tune it there.

QUIT WORRYING ABOUT WHERE YOUR TOTAL NUMBER IS!!!

Address that AFTER you get the initial right.

It's nice that it's better, I guess if you want practice messing around it's a decent way to go.

Vacuum gauge is nice to have for setting the idle mix screws, not required to find initial timing point.
 
For all the high dollar sh** that MSD makes, I'm REALLY surprised to hear they don't make more of a selection of advance bushings. WTF, over?
 
I dunno.....with that cam, I don't think you'll ever get it to run where it's not turning your garage into a gas chamber while it's idling. I would wanna know what the vacuum is.....that also will tell you what power valve you need, right?
 
For all the high dollar sh** that MSD makes, I'm REALLY surprised to hear they don't make more of a selection of advance bushings. WTF, over?

They will for $200.00 , I would make one with a chizzle and hammer before I would ever do that........

Their answer is to lock out the timing and run it full advanced everywhere. Then.......buy one of their other products that has the Start Retard Feature. $$$$$$$$. lol
 
I am following this thread because I need to learn about timing and carb tuning as well. Lots of good info here.

ya i have never tuned an entire ignition curve before. i have only done the set the total at 3500 rpm and run it method. the msd set up i have is completely tune-able and has got my brain in a knot.
 
agreed on the MSD stuff not being well suited to our application(s). I have a Mopar electronic dizzy and orange box i'm seriously thinking of giving a try setting up.
 
Well today I got a lot done. I got the initial timing set. Ended up at 22* initial at 1050 in park and 950 in gear. It would take another 6 degrees but I like the idea of having a little advance built in. I am at 36.5 total and all in by 2700 rpm with both blue springs. I then set the floats and fine tuned the fuel pressure. I set the idle mixture screws at 1-1/2 turns out and reset the idle speed.


HOLLY ****!!!! it was a whole new animal. I had instant torque. The car came alive. Took my ladies brother for a quick ride and he couldn't put a sentance together when we pulled up in the driveway. I still have a lot to learn and lots of tuning but its coming together.
 
That's fantastic that your getting a handle on it :thumbrig:. It's a beautiful car you've put together and now you can start to really enjoy it. Just in time for warm weather, yea baby :D.
 
Well today I got a lot done. I got the initial timing set. Ended up at 22* initial at 1050 in park and 950 in gear. It would take another 6 degrees but I like the idea of having a little advance built in. I am at 36.5 total and all in by 2700 rpm with both blue springs. I then set the floats and fine tuned the fuel pressure. I set the idle mixture screws at 1-1/2 turns out and reset the idle speed.


HOLLY ****!!!! it was a whole new animal. I had instant torque. The car came alive. Took my ladies brother for a quick ride and he couldn't put a sentance together when we pulled up in the driveway. I still have a lot to learn and lots of tuning but its coming together.

I try to tole you!! haaaaa Good Job!:D
 
Very cool. Nice job.

If I was in your shoes, I'd still order the 10* bushing. There's more on the table for you if you want it.

They do tend to run better when you get the initial timing set up better!
 
I have the 10* bushing sitting on bench in the shop. I am still not completely confident with tuning and took baby steps. I made steps in the right direction. That for me is a huge motivator. I may play with it tomorrow and try more initial.
 
Maybe do the vacuum gauge deal.

Get the idle mix screws dialed in at 22*, then bump it to 26* and see if you have any significant difference at same idle speed. If the change is small, run it where you have it now.

I bet it fires off almost right away when you bump the starter.
 
Maybe do the vacuum gauge deal.

Get the idle mix screws dialed in at 22*, then bump it to 26* and see if you have any significant difference at same idle speed. If the change is small, run it where you have it now.

I bet it fires off almost right away when you bump the starter.

Ya it fires right away. I couldn't believe how much harder it ran. I hardly touched the carb and it leaned way out just with timing.
 
i do not own a set of calipers. I noticed in another thread that Maddart was using the same bushings. I am pretty sure he has a set of calipers and can get you the #'s.
 
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