marco_chevy

saterday morning, i will see a pro of carburetor.. He told me, i will find your problem ! It's one of the best tuner in my area.. 10x better than me ...

I will let you know what was the problem



For MSD, i receive an anser, and they told me to chek my map sensor, that is supposed to be about 14.7 whit motor off... and mine is 6.2... But the pills can not work correctly whit 14.7 = + 0 advance at WOT..

i asked him to explain me how work the pills whit 0 vaccum advance.. 17 degre at 6000 rpm WOT will be very very bad timing.!

I will try an other MAP, i also have a silverado 5.3 whit the same number, i think! i will just connect it to the msd and see the number in the msd software...

rojs234

iTrader: (5)

I keep telling myself to quit, but I just can't help myself, LOL. For some reason, you don't seem to understand that, if your box was working like it was designed to, the pills that came with it do not have anywhere near the correct curve for the engine you have. I'm not sure those curves would even work with a stock efi engine. MSD seems to have gone from one extreme (too much total advance) on the 6010 to the other (not nearly enough advance) on the 6012 box. You seem to have lucked out on yours since it is somehow giving you the timing that works. I'm not putting you down, but you have obviously never seen the timing curves of an old distributor type ignition system. Yea, I'm that old . The MSD RPM curve takes the place of the old mechanical advance. You set this or the MSD RPM curve for the most timing your engine can handle under various conditions at full throttle maximum load at the different RPM's. The vacuum advance or the MSD vacuum curve is set for the most timing the engine likes at light loads and high vacuum levels. Most engines can stand between 40-48* at high vacuum levels as long as you don't bring the advance in too early. If you do, you'll get "pinging" under light loads at lower RPM's, especially if your bringing in your total advance on your RPM curve at a lower RPM, like 2500-3000 on a performance type engine such as yours. As you have stated...at full throttle
0" of vacuum you will have whatever total advance you have set in your RPM curve at the RPM you hit full throttle. In your case, with the # 4 MSD pill, you will have 20* @ 2000 RPM and at 5000 RPM you will have 16*. This is not even close to being right for your engine. That is why I said in the earlier post that if you get your MAP or box to work correctly, you will need to set up your own curve on your laptop. This is easy with the MSD boxes. I have worked for weeks at a time dialing in the old distributors....making bushings, brazing up slots or closing them with key stock and epoxy and figuring out ways to either slow down or limit the vacuum advance. Ah, the good ol days..NOT. Anyway, glad to hear you took your carb to a pro. Ron

marco_chevy

I just return from a ride whit the carb. This morning, i bring my carb to a pro. He chek all the carb, and told me that it is a very great carb, a 650 body, whit 750 booster and trottle plate, and other componant, well ported, and made like it supposed to be.. I was glad to here this. He chek it whit a convetionnal flow bench, and the carb make 845 cfm, have very good signal, and the signal are very synchronised!

FInally, he ajusted the fuel bowl level( whit bowl in his hand) and told me it was about 1/4 in too low. He change 6.5 power valve for a new one because the old one have some sign of wear ( but working correcly), he change fuel pump cam for one that give fuel sooner, he also drill the primary idle air bleed, from 60 to 70 and chek all the other part.

When i reinstalled the carb, i chek fuel pressure, it is 6-6 1/4, i chek fuel level, both are = to the screw.

I go ride and all is good.. afr at idle, at cruise, acceleration are very nice, and after several test, at 50, 60, 70 mph, i try to push 1/4, 1/2, 3/4 in on the fuel pedal, and the aft never go more than 16.5.... and ofen about 15.. Before, it was 18-19-20, and sometime, the motor turn down for 1-2 second.

It's mean that my problem is now a old history!

It was fuel bowl level, old PV, to small idle air bleed ? a mix of all! i dont know.

But now, it's work fine....


reste to try an other MAP sensor an other things, but for now, timing is excellent!

speedtigger

iTrader: (16)

Happy Day!

team39763

iTrader: (3)

Glad to hear you got it sorted out.

marco_chevy

i must store my car in the garage for the winter ( snow will arrive in 1-2 weeks), but it will be ready for next season

Pop N Wood

iTrader: (1)

Good to hear. Funny it comes down to something as basic as float levels.

Looking forward to some track times on that bad boy.

I still think rojs234 has some valid points on the timing curve. Maybe a few HP to be had there.

marco_chevy

the number of my timing curve are not the good one, but total timing is good, i think? Not ?

marco_chevy

i start a new post for my car, future project may-be, for the next summer... injected, whit my carburetor intake..

what is the best?

https://ls1tech.com/forums/fueling-i...l#post14163131

marco_chevy

nobody have experience whit this kind of injection ?