My bad!! I was thinking of a different # cam. That one is quite a bit more aggressive, but I stand by what I said about the amount of spark advance. If what you posted a picture of is the advance curves you are running, you don't have nearly enough timing in the engine. I run an engine that is similar to yours....6.0 aluminum block, L92 heads, same intake with a 750 VS. Cam is 222-234 @.050...112 LA...551 lift. Please disregard what I said about using the pills from a 6010 box in your 6012 box because they might damage it, but please DO rework your timing curve to something close to what I suggested in my earlier post. Also, change your power valve to a 6.5 like the other guys said and I think most of your problems will go away. Now...I have a couple questions. What transmission are you running...auto or 6 speed?? Reason I ask is, from your pics, it looks like you are still using 30CC accelerator pumps. Is that working for you? Just curious. Ron

 

The trans i'm running is the 69 camaro th350 rebuilt, and work very good whit this set-up.. 5 bolts on 6 are direct fit, and i use a crank spacer for have it fit on my tork/stall, very nice item for few buck.

For my timing curve, all work good... the thing you did not know, it's the number give by my map sensor..

On Idle, map sensor give me between 2-3, + 20- degre..

On cruise, map give me bwtween 3-4, + 20 degre, total of 40 at 3000-3500 rpm.

WOT, map sensor give me 6, + 15 degre, for total of 33-34 degre... it's why all run very good.

I try to change setting for 2 bar map sensor, 1 bar, and it never go do 14 psi a

I try the orignal map of the 6.0L motor, and i try a new aftermarket replacement, and it always have this number.

I was thinking that number are bad, and i have a wrong map sensor reading, but if i look the preset curve of MSD



you can see that i have about the same number of the pills 4, only few change.... same MAP advance, 4 psia give +20, 8 psia give + 10, mean that at 6 psia give + 15, like my curve. They give +19 at 6000 rpm, i have + 18 + 15 ( map advance), total of 33...

I dont know why map give this number

 

I have been sitting here reading your post, and trying to figure out a reply that makes sense. The only thing I know to say is there is something seriously whacko!! If your box and MAP are working correctly and you have a proper vacuum source, it SHOULD work something like this. Your RPM curve shows 3-4 * at 1000 RPM. You said you have 11" of vacuum @ 1000RPM.
11" of vacuum is around 9 1/2 -10 psia. Your MAP would add possibly 7* for a total of maybe 12* @ 1000RPM. Most guys on here would tell you that you need 20-22* at 800-1000RPM for that cam to idle properly and have good response when you hammer it. With 22* and nothing added by the MAP it should idle at probably 800-850 with around 12" of vacuum. Moving on..... at 3000RPM, your stated cruise speed, you probably do have enough vacuum for the MAP to add 20*...BUT when you crowd the throttle or floor it you lose all or most of the vacuum and then you only have 20* total..not enough!! Just the fact that you put a load on the engine will lean it out, then the fact that your 3.5 PV is slower to open than a 6.5 makes it worse. If you have verified that you actually have 32-33 * at wide open throttle, then there is something wrong with your box, or your MAP or your vacuum source. I suspect the vacuum source because I think there is a default that works when you have the MAP sensor plugged in and no vacuum. I will have to check this out on my box, maybe tomorrow. If you haven't already, you can drive around with it hooked up to your lap top. If you do, maximize the 3 dials that show timing, RPM and PSIA and watch them or have a buddy watch them and see if the PSIA is changing as you load the engine and see what your timing is at full throttle and cruise and idle. Sorry to be so long winded but I really think your advance curves are not helping your engine perform properly. Later, Ron

 

It is kind of odd that you have so much vac advance and no static advance at low RPM, especially with cam with so little vacuum at idle!

Let us know what happens whatever you do.

 

Ok.. thanks guys for your interest...

Last time i have connected my laptop when running, the total timing at Idle is 22( vac is 2-3 ), total at cruise at 3000 rpm is 40( vac is 3-4), and total at wide open trottle, it's 33 ( vac is 6 ) ... work very good.

If i have something wrong, why the pills #4 of msd 6012 is the same, or very near of my curve ? If i run the msd #4 pills, it give 99% same result, 1-2 degre difference!

I will redo a vacuum test this week at idle, and cruise... take new number!

It's possible that the gm map sensor on this motor is an 1.5 bar, and not an 1 bar? it's why it give differente number!

Anyway, my carb have a problem, and the problem was there whit my other motor, chevy 355.

 

I would have figured you would have the carburetor sorted out by now. Did you change the booster bleed jets yet?

 

You're getting me confused. When you say your idle timing is 22* (vacuum is 2-3), do you mean vacuum is 2-3 psia as read on the MSD dial or do you mean vacuum is adding 2-3 degrees advance?? Same question for cruise and full throttle. The next question I have is meant jokingly, so don't take it the wrong way. Do you have your vacuum line to your MAP hooked somewhere that might have a check valve in it?, such as the brake booster line? The reason I ask is if I am understanding you correctly, your vacuum is not dropping like it should at full throttle or acting correctly at idle. Just for info, the #4 pill for a 6010 box has this curve...0 RPM 15*,1000 RPM 28*, 2000RPM
29*, 6000 RPM 36 *. The MAP curve is 9psia= 0*, 7psia= 6*, 6psia= 6* and
0psia= 6*. This would be a good beginning curve for your engine except you might want to drop back to 33* instead of 36*. There is something seriously wrong with the numbers you are getting. Both the 6012 and 6010 are made to take the place of a distributor. The MAP curve is there to simulate the vacuum advance on the old distributors. The vacuum advance was there to add spark advance under light load cruise conditions, mostly to help fuel economy, but it also helps keep the plugs clean. Under any kind of load such as pulling a hill or full throttle passing, etc. it retards and reverts back to the RPM curve. In your case (6012# 4 pill) you should never have over 20* total at full throttle and actually should be as little as 16* @5000 and 19* @6000.
YOU may be satisfied with it, but it is not working like it is supposed to. Also,
if it is giving the numbers you say, there would be no point in even having the MAP curve.

 

*marco_chevy*, I owe you an apology. Looking back, I realize I inadvertantly hi-jacked your thread. I will bow out of the discussion and let you get back to fixing your carburetor. Sorry! Ron

 

1- Idle timing is 22, Vacuum = 2-3, it's 2-3 psia as read on my laptop, by the map sensor and the msd software., give + 20 degre advance. same for cruise and wot

2- My map sensor is connected directly in the phoenelic spacer, between intake and carb, very nice place.



The msd curve pills#3 and #4 for msd 6012 is the one write on it and very near of my own curve. ( may be i can put pills #3 or #4 and have same result).



I think my numbers are good if the number of MSD are good..

The vacuum test whit a gauge in '' in HG '' will be redone this week, at idle and at cruise,in a gear, and write it back here.. ( whit gauge pluged direct to the carb, whit ose until my windsheild.

I dont know why, but my number timing and psia are good... they are a mix between MSD 6012 Pills # 3 and #4.

See by yourself... It's impossible that the vaccum advance go to 0 degre a WOT ( in this case), because total timing will be 17( pills #3) or 19 ( pills #4), very too low degre... For have 32-33 degre ( best WOT timing), vacuum advance need to be about + 15 ( need exactly 6 psia).

It can be the MAP sensor of GM that read like a 1.5 BAR and give not the real number? I try to program it whit 2 BAR map sensor, and give me different, bad number.

I dont think it's my set-up that is trouble, because i can run the pills #3 and #4 give whit the msd 6012 box, and my car will run very nice.

 

Really no problem Ron , it's my post, and it's my car ... i like to learn about it...

For my carb, i will try it later this week... i'm too busy now for chek this out.

 

If you are OK with this, I'm going to jump in here again. The readings you are getting, in psia are not possible! At idle, you said you were seeing somewhere between 8-11" of vacuum on a guage...right? That reading of 2-3 psia that you said showed on your MSD dial is something like 24" of vacuum!!
That's impossible! You can see this from your own vacuum readings. I don't think an engine like yours with the cam you have could even generate that much vacuum going down the road at 4000 RPM LOL. Mine couldn't. If your vacuum gauge has a 3/16 or 1/4" hose fitting on it..hook it up to the small nipple on the base of your carb under the front fuel bowl and drive around for awhile. Tape it to the windshield, so you can watch it. When you get to your 3000RPM cruise speed, I will almost bet it won't be over 20" vacuum and when you floor it, close to 0" vacuum. What I am trying to say is there is something wrong with either the way you have it configured, or your MAP is fubarred or your box is, because it is not working the way it is supposed to.

 

Ok Ron.... this evening, i have installed vacuum gauge in in HG on my windsheil, and plug it in the front of the carb, under the fuel bowl, whit 3 feets ose. I also have connected my laptop to my msd... I will take a ride tomorow Number will be better, because last time, gauge was connected between intake and booster brake.... wrong place.

I'm sure my MSD box is good... i have the same number of MSD... i'm sure all is ok.... look my curve, it's a mix of the pills#3 and #4.... it's why i think all is ok!

Someone else have a 6012 msd box connected to a gm MAP sensor ?

Someone know how many BAR is a GM map sensor ?

 

OK..when you get your laptop hooked up to your box, try this. Turn it on and bring up the curves page. Open the data box on the left and make sure you're set for a 1 bar MAP (0-15psia). Also, make sure that you don't have any minimum or maximum advance values set. Default values are min. 5 and max. 45 I think. Now maximize the 3 dials box, so you can see them good and then turn on the ignition but DO NOT start the engine. Now... open the throttle blades so your MAP is open to the outside ambient air and now check the psia dial. It should read atmospheric pressure. Mine generally reads around 13.8 psia, but I am at approximately 1500 ft. altitude. If you are at sea level, you will be closer to 14.7. Obviously if you are in the mountains it will be less. If you get some weird reading, like 2-3psia, first make sure you don't have a dirt dauber nest in your MAP or some other obstruction, (I"M kidding), then try a different MAP!! If it still doesn't read right, check your wires at the MAP plug in. If you have a multi-meter, you can check the brwn wire for ground continuity, and the orange should have 5 volts. The Lt grn wire is the sensor signal and should show between 0-5 volts depending on how much vacuum is applied. If it still won't read, I would call MSD tech and ask them why?? Ron

 

Ok ... i just arrive from a run...

motor hot, whit gauge connected direct to the carb..

idle , between 4 and 6 in HG
cruise 3000rpm, about 14-15 in HG
wot, gauge go to 0
motor off, gauge is 0


On my MSD software:

idle, 4 psia, ( + 20 degre)
cruise , 3 psia, sometime 4
WOT 6 psia ( + 15 degre)

motor off, wot or not, 6.2 psia!

total timing idle, 22 degre
cruise, 39-40 degre
WOT 33-34 degre

If i change 1 bar for 2 bar setup,

motor off is 11.4 psia
idle is about 9
3000rpm is 4

If i change 2 bar for 3 bar

motor off is 16.7 psia

So.. i think all work good, but number from map sensor is not good.

it's like i have a 2.5 BAR !....

If i can sellect 2.5 BAR, psia will be 14.1!

GM map sensor 9359409 or american standar AS59

But the result is good....

and i always have 20 afr in small acceleration...

i will need 3.5 power valve?

 

This is very puzzling. Your vacuum guage readings look to be correct for an engine with the cam you have. I would have thought the idle vacuum would have been higher, but your cam does have quite a bit of overlap. I log runs on mine with an Inovate LM 1 with an RPM convertor with a MAP channel, and my cruise is usually around 7-7 1/2 psia, which is around 15" of vacuum. Mine idles around 11-12" of vacuum @ 800RPM with a milder cam. What is confusing, is your MSD dial readings are not coming even close to being equal to your vacuum readings. Idle 4 psia-about 22" hg, actual- 4-6 hg...cruise 3-4 psia-about 24-22" hg, actual-14-15 hg....wide open 6 psia-about 17-18" hg, actually 0" hg as it should be at wide open. You should be for sure using a 1 bar MAP and the MSD should be set for 1 bar. Do you have a different MAP to try?? I said it before...it's like you have a check valve in the hose to the MAP that is keeping the psia readings much higher than they should be. By the way, *3 pedals * has a thread in this forum titled *psia vs vacuum chart* that has a chart to convert psia to hg, if you want to see for yourself. I personally would call MSD tech and try to get the thing to work like it is supposed to so that I could try different timing curves. I can't believe no one else on here has posted how their 6012 box psia readings look. Come on guys!! As for your other question, I would definately try at least a 6.5 PV in place of your 3.5, and no, it will not make it richer at idle. The power valve restrictions supply fuel to the main wells when the vacuum drops to a certain level ( as the # implies) The main wells supply the boosters in the throttle bores when the engine is at a high enough speed to cause the main circuit (boosters) to start flowing. The power valve could be wide open at idle and it would make no difference. One of the other guys said keep it aways below cruise vacuum and he is right. You don't want it to open too early, but try to have a balance so that when you crowd the throttle and the vacuum drops, it will open and supply the extra fuel you need, as you noted in your very lean afr readings. Keep tinkering, you'll get it! Ron

 

thanks Ron...

I can not call msd, because i'm not really good in english... i'm from Quebec, in canada ..

I can try to send them an email, but may-be the anser will be 1 week later !

For choose the good power valve, i need to refer to the 14-15 in HG cruise, or the 4-5-6 in HG idle ?

I will see this evening what is the power valve i have( i dont know now! 3.5 was an exemple..).

I will also chek the number of my innner bleed jet ( main ).

yesterday, it was cold.. about + 3-4 degre.. my problem was more present! when push pedal of 1/2 inch at 3000rpm, afr go to 19-20.. if i puch 1 inch, whitout toutch to the secondary, afr go up to 25:1 and motor pratically turned off... not very good!

So, i will chek power valve, change it if needed, and after, try some air bleed jet.

how many BAR is the GM map sensor 9359409 ?

and what the part that i dont understand, yesterday i try pills #3 and #4, and the total timing was the same + or - 1degre... it's mean that the pills are preset for this king of vacuum read by this kind of MAP sensor...

If the vacuum go to 14.7, and advance is + 0... total timing will be +17 or +19.... at WOT = IMPOSSIBLE... +33, +34 are excellent!

 

I don't have a way to check the number on your MAP. Maybe someone else on here can. Can you possibly borrow one off a friend's LS1 or a 5.3 or 6.0 truck maybe?? Unless MSD has totally changed the way the 6012 box works compared to the 6010's, there is something not right. That is why I think it is either the MAP sensor or something is wrong with the box. I will say....if youchange the MAP and it starts working like I'm telling you it should (like my 6010) you WILL DEFINATELY HAVE TO CHANGE THE TIMING CURVES with your laptop. But that's a good thing I think, because then you can experiment with more timing at idle, and bringing the total in quicker, etc. The test I was telling you to do with engine stopped was to see if your MAP sensor would read atmospheric pressure, which it should if it is worrking correctly. IF you don't want to mess with me telling you that it's not right and you're satisfied with it just like it is, just say the word and I will stop bugging you, and no hard feelings, but I thought you said you wanted to learn about your car?? I'm sorry about the language problem, but truthfully, you are probably having more trouble understanding my babbling than I am with understanding you. LOL. I don't think there is anything wrong with your carb except the power valve. I would try a 6.5 PV. While you have it apart, check the passage in the base that supplies vacuum to the PV. Make sure it is not carboned up or a gasket blocking it, or I have heard some were not drilled properly. Most have a little spring loaded check valve for blowout protection. Sometimes these get fubarred. Have fun! Ron

 

thanks Ron...

the next step for the msd reading, i to ask a MSD tech... i will do that this evening.. and have anser in ??? days!

 

e-mail is sent to msd tech! waiting 48h for anser

I remake test this evening...

vacuum go between 5 and 6, but rpm go between 650 and 750...

at 800 rpm, vacuum is about 7...

i chek and all look good.. i try brake cleaner, and no more rpm! at 1000 rpm, vac go to 10-12.

 

ok... chek my metering block... it's normal or modified?




power valve is right 6 5... it's mean a 6.5 ? this is the good one!

also, chek the 8 air bleed jet P for primary, and S for secondary... they look to be the same size except the 2 outer jet in primary! i can not see any size on any jet! how to know the size ?



I need help