ducky1

iTrader: (7)

I have an LS2 with 243 heads, headers, Vic Jr intake, comp cam @.050 lift intake 243 exhaust 248 in my road race track car. I installed a 750 Holley carb from Pro-Systems with 73 main jets, .080 dia air bleed hole in the main butterflys, 23 air jets and the idle air screws out 2 turns, float bowl level in the middle of the glass. Car starts eazy and idles fine, motor pulls great, but I can't run it for more that 10 minutes before the plugs turn black and start mis-firing. I am running AC 41-110 plugs. All eight plugs look the same black color.
I thought Patrick would set me you with a sweet carburator after I gave him all my engine specs and paid him a good bit of $$ for the carbutator. But the plugs turn black and short out in no time.
Any suggestions?
I plan on calling Patrick tomorrow and see what he says.

burgers

iTrader: (77)

What is you fuel pressure regulator set at?

DMMizell

iTrader: (1)

Why not give Patrick a shot at resolving your issue BEFORE posting?
He answers emails and his phone on the weekends....

xpndbl3

iTrader: (23)

what's your fuel pressure set at? what's your timing curve look like? Are they black from a certain rpm range? Just wot? lots of idle time? etc.

S10xGN

iTrader: (11)

I'm ASSuming you mean the idle "fuel" screws. Mine are out 5/8 turn each, 2 turns on mine and it would be stalling from fuel overload for sure!

ducky1

iTrader: (7)

I'm runnng 9 psi fuel prerssure.
The idle fuel ( I thought they were air screws) were set at 2 turns out from Pro-systems.
And I will give Patrick a call Monday first thing. I was not trying to put him under the bus, just looking for help and didn't figure he would be taking work calls on Sunday.
Timing is set at 8 degrees 0 rpm, ramping up to 28 degrees at 3000rpm. then flat at 28 degrees out.

Pop N Wood

iTrader: (1)

I'm pretty sure he is going to tell you to adjust the idle mixture screws.

Your fuel pressue seems kinda high and you will probably benefit from more top end timing too.

Prorac1

iTrader: (4)

Wouldnt adding some timing at idle help as well? Just my .02. Eric L

xpndbl3

iTrader: (23)

7 psi fuel pressure is all you need, that's part of the overly rich condition. Next turn those idle mixture screws in a little try 1.5 turns out if a 2 corner idle system, if 4 corner idle system they may only want 3/4 turn out. Next your timing is all wrong, try 12 degrees for 0-500rpm, then at least 20-24 degrees from 500-1300, then ramp it up to 32 from 2000rpm on up. You may need more timing 34/36 degrees, shoot for best mph at the track if you're racing it or read timing marks on the plugs. Also more timing at idle will DEFINITELY clean up the plugs right there.

My curve with a bigger cam:

12 degrees while cranking 0-500rpm
ramped up to 24 degrees at 500-1300rpm
34 total from 2000-7600rpm

This cleaned up the idle considerably and was worth 2mph over 32 total at the track. Timing marks looked perfect so I stopped at 34 total, some guys run 36 even.

burgers

iTrader: (77)

Fuel pressure is way to High as stated above it should be 6.5-7 psi

chris-m

all as above, 7psi is enough and if you add some timing in with vaccum advance so it idlles at 28-35 degrees etc it will clean it up no end. mine used to make your eyes water at idle till the timing was advanced

ducky1

iTrader: (7)

Thanks guys.

I called Pro-Systems today and they said to drop the fuel pressure to 7psi, like you guys said.

They said to drop the float level to 1/4 in the fuel bowel level viewing glass.

I boosted the timing like you said.

I turned in the idle fuel screws (4 screws) to 3/4 out.

Car started and ran fine, cold, it had a little lean stumble, which should be better as it gets hot (its 8:45pm, dark and my neighbors dont really like a loud car with no lights running down the street in the dark ).

Thanks for the help.

ducky1

iTrader: (7)

One more thing, I saw that the MSD 6012 system on my lap top ask if I have LS1 or LS2 coils. I got these used off the forum and an mot sure which one I have. I checked and some have a part number 3Z02n and some have a part number 5X21-5. How do I check to see if they are LS1 or LS2? And does it matter?

ducky1

iTrader: (7)

One more thing, I saw that the MSD 6012 system on my lap top ask if I have LS1 or LS2 coils. I got these used off the forum and an not sure which one I have. I checked and some have a part number 3Z02 and some have a part number 5X21-5. How do I check to see if they are LS1 or LS2? And does it matter?

cody161

iTrader: (18)

If it had a lean stumble then back the idle mixture screws out to 1 turn each.

Pop N Wood

iTrader: (1)

The two are visibly different. LS1 on the left, LS2 in the middle and I think truck coil on the right



Best way to set your idle mixture screws is with a wideband. Oldschool way is to ajust them for max manifold vacuum. The mixture is really sensitive to even slight turns of the screws.

http://www.holley.com/data/TechServi...ech%20Info.pdf

ducky1

iTrader: (7)

Well I looked at my coils and they dont look like any of these coils. They look most like the center "LS2" coil, but with the spart pluf wire right over the mounting bolts. Also I have a 2003 Chev Suburban with a 5.3 motor and it have the same coils that are on my LS2 engine. The exact same coils!
So does it really matter if I tell the MSD I have LS1 or LS2 coils? Is there a differance in restiance or out put voltage?

cody161

iTrader: (18)

There is a right way to set the mixture screws without a wideband and it isn't by adjusting for maximum manifold vacuum.

Pop N Wood

iTrader: (1)

LS2 coils are significantly more powerful than the LS1 coils. Truck coils have more ***** yet.

I have no idea what the MSD box does differently. You could probably go to the MSD user forum and find out. If it were me, if they aren't LS1 coils then put it at the LS2 setting.

ducky1

iTrader: (7)

So cody161, whats the right way to adjust the isle mixture?
pop N Wood, I called the MSD tech line and asked the question about the lap top option for LS1 or LS2 coils and he said "Gee, i dont know why that option is in the 6012 LS2 MSD software". Doesn't make me feel too good about their advice.