MSD and plug gap

[HPjunkie]

I have an LM-1 O2 sensor hooked up to my motor and I get a lot of spikes of oxygen showing up. Someone said those are misses. My plug gap is set at .035. I just read the ***boat article where they set the gaps at .045 for a BB Chev blower motor. I was thinking Maybe I should close up the gap to 030. This because of my motor being blown as well. What about heat range? I have Alum heads, no t-stat, and -7 NGK plugs. Any suggestions would be great. Greg

[WETTE VETTE]

How high/low are the spikes? On my o2 readings at WOT they are pretty consistent between 12.5 and 12.7 with the occasional 12.9 and 12.3. The 12.9 or 12.3 may show up once or twice throughout a WOT pass lasting approximately 30 seconds once at 6500 RPM. I tun NGK -9's gapped at .035 on a 10:1 solid roller 598" NA motor. I'm not surprised to see the numbers move around a bit, but would like to hear opinions or experiences on how much is normal.
Craig

[HPjunkie]

I could email you a map from the lm1. I might be able to post a link. These are way out like 22 to 1 for 1-2 seconds. I dont know what to think. Do you use the lm1? The boat seems to run fine. These maps just drive me nuts. Its at all speeds. If you can confirm my thought or help that would be greatly appreciated. Greg

[WETTE VETTE]

I also run a LM1 and haven't seen that type of behavior. At idle in gear when the RPM's are less than 1000 I see 17/1, but there is a good explanation. Reversion is pulling some fresh air in and throwing off the O2 readings. Everywhere else the readings are as I discussed in my earlier post. Where is your sensor located in your exhaust?

[HPjunkie]

Its in the riser above the manifold. about 1/2 inch above the parting line. Id like to send you the file. Is your email in the profile?

[WETTE VETTE]

I just PM'd you my email. How do the plugs look after a WOT pass? That, with the O2 is the way to get the motor dialed in. I don't totally trust the O2 or my plug reading skills beyond a point. However if the plug readings and the O2 numbers jive I feel pretty good about the tune.

[HPjunkie]

You got mail! Let me know what you think? Thanks Greg

[Blown Income]

-7 NGK plugs are a little warm for my taste in a blown motor, try the -9 if you like the NGK, I've been told and had good luck with Autolite AR12.

[MACHINEHEAD]

Dont know the lm1 but it sounds like a default ratio when there is no signal or interupted signal. Check your grounds and wiring. I have never seen an engine go to 22 to 1 and back again in 1-2 seconds. If this is a common occurance it would have melted down by now, easy. A blown engine under full load at even 14to1 for 1-2 seconds would be a pile after the third or fourth time. Its somthing simple, maybe just a moistened O2 sensor

[born2burn]

HPJunkie-
Going through the same thing you are currently going through with my blown 600cid. I was told by Innovates tech that it could be noise through the ignition. They said to try powering the LM with its own power source such as a designated 12V battery strictly by itself. I will let you know if I get any success and hopefully you can do the same for me.