LSwonderfull

I have been fighting getting my 402" LS2 to turn over 6900 rpm, at first i blamed valve springs but now i believe it is a ignition break down from inadequate coil saturation time? Can anyone help me with this?
MSD is looking in to this for me, no answers yet.

AUSTRALS1A

What led you to that conclusion?... Not being smart just trying to get my head around the problem. Does the engine break down?...or is the power just sharply falling away?

LSwonderfull

The engine violently shakes and pops when you reach 6900 rpm, no valvetrain damage or spring tension loss occurs. I talked briefly with a tech at MSD and he feels it could be a problem with controller coil dwell time being inadequate, he is consulting the engineer that designed the LS1 controller.
I figure they didnt reallize customers would be looking for over 7k operation ?

Old Geezer

iTrader: (3)

Have you tried a better grade fuel?? 91 and west coast "grade", on top of "91", would be a place I'd look.

LSwonderfull

My friend Joe Sherman and i have considered this and he nor i have ever seen anything like the phenomenon we witnessed first on his dyno than in the car at several different race outings. Detonation from inadequate octane does not show up as a chaotic missfire like this motor is experiencing, there are no signs of detonation on the spark plugs either. I'm open minded to anything that could be causing this problem but it seems to be ignition breakdown to me. I dont believe most people using carb conversion MSD controller are spinning above 6900 rpm so this problem is mostly being uncovered by me. Any help appreciated.....

Pro Stock John

iTrader: (34)

There are a ton of guys in the conversion/hybrid forum running that box with no problems, ask in there.

LSwonderfull

John response there has been very sluggish, can anyone in here offer any help?

Schwanke Engines

iTrader: (1)

You could try switching to a truck type coil. I know that the required dwell times are different for each coil, and it just might be the ticket. I know we run the 6012 boxes just fine so far to 7400 on dirt modifieds.
Are you using the software to set the timng, or the chips?

LSwonderfull

I am using the software, and i have verified on the dyno that the timing set is accurate, do you use truck coils?

airflowdevelop

aftermarket plug wires by chance?

LSwonderfull

yes i am using msd wires but origonal dyno testing was with factory wires,and problem was there with both sets, why do you ask?

turningfast

Have you tried tightening up the plug gaps? Since dwell time is basically how much time the primary side of the coil gets saturated with voltage before releasing the secondary spark, a smaller gap may help by making it easier for the spark to jump the gap. From the way you describe it, it does sound like spark blow out or a weak spark.

LSXS10

iTrader: (37)

I had the same problem at about 65-6700 with alot of n20. I went down on the plug gap and it didnt seem to help, i would like to know this as well..

Schwanke Engines

iTrader: (1)

Yes, we use the truck coils.

fossil

iTrader: (1)

Does it do this real bad on the 2-3 shift (if you have a auto trans)? I have tried alot of different engines, 5 to be exact and alot of different valvetrain options. My most troublesome proplems, have been in the proper valvetrain set up (harmonics).

LSwonderfull

Yes it does it on 2-3 shift but its rpm related, i am seriously thinking my plug gaps are too large for the MSD and factory coils, i will tighten them up and retest sunday. I have upgraded my valve springs once and it had zero effect on problem.

fossil

iTrader: (1)

Too much valvetrain preload caused this on mine before (pushrods too long). I try to run as little as possible preload on lifters, like .030"-.040" and this has worked for me.

LSwonderfull

Thanks yes i was very careful setting my preload, it is right at .030".
I closed up my spark plug gaps and the problem was still there, any more people successfully running MSD 6010 above 7k with pump gas LS2?

LSwonderfull

Ok i found my problem finally, the engine goes into a uncontrolled combustion with over 6800 rpm and 34* of advance with 91 octane pump gas. First i reset total timing to 26* and it revved clean to 7500 no problem. Next i pumped all the 91 octane out and added c-16 VP and i reset timing back to
34* again, this also ran great to 7500 with no hiccups or glitches.
Thanks to everyone who chimed in, i plan on running 34* with a mix of race gas and pump.

Old Geezer

iTrader: (3)